Prof Paresh Vyas MRCP FRCP FRCPath

Research Area: Developmental and Stem Cell Biology
Technology Exchange: Biobanking, Bioinformatics, Cell sorting, Computational biology, ES cell / homologous recombination, Flow cytometry, Mass spectrometry, Protein interaction, Transcript profiling and Transgenesis
Scientific Themes: Haematology and Developmental Biology & Stem Cells
Keywords: Leukaemia, stem cells, genomics, therapy
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Our aim is to characterise the heterogeneous populations of leukaemia propagating cells in adult and childhood Acute Myeloid Leukaemia (AML) at functional, genetic, epigenetic and molecular levels, eventually at a single cell level, to improve our basic understanding of leukaemia initiation and propagation. The ultimate aim is to translate this knowledge to improve survival rates in patients.

Name Department Institution Country
Prof Catherine Porcher Nuffield Division of Clinical Laboratory Sciences Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Prof Irv Weissman Department fo Pathology Stem Cell Biology & Regenerative Medicine, Stanford University United States
Dr Ravi Majeti Department of Haematology Stem Cell Biology and Regenrative Medicine, Stanford University United States
Prof Claus Nerlov Nuffield Division of Clinical Laboratory Sciences Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Prof Sten Eirik W Jacobsen Nuffield Division of Clinical Laboratory Sciences Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Prof Charles Craddock FRCP FRCPath Centre for Clinical Haematology University Hospitals Birmingham NHS Foundation Trust United Kingdom
Prof Adam Mead MRCP FRCPath Weatherall Institute of Molecular Medicine Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Prof Thomas Milne Nuffield Division of Clinical Laboratory Sciences Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Dr Alexander Sternberg FRCP FRCPath The University of Oxford United Kingdom
Prof Tariq Enver Cancer Institute UCL United Kingdom
Prof Jacqueline Boultwood Nuffield Division of Clinical Laboratory Sciences Oxford University, John Radcliffe Hospital United Kingdom
Prof David Grimwade FRCP FRCPath NHS United Kingdom
Prof Nigel Russell FRCP FRCPath University of Nottingham United Kingdom
Prof Jamie Cavenagh FRCP FRCPath Department of Haematology St Bartholomew's Hospital, Quuen Mary, University of London United Kingdom
Prof Clark Richard FRCP FRCPath Department of Haematology Royal Liverpool University Hospital United Kingdom
Dr Peter Campbell Cancer Genome Project Sanger Centre United Kingdom
Prof David Bowen FRCP FRCPath Department of Haematology Leeds University Hospitals NHS Trust United Kingdom
Dr Anna Schuh Nuffield Division of Clinical Laboratory Sciences Oxford University, John Radcliffe Hospital United Kingdom
Prof Alan Burnett FMedSci FRCP FRCPath Cardiff University United Kingdom
Dr Brenda Gibson FRCP FRCPath Department of Haematology Royal Hospital for Sick Children United Kingdom
Dr Philip Ancliff FRCP FRCPath Great Ormond Street Hospital United Kingdom
Prof Mitch Weiss Department of Pediatric Hematology Children's Hospital of Philidelphia United States
Prof Ajay Vora FRCP FRCPath Department of Haematology Sheffield Children's Hospital United Kingdom
Prof Owen Smith FRCP FRCPath Our Ladies Children's Hospital Ireland
Dr Jan-Henning Klusmann Department of Pediatric Hematology Hannover University Germany
Dr Henrik Hasle Department of Paediatrics Skejby Hospital, Aarhus University Denmark
Dr John Strouboulis BSRC Alexander Fleming Greece
Prof Irene Roberts Weatherall Institute of Molecular Medicine Oxford University, Weatherall Institute of Molecular Medicine United Kingdom
Craddock C, Houlton AE, Quek LS, Ferguson P, Gbandi E, Roberts C, Metzner M, Garcia-Martin N, Kennedy A, Hamblin A et al. 2017. Outcome of Azacitidine Therapy in Acute Myeloid Leukemia is not Improved by Concurrent Vorinostat Therapy but is Predicted by a Diagnostic Molecular Signature. Clin Cancer Res, | Show Abstract | Read more

Purpose: Azacitidine (AZA) is a novel therapeutic option in older patients with acute myeloid leukemia (AML) but its rational utilization is compromised by the fact that neither the determinants of clinical response nor its mechanism of action are defined. Co-administration of histone deacetylase inhibitors, such as vorinostat (VOR), is reported to improve the clinical activity of AZA but this has not been prospectively studied in AML. Experimental Design: We compared outcomes in 259 adults with AML (n=217) and MDS (n=42) randomized to receive either AZA monotherapy (75 mg/m(2) × seven days every 28 days) or AZA combined with VOR 300 mg bd on days 3-9 po. Next generation sequencing was performed in 250 patients on 41 genes commonly mutated in AML. Serial immunophenotyping of progenitor cells was performed in 47 patients. Results: Co-administration of VOR did not increase the overall response rate (P=0.84) or overall survival (OS) (P=0.32). Specifically, no benefit was identified in either de novo or relapsed AML. Mutations in the genes CDKN2A (P=0.0001), IDH1 (P=0.004) and TP53 (P=0.003) was associated with reduced OS. Lymphoid multi-potential progenitor populations were greatly expanded at diagnosis and although reduced in size in responding patients remained detectable throughout treatment. Conclusion: This study demonstrates no benefit of concurrent administration of VOR with AZA but identifies a mutational signature predictive of outcome after AZA based therapy. The correlation between heterozygous loss of function CDKN2A mutations and decreased OS implicates induction of cell cycle arrest as a mechanism by which AZA exerts its clinical activity.

Amatangelo MD, Quek L, Shih A, Stein EM, Roshal M, David MD, Marteyn B, Farnoud NR, de Botton S, Bernard OA et al. 2017. Enasidenib induces acute myeloid leukemia cell differentiation to promote clinical response. Blood, 130 (6), pp. 732-741. | Show Abstract | Read more

Recurrent mutations at R140 and R172 in isocitrate dehydrogenase 2 (IDH2) occur in many cancers, including ∼12% of acute myeloid leukemia (AML). In preclinical models these mutations cause accumulation of the oncogenic metabolite R-2-hydroxyglutarate (2-HG) and induce hematopoietic differentiation block. Single-agent enasidenib (AG-221/CC-90007), a selective mutant IDH2 (mIDH2) inhibitor, produced an overall response rate of 40.3% in relapsed/refractory AML (rrAML) patients with mIDH2 in a phase 1 trial. However, its mechanism of action and biomarkers associated with response remain unclear. Here, we measured 2-HG, mIDH2 allele burden, and co-occurring somatic mutations in sequential patient samples from the clinical trial and correlated these with clinical response. Furthermore, we used flow cytometry to assess inhibition of mIDH2 on hematopoietic differentiation. We observed potent 2-HG suppression in both R140 and R172 mIDH2 AML subtypes, with different kinetics, which preceded clinical response. Suppression of 2-HG alone did not predict response, because most nonresponding patients also exhibited 2-HG suppression. Complete remission (CR) with persistence of mIDH2 and normalization of hematopoietic stem and progenitor compartments with emergence of functional mIDH2 neutrophils were observed. In a subset of CR patients, mIDH2 allele burden was reduced and remained undetectable with response. Co-occurring mutations in NRAS and other MAPK pathway effectors were enriched in nonresponding patients, consistent with RAS signaling contributing to primary therapeutic resistance. Together, these data support differentiation as the main mechanism of enasidenib efficacy in relapsed/refractory AML patients and provide insight into resistance mechanisms to inform future mechanism-based combination treatment studies.

Stein EM, DiNardo CD, Pollyea DA, Fathi AT, Roboz GJ, Altman JK, Stone RM, DeAngelo DJ, Levine RL, Flinn IW et al. 2017. Enasidenib in mutant IDH2 relapsed or refractory acute myeloid leukemia. Blood, 130 (6), pp. 722-731. | Show Abstract | Read more

Recurrent mutations in isocitrate dehydrogenase 2 (IDH2) occur in ∼12% of patients with acute myeloid leukemia (AML). Mutated IDH2 proteins neomorphically synthesize 2-hydroxyglutarate resulting in DNA and histone hypermethylation, which leads to blocked cellular differentiation. Enasidenib (AG-221/CC-90007) is a first-in-class, oral, selective inhibitor of mutant-IDH2 enzymes. This first-in-human phase 1/2 study assessed the maximum tolerated dose (MTD), pharmacokinetic and pharmacodynamic profiles, safety, and clinical activity of enasidenib in patients with mutant-IDH2 advanced myeloid malignancies. We assessed safety outcomes for all patients and clinical efficacy in the largest patient subgroup, those with relapsed or refractory AML, from the phase 1 dose-escalation and expansion phases of the study. In the dose-escalation phase, an MTD was not reached at doses ranging from 50 to 650 mg per day. Enasidenib 100 mg once daily was selected for the expansion phase on the basis of pharmacokinetic and pharmacodynamic profiles and demonstrated efficacy. Grade 3 to 4 enasidenib-related adverse events included indirect hyperbilirubinemia (12%) and IDH-inhibitor-associated differentiation syndrome (7%). Among patients with relapsed or refractory AML, overall response rate was 40.3%, with a median response duration of 5.8 months. Responses were associated with cellular differentiation and maturation, typically without evidence of aplasia. Median overall survival among relapsed/refractory patients was 9.3 months, and for the 34 patients (19.3%) who attained complete remission, overall survival was 19.7 months. Continuous daily enasidenib treatment was generally well tolerated and induced hematologic responses in patients for whom prior AML therapy had failed. Inducing differentiation of myeloblasts, not cytotoxicity, seems to drive the clinical efficacy of enasidenib. This trial was registered at www.clinicaltrials.gov as #NCT01915498.

Yip BH, Steeples V, Repapi E, Armstrong RN, Llorian M, Roy S, Shaw J, Dolatshad H, Taylor S, Verma A et al. 2017. The U2AF1S34F mutation induces lineage-specific splicing alterations in myelodysplastic syndromes. J Clin Invest, 127 (6), pp. 2206-2221. | Show Abstract | Read more

Mutations of the splicing factor-encoding gene U2AF1 are frequent in the myelodysplastic syndromes (MDS), a myeloid malignancy, and other cancers. Patients with MDS suffer from peripheral blood cytopenias, including anemia, and an increasing percentage of bone marrow myeloblasts. We studied the impact of the common U2AF1S34F mutation on cellular function and mRNA splicing in the main cell lineages affected in MDS. We demonstrated that U2AF1S34F expression in human hematopoietic progenitors impairs erythroid differentiation and skews granulomonocytic differentiation toward granulocytes. RNA sequencing of erythroid and granulomonocytic colonies revealed that U2AF1S34F induced a higher number of cassette exon splicing events in granulomonocytic cells than in erythroid cells. U2AF1S34F altered mRNA splicing of many transcripts that were expressed in both cell types in a lineage-specific manner. In hematopoietic progenitors, the introduction of isoform changes identified in the U2AF1S34F target genes H2AFY, encoding an H2A histone variant, and STRAP, encoding serine/threonine kinase receptor-associated protein, recapitulated phenotypes associated with U2AF1S34F expression in erythroid and granulomonocytic cells, suggesting a causal link. Furthermore, we showed that isoform modulation of H2AFY and STRAP rescues the erythroid differentiation defect in U2AF1S34F MDS cells, suggesting that splicing modulators could be used therapeutically. These data have critical implications for understanding MDS phenotypic heterogeneity and support the development of therapies targeting splicing abnormalities.

Giustacchini A, Thongjuea S, Barkas N, Woll PS, Povinelli BJ, Booth CAG, Sopp P, Norfo R, Rodriguez-Meira A, Ashley N et al. 2017. Single-cell transcriptomics uncovers distinct molecular signatures of stem cells in chronic myeloid leukemia. Nat Med, 23 (6), pp. 692-702. | Show Abstract | Read more

Recent advances in single-cell transcriptomics are ideally placed to unravel intratumoral heterogeneity and selective resistance of cancer stem cell (SC) subpopulations to molecularly targeted cancer therapies. However, current single-cell RNA-sequencing approaches lack the sensitivity required to reliably detect somatic mutations. We developed a method that combines high-sensitivity mutation detection with whole-transcriptome analysis of the same single cell. We applied this technique to analyze more than 2,000 SCs from patients with chronic myeloid leukemia (CML) throughout the disease course, revealing heterogeneity of CML-SCs, including the identification of a subgroup of CML-SCs with a distinct molecular signature that selectively persisted during prolonged therapy. Analysis of nonleukemic SCs from patients with CML also provided new insights into cell-extrinsic disruption of hematopoiesis in CML associated with clinical outcome. Furthermore, we used this single-cell approach to identify a blast-crisis-specific SC population, which was also present in a subclone of CML-SCs during the chronic phase in a patient who subsequently developed blast crisis. This approach, which might be broadly applied to any malignancy, illustrates how single-cell analysis can identify subpopulations of therapy-resistant SCs that are not apparent through cell-population analysis.

Labuhn M, Perkins K, El Kathib M, Taub J, Heckl D, Vyas P, Klusmann JH. 2017. Activating CSF2RB Mutations Contribute to the Leukemic Transformation from TAM to ML-DS ANNALS OF HEMATOLOGY, 96 pp. S78-S78.

Ferguson P, Hills RK, Grech A, Betteridge S, Kjeldsen L, Dennis M, Vyas P, Goldstone AH, Milligan D, Clark RE et al. 2016. An operational definition of primary refractory acute myeloid leukemia allowing early identification of patients who may benefit from allogeneic stem cell transplantation. Haematologica, 101 (11), pp. 1351-1358. | Show Abstract | Read more

Up to 30% of adults with acute myeloid leukemia fail to achieve a complete remission after induction chemotherapy - termed primary refractory acute myeloid leukemia. There is no universally agreed definition of primary refractory disease, nor have the optimal treatment modalities been defined. We studied 8907 patients with newly diagnosed acute myeloid leukemia, and examined outcomes in patients with refractory disease defined using differing criteria which have previously been proposed. These included failure to achieve complete remission after one cycle of induction chemotherapy (RES), less than a 50% reduction in blast numbers with >15% residual blasts after one cycle of induction chemotherapy (REF1) and failure to achieve complete remission after two courses of induction chemotherapy (REF2). 5-year overall survival was decreased in patients fulfilling any criteria for refractory disease, compared with patients achieving a complete remission after one cycle of induction chemotherapy: 9% and 8% in patients with REF1 and REF2 versus 40% (P<0.0001). Allogeneic stem cell transplantation improved survival in the REF1 (HR 0.58 (0.46-0.74), P=0.00001) and REF2 (HR 0.55 (0.41-0.74), P=0.0001) cohorts. The utilization of REF1 criteria permits the early identification of patients whose outcome after one course of induction chemotherapy is very poor, and informs a novel definition of primary refractory acute myeloid leukemia. Furthermore, these data demonstrate that allogeneic stem cell transplantation represents an effective therapeutic modality in selected patients with primary refractory acute myeloid leukemia.

Desborough M, Hadjinicolaou AV, Chaimani A, Trivella M, Vyas P, Doree C, Hopewell S, Stanworth SJ, Estcourt LJ. 2016. Alternative agents to prophylactic platelet transfusion for preventing bleeding in people with thrombocytopenia due to chronic bone marrow failure: a meta-analysis and systematic review. Cochrane Database Syst Rev, 10 (10), pp. CD012055. | Show Abstract | Read more

BACKGROUND: People with thrombocytopenia due to bone marrow failure are vulnerable to bleeding. Platelet transfusions have limited efficacy in this setting and alternative agents that could replace, or reduce platelet transfusion, and are effective at reducing bleeding are needed. OBJECTIVES: To compare the relative efficacy of different interventions for patients with thrombocytopenia due to chronic bone marrow failure and to derive a hierarchy of potential alternative treatments to platelet transfusions. SEARCH METHODS: We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (the Cochrane Library 2016, Issue 3), MEDLINE (from 1946), Embase (from 1974), CINAHL (from 1937), the Transfusion Evidence Library (from 1980) and ongoing trial databases to 27 April 2016. SELECTION CRITERIA: We included randomised controlled trials in people with thrombocytopenia due to chronic bone marrow failure who were allocated to either an alternative to platelet transfusion (artificial platelet substitutes, platelet-poor plasma, fibrinogen concentrate, recombinant activated factor VII (rFVIIa), desmopressin (DDAVP), recombinant factor XIII (rFXIII), recombinant interleukin (rIL)6 or rIL11, or thrombopoietin (TPO) mimetics) or a comparator (placebo, standard of care or platelet transfusion). We excluded people undergoing intensive chemotherapy or stem cell transfusion. DATA COLLECTION AND ANALYSIS: Two review authors independently screened search results, extracted data and assessed trial quality. We estimated summary risk ratios (RR) for dichotomous outcomes. We planned to use summary mean differences (MD) for continuous outcomes. All summary measures are presented with 95% confidence intervals (CI).We could not perform a network meta-analysis because the included studies had important differences in the baseline severity of disease for the participants and in the number of participants undergoing chemotherapy. This raised important concerns about the plausibility of the transitivity assumption in the final dataset and we could not evaluate transitivity statistically because of the small number of trials per comparison. Therefore, we could only perform direct pairwise meta-analyses of included interventions.We employed a random-effects model for all analyses. We assessed statistical heterogeneity using the I(2) statistic and its 95% CI. The risk of bias of each study included was assessed using the Cochrane 'Risk of bias' tool. The quality of the evidence was assessed using GRADE methods. MAIN RESULTS: We identified seven completed trials (472 participants), and four ongoing trials (recruiting 837 participants) which are due to be completed by December 2020. Of the seven completed trials, five trials (456 participants) compared a TPO mimetic versus placebo (four romiplostim trials, and one eltrombopag trial), one trial (eight participants) compared DDAVP with placebo and one trial (eight participants) compared tranexamic acid with placebo. In the DDAVP trial, the only outcome reported was the bleeding time. In the tranexamic acid trial there were methodological flaws and bleeding definitions were subject to significant bias. Consequently, these trials could not be incorporated into the quantitative synthesis. No randomised trial of artificial platelet substitutes, platelet-poor plasma, fibrinogen concentrate, rFVIIa, rFXIII, rIL6 or rIL11 was identified.We assessed all five trials of TPO mimetics included in this review to be at high risk of bias because the trials were funded by the manufacturers of the TPO mimetics and the authors had financial stakes in the sponsoring companies.The GRADE quality of the evidence was very low to moderate across the different outcomes.There was insufficient evidence to detect a difference in the number of participants with at least one bleeding episode between TPO mimetics and placebo (RR 0.86, 95% CI 0.56 to 1.31, four trials, 206 participants, low-quality evidence).There was insufficient evidence to detect a difference in the risk of a life-threatening bleed between those treated with a TPO mimetic and placebo (RR 0.31, 95% CI 0.04 to 2.26, one trial, 39 participants, low-quality evidence).There was insufficient evidence to detect a difference in the risk of all-cause mortality between those treated with a TPO mimetic and placebo (RR 0.74, 95%CI 0.52 to 1.05, five trials, 456 participants, very low-quality evidence).There was a significant reduction in the number of participants receiving any platelet transfusion between those treated with TPO mimetics and placebo (RR 0.76, 95% CI 0.61 to 0.95, four trials, 206 participants, moderate-quality evidence).There was no evidence for a difference in the incidence of transfusion reactions between those treated with TPO mimetics and placebo (pOR 0.06, 95% CI 0.00 to 3.44, one trial, 98 participants, very low-quality evidence).There was no evidence for a difference in thromboembolic events between TPO mimetics and placebo (RR 1.41, 95%CI 0.39 to 5.01, five trials, 456 participants, very-low quality evidence).There was no evidence for a difference in drug reactions between TPO mimetics and placebo (RR 1.12, 95% CI 0.83 to 1.51, five trials, 455 participants, low-quality evidence).No trial reported the number of days of bleeding per participant, platelet transfusion episodes, mean red cell transfusions per participant, red cell transfusion episodes, transfusion-transmitted infections, formation of antiplatelet antibodies or platelet refractoriness.In order to demonstrate a reduction in bleeding events from 26 in 100 to 16 in 100 participants, a study would need to recruit 514 participants (80% power, 5% significance). AUTHORS' CONCLUSIONS: There is insufficient evidence at present for thrombopoietin (TPO) mimetics for the prevention of bleeding for people with thrombocytopenia due to chronic bone marrow failure. There is no randomised controlled trial evidence for artificial platelet substitutes, platelet-poor plasma, fibrinogen concentrate, rFVIIa, rFXIII or rIL6 or rIL11, antifibrinolytics or DDAVP in this setting.

Bhatnagar N, Nizery L, Tunstall O, Vyas P, Roberts I. 2016. Transient Abnormal Myelopoiesis and AML in Down Syndrome: an Update. Curr Hematol Malig Rep, 11 (5), pp. 333-341. | Show Abstract | Read more

Children with constitutional trisomy 21 (Down syndrome (DS)) have a unique predisposition to develop myeloid leukaemia of Down syndrome (ML-DS). This disorder is preceded by a transient neonatal preleukaemic syndrome, transient abnormal myelopoiesis (TAM). TAM and ML-DS are caused by co-operation between trisomy 21, which itself perturbs fetal haematopoiesis and acquired mutations in the key haematopoietic transcription factor gene GATA1. These mutations are found in almost one third of DS neonates and are frequently clinically and haematologcially 'silent'. While the majority of cases of TAM undergo spontaneous remission, ∼10 % will progress to ML-DS by acquiring transforming mutations in additional oncogenes. Recent advances in the unique biological, cytogenetic and molecular characteristics of TAM and ML-DS are reviewed here.

Quek L, Otto GW, Garnett C, Lhermitte L, Karamitros D, Stoilova B, Lau IJ, Doondeea J, Usukhbayar B, Kennedy A et al. 2016. Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage. J Exp Med, 213 (8), pp. 1513-1535. | Show Abstract | Read more

Our understanding of the perturbation of normal cellular differentiation hierarchies to create tumor-propagating stem cell populations is incomplete. In human acute myeloid leukemia (AML), current models suggest transformation creates leukemic stem cell (LSC) populations arrested at a progenitor-like stage expressing cell surface CD34. We show that in ∼25% of AML, with a distinct genetic mutation pattern where >98% of cells are CD34(-), there are multiple, nonhierarchically arranged CD34(+) and CD34(-) LSC populations. Within CD34(-) and CD34(+) LSC-containing populations, LSC frequencies are similar; there are shared clonal structures and near-identical transcriptional signatures. CD34(-) LSCs have disordered global transcription profiles, but these profiles are enriched for transcriptional signatures of normal CD34(-) mature granulocyte-macrophage precursors, downstream of progenitors. But unlike mature precursors, LSCs express multiple normal stem cell transcriptional regulators previously implicated in LSC function. This suggests a new refined model of the relationship between LSCs and normal hemopoiesis in which the nature of genetic/epigenetic changes determines the disordered transcriptional program, resulting in LSC differentiation arrest at stages that are most like either progenitor or precursor stages of hemopoiesis.

Zabkiewicz J, Gilmour M, Hills R, Vyas P, Bone E, Davidson A, Burnett A, Knapper S. 2016. The targeted histone deacetylase inhibitor tefinostat (CHR-2845) shows selective in vitro efficacy in monocytoid-lineage leukaemias. Oncotarget, 7 (13), pp. 16650-16662. | Show Abstract | Read more

Tefinostat (CHR-2845) is a novel monocyte/macrophage-targeted histone deacetylase (HDAC) inhibitor which is cleaved into its active acid by the intracellular esterase human carboxylesterase-1 (hCE-1). The in vitro efficacy of tefinostat was characterised in cell lines and in a cohort of 73 primary AML and CMML samples. Dose-dependent induction of apoptosis and significant growth inhibitory effects were seen in myelomonocytic (M4), monocytic/monoblastic (M5) and CMML samples in comparison to non-monocytoid AML sub-types (p = 0.007). Importantly, no growth inhibitory effects were seen in normal bone marrow CD34+ cells exposed to AML-toxic doses of tefinostat in clonogenic assays. Expression of hCE-1 was measured by intracellular flow cytometry and immunoblotting across the cohort, with highest levels seen in M5 AML patients. hCE-1 levels correlated with significantly increased tefinostat sensitivity (low EC50) as measured by growth inhibition assays (p = 0.001) and concomitant elevation of the mature monocytoid marker CD14+. Strong induction of intracellular histone protein acetylation was observed in tefinostat-responsive samples, as were high levels of the DNA damage sensor γ-H2A.X, highlighting potential biomarkers of patient responsiveness. Synergistic interaction between tefinostat and the current standard treatment cytarabine was demonstrated in dose response and clonogenic assays using simultaneous drug addition in primary samples (median Combination Index value = 0.51). These data provide a strong rationale for the further clinical evaluation of tefinostat in monocytoid-lineage haematological neoplasms including CMML and monocyte-lineage AMLs.

Desborough M, Estcourt LJ, Chaimani A, Doree C, Hopewell S, Trivella M, Hadjinicolaou AV, Vyas P, Stanworth SJ. 2016. Alternative agents versus prophylactic platelet transfusion for preventing bleeding in patients with thrombocytopenia due to chronic bone marrow failure: a network meta-analysis and systematic review. Cochrane Database Syst Rev, 2016 (1), | Show Abstract | Read more

This is the protocol for a review and there is no abstract. The objectives are as follows: To compare the relative efficacy of different treatments for thrombocytopenia (artificial platelet substitutes, platelet-poor plasma, fibrinogen, rFVIIa, rFXIII, thrombopoietin mimetics, antifibrinolytic drugs or platelet transfusions) in patients with chronic bone marrow failure and to derive a hierarchy of potential alternate treatments to platelet transfusions.

Ivey A, Hills RK, Simpson MA, Jovanovic JV, Gilkes A, Grech A, Patel Y, Bhudia N, Farah H, Mason J et al. 2016. Assessment of Minimal Residual Disease in Standard-Risk AML. N Engl J Med, 374 (5), pp. 422-433. | Show Abstract | Read more

BACKGROUND: Despite the molecular heterogeneity of standard-risk acute myeloid leukemia (AML), treatment decisions are based on a limited number of molecular genetic markers and morphology-based assessment of remission. Sensitive detection of a leukemia-specific marker (e.g., a mutation in the gene encoding nucleophosmin [NPM1]) could improve prognostication by identifying submicroscopic disease during remission. METHODS: We used a reverse-transcriptase quantitative polymerase-chain-reaction assay to detect minimal residual disease in 2569 samples obtained from 346 patients with NPM1-mutated AML who had undergone intensive treatment in the National Cancer Research Institute AML17 trial. We used a custom 51-gene panel to perform targeted sequencing of 223 samples obtained at the time of diagnosis and 49 samples obtained at the time of relapse. Mutations associated with preleukemic clones were tracked by means of digital polymerase chain reaction. RESULTS: Molecular profiling highlighted the complexity of NPM1-mutated AML, with segregation of patients into more than 150 subgroups, thus precluding reliable outcome prediction. The determination of minimal-residual-disease status was more informative. Persistence of NPM1-mutated transcripts in blood was present in 15% of the patients after the second chemotherapy cycle and was associated with a greater risk of relapse after 3 years of follow-up than was an absence of such transcripts (82% vs. 30%; hazard ratio, 4.80; 95% confidence interval [CI], 2.95 to 7.80; P<0.001) and a lower rate of survival (24% vs. 75%; hazard ratio for death, 4.38; 95% CI, 2.57 to 7.47; P<0.001). The presence of minimal residual disease was the only independent prognostic factor for death in multivariate analysis (hazard ratio, 4.84; 95% CI, 2.57 to 9.15; P<0.001). These results were validated in an independent cohort. On sequential monitoring of minimal residual disease, relapse was reliably predicted by a rising level of NPM1-mutated transcripts. Although mutations associated with preleukemic clones remained detectable during ongoing remission after chemotherapy, NPM1 mutations were detected in 69 of 70 patients at the time of relapse and provided a better marker of disease status. CONCLUSIONS: The presence of minimal residual disease, as determined by quantitation of NPM1-mutated transcripts, provided powerful prognostic information independent of other risk factors. (Funded by Bloodwise and the National Institute for Health Research; Current Controlled Trials number, ISRCTN55675535.).

Andreeff M, Kelly KR, Yee K, Assouline S, Strair R, Popplewell L, Bowen D, Martinelli G, Drummond MW, Vyas P et al. 2016. Results of the Phase I Trial of RG7112, a Small-Molecule MDM2 Antagonist in Leukemia. Clin Cancer Res, 22 (4), pp. 868-876. | Show Abstract | Read more

PURPOSE: RG7112 is a small-molecule MDM2 antagonist. MDM2 is a negative regulator of the tumor suppressor p53 and frequently overexpressed in leukemias. Thus, a phase I study of RG7112 in patients with hematologic malignancies was conducted. EXPERIMENTAL DESIGN: Primary study objectives included determination of the dose and safety profile of RG7112. Secondary objectives included evaluation of pharmacokinetics; pharmacodynamics, such as TP53-mutation status and MDM2 expression; and preliminary clinical activity. Patients were divided into two cohorts: Stratum A [relapsed/refractory acute myeloid leukemia (AML; except acute promyelocytic leukemia), acute lymphoblastic leukemia, and chronic myelogenous leukemia] and Stratum B (relapsed/refractory chronic lymphocytic leukemia/small cell lymphocytic leukemia; CLL/sCLL). Some Stratum A patients were treated at the MTD to assess clinical activity. RESULTS: RG7112 was administered to 116 patients (96 patients in Stratum A and 20 patients in Stratum B). All patients experienced at least 1 adverse event, and 3 dose-limiting toxicities were reported. Pharmacokinetic analysis indicated that twice-daily dosing enhanced daily exposure. Antileukemia activity was observed in the 30 patients with AML assessed at the MTD, including 5 patients who met International Working Group (IWG) criteria for response. Exploratory analysis revealed TP53 mutations in 14% of Stratum A patients and in 40% of Stratum B patients. Two patients with TP53 mutations exhibited clinical activity. p53 target genes were induced only in TP53 wild-type leukemic cells. Baseline expression levels of MDM2 correlated positively with clinical response. CONCLUSIONS: RG7112 demonstrated clinical activity against relapsed/refractory AML and CLL/sCLL. MDM2 inhibition resulted in p53 stabilization and transcriptional activation of p53-target genes. We provide proof-of-concept that MDM2 inhibition restores p53 function and generates clinical responses in hematologic malignancies.

Gu Y, Estcourt LJ, Doree C, Hopewell S, Vyas P. 2015. Comparison of a restrictive versus liberal red cell transfusion policy for patients with myelodysplasia, aplastic anaemia, and other congenital bone marrow failure disorders. Cochrane Database Syst Rev, (10), pp. CD011577. | Show Abstract | Read more

BACKGROUND: Bone marrow failure disorders include a heterogenous group of disorders, of which myelodysplastic syndrome (MDS), forms the largest subgroup. MDS is predominantly a disease of the elderly, with many elderly people managed conservatively with regular allogeneic red blood cell (RBC) transfusions to treat their anaemia. However, RBC transfusions are not without risk. Despite regular transfusions playing a central role in treating such patients, the optimal RBC transfusion strategy (restrictive versus liberal) is currently unclear. OBJECTIVES: To assess the efficacy and safety of a restrictive versus liberal red blood cell transfusion strategy for patients with myelodysplasia, acquired aplastic anaemia, and other inherited bone marrow failure disorders. SEARCH METHODS: We searched for randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2015, Issue 4), Ovid MEDLINE (from 1946), Ovid EMBASE (from 1974), EBSCO CINAHL (from 1937), the Transfusion Evidence Library (from 1980) and ongoing trial databases to 26th May 2015. SELECTION CRITERIA: RCTs including patients with long-term bone marrow failure disorders that require allogeneic blood transfusion, who are not being actively treated with a haematopoietic stem cell transplant, or intensive chemotherapy. DATA COLLECTION AND ANALYSIS: We used standard Cochrane review methodology. One author initially screened all references, and excluded any that were clearly irrelevant or duplicates. Two authors then independently screened all abstracts of articles, identified by the review search strategy, for relevancy. Two authors independently assessed the full text of all potentially relevant articles for eligibility, completed the data extraction and assessed the studies for risk of bias using The Cochrane Collaboration's 'Risk of bias' tool. MAIN RESULTS: We included one trial (13 participants) and identified three ongoing trials that assess RBC transfusion strategies in people with MDS.The quality of the evidence was very low across different outcomes according to GRADE methodology.The one included study randomised participants to a restrictive [haemoglobin (Hb) transfusion trigger < 72 g/L, 8 participants] or liberal [Hb trigger < 96 g/L, 5 participants] transfusion policy. There was insufficient evidence to determine a difference in all-cause mortality (1 RCT; 13 participants; RR 0.13, 95% CI 0.01 to 2.32; very low quality evidence). There was insufficient evidence to determine a difference in the number of red blood cell transfusions (1 RCT; 13 participants; 1.8 units per patient per month in the liberal group, compared to 0.8 in the restrictive arm, no standard deviation was reported; very low quality evidence). There were no anaemia-related complications reported (cardiac failure) and no reported effect on activity levels (no statistics provided). The study did not report: mortality due to bleeding/infection/transfusion reactions or iron overload, quality of life, frequency and length of hospital admissions, serious infections (requiring admission to hospital), or serious bleeding (e.g. WHO/CTCAE grade 3 (or equivalent) or above). AUTHORS' CONCLUSIONS: This review indicates that there is currently a lack of evidence for the recommendation of a particular transfusion strategy for bone marrow failure patients undergoing supportive treatment only. The one RCT included in this review was only published as an abstract and contained only 13 participants. Further randomised trials with robust methodology are required to develop the optimal transfusion strategy for such patients, particularly as the incidence of the main group of bone marrow failure disorders, MDS, rises with an ageing population.

Taylor JC, Martin HC, Lise S, Broxholme J, Cazier JB, Rimmer A, Kanapin A, Lunter G, Fiddy S, Allan C et al. 2015. Factors influencing success of clinical genome sequencing across a broad spectrum of disorders. Nat Genet, 47 (7), pp. 717-726. | Show Abstract | Read more

To assess factors influencing the success of whole-genome sequencing for mainstream clinical diagnosis, we sequenced 217 individuals from 156 independent cases or families across a broad spectrum of disorders in whom previous screening had identified no pathogenic variants. We quantified the number of candidate variants identified using different strategies for variant calling, filtering, annotation and prioritization. We found that jointly calling variants across samples, filtering against both local and external databases, deploying multiple annotation tools and using familial transmission above biological plausibility contributed to accuracy. Overall, we identified disease-causing variants in 21% of cases, with the proportion increasing to 34% (23/68) for mendelian disorders and 57% (8/14) in family trios. We also discovered 32 potentially clinically actionable variants in 18 genes unrelated to the referral disorder, although only 4 were ultimately considered reportable. Our results demonstrate the value of genome sequencing for routine clinical diagnosis but also highlight many outstanding challenges.

Tamblyn JA, Norton A, Spurgeon L, Donovan V, Bedford Russell A, Bonnici J, Perkins K, Vyas P, Roberts I, Kilby MD. 2016. Prenatal therapy in transient abnormal myelopoiesis: a systematic review. Arch Dis Child Fetal Neonatal Ed, 101 (1), pp. F67-F71. | Show Abstract | Read more

OBJECTIVE: To systematically review current evidence regarding prenatal diagnosis and management of transient abnormal myelopoiesis (TAM) in fetuses with trisomy 21. A novel case of GATA1-positive TAM, in which following serial in utero blood transfusion clinical improvement and postnatal remission were observed, is included. SEARCH STRATEGY AND DATA COLLECTION: A systematic search of electronic databases (inception to October 2014) and reference lists, hand-searching of journals and expert contact. All confirmed cases of prenatal TAM were included for analysis. Data on study characteristics, design and quality were obtained. RESULTS: Of 73 potentially relevant citations identified, 22 studies were included, describing 39 fetuses. All studies included comprised single case or small cohort studies; overall quality was 'very low'. Fetal/neonatal outcome was poor; 12 stillbirths (30.8%), 4 neonatal deaths (10.2%) and 7 infant deaths (17.9%). In two cases, the pregnancy was terminated (5.1%). TAM was primarily detected in the third trimester (79.4%), and in 14 a retrospective diagnosis was made postpartum. Ultrasound features indicative of TAM included hepatomegaly±splenomegaly (79.5%), hydrops fetalis (30.8%), pericardial effusion (23.1%) and aberrant liquor volume (15.4%). When performed, liver function tests were abnormal in 91.6% of cases. CONCLUSIONS: Prenatal TAM presents a challenging diagnosis, and prognosis is poor, with consistently high mortality. A low threshold to measure haematological and biochemical markers is advised when clinical features typical of TAM are detected in the context of trisomy 21. Larger prospective studies are warranted to accurately ascertain the role of GATA1 analysis and potential value of prenatal therapy.

Tamblyn J, Norton A, Spurgeon L, Donovan V, Bedford-Russell A, Bonnici J, Perkins K, Vyas P, Roberts I, Kilby M. 2015. A systematic review of the prenatal diagnosis and management of transient abnormal myelopoiesis BJOG-AN INTERNATIONAL JOURNAL OF OBSTETRICS AND GYNAECOLOGY, 122 pp. 55-56.

Gu Y, Estcourt LJ, Doree C, Trivella M, Hopewell S, Vyas P. 2015. Comparison of a restrictive versus liberal red cell transfusion policy for patients with myelodysplasia, aplastic anaemia, and other congenital bone marrow failure disorders. Cochrane Database Syst Rev, 3 | Show Abstract | Read more

This is the protocol for a review and there is no abstract. The objectives are as follows: To assess the efficacy and safety of a restrictive versus liberal red cell transfusion strategy for patients with long-term bone marrow failure. These include myelodysplasia, acquired aplastic anaemia, and other inherited bone marrow failure disorders.

Vyas P, Appelbaum FR, Craddock C. 2015. Reprint of: Allogeneic hematopoietic cell transplantation for acute myeloid leukemia. Biol Blood Marrow Transplant, 21 (2 Suppl), pp. S3-10. | Show Abstract | Read more

Allogeneic stem cell transplantation is an increasingly important treatment option in the management of adult acute myeloid leukemia (AML). The major causes of treatment failure remain disease relapse and treatment toxicity. In this review, Dr Vyas presents an overview of important recent data defining molecular factors associated with treatment failure in AML. He also identifies the emerging importance of leukemia stem cell biology in determining both response to therapy and relapse risk in AML. Dr Appelbaum discusses advances in the design and delivery of both myeloablative and reduced-intensity conditioning regimens, highlighting novel strategies with the potential to improve outcome. Dr Craddock discusses the development of both novel conditioning regimens and post-transplantation strategies aimed at reducing the risk of disease relapse.

Maloney KW, Taub JW, Ravindranath Y, Roberts I, Vyas P. 2015. Down Syndrome Preleukemia and Leukemia PEDIATRIC CLINICS OF NORTH AMERICA, 62 (1), pp. 121-+. | Read more

Maloney KW, Taub JW, Ravindranath Y, Roberts I, Vyas P. 2015. Down syndrome preleukemia and leukemia. Pediatr Clin North Am, 62 (1), pp. 121-137. | Show Abstract | Read more

Children with Down syndrome (DS) and acute leukemias acute have unique biological, cytogenetic, and intrinsic factors that affect their treatment and outcome. Myeloid leukemia of Down syndrome (ML-DS) is associated with high event-free survival (EFS) rates and frequently preceded by a preleukemia condition, the transient abnormal hematopoiesis (TAM) present at birth. For acute lymphoblastic leukemia (ALL), their EFS and overall survival are poorer than non-DS ALL, it is important to enroll them on therapeutic trials, including relapse trials; investigate new agents that could potentially improve their leukemia-free survival; and strive to maximize the supportive care these patients need.

Khan N, Freeman SD, Virgo P, Couzens S, Richardson P, Thomas I, Grech A, Vyas P, Grimwade D, Russell NH et al. 2015. An immunophenotypic pre-treatment predictor for poor response to induction chemotherapy in older acute myeloid leukaemia patients: Blood frequency of CD34&lt;sup&gt;+&lt;/sup&gt; CD38&lt;sup&gt;low&lt;/sup&gt; blasts British Journal of Haematology, 170 (1), pp. 80-84. | Show Abstract | Read more

© 2015 John Wiley & Sons Ltd. Many older patients with acute myeloid leukaemia (AML) that receive standard intensive chemotherapy fail to achieve complete remission (CR). Upfront identification of patients unlikely to benefit from standard induction chemotherapy would be important for exploration of novel therapies. This study evaluated if a flow cytometric assay measuring pre-treatment CD34 < sup > + < /sup > CD38 < sup > low < /sup > blast frequency could predict therapeutic-resistance in 736 AML patients entered into the UK National Cancer Research Institute AML16 trial. High peripheral blood CD34 < sup > + < /sup > CD38 < sup > low < /sup > blast frequency ( > 7% of leucocytes), present in 18% of assessable patients, conferred significantly reduced CR rates (38% vs. 76%, P < 0·0001) and poor survival, and was independently prognostic for all endpoints of treatment resistance by multivariate analysis.

Khan N, Freeman SD, Virgo P, Couzens S, Richardson P, Thomas I, Grech A, Vyas P, Grimwade D, Russell NH et al. 2015. An immunophenotypic pre-treatment predictor for poor response to induction chemotherapy in older acute myeloid leukaemia patients: blood frequency of CD34+ CD38 low blasts. Br J Haematol, 170 (1), pp. 80-84. | Show Abstract | Read more

Many older patients with acute myeloid leukaemia (AML) that receive standard intensive chemotherapy fail to achieve complete remission (CR). Upfront identification of patients unlikely to benefit from standard induction chemotherapy would be important for exploration of novel therapies. This study evaluated if a flow cytometric assay measuring pre-treatment CD34(+) CD38(low) blast frequency could predict therapeutic-resistance in 736 AML patients entered into the UK National Cancer Research Institute AML16 trial. High peripheral blood CD34(+) CD38(low) blast frequency (>7% of leucocytes), present in 18% of assessable patients, conferred significantly reduced CR rates (38% vs. 76%, P < 0.0001) and poor survival, and was independently prognostic for all endpoints of treatment resistance by multivariate analysis.

Gerstung M, Pellagatti A, Malcovati L, Giagounidis A, Porta MG, Jädersten M, Dolatshad H, Verma A, Cross NC, Vyas P et al. 2015. Combining gene mutation with gene expression data improves outcome prediction in myelodysplastic syndromes. Nat Commun, 6 pp. 5901. | Show Abstract | Read more

Cancer is a genetic disease, but two patients rarely have identical genotypes. Similarly, patients differ in their clinicopathological parameters, but how genotypic and phenotypic heterogeneity are interconnected is not well understood. Here we build statistical models to disentangle the effect of 12 recurrently mutated genes and 4 cytogenetic alterations on gene expression, diagnostic clinical variables and outcome in 124 patients with myelodysplastic syndromes. Overall, one or more genetic lesions correlate with expression levels of ~20% of all genes, explaining 20-65% of observed expression variability. Differential expression patterns vary between mutations and reflect the underlying biology, such as aberrant polycomb repression for ASXL1 and EZH2 mutations or perturbed gene dosage for copy-number changes. In predicting survival, genomic, transcriptomic and diagnostic clinical variables all have utility, with the largest contribution from the transcriptome. Similar observations are made on the TCGA acute myeloid leukaemia cohort, confirming the general trends reported here.

Vyas P, Appelbaum FR, Craddock C. 2015. Allogeneic hematopoietic cell transplantation for acute myeloid leukemia. Biol Blood Marrow Transplant, 21 (1), pp. 8-15. | Show Abstract | Read more

Allogeneic stem cell transplantation is an increasingly important treatment option in the management of adult acute myeloid leukemia (AML). The major causes of treatment failure remain disease relapse and treatment toxicity. In this review, Dr Vyas presents an overview of important recent data defining molecular factors associated with treatment failure in AML. He also identifies the emerging importance of leukemia stem cell biology in determining both response to therapy and relapse risk in AML. Dr Appelbaum discusses advances in the design and delivery of both myeloablative and reduced-intensity conditioning regimens, highlighting novel strategies with the potential to improve outcome. Dr Craddock discusses the development of both novel conditioning regimens and post-transplantation strategies aimed at reducing the risk of disease relapse.

Craddock C, Jilani N, Siddique S, Yap C, Khan J, Nagra S, Ward J, Ferguson P, Hazlewood P, Buka R et al. 2016. Tolerability and Clinical Activity of Post-Transplantation Azacitidine in Patients Allografted for Acute Myeloid Leukemia Treated on the RICAZA Trial. Biol Blood Marrow Transplant, 22 (2), pp. 385-390. | Show Abstract | Read more

Disease relapse is the major causes of treatment failure after allogeneic stem cell transplantation (SCT) in patients with acute myeloid leukemia (AML). As well as demonstrating significant clinical activity in AML, azacitidine (AZA) upregulates putative tumor antigens, inducing a CD8(+) T cell response with the potential to augment a graft-versus-leukemia effect. We, therefore, studied the feasibility and clinical sequelae of the administration of AZA during the first year after transplantation in 51 patients with AML undergoing allogeneic SCT. Fourteen patients did not commence AZA either because of transplantation complications or withdrawal of consent. Thirty-seven patients commenced AZA at a median of 54 days (range, 40 to 194 days) after transplantation, which was well tolerated in the majority of patients. Thirty-one patients completed 3 or more cycles of AZA. Sixteen patients relapsed at a median time of 8 months after transplantation. No patient developed extensive chronic graft-versus-host disease. The induction of a post-transplantation CD8(+) T cell response to 1 or more tumor-specific peptides was studied in 28 patients. Induction of a CD8(+) T cell response was associated with a reduced risk of disease relapse (hazard ratio [HR], .30; 95% confidence interval [CI], .10 to .85; P = .02) and improved relapse-free survival (HR, .29; 95% CI, .10 to .83; P = .02) taking into account death as a competing risk. In conclusion, AZA is well tolerated after transplantation and appears to have the capacity to reduce the relapse risk in patients who demonstrate a CD8(+) T cell response to tumor antigens. These observations require confirmation in a prospective clinical trial.

Kinstrie R, Karamitros D, Goardon N, Morrison H, Clark RE, Vyas P, Copland M. 2014. Leukemia Stem Cell Potential of Different Progenitor Subpopulations in Myeloid Blast Phase CML BLOOD, 124 (21),

Quek L, Otto G, Garnett C, Lhermitte L, Lau I-J, Karamitros D, Doondeea J, Usukhbayar B, Goardon N, Ivey A et al. 2014. Functional and Genetic Heterogeneity of Distinct Leukemic Stem Cell Populations in CD34-Human Acute Myeloid Leukemia BLOOD, 124 (21),

Bhatnagar N, Perkins K, Filippi S, Richmond H, Bonnici J, Alford K, Hall G, Juban G, McGowan S, Roy A et al. 2014. Clinical and Hematologic Impact of Fetal and Perinatal Variables on Mutant GATA1 Clone Size in Neonates with Down Syndrome BLOOD, 124 (21),

Vyas P. 2014. Targeting HIF function: the debate continues. Blood, 124 (24), pp. 3510-3511. | Show Abstract | Read more

© 2014 by The American Society of Hematology. In this issue of Blood, Velasco-Hernandez et al 1 come to an important and at first sight, unexpected, conclusion that hypoxia inducible factor 1α (HIF-1α) may be a tumor suppressor gene.

Bradbury C, Houlton AE, Akiki S, Gregg R, Rindl M, Khan J, Ward J, Khan N, Griffiths M, Nagra S et al. 2015. Prognostic value of monitoring a candidate immunophenotypic leukaemic stem/progenitor cell population in patients allografted for acute myeloid leukaemia. Leukemia, 29 (4), pp. 988-991. | Read more

Ju YS, Alexandrov LB, Gerstung M, Martincorena I, Nik-Zainal S, Ramakrishna M, Davies HR, Papaemmanuil E, Gundem G, Shlien A et al. 2014. Origins and functional consequences of somatic mitochondrial DNA mutations in human cancer. Elife, 3 | Show Abstract | Read more

Recent sequencing studies have extensively explored the somatic alterations present in the nuclear genomes of cancers. Although mitochondria control energy metabolism and apoptosis, the origins and impact of cancer-associated mutations in mtDNA are unclear. In this study, we analyzed somatic alterations in mtDNA from 1675 tumors. We identified 1907 somatic substitutions, which exhibited dramatic replicative strand bias, predominantly C > T and A > G on the mitochondrial heavy strand. This strand-asymmetric signature differs from those found in nuclear cancer genomes but matches the inferred germline process shaping primate mtDNA sequence content. A number of mtDNA mutations showed considerable heterogeneity across tumor types. Missense mutations were selectively neutral and often gradually drifted towards homoplasmy over time. In contrast, mutations resulting in protein truncation undergo negative selection and were almost exclusively heteroplasmic. Our findings indicate that the endogenous mutational mechanism has far greater impact than any other external mutagens in mitochondria and is fundamentally linked to mtDNA replication.

Santini V, Prebet T, Fenaux P, Gattermann N, Nilsson L, Pfeilstöcker M, Vyas P, List AF. 2014. Minimizing risk of hypomethylating agent failure in patients with higher-risk MDS and practical management recommendations. Leuk Res, 38 (12), pp. 1381-1391. | Show Abstract | Read more

In Europe, azacitidine is the only hypomethylating agent approved for the treatment of patients with int-2-/high-risk myelodysplastic syndromes, offering significantly improved survival compared with conventional care. However, not all patients treated with azacitidine respond to treatment, and the vast majority of responders subsequently relapse. Currently, no standard care regimens have been established for patients after failure of azacitidine. Here, we discuss treatment options after loss of response or progression on azacitidine. In addition, we briefly consider optimization of first-line treatment along with potential biomarkers for identifying and monitoring response during treatment with azacitidine.

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Woll PS, Kjällquist U, Chowdhury O, Doolittle H, Wedge DC, Thongjuea S, Erlandsson R, Ngara M, Anderson K, Deng Q et al. 2014. Myelodysplastic syndromes are propagated by rare and distinct human cancer stem cells in vivo Cancer Cell, 25 (6), pp. 794-808. | Show Abstract | Read more

Evidence for distinct human cancer stem cells (CSCs) remains contentious and the degree to which differentcancer cells contribute to propagating malignancies in patients remains unexplored. In low- to intermediate-risk myelodysplastic syndromes (MDS), we establish the existence of rare multipotent MDS stem cells (MDS-SCs), and their hierarchical relationship to lineage-restricted MDS progenitors. All identified somatically acquired genetic lesions were backtracked to distinct MDS-SCs, establishing their distinct MDS-propagating function invivo. In isolated del(5q)-MDS, acquisition of del(5q) preceded diverse recurrent driver mutations. Sequential analysis in del(5q)-MDS revealed genetic evolution in MDS-SCs and MDS-progenitors prior to leukemic transformation. These findings provide definitive evidence for rare human MDS-SCs invivo, with extensive implications for the targeting of the cells required and sufficient for MDS-propagation. © 2014 Elsevier Inc.

Maroz A, Stachorski L, Emmrich S, Reinhardt K, Xu J, Shao Z, Käbler S, Dertmann T, Hitzler J, Roberts I et al. 2014. GATA1s induces hyperproliferation of eosinophil precursors in Down syndrome transient leukemia Leukemia, 28 (6), pp. 1259-1270. | Show Abstract | Read more

Transient leukemia (TL) is evident in 5-10% of all neonates with Down syndrome (DS) and associated with N-terminal truncating GATA1 mutations (GATA1s). Here we report that TL-cell clones generate abundant eosinophils in a substantial fraction of patients. Sorted eosinophils from patients with TL and eosinophilia carried the same GATA1s mutations as sorted TL blasts, consistent with their clonal origin. TL blasts exhibited a genetic program characteristic of eosinophils and differentiated along the eosinophil lineage in vitro. Similarly, ectopic expression of Gata1s, but not Gata1, in wild-type CD34 + -hematopoietic stem and progenitor cells induced hyperproliferation of eosinophil promyelocytes in vitro. Although GATA1s retained the function of GATA1 to induce eosinophil genes by occupying their promoter regions, GATA1s was impaired in its ability to repress oncogenic MYC and the pro-proliferative E2F transcription network. Chromatin Immunoprecipitation Sequencing (ChIP-seq) indicated reduced GATA1s occupancy at the MYC promoter. Knockdown of MYC, or the obligate E2F-cooperation partner DP1, rescued the GATA1s-induced hyperproliferative phenotype. In agreement, terminal eosinophil maturation was blocked in Gata1 Δe2 knockin mice, exclusively expressing Gata1s, leading to accumulation of eosinophil precursors in blood and bone marrow. These data suggest a direct relationship between the N-terminal truncating mutations of GATA1 and clonal eosinophilia in DS patients. © 2014 Macmillan Publishers Limited.

Woll PS, Kjällquist U, Chowdhury O, Doolittle H, Wedge DC, Thongjuea S, Erlandsson R, Ngara M, Anderson K, Deng Q et al. 2014. Myelodysplastic syndromes are propagated by rare and distinct human cancer stem cells in vivo. Cancer Cell, 25 (6), pp. 794-808. | Show Abstract | Read more

Evidence for distinct human cancer stem cells (CSCs) remains contentious and the degree to which different cancer cells contribute to propagating malignancies in patients remains unexplored. In low- to intermediate-risk myelodysplastic syndromes (MDS), we establish the existence of rare multipotent MDS stem cells (MDS-SCs), and their hierarchical relationship to lineage-restricted MDS progenitors. All identified somatically acquired genetic lesions were backtracked to distinct MDS-SCs, establishing their distinct MDS-propagating function in vivo. In isolated del(5q)-MDS, acquisition of del(5q) preceded diverse recurrent driver mutations. Sequential analysis in del(5q)-MDS revealed genetic evolution in MDS-SCs and MDS-progenitors prior to leukemic transformation. These findings provide definitive evidence for rare human MDS-SCs in vivo, with extensive implications for the targeting of the cells required and sufficient for MDS-propagation.

Nagra S, Goodyear OC, Khan J, Jilani NY, Ferguson P, Russell N, Dennis M, Vyas P, Siddique S, Craddock C. 2014. Induction of a CD8+T Cell Response to Tumor Antigens Is Associated with Improved Survival in Patients Transplanted for Acute Myeloid Leukemia BIOLOGY OF BLOOD AND MARROW TRANSPLANTATION, 20 (2), pp. S156-S156.

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Killick SB, Carter C, Culligan D, Dalley C, Das-Gupta E, Drummond M, Enright H, Jones GL, Kell J, Mills J et al. 2014. Guidelines for the diagnosis and management of adult myelodysplastic syndromes British Journal of Haematology, 164 (4), pp. 503-525. | Read more

Vyas P. 2014. Myelodysplastic and Myeloproliferative diseases in children: Current concepts Pediatric and Adolescent Medicine, 17 pp. 81-97. | Show Abstract | Read more

Copyright © 2014 S. Karger AG, Basel. Paediatric myelodysplasia syndromes (MDS) and myeloproliferative disorders (MPD) are rare and genetically and clinically heterogeneous. This review focuses on recent studies outlining the partially characterised pathogenetic germline and/or acquired genetic changes in these disorders, how these changes perturb haemopoiesis and the implications for clinical practice. Identification of causative genetic changes in paediatric MDS/MPD will gather pace as genomes of these disorders are sequenced. These genetic findings are likely to provide a clearer definition of clinically and biologically distinct entities and improve classification of these disorders. Analysis of genetic changes in sequential samples as a disease progresses will allow an understanding of how acquisition of genetic changes during clinical follow-up may mark different clinical courses. Finally, studying the function of the altered proteins resulting from genetic change will hopefully lead to a deeper understanding of the cellular and molecular basis of these disorders with the potential to improve clinical management. Within paediatric MDS/MPD, entities such as juvenile myelomonocytic leukemia and myeloid disorders in Down syndrome are better defined, whereas others, such as sporadic myelodysplasia and essential thrombocytosis and primary polycythaemia have been more difficult to study because of their rarity and clinical and genetic heterogeneity. This review will not cover Philadelphia-positive chronic myeloid leukaemia.

Maroz A, Stachorski L, Emmrich S, Reinhardt K, Xu J, Shao Z, Käbler S, Dertmann T, Hitzler J, Roberts I et al. 2014. GATA1s induces hyperproliferation of eosinophil precursors in Down syndrome transient leukemia. Leukemia, 28 (6), pp. 1259-1270. | Show Abstract | Read more

Transient leukemia (TL) is evident in 5-10% of all neonates with Down syndrome (DS) and associated with N-terminal truncating GATA1 mutations (GATA1s). Here we report that TL-cell clones generate abundant eosinophils in a substantial fraction of patients. Sorted eosinophils from patients with TL and eosinophilia carried the same GATA1s mutations as sorted TL blasts, consistent with their clonal origin. TL blasts exhibited a genetic program characteristic of eosinophils and differentiated along the eosinophil lineage in vitro. Similarly, ectopic expression of Gata1s, but not Gata1, in wild-type CD34(+)-hematopoietic stem and progenitor cells induced hyperproliferation of eosinophil promyelocytes in vitro. Although GATA1s retained the function of GATA1 to induce eosinophil genes by occupying their promoter regions, GATA1s was impaired in its ability to repress oncogenic MYC and the pro-proliferative E2F transcription network. Chromatin Immunoprecipitation Sequencing (ChIP-seq) indicated reduced GATA1s occupancy at the MYC promoter. Knockdown of MYC, or the obligate E2F-cooperation partner DP1, rescued the GATA1s-induced hyperproliferative phenotype. In agreement, terminal eosinophil maturation was blocked in Gata1(Δe2) knockin mice, exclusively expressing Gata1s, leading to accumulation of eosinophil precursors in blood and bone marrow. These data suggest a direct relationship between the N-terminal truncating mutations of GATA1 and clonal eosinophilia in DS patients.

Roberts I, O'Connor D, Roy A, Cowan G, Vyas P. 2013. The impact of trisomy 21 on foetal haematopoiesis. Blood Cells Mol Dis, 51 (4), pp. 277-281. | Show Abstract | Read more

The high frequency of a unique neonatal preleukaemic syndrome, transient abnormal myelopoiesis (TAM), and subsequent acute myeloid leukaemia in early childhood in patients with trisomy 21 (Down syndrome) points to a specific role for trisomy 21 in transforming foetal haematopoietic cells. N-terminal truncating mutations in the key haematopoietic transcription factor GATA1 are acquired during foetal life in virtually every case. These mutations are not leukaemogenic in the absence of trisomy 21. In mouse models, deregulated expression of chromosome 21-encoded genes is implicated in leukaemic transformation, but does not recapitulate the effects of trisomy 21 in a human context. Recent work using primary human foetal liver and bone marrow cells, human embryonic stem cells and iPS cells shows that prior to acquisition of GATA1 mutations, trisomy 21 itself alters human foetal haematopoietic stem cell and progenitor cell biology causing multiple abnormalities in myelopoiesis and B-lymphopoiesis. The molecular basis by which trisomy 21 exerts these effects is likely to be extremely complex, to be tissue-specific and lineage-specific and to be dependent on ontogeny-related characteristics of the foetal microenvironment.

Papaemmanuil E, Gerstung M, Malcovati L, Tauro S, Gundem G, Van Loo P, Yoon CJ, Ellis P, Wedge DC, Pellagatti A et al. 2013. Clinical and biological implications of driver mutations in myelodysplastic syndromes. Blood, 122 (22), pp. 3616-3627. | Show Abstract | Read more

Myelodysplastic syndromes (MDS) are a heterogeneous group of chronic hematological malignancies characterized by dysplasia, ineffective hematopoiesis and a variable risk of progression to acute myeloid leukemia. Sequencing of MDS genomes has identified mutations in genes implicated in RNA splicing, DNA modification, chromatin regulation, and cell signaling. We sequenced 111 genes across 738 patients with MDS or closely related neoplasms (including chronic myelomonocytic leukemia and MDS-myeloproliferative neoplasms) to explore the role of acquired mutations in MDS biology and clinical phenotype. Seventy-eight percent of patients had 1 or more oncogenic mutations. We identify complex patterns of pairwise association between genes, indicative of epistatic interactions involving components of the spliceosome machinery and epigenetic modifiers. Coupled with inferences on subclonal mutations, these data suggest a hypothesis of genetic "predestination," in which early driver mutations, typically affecting genes involved in RNA splicing, dictate future trajectories of disease evolution with distinct clinical phenotypes. Driver mutations had equivalent prognostic significance, whether clonal or subclonal, and leukemia-free survival deteriorated steadily as numbers of driver mutations increased. Thus, analysis of oncogenic mutations in large, well-characterized cohorts of patients illustrates the interconnections between the cancer genome and disease biology, with considerable potential for clinical application.

Roberts I, Alford K, Hall G, Juban G, Richmond H, Norton A, Vallance G, Perkins K, Marchi E, McGowan S et al. 2013. GATA1-mutant clones are frequent and often unsuspected in babies with Down syndrome: identification of a population at risk of leukemia. Blood, 122 (24), pp. 3908-3917. | Show Abstract | Read more

Transient abnormal myelopoiesis (TAM), a preleukemic disorder unique to neonates with Down syndrome (DS), may transform to childhood acute myeloid leukemia (ML-DS). Acquired GATA1 mutations are present in both TAM and ML-DS. Current definitions of TAM specify neither the percentage of blasts nor the role of GATA1 mutation analysis. To define TAM, we prospectively analyzed clinical findings, blood counts and smears, and GATA1 mutation status in 200 DS neonates. All DS neonates had multiple blood count and smear abnormalities. Surprisingly, 195 of 200 (97.5%) had circulating blasts. GATA1 mutations were detected by Sanger sequencing/denaturing high performance liquid chromatography (Ss/DHPLC) in 17 of 200 (8.5%), all with blasts >10%. Furthermore low-abundance GATA1 mutant clones were detected by targeted next-generation resequencing (NGS) in 18 of 88 (20.4%; sensitivity ∼0.3%) DS neonates without Ss/DHPLC-detectable GATA1 mutations. No clinical or hematologic features distinguished these 18 neonates. We suggest the term "silent TAM" for neonates with DS with GATA1 mutations detectable only by NGS. To identify all babies at risk of ML-DS, we suggest GATA1 mutation and blood count and smear analyses should be performed in DS neonates. Ss/DPHLC can be used for initial screening, but where GATA1 mutations are undetectable by Ss/DHPLC, NGS-based methods can identify neonates with small GATA1 mutant clones.

ElOmari K, Hoosdally SJ, Tuladhar K, Karia D, Hall-Ponselé E, Platonova O, Vyas P, Patient R, Porcher C, Mancini EJ. 2013. Structural Basis for LMO2-Driven Recruitment of the SCL: E47bHLH Heterodimer to Hematopoietic-Specific Transcriptional Targets Cell Reports, 4 (1), pp. 135-147. | Show Abstract | Read more

Cell fate is governed by combinatorial actions of transcriptional regulators assembling into multiprotein complexes. However, the molecular details of how these complexes form are poorly understood. One such complex, which contains the basic-helix-loop-helix heterodimer SCL:E47 and bridging proteins LMO2:LDB1, critically regulates hematopoiesis and induces Tcell leukemia. Here, we report the crystal structure of (SCL:E47) bHLH :LMO2:LDB1 LID bound to DNA, providing a molecular account of the network of interactions assembling this complex. This reveals an unexpected role for LMO2. Upon binding to SCL, LMO2 induces new hydrogen bonds in SCL:E47, thereby strengthening heterodimer formation. This imposes a rotation movement onto E47 that weakens the heterodimer:DNA interaction, shifting the main DNA-binding activity onto additional protein partners. Along with biochemical analyses, this illustrates, at an atomic level, how hematopoietic-specific SCL sequesters ubiquitous E47 and associated cofactors and supports SCL'sreported DNA-binding-independent functions. Importantly, this work will drive the design of small molecules inhibiting leukemogenic processes. © 2013 The Authors.

El Omari K, Hoosdally SJ, Tuladhar K, Karia D, Hall-Ponselé E, Platonova O, Vyas P, Patient R, Porcher C, Mancini EJ. 2013. Structural basis for LMO2-driven recruitment of the SCL:E47bHLH heterodimer to hematopoietic-specific transcriptional targets. Cell Rep, 4 (1), pp. 135-147. | Show Abstract | Read more

Cell fate is governed by combinatorial actions of transcriptional regulators assembling into multiprotein complexes. However, the molecular details of how these complexes form are poorly understood. One such complex, which contains the basic-helix-loop-helix heterodimer SCL:E47 and bridging proteins LMO2:LDB1, critically regulates hematopoiesis and induces T cell leukemia. Here, we report the crystal structure of (SCL:E47)bHLH:LMO2:LDB1LID bound to DNA, providing a molecular account of the network of interactions assembling this complex. This reveals an unexpected role for LMO2. Upon binding to SCL, LMO2 induces new hydrogen bonds in SCL:E47, thereby strengthening heterodimer formation. This imposes a rotation movement onto E47 that weakens the heterodimer:DNA interaction, shifting the main DNA-binding activity onto additional protein partners. Along with biochemical analyses, this illustrates, at an atomic level, how hematopoietic-specific SCL sequesters ubiquitous E47 and associated cofactors and supports SCL's reported DNA-binding-independent functions. Importantly, this work will drive the design of small molecules inhibiting leukemogenic processes.

Mussai F, De Santo C, Abu-Dayyeh I, Booth S, Quek L, McEwen-Smith RM, Qureshi A, Dazzi F, Vyas P, Cerundolo V. 2013. Acute myeloid leukemia creates an arginase-dependent immunosuppressive microenvironment. Blood, 122 (5), pp. 749-758. | Show Abstract | Read more

Acute myeloid leukemia (AML) is the most common acute leukemia in adults and the second most common frequent leukemia of childhood. Patients may present with lymphopenia or pancytopenia at diagnosis. We investigated the mechanisms by which AML causes pancytopenia and suppresses patients' immune response. This study identified for the first time that AML blasts alter the immune microenvironment through enhanced arginine metabolism. Arginase II is expressed and released from AML blasts and is present at high concentrations in the plasma of patients with AML, resulting in suppression of T-cell proliferation. We extended these results by demonstrating an arginase-dependent ability of AML blasts to polarize surrounding monocytes into a suppressive M2-like phenotype in vitro and in engrafted nonobese diabetic-severe combined immunodeficiency mice. In addition, AML blasts can suppress the proliferation and differentiation of murine granulocyte-monocyte progenitors and human CD34(+) progenitors. Finally, the study showed that the immunosuppressive activity of AML blasts can be modulated through small-molecule inhibitors of arginase and inducible nitric oxide synthase, suggesting a novel therapeutic target in AML. The results strongly support the hypothesis that AML creates an immunosuppressive microenvironment that contributes to the pancytopenia observed at diagnosis.

Papaemmanuil E, Gerstung M, Malcovati L, Tauro S, Gundem G, Van-Loo P, Pellagati A, Groves M, Cross N, Gambacorti-Passerini C et al. 2013. Clinical and biological implications of gene mutations in MDS LEUKEMIA RESEARCH, 37 pp. S9-S9.

Mead AJ, Kharazi S, Atkinson D, Macaulay I, Pecquet C, Loughran S, Lutteropp M, Woll P, Chowdhury O, Luc S et al. 2013. FLT3-ITDs instruct a myeloid differentiation and transformation bias in lymphomyeloid multipotent progenitors. Cell Rep, 3 (6), pp. 1766-1776. | Show Abstract | Read more

Whether signals mediated via growth factor receptors (GFRs) might influence lineage fate in multipotent progenitors (MPPs) is unclear. We explored this issue in a mouse knockin model of gain-of-function Flt3-ITD mutation because FLT3-ITDs are paradoxically restricted to acute myeloid leukemia even though Flt3 primarily promotes lymphoid development during normal hematopoiesis. When expressed in MPPs, Flt3-ITD collaborated with Runx1 mutation to induce high-penetrance aggressive leukemias that were exclusively of the myeloid phenotype. Flt3-ITDs preferentially expanded MPPs with reduced lymphoid and increased myeloid transcriptional priming while compromising early B and T lymphopoiesis. Flt3-ITD-induced myeloid lineage bias involved upregulation of the transcription factor Pu.1, which is a direct target gene of Stat3, an aberrantly activated target of Flt3-ITDs, further establishing how lineage bias can be inflicted on MPPs through aberrant GFR signaling. Collectively, these findings provide new insights into how oncogenic mutations might subvert the normal process of lineage commitment and dictate the phenotype of resulting malignancies.

Mead AJ, Chowdhury O, Pecquet C, Dusa A, Woll P, Atkinson D, Burns A, Score J, Rugless M, Clifford R et al. 2013. Impact of isolated germline JAK2V617I mutation on human hematopoiesis. Blood, 121 (20), pp. 4156-4165. | Show Abstract | Read more

The association between somatic JAK2 mutation and myeloproliferative neoplasms (MPNs) is now well established. However, because JAK2 mutations are associated with heterogeneous clinical phenotypes and often occur as secondary genetic events, some aspects of JAK2 mutation biology remain to be understood. We recently described a germline JAK2V617I mutation in a family with hereditary thrombocytosis and herein characterize the hematopoietic and signaling impact of JAK2V617I. Through targeted sequencing of MPN-associated mutations, exome sequencing, and clonality analysis, we demonstrate that JAK2V617I is likely to be the sole driver mutation in JAK2V617I-positive individuals with thrombocytosis. Phenotypic hematopoietic stem cells (HSCs) were increased in the blood and bone marrow of JAK2V617I-positive individuals and were sustained at higher levels than controls after xenotransplantation. In signaling and transcriptional assays, JAK2V617I demonstrated more activity than wild-type JAK2 but substantially less than JAK2V617F. After cytokine stimulation, JAK2V617I resulted in markedly increased downstream signaling compared with wild-type JAK2 and comparable with JAK2V617F. These findings demonstrate that JAK2V617I induces sufficient cytokine hyperresponsiveness in the absence of other molecular events to induce a homogeneous MPN-like phenotype. We also provide evidence that the JAK2V617I mutation may expand the HSC pool, providing insights into both JAK2 mutation biology and MPN disease pathogenesis.

Leung A, Ciau-Uitz A, Pinheiro P, Monteiro R, Zuo J, Vyas P, Patient R, Porcher C. 2013. Uncoupling VEGFA functions in arteriogenesis and hematopoietic stem cell specification. Dev Cell, 24 (2), pp. 144-158. | Show Abstract | Read more

VEGFA signaling is critical for endothelial and hematopoietic stem cell (HSC) specification. However, blood defects resulting from perturbation of the VEGFA pathway are always accompanied by impaired vascular/arterial development. Because HSCs derive from arterial cells, it is unclear whether VEGFA directly contributes to HSC specification. This is an important question for our understanding of how HSCs are formed and for developing their production in vitro. Through knockdown of the regulator ETO2 in embryogenesis, we report a specific decrease in expression of medium/long Vegfa isoforms in somites. This leads to absence of Notch1 expression and failure of HSC specification in the dorsal aorta (DA), independently of vessel formation and arterial specification. Vegfa hypomorphs and isoform-specific (medium/long) morphants not only recapitulate this phenotype but also demonstrate that VEGFA short isoform is sufficient for DA development. Therefore, sequential, isoform-specific VEGFA signaling successively induces the endothelial, arterial, and HSC programs in the DA.

Roy A, Cowan G, Vyas P, Roberts I. 2013. The impact of trisomy 21 on early human hematopoiesis. Cell Cycle, 12 (4), pp. 533-534. | Read more

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Leung A, Ciau-Uitz A, Pinheiro P, Monteiro R, Zuo J, Vyas P, Patient R, Porcher C. 2013. Uncoupling VEGFA Functions in Arteriogenesis and Hematopoietic Stem Cell Specification Developmental Cell, 24 (2), pp. 144-158. | Show Abstract | Read more

VEGFA signaling is critical for endothelial and hematopoietic stem cell (HSC) specification. However, blood defects resulting from perturbation of the VEGFA pathway are always accompanied by impaired vascular/arterial development. Because HSCs derive from arterial cells, it is unclear whether VEGFA directly contributes to HSC specification. This is an important question for our understanding of how HSCs are formed and for developing their production in vitro. Through knockdown of the regulator ETO2 in embryogenesis, we report a specific decrease in expression of medium/long Vegfa isoforms in somites. This leads to absence of Notch1 expression and failure of HSC specification in the dorsal aorta (DA), independently of vessel formation and arterial specification. Vegfa hypomorphs and isoform-specific (medium/long) morphants not only recapitulate this phenotype but also demonstrate that VEGFA short isoform is sufficient for DA development. Therefore, sequential, isoform-specific VEGFA signaling successively induces the endothelial, arterial, and HSC programs in the DA.

Killick SB, Carter C, Culligan D, Dalley C, Das-Gupta E, Drummond M, Enright H, Jones GL, Kell J, Mills J et al. 2014. Guidelines for the diagnosis and management of adult myelodysplastic syndromes. Br J Haematol, 164 (4), pp. 503-525. | Read more

Dennis M, Culligan D, Karamitros D, Vyas P, Johnson P, Russell NH, Cavenagh J, Szubert A, Hartley S, Brown J, Bowen D. 2013. Lenalidomide monotherapy and in combination with cytarabine, daunorubicin and etoposide for high-risk myelodysplasia and acute myeloid leukaemia with chromosome 5 abnormalities. Leuk Res Rep, 2 (2), pp. 70-74. | Show Abstract | Read more

Patients with high risk myelodysplasia (HR-MDS) and acute myeloid leukaemia (AML) with chromosomal changes involving deletion of the long arm of chromosome 5 (del5q), especially with complex karyotype, rarely have a durable response to combination chemotherapy. In the subgroup with monosomal karyotype there are no long term survivors (Fang et al., 2011) [1]. Recent experience indicates that the incidence of del5q in AML is ~20-30%, with only 20-25% of patients achieving complete remission (CR) (Farag et al., 2006) [2]. Additionally, therapy has significant toxicity, with induction death rates ~20% even in younger patients (Juliusson et al., 2009) [3]. This lack of efficacy provides the clinical rationale for combination/sequential therapy with Lenalidomide and combination chemotherapy. Dose dependent haematological toxicity is the major safety concern with such a combination protocol. Therefore we conducted a phase 2 study, AML Len5 (ISRCTN58492795), to assess safety, tolerability and efficacy of lenalidomide monotherapy, followed by lenalidomide with intensive chemotherapy in patients with primary/relapsed/refractory high risk MDS or AML with abnormalities of chromosome 5.

Eyre T, Schwab CJ, Kinstrie R, McGuire AK, Strefford J, Peniket A, Mead A, Littlewood T, Holyoake TL, Copland M et al. 2012. Episomal amplification of NUP214-ABL1 fusion gene in B-cell acute lymphoblastic leukemia. Blood, 120 (22), pp. 4441-4443. | Read more

Craddock C, Quek L, Goardon N, Freeman S, Siddique S, Raghavan M, Aztberger A, Schuh A, Grimwade D, Ivey A et al. 2013. Azacitidine fails to eradicate leukemic stem/progenitor cell populations in patients with acute myeloid leukemia and myelodysplasia. Leukemia, 27 (5), pp. 1028-1036. | Show Abstract | Read more

Epigenetic therapies demonstrate significant clinical activity in acute myeloid leukemia (AML) and myelodysplasia (MDS) and constitute an important new class of therapeutic agents. However hematological responses are not durable and disease relapse appears inevitable. Experimentally, leukemic stem/progenitor cells (LSC) propagate disease in animal models of AML and it has been postulated that their relative chemo-resistance contributes to disease relapse. We serially measured LSC numbers in patients with high-risk AML and MDS treated with 5'-azacitidine and sodium valproate (VAL-AZA). Fifteen out of seventy-nine patients achieved a complete remission (CR) or complete remission with incomplete blood count recovery (CRi) with VAL-AZA therapy. There was no significant reduction in the size of the LSC-containing population in non-responders. While the LSC-containing population was substantially reduced in all patients achieving a CR/CRi it was never eradicated and expansion of this population antedated morphological relapse. Similar studies were performed in seven patients with newly diagnosed AML treated with induction chemotherapy. Eradication of the LSC-containing population was observed in three patients all of whom achieved a durable CR in contrast to patients with resistant disease where LSC persistence was observed. LSC quantitation provides a novel biomarker of disease response and relapse in patients with AML treated with epigenetic therapies. New drugs that target this cellular population in vivo are required.

Roy A, Cowan G, Mead AJ, Filippi S, Bohn G, Chaidos A, Tunstall O, Chan JK, Choolani M, Bennett P et al. 2012. Perturbation of fetal liver hematopoietic stem and progenitor cell development by trisomy 21. Proc Natl Acad Sci U S A, 109 (43), pp. 17579-17584. | Show Abstract | Read more

The 40-fold increase in childhood megakaryocyte-erythroid and B-cell leukemia in Down syndrome implicates trisomy 21 (T21) in perturbing fetal hematopoiesis. Here, we show that compared with primary disomic controls, primary T21 fetal liver (FL) hematopoietic stem cells (HSC) and megakaryocyte-erythroid progenitors are markedly increased, whereas granulocyte-macrophage progenitors are reduced. Commensurately, HSC and megakaryocyte-erythroid progenitors show higher clonogenicity, with increased megakaryocyte, megakaryocyte-erythroid, and replatable blast colonies. Biased megakaryocyte-erythroid-primed gene expression was detected as early as the HSC compartment. In lymphopoiesis, T21 FL lymphoid-primed multipotential progenitors and early lymphoid progenitor numbers are maintained, but there was a 10-fold reduction in committed PreproB-lymphoid progenitors and the functional B-cell potential of HSC and early lymphoid progenitor is severely impaired, in tandem with reduced early lymphoid gene expression. The same pattern was seen in all T21 FL samples and no samples had GATA1 mutations. Therefore, T21 itself causes multiple distinct defects in FL myelo- and lymphopoiesis.

Della Porta MG, Picone C, Pascutto C, Malcovati L, Tamura H, Handa H, Czader M, Freeman S, Vyas P, Porwit A et al. 2012. Multicenter validation of a reproducible flow cytometric score for the diagnosis of low-grade myelodysplastic syndromes: results of a European LeukemiaNET study. Haematologica, 97 (8), pp. 1209-1217. | Show Abstract | Read more

BACKGROUND: The current World Health Organization classification of myelodysplastic syndromes is based morphological evaluation of bone marrow dysplasia. In clinical practice, the reproducibility of the recognition of dysplasia is usually poor especially in cases that lack specific markers such as ring sideroblasts and clonal cytogenetic abnormalities. DESIGN AND METHODS: We aimed to develop and validate a flow cytometric score for the diagnosis of myelodysplastic syndrome. Four reproducible parameters were analyzed: CD34(+) myeloblast-related and B-progenitor-related cluster size (defined by CD45 expression and side scatter characteristics CD34(+) marrow cells), myeloblast CD45 expression and granulocyte side scatter value. The study comprised a "learning cohort" (n=538) to define the score and a "validation cohort" (n=259) to confirm its diagnostic value. RESULTS: With respect to non-clonal cytopenias, patients with myelodysplastic syndrome had increased myeloblast-related cluster size, decreased B-progenitor-related cluster size, aberrant CD45 expression and reduced granulocyte side scatter (P<0.001). To define the flow cytometric score, these four parameters were combined in a regression model and the weight for each variable was estimated based on coefficients from that model. In the learning cohort a correct diagnosis of myelodysplastic syndrome was formulated in 198/281 cases (sensitivity 70%), while 18 false-positive results were noted among 257 controls (specificity 93%). Sixty-five percent of patients without specific markers of dysplasia (ring sideroblasts and clonal cytogenetic abnormalities) were correctly classified. A high value of the flow cytometric score was associated with multilineage dysplasia (P=0.001), transfusion dependency (P=0.02), and poor-risk cytogenetics (P=0.04). The sensitivity and specificity in the validation cohort (69% and 92%, respectively) were comparable to those in the learning cohort. The likelihood ratio of the flow cytometric score was 10. CONCLUSIONS: A flow cytometric score may help to establish the diagnosis of myelodysplastic syndrome, especially when morphology and cytogenetics are indeterminate.

Goodyear OC, Dennis M, Jilani NY, Loke J, Siddique S, Ryan G, Nunnick J, Khanum R, Raghavan M, Cook M et al. 2012. Azacitidine augments expansion of regulatory T cells after allogeneic stem cell transplantation in patients with acute myeloid leukemia (AML). Blood, 119 (14), pp. 3361-3369. | Show Abstract | Read more

Strategies that augment a GVL effect without increasing the risk of GVHD are required to improve the outcome after allogeneic stem cell transplantation (SCT). Azacitidine (AZA) up-regulates the expression of tumor Ags on leukemic blasts in vitro and expands the numbers of immunomodulatory T regulatory cells (Tregs) in animal models. Reasoning that AZA might selectively augment a GVL effect, we studied the immunologic sequelae of AZA administration after allogeneic SCT. Twenty-seven patients who had undergone a reduced intensity allogeneic transplantation for acute myeloid leukemia were treated with monthly courses of AZA, and CD8(+) T-cell responses to candidate tumor Ags and circulating Tregs were measured. AZA after transplantation was well tolerated, and its administration was associated with a low incidence of GVHD. Administration of AZA increased the number of Tregs within the first 3 months after transplantation compared with a control population (P = .0127). AZA administration also induced a cytotoxic CD8(+) T-cell response to several tumor Ags, including melanoma-associated Ag 1, B melanoma antigen 1, and Wilm tumor Ag 1. These data support the further examination of AZA after transplantation as a mechanism of augmenting a GVL effect without a concomitant increase in GVHD.

Jan M, Snyder TM, Corces-Zimmerman MR, Vyas P, Weissman IL, Quake SR, Majeti R. 2012. Clonal evolution of preleukemic hematopoietic stem cells precedes human acute myeloid leukemia. Sci Transl Med, 4 (149), pp. 149ra118. | Show Abstract | Read more

Given that most bone marrow cells are short-lived, the accumulation of multiple leukemogenic mutations in a single clonal lineage has been difficult to explain. We propose that serial acquisition of mutations occurs in self-renewing hematopoietic stem cells (HSCs). We investigated this model through genomic analysis of HSCs from six patients with de novo acute myeloid leukemia (AML). Using exome sequencing, we identified mutations present in individual AML patients harboring the FLT3-ITD (internal tandem duplication) mutation. We then screened the residual HSCs and detected some of these mutations including mutations in the NPM1, TET2, and SMC1A genes. Finally, through single-cell analysis, we determined that a clonal progression of multiple mutations occurred in the HSCs of some AML patients. These preleukemic HSCs suggest the clonal evolution of AML genomes from founder mutations, revealing a potential mechanism contributing to relapse. Such preleukemic HSCs may constitute a cellular reservoir that should be targeted therapeutically for more durable remissions.

Roy A, Roberts I, Vyas P. 2012. Biology and management of transient abnormal myelopoiesis (TAM) in children with Down syndrome. Semin Fetal Neonatal Med, 17 (4), pp. 196-201. | Show Abstract | Read more

Children with Down syndrome (DS) have an increased risk of Acute Myeloid Leukaemia (ML-DS), particularly megakaryoblastic leukaemia, which is clonally -related to the neonatal myeloproliferative syndrome, Transient Abnormal Myelopoiesis (TAM) unique to infants with DS. Molecular, biological, and clinical data indicate that TAM is initiated before birth when fetal liver haematopoietic cells trisomic for chromosome 21 acquire mutations in GATA1. TAM usually resolves spontaneously by 6 months; however 20-30% subsequently develop ML-DS harbouring the same GATA1 mutation(s). This review focuses on recent studies describing haematological, clinical and biological features of TAM and discusses approaches to diagnose, treat and monitor minimal residual disease in TAM. An important unanswered question is whether ML-DS is always preceded by TAM as it may be clinically and possibly haematologically 'silent'. We have briefly discussed the role of population-based screening for TAM and development of treatment strategies to eliminate the preleukaemic TAM clone, thereby preventing ML-DS.

Frisan E, Vandekerckhove J, de Thonel A, Pierre-Eugène C, Sternberg A, Arlet JB, Floquet C, Gyan E, Kosmider O, Dreyfus F et al. 2012. Defective nuclear localization of Hsp70 is associated with dyserythropoiesis and GATA-1 cleavage in myelodysplastic syndromes. Blood, 119 (6), pp. 1532-1542. | Show Abstract | Read more

Normal human erythroid cell maturation requests the transcription factor GATA-1 and a transient activation of caspase-3, with GATA-1 being protected from caspase-3-mediated cleavage by interaction with the chaperone heat shock protein 70 (Hsp70) in the nucleus. Erythroid cell dysplasia observed in early myelodysplastic syndromes (MDS) involves impairment of differentiation and excess of apoptosis with a burst of caspase activation. Analysis of gene expression in MDS erythroblasts obtained by ex vivo cultures demonstrates the down-regulation of a set of GATA-1 transcriptional target genes, including GYPA that encodes glycophorin A (GPA), and the up-regulation of members of the HSP70 family. GATA-1 protein expression is decreased in MDS erythroblasts, but restores in the presence of a pan-caspase inhibitor. Expression of a mutated GATA-1 that cannot be cleaved by caspase-3 rescues the transcription of GATA-1 targets, and the erythroid differentiation, but does not improve survival. Hsp70 fails to protect GATA-1 from caspases because the protein does not accumulate in the nucleus with active caspase-3. Expression of a nucleus-targeted mutant of Hsp70 protects GATA-1 and rescues MDS erythroid cell differentiation. Alteration of Hsp70 cytosolic-nuclear shuttling is a major feature of MDS that favors GATA-1 cleavage and differentiation impairment, but not apoptosis, in dysplastic erythroblasts.

Roberts I, Vyas P. 2011. Enigmatic variation. Blood, 118 (26), pp. 6723-6724. | Show Abstract | Read more

Variability in presentation and prognosis of transient myeloproliferative disorder (TMD) in infants with Down syndrome (DS) has perplexed clinicians and scientists for decades and is explored in this issue of Blood by Gamis and colleagues from the Children's Oncology Group (COG).

Medd P, Monk I, Danby R, Malladi R, Clifford R, Ellis A, Roberts D, Hatton C, Vyas P, Littlewood T, Peniket A. 2011. Methotrexate dose delivery is more important than ciclosporin level in graft-versus-host disease prophylaxis following T-replete reduced-intensity sibling allogeneic stem cell transplant. Int J Hematol, 94 (3), pp. 266-278. | Show Abstract | Read more

We investigated the contributions of methotrexate (MTX) and ciclosporin (CsA) prophylaxis to acute/chronic graft-versus-host disease (a/cGvHD) prevention following reduced-intensity conditioned allogeneic haematopoietic stem cell transplant (HSCT). Ninety-two fludarabine-melphalan sibling allo-SCT received CsA. Nine, 30 and 47 patients received no MTX, 2-3 doses and 4 doses, respectively. Cumulative CsA blood level to day 21 (CsA(21)) was calculated. Grades II-IV aGvHD incidence was 37.2%. In multivariate analysis, MTX omission and increasing donor age significantly associated with aGvHD incidence whilst MTX reduction and CsA(21) did not. Median duration of first immunosuppressive therapy (IST) for aGvHD was 68 days; duration of first IST was significantly longer in older patients but was not associated with MTX or CsA(21). Extensive cGvHD incidence was 60.6% at 1 year. Reduction of MTX to 2-3 doses, but not MTX omission or CsA(21), was associated with greater incidence of cGvHD affecting ≥3 organs. Median IST duration was 22 months; neither MTX nor CsA(21) influenced this. IST duration was significantly greater in patients receiving a CD34 dose below median. Neither MTX nor CsA(21) altered survival or relapse outcomes. MTX influences GvHD following T-replete RIC sibling HSCT.

Alford KA, Reinhardt K, Garnett C, Norton A, Böhmer K, von Neuhoff C, Kolenova A, Marchi E, Klusmann JH, Roberts I et al. 2011. Analysis of GATA1 mutations in Down syndrome transient myeloproliferative disorder and myeloid leukemia. Blood, 118 (8), pp. 2222-2238. | Show Abstract | Read more

Children with Down syndrome (DS) up to the age of 4 years are at a 150-fold excess risk of developing myeloid leukemia (ML-DS). Approximately 4%-5% of newborns with DS develop transient myeloproliferative disorder (TMD). Blast cell structure and immunophenotype are similar in TMD and ML-DS. A mutation in the hematopoietic transcription factor GATA1 is present in almost all cases. Here, we show that simple techniques detect GATA1 mutations in the largest series of TMD (n = 134; 88%) and ML-DS (n = 103; 85%) cases tested. Furthermore, no significant difference in the mutational spectrum between the 2 disorders was seen. Thus, the type of GATA1 sequence mutation is not a reliable tool and is not prognostic of which patients with TMD are probable to develop ML-DS.

Roy NB, Myerson S, Schuh AH, Bignell P, Patel R, Wainscoat JS, McGowan S, Marchi E, Atoyebi W, Littlewood T et al. 2011. Cardiac iron overload in transfusion-dependent patients with myelodysplastic syndromes. Br J Haematol, 154 (4), pp. 521-524. | Show Abstract | Read more

Transfusion-dependent myelodysplastic (MDS) patients are prone to iron overload. We evaluated 43 transfused MDS patients with T2* magnetic resonance imaging scans. 81% had liver and 16·8% cardiac iron overload. Liver R2* (1000/T2*), but not cardiac R2*, was correlated with number of units transfused (r=0·72, P<0·0001) and ferritin (r=0·53, P<0·0001). The area under the curve of a time-ferritin plot was found to be much greater in patients with cardiac iron loading (median 53·7x10(5) Megaunits vs. 12·2x10(5) Megaunits, P=0·002). HFE, HFE2, HAMP or SLC40A1 genotypes were not predictors of iron overload in these patients.

García P, Berlanga O, Vegiopoulos A, Vyas P, Frampton J. 2011. c-Myb and GATA-1 alternate dominant roles during megakaryocyte differentiation. J Thromb Haemost, 9 (8), pp. 1572-1581. | Show Abstract | Read more

BACKGROUND: Transcription factors are essential for blood cell formation. Mice expressing low levels of c-Myb (c-Myb(low)) have an increased number of bone marrow megakaryocytes (MKs) and corresponding thrombocytosis. In contrast, mice engineered to express low levels of GATA-1 (GATA-1(low)) in the megakaryocytic lineage exhibit aberrant megakaryocytopoiesis with hyperproliferation of progenitors and defective terminal differentiation leading to thrombocytopenia. These seemingly opposite roles may affect platelet turnover and thus be of clinical relevance. OBJECTIVE: To determine how these two transcription factors act together to control megakaryocytopoiesis and platelet formation. METHODS: We used a combination of cellular and molecular in vitro assays to examine the ability of bone marrow cells from mice expressing low levels of both c-Myb and GATA-1 (referred to as double(low)) to produce MKs and platelets. RESULTS: Double(low) cells, or those with low GATA-1 levels in which c-Myb is conditionally deleted, lack the hyperproliferative capacity of GATA-1(low) cells, allowing the cells to proceed towards more committed MKs that are, however, impaired in their capacity to produce fully differentiated cells, as confirmed by the abundance of morphologically aberrant cells that lack the ability to form proplatelets. CONCLUSION: c-Myb and GATA-1 act in concert to achieve correct megakaryocytic differentiation. GATA-1 regulates both the proliferation of megakaryocytic progenitors and their terminal maturation. c-Myb also acts at the level of the progenitor by influencing its commitment to differentiation, but in contrast to GATA-1 it does not have any effect on the process of terminal differentiation.

Chagraoui H, Kassouf M, Banerjee S, Goardon N, Clark K, Atzberger A, Pearce AC, Skoda RC, Ferguson DJ, Watson SP et al. 2011. SCL-mediated regulation of the cell-cycle regulator p21 is critical for murine megakaryopoiesis. Blood, 118 (3), pp. 723-735. | Show Abstract | Read more

Megakaryopoiesis is a complex process that involves major cellular and nuclear changes and relies on controlled coordination of cellular proliferation and differentiation. These mechanisms are orchestrated in part by transcriptional regulators. The key hematopoietic transcription factor stem cell leukemia (SCL)/TAL1 is required in early hematopoietic progenitors for specification of the megakaryocytic lineage. These early functions have, so far, prevented full investigation of its role in megakaryocyte development in loss-of-function studies. Here, we report that SCL critically controls terminal megakaryocyte maturation. In vivo deletion of Scl specifically in the megakaryocytic lineage affects all key attributes of megakaryocyte progenitors (MkPs), namely, proliferation, ploidization, cytoplasmic maturation, and platelet release. Genome-wide expression analysis reveals increased expression of the cell-cycle regulator p21 in Scl-deleted MkPs. Importantly, p21 knockdown-mediated rescue of Scl-mutant MkPs shows full restoration of cell-cycle progression and partial rescue of the nuclear and cytoplasmic maturation defects. Therefore, SCL-mediated transcriptional control of p21 is essential for terminal maturation of MkPs. Our study provides a mechanistic link between a major hematopoietic transcriptional regulator, cell-cycle progression, and megakaryocytic differentiation.

Pellagatti A, Cazzola M, Giagounidis A, Perry J, Malcovati L, Della Porta MG, Jädersten M, Killick S, Vyas P, Hellström-Lindberg E et al. 2011. Marked down-regulation of nucleophosmin-1 is associated with advanced del(5q) myelodysplastic syndrome. Br J Haematol, 155 (2), pp. 272-274. | Read more

Vyas P, Jacobsen SE. 2011. Clever leukemic stem cells branch out. Cell Stem Cell, 8 (3), pp. 242-244. | Show Abstract | Read more

Individual tumors harbor heterogeneous populations of genetically distinct subclones. Two recent papers in Nature by Notta et al. (2011) and Anderson et al. (2011) reveal genetic heterogeneity in functional leukemic stem cells, which has important implications for how both cancer and normal stem cell populations may adapt to selective pressure.

Goardon N, Marchi E, Atzberger A, Quek L, Schuh A, Soneji S, Woll P, Mead A, Alford KA, Rout R et al. 2011. Coexistence of LMPP-like and GMP-like leukemia stem cells in acute myeloid leukemia. Cancer Cell, 19 (1), pp. 138-152. | Show Abstract | Read more

The relationships between normal and leukemic stem/progenitor cells are unclear. We show that in ∼80% of primary human CD34+ acute myeloid leukemia (AML), two expanded populations with hemopoietic progenitor immunophenotype coexist in most patients. Both populations have leukemic stem cell (LSC) activity and are hierarchically ordered; one LSC population gives rise to the other. Global gene expression profiling shows the LSC populations are molecularly distinct and resemble normal progenitors but not stem cells. The more mature LSC population most closely mirrors normal granulocyte-macrophage progenitors (GMP) and the immature LSC population a previously uncharacterized progenitor functionally similar to lymphoid-primed multipotential progenitors (LMPPs). This suggests that in most cases primary CD34+ AML is a progenitor disease where LSCs acquire abnormal self-renewal potential.

García P, Berlanga O, Vegiopoulos A, Vyas P, Frampton J. 2011. c-Myb and GATA-1 alternate dominant roles during megakaryocyte differentiation Journal of Thrombosis and Haemostasis, 9 (8), pp. 1572-1581. | Show Abstract | Read more

Background: Transcription factors are essential for blood cell formation. Mice expressing low levels of c-Myb (c-Myb low ) have an increased number of bone marrow megakaryocytes (MKs) and corresponding thrombocytosis. In contrast, mice engineered to express low levels of GATA-1 (GATA-1 low ) in the megakaryocytic lineage exhibit aberrant megakaryocytopoiesis with hyperproliferation of progenitors and defective terminal differentiation leading to thrombocytopenia. These seemingly opposite roles may affect platelet turnover and thus be of clinical relevance. Objective: To determine how these two transcription factors act together to control megakaryocytopoiesis and platelet formation. Methods: We used a combination of cellular and molecular in vitro assays to examine the ability of bone marrow cells from mice expressing low levels of both c-Myb and GATA-1 (referred to as double low ) to produce MKs and platelets. Results: Double low cells, or those with low GATA-1 levels in which c-Myb is conditionally deleted, lack the hyperproliferative capacity of GATA-1 low cells, allowing the cells to proceed towards more committed MKs that are, however, impaired in their capacity to produce fully differentiated cells, as confirmed by the abundance of morphologically aberrant cells that lack the ability to form proplatelets. Conclusion: c-Myb and GATA-1 act in concert to achieve correct megakaryocytic differentiation. GATA-1 regulates both the proliferation of megakaryocytic progenitors and their terminal maturation. c-Myb also acts at the level of the progenitor by influencing its commitment to differentiation, but in contrast to GATA-1 it does not have any effect on the process of terminal differentiation. © 2011 International Society on Thrombosis and Haemostasis.

De Gobbi M, Garrick D, Lynch M, Vernimmen D, Hughes JR, Goardon N, Luc S, Lower KM, Sloane-Stanley JA, Pina C et al. 2011. Generation of bivalent chromatin domains during cell fate decisions. Epigenetics Chromatin, 4 (1), pp. 9. | Show Abstract | Read more

BACKGROUND: In self-renewing, pluripotent cells, bivalent chromatin modification is thought to silence (H3K27me3) lineage control genes while 'poising' (H3K4me3) them for subsequent activation during differentiation, implying an important role for epigenetic modification in directing cell fate decisions. However, rather than representing an equivalently balanced epigenetic mark, the patterns and levels of histone modifications at bivalent genes can vary widely and the criteria for identifying this chromatin signature are poorly defined. RESULTS: Here, we initially show how chromatin status alters during lineage commitment and differentiation at a single well characterised bivalent locus. In addition we have determined how chromatin modifications at this locus change with gene expression in both ensemble and single cell analyses. We also show, on a global scale, how mRNA expression may be reflected in the ratio of H3K4me3/H3K27me3. CONCLUSIONS: While truly 'poised' bivalently modified genes may exist, the original hypothesis that all bivalent genes are epigenetically premarked for subsequent expression might be oversimplistic. In fact, from the data presented in the present work, it is equally possible that many genes that appear to be bivalent in pluripotent and multipotent cells may simply be stochastically expressed at low levels in the process of multilineage priming. Although both situations could be considered to be forms of 'poising', the underlying mechanisms and the associated implications are clearly different.

Medd P, Monk I, Danby R, Malladi R, Clifford R, Ellis A, Roberts D, Hatton C, Vyas P, Littlewood T, Peniket A. 2011. Methotrexate dose delivery is more important than ciclosporin level in graft-versus-host disease prophylaxis following T-replete reduced-intensity sibling allogeneic stem cell transplant International Journal of Hematology, pp. 1-13.

Papaemmanuil E, Cazzola M, Boultwood J, Malcovati L, Vyas P, Bowen D, Pellagatti A, Wainscoat JS, Hellstrom-Lindberg E, Gambacorti-Passerini C et al. 2011. Somatic SF3B1 mutation in myelodysplasia with ring sideroblasts. N Engl J Med, 365 (15), pp. 1384-1395. | Show Abstract | Read more

BACKGROUND: Myelodysplastic syndromes are a diverse and common group of chronic hematologic cancers. The identification of new genetic lesions could facilitate new diagnostic and therapeutic strategies. METHODS: We used massively parallel sequencing technology to identify somatically acquired point mutations across all protein-coding exons in the genome in 9 patients with low-grade myelodysplasia. Targeted resequencing of the gene encoding RNA splicing factor 3B, subunit 1 (SF3B1), was also performed in a cohort of 2087 patients with myeloid or other cancers. RESULTS: We identified 64 point mutations in the 9 patients. Recurrent somatically acquired mutations were identified in SF3B1. Follow-up revealed SF3B1 mutations in 72 of 354 patients (20%) with myelodysplastic syndromes, with particularly high frequency among patients whose disease was characterized by ring sideroblasts (53 of 82 [65%]). The gene was also mutated in 1 to 5% of patients with a variety of other tumor types. The observed mutations were less deleterious than was expected on the basis of chance, suggesting that the mutated protein retains structural integrity with altered function. SF3B1 mutations were associated with down-regulation of key gene networks, including core mitochondrial pathways. Clinically, patients with SF3B1 mutations had fewer cytopenias and longer event-free survival than patients without SF3B1 mutations. CONCLUSIONS: Mutations in SF3B1 implicate abnormalities of messenger RNA splicing in the pathogenesis of myelodysplastic syndromes. (Funded by the Wellcome Trust and others.).

El Omari K, Hoosdally SJ, Tuladhar K, Karia D, Vyas P, Patient R, Porcher C, Mancini EJ. 2011. Structure of the leukemia oncogene LMO2: implications for the assembly of a hematopoietic transcription factor complex. Blood, 117 (7), pp. 2146-2156. | Show Abstract | Read more

The LIM only protein 2 (LMO2) is a key regulator of hematopoietic stem cell development whose ectopic expression in T cells leads to the onset of acute lymphoblastic leukemia. Through its LIM domains, LMO2 is thought to function as the scaffold for a DNA-binding transcription regulator complex, including the basic helix-loop-helix proteins SCL/TAL1 and E47, the zinc finger protein GATA-1, and LIM-domain interacting protein LDB1. To understand the role of LMO2 in the formation of this complex and ultimately to dissect its function in normal and aberrant hematopoiesis, we solved the crystal structure of LMO2 in complex with the LID domain of LDB1 at 2.4 Å resolution. We observe a largely unstructured LMO2 kept in register by the LID binding both LIM domains. Comparison of independently determined crystal structures of LMO2 reveals large movements around a conserved hinge between the LIM domains. We demonstrate that such conformational flexibility is necessary for binding of LMO2 to its partner protein SCL/TAL1 in vitro and for the function of this complex in vivo. These results, together with molecular docking and analysis of evolutionarily conserved residues, yield the first structural model of the DNA-binding complex containing LMO2, LDB1, SCL/TAL1, and GATA-1.

Goodyear O, Agathanggelou A, Novitzky-Basso I, Siddique S, McSkeane T, Ryan G, Vyas P, Cavenagh J, Stankovic T, Moss P, Craddock C. 2010. Induction of a CD8+ T-cell response to the MAGE cancer testis antigen by combined treatment with azacitidine and sodium valproate in patients with acute myeloid leukemia and myelodysplasia. Blood, 116 (11), pp. 1908-1918. | Show Abstract | Read more

Epigenetic therapies, including DNA methyltransferase and histone deacetylase inhibitors, represent important new treatment modalities in hematologic malignancies, but their mechanism of action remains unknown. We reasoned that up-regulation of epigenetically silenced tumor antigens may induce an immunologically mediated antitumor response and contribute to their clinical activity. In this study, we demonstrate that azacitidine (AZA) and sodium valproate (VPA) up-regulate expression of melanoma-associated antigens (MAGE antigens) on acute myeloid leukemia (AML) and myeloma cell lines. In separate studies, we observed that prior exposure to AZA/VPA increased recognition of myeloma cell lines by a MAGE-specific CD8(+) cytotoxic T-lymphocyte (CTL) clone. We therefore measured CTL responses to MAGE antigens in 21 patients with AML or myelodysplasia treated with AZA/VPA. CTL responses to MAGE antigens were documented in only 1 patient before therapy; however, treatment with AZA/VPA induced a CTL response in 10 patients. Eight of the 11 patients with circulating MAGE CTLs achieved a major clinical response after AZA/VPA therapy. This is the first demonstration of a MAGE-specific CTL response in AML. Furthermore, it appears that epigenetic therapies have the capacity to induce a CTL response to MAGE antigens in vivo that may contribute to their clinical activity in AML.

Tehranchi R, Woll PS, Anderson K, Buza-Vidas N, Mizukami T, Mead AJ, Astrand-Grundström I, Strömbeck B, Horvat A, Ferry H et al. 2010. Persistent malignant stem cells in del(5q) myelodysplasia in remission. N Engl J Med, 363 (11), pp. 1025-1037. | Show Abstract | Read more

BACKGROUND: The in vivo clinical significance of malignant stem cells remains unclear. METHODS: Patients who have the 5q deletion (del[5q]) myelodysplastic syndrome (interstitial deletions involving the long arm of chromosome 5) have complete clinical and cytogenetic remissions in response to lenalidomide treatment, but they often have relapse. To determine whether the persistence of rare but distinct malignant stem cells accounts for such relapses, we examined bone marrow specimens obtained from seven patients with the del(5q) myelodysplastic syndrome who became transfusion-independent while receiving lenalidomide treatment and entered cytogenetic remission. RESULTS: Virtually all CD34+, CD38+ progenitor cells and stem cells that were positive for CD34 and CD90, with undetectable or low CD38 (CD38−/low), had the 5q deletion before treatment. Although lenalidomide efficiently reduced these progenitors in patients in complete remission, a larger fraction of the minor, quiescent, CD34+,CD38-/low, CD90+ del(5q) stem cells as well as functionally defined del(5q) stem cells remained distinctly resistant to lenalidomide. Over time, lenalidomide resistance developed in most of the patients in partial and complete remission, with recurrence or expansion of the del(5q) clone and clinical and cytogenetic progression. CONCLUSIONS: In these patients with the del(5q) myelodysplastic syndrome, we identified rare and phenotypically distinct del(5q) myelodysplastic syndrome stem cells that were also selectively resistant to therapeutic targeting at the time of complete clinical and cytogenetic remission. (Funded by the EuroCancerStemCell Consortium and others.)

Grimwade D, Vyas P, Freeman S. 2010. Assessment of minimal residual disease in acute myeloid leukemia. Curr Opin Oncol, 22 (6), pp. 656-663. | Show Abstract | Read more

PURPOSE OF REVIEW: The last 15 years have witnessed significant improvements in technologies to detect minimal residual disease (MRD) in acute myeloid leukemia (AML). We review recent studies highlighting the potential for novel and standardized assays to provide independent prognostic information and develop more personalized treatment approaches. RECENT FINDINGS: Progress includes establishment of optimized real-time quantitative PCR (RQ-PCR) assays for WT1 (commonly overexpressed and a putative therapeutic target) and mutant NPM1 genes. Moreover, sequential MRD monitoring using an internationally standardized PML-RARA RQ-PCR assay has been successfully used to guide molecularly targeted therapy in acute promyelocytic leukemia (APL). There have also been significant advances in multiparameter flow cytometry (MFC) to detect MRD, with introduction of 6-10 color technology and improved understanding of the immunophenotype of leukemic stem cells. SUMMARY: Sensitive MRD detection using MFC and/or RQ-PCR has become feasible in virtually all AML patients. MRD monitoring is now considered a standard of care in APL. Recent studies provide a strong rationale for prospective trials investigating the merits of extending MRD detection to alter therapy and potentially improve outcome in other AML subtypes.

Szende A, Brazier J, Schaefer C, Deuson R, Isitt JJ, Vyas P. 2010. Measurement of utility values in the UK for health states related to immune thrombocytopenic purpura. Curr Med Res Opin, 26 (8), pp. 1893-1903. | Show Abstract | Read more

OBJECTIVE: To measure utility values associated with immune (idiopathic) thrombocytopenic purpura (ITP), as perceived by the United Kingdom (UK) general public. RESEARCH DESIGN AND METHODS: A multi-step process, including clinical trial data, literature review, and patient focus group, was used to develop ITP health states valued in a web survey. Six ITP health states were defined based on platelet levels, risk of bleeding and key adverse events/disease complications. Clinical trial data on bleeding and ITP-specific quality of life data were key sources for developing health-state descriptions. 359 respondents, randomly selected from a managed web panel in the UK, completed the web-based Time Trade-Off survey. Wilcoxon signed-rank test was used to compare differences between each pair of health states. RESULTS: Sample characteristics (mean age: 47.9 +/- 16.9 years; 54% female) were comparable to the UK general population. ITP health states were valued as significantly worse than perfect health. Experiencing bleeding episodes was a more important driver than low platelet levels in valuing a health state to be worse. Substantial disutilities were associated with surviving an intracranial haemorrhage. Mean (SD) utility values for each ITP health state are: HS1: platelets >or=50 x 10(9)/L, no outpatient bleed: 0.863 +/- 0.15; HS2: platelets >or=50 x 10(9)/L, outpatient bleed: 0.734 +/- 0.19; HS3: platelets <50 x 10(9)/L, no outpatient bleed: 0.841 +/- 0.19; HS4: platelets <50 x 10(9)/L, outpatient bleed: 0.732 +/- 0.19; HS5: intracranial haemorrhage (2-6 months): 0.038 +/- 0.46; HS6: steroid treatment adverse events: 0.758 +/- 0.20. Potential limitations relate to web user population characteristics and lack of comparative testing of web-based TTO methods. CONCLUSIONS: Results provide evidence that the UK general population associate substantial loss of value living with ITP, suggesting an important role for new ITP treatments. Utility values based on these health states may be useful in future cost-effectiveness studies of existing and/or new ITP treatments.

Kassouf MT, Hughes JR, Taylor S, McGowan SJ, Soneji S, Green AL, Vyas P, Porcher C. 2010. Genome-wide identification of TAL1's functional targets: insights into its mechanisms of action in primary erythroid cells. Genome Res, 20 (8), pp. 1064-1083. | Show Abstract | Read more

Coordination of cellular processes through the establishment of tissue-specific gene expression programs is essential for lineage maturation. The basic helix-loop-helix hemopoietic transcriptional regulator TAL1 (formerly SCL) is required for terminal differentiation of red blood cells. To gain insight into TAL1 function and mechanisms of action in erythropoiesis, we performed ChIP-sequencing and gene expression analyses from primary fetal liver erythroid cells. We show that TAL1 coordinates expression of genes in most known red cell-specific processes. The majority of TAL1's genomic targets require direct DNA-binding activity. However, one-fifth of TAL1's target sequences, mainly among those showing high affinity for TAL1, can recruit the factor independently of its DNA binding activity. An unbiased DNA motif search of sequences bound by TAL1 identified CAGNTG as TAL1-preferred E-box motif in erythroid cells. Novel motifs were also characterized that may help distinguish activated from repressed genes and suggest a new mechanism by which TAL1 may be recruited to DNA. Finally, analysis of recruitment of GATA1, a protein partner of TAL1, to sequences occupied by TAL1 suggests that TAL1's binding is necessary prior or simultaneous to that of GATA1. This work provides the framework to study regulatory networks leading to erythroid terminal maturation and to model mechanisms of action of tissue-specific transcription factors.

Craddock C, Nagra S, Peniket A, Brookes C, Buckley L, Nikolousis E, Duncan N, Tauro S, Yin J, Liakopoulou E et al. 2010. Factors predicting long-term survival after T-cell depleted reduced intensity allogeneic stem cell transplantation for acute myeloid leukemia. Haematologica, 95 (6), pp. 989-995. | Show Abstract | Read more

BACKGROUND: Reduced intensity conditioning regimens permit the delivery of a potentially curative graft-versus-leukemia effect in older patients with acute myeloid leukemia. Although T-cell depletion is increasingly used to reduce the risk of graft-versus-host disease its impact on the graft-versus-leukemia effect and long-term outcome post-transplant is unknown. DESIGN AND METHODS: We have characterized pre- and post-transplant factors determining overall survival in 168 patients with acute myeloid leukemia transplanted using an alemtuzumab based reduced intensity conditioning regimen with a median duration of follow-up of 37 months. RESULTS: The 3-year overall survival for patients transplanted in CR1 or CR2/CR3 was 50% (95% CI, 38% to 62%) and 44% (95% CI, 31% to 56%), respectively compared to 15% (95% CI, 2% to 36%) for patients with relapsed/refractory disease. Multivariate analysis demonstrated that both survival and disease relapse were influenced by status at transplant (P=0.008) and presentation cytogenetics (P=0.01). Increased exposure to cyclosporine A (CsA) in the first 21 days post-transplant was associated with an increased relapse risk (P<0.0001) and decreased overall survival (P<0.0001). CONCLUSIONS: Disease stage, presentation karyotype and post-transplant CsA exposure are important predictors of outcome in patients undergoing a T-cell depleted reduced intensity conditioning allograft for acute myeloid leukemia. These data confirm the presence of a potent graft-versus-leukemia effect after a T-cell depleted reduced intensity conditioning allograft in acute myeloid leukemia and identify CsA exposure as a manipulable determinant of outcome in this setting.

Drissen R, Guyot B, Zhang L, Atzberger A, Sloane-Stanley J, Wood B, Porcher C, Vyas P. 2010. Lineage-specific combinatorial action of enhancers regulates mouse erythroid Gata1 expression. Blood, 115 (17), pp. 3463-3471. | Show Abstract | Read more

Precise spatiotemporal control of Gata1 expression is required in both early hematopoietic progenitors to determine erythroid/megakaryocyte versus granulocyte/monocyte lineage output and in the subsequent differentiation of erythroid cells and megakaryocytes. An enhancer element upstream of the mouse Gata1 IE (1st exon erythroid) promoter, mHS-3.5, can direct both erythroid and megakaryocytic expression. However, loss of this element ablates only megakaryocytes, implying that an additional element has erythroid specificity. Here, we identify a double DNaseI hypersensitive site, mHS-25/6, as having erythroid but not megakaryocytic activity in primary cells. It binds an activating transcription factor complex in erythroid cells where it also makes physical contact with the Gata1 promoter. Deletion of mHS-25/6 or mHS-3.5 in embryonic stem cells has only a modest effect on in vitro erythroid differentiation, whereas loss of both elements ablates both primitive and definitive erythropoiesis with an almost complete loss of Gata1 expression. Surprisingly, Gata2 expression was also concomitantly low, suggesting a more complex interaction between these 2 factors than currently envisaged. Thus, whereas mHS-3.5 alone is sufficient for megakaryocytic development, mHS-3.5 and mHS-25/6 collectively regulate erythroid Gata1 expression, demonstrating lineage-specific differences in Gata1 cis-element use important for development of these 2 cell types.

Zwaan CM, Reinhardt D, Hitzler J, Vyas P. 2010. Acute leukemias in children with Down syndrome. Hematol Oncol Clin North Am, 24 (1), pp. 19-34. | Show Abstract | Read more

Children with Down syndrome have an increased risk for developing both acute myeloid as well as lymphoblastic leukemia. These leukemias differ in presenting characteristics and underlying biology when compared with leukemias occurring in non-Down syndrome children. Myeloid leukemia in children with Down syndrome is preceded by a preleukemic clone (transient leukemia or transient myeloproliferative disorder), which may disappear spontaneously, but may also need treatment in case of severe symptoms. Twenty percent of children with transient leukemia subsequently develop myeloid leukemia. This transition offers a unique model to study the stepwise development of leukemia and of gene dosage effects mediated by aneuploidy.

Roy A, Roberts I, Norton A, Vyas P. 2009. Acute megakaryoblastic leukaemia (AMKL) and transient myeloproliferative disorder (TMD) in Down syndrome: a multi-step model of myeloid leukaemogenesis. Br J Haematol, 147 (1), pp. 3-12. | Show Abstract | Read more

Children with Down syndrome (DS) have a marked increase in susceptibility to Acute Megakaryoblastic Leukaemia (DS-AMKL) and the closely linked neonatal preleukaemic syndrome, Transient Myeloproliferative Disorder (DS-TMD). The distinct stages of DS-TMD and DS-AMKL provide an excellent tractable model to study leukaemogenesis. This review focuses on recent studies describing clinical, haematological and biological features of DS-AMKL and DS-TMD. The findings from these studies suggest that mutations in the key haemopoietic regulator GATA1 (GATA binding protein 1) in DS-AMKL and DS-TMD may be useful in diagnosis and assessing minimal residual disease. These findings raise the possibility of population-based screening strategies for DS-TMD and the development of treatment to eliminate the preleukaemic TMD clone to prevent DS-AMKL. Advances in our understanding of perturbed haemopoiesis in DS, the role of GATA1 and of cooperating mutations are also discussed. These findings have implications for leukaemia biology more broadly given the frequency of acquired trisomy in other human leukaemias.

Szende A, Brazier J, Schaefer C, Deuson R, Isitt J, Vyas P. 2009. MEASUREMENT OF HEALTH UTILITY VALUES IN THE UK FOR HEALTH STATES RELATED TO IMMUNE (IDIOPATHIC) THROMBOCYTOPENIC PURPURA (ITP) VALUE IN HEALTH, 12 (7), pp. A383-A383. | Read more

Gupta R, Vyas P, Enver T. 2009. Molecular targeting of cancer stem cells. Cell Stem Cell, 5 (2), pp. 125-126. | Show Abstract | Read more

Cancer stem cells may be important targets for new anticancer drugs. In two recent articles in Cell Stem Cell, Jin et al. (2009) and Hoey et al. (2009) provide proof of principle for this idea in experimental models of solid tumors and leukemias, respectively.

Goardon N, Nikolousis E, Sternberg A, Chu WK, Craddock C, Richardson P, Benson R, Drayson M, Standen G, Vyas P, Freeman S. 2009. Reduced CD38 expression on CD34+ cells as a diagnostic test in myelodysplastic syndromes. Haematologica, 94 (8), pp. 1160-1163. | Show Abstract | Read more

Diagnosis of myelodysplastic syndrome can be difficult especially in cases with a low blast count and a normal karyotype. Flow cytometry has been used to distinguish myelodysplastic syndrome from non-clonal cytopenias. No one single simple flow cytometric parameter has been proposed to be diagnostic of myelodysplastic syndrome. We have studied samples from 100 myelodysplastic syndrome patients and as control samples; 70 non-clonal cytopenias, 5 subjects with normal hematology, 31 patients with acute myeloid leukemia and 11 with chronic myelomonocytic leukemia or myeloproliferative disorder. We show that reduced relative mean fluorescence of CD38 below a threshold value on CD34(+) cells diagnosed low-grade myelodysplastic syndrome with 95% sensitivity (95% confidence interval, 87-99%) and 92% specificity (95% confidence interval, 82-97%). This simple flow cytometric test may be of value in the routine clinical diagnosis of myelodysplastic syndrome, especially in cases with a low blast count and normal karyotype.

van de Loosdrecht AA, Alhan C, Béné MC, Della Porta MG, Dräger AM, Feuillard J, Font P, Germing U, Haase D, Homburg CH et al. 2009. Standardization of flow cytometry in myelodysplastic syndromes: report from the first European LeukemiaNet working conference on flow cytometry in myelodysplastic syndromes. Haematologica, 94 (8), pp. 1124-1134. | Show Abstract | Read more

The myelodysplastic syndromes are a group of clonal hematopoietic stem cell diseases characterized by cytopenia(s), dysplasia in one or more cell lineages and increased risk of evolution to acute myeloid leukemia (AML). Recent advances in immunophenotyping of hematopoietic progenitor and maturing cells in dysplastic bone marrow point to a useful role for multiparameter flow cytometry (FCM) in the diagnosis and prognostication of myelodysplastic syndromes. In March 2008, representatives from 18 European institutes participated in a European LeukemiaNet (ELN) workshop held in Amsterdam as a first step towards standardization of FCM in myelodysplastic syndromes. Consensus was reached regarding standard methods for cell sampling, handling and processing. The group also defined minimal combinations of antibodies to analyze aberrant immunophenotypes and thus dysplasia. Examples are altered numbers of CD34(+) precursors, aberrant expression of markers on myeloblasts, maturing myeloid cells, monocytes or erythroid precursors and the expression of lineage infidelity markers. When applied in practice, aberrant FCM patterns correlate well with morphology, the subclassification of myelodysplastic syndromes, and prognostic scoring systems. However, the group also concluded that despite strong evidence for an impact of FCM in myelodysplastic syndromes, further (prospective) validation of markers and immunophenotypic patterns are required against control patient groups as well as further standardization in multi-center studies. Standardization of FCM in myelodysplastic syndromes may thus contribute to improved diagnosis and prognostication of myelodysplastic syndromes in the future.

Rodrigues NP, Boyd AS, Fugazza C, May GE, Guo Y, Tipping AJ, Scadden DT, Vyas P, Enver T. 2008. GATA-2 regulates granulocyte-macrophage progenitor cell function. Blood, 112 (13), pp. 4862-4873. | Show Abstract | Read more

The zinc finger transcription factor GATA-2 has been implicated in the regulation of hematopoietic stem cells. Herein, we explored the role of GATA-2 as a candidate regulator of the hematopoietic progenitor cell compartment. We showed that bone marrow from GATA-2 heterozygote (GATA-2(+/-)) mice displayed attenuated granulocyte-macrophage progenitor function in colony-forming cell (CFC) and serial replating CFC assays. This defect was mapped to the Lin(-)CD117(+)Sca-1(-)CD34(+)CD16/32(high) granulocyte-macrophage progenitor (GMP) compartment of GATA-2(+/-) marrow, which was reduced in size and functionally impaired in CFC assays and competitive transplantation. Similar functional impairments were obtained using a RNA interference approach to stably knockdown GATA-2 in wild-type GMP. Although apoptosis and cell-cycle distribution remained unperturbed in GATA-2(+/-) GMP, quiescent cells from GATA-2(+/-) GMP exhibited altered functionality. Gene expression analysis showed attenuated expression of HES-1 mRNA in GATA-2-deficient GMP. Binding of GATA-2 to the HES-1 locus was detected in the myeloid progenitor cell line 32Dcl3, and enforced expression of HES-1 expression in GATA-2(+/-) GMP rectified the functional defect, suggesting that GATA-2 regulates myeloid progenitor function through HES-1. These data collectively point to GATA-2 as a novel, pivotal determinant of GMP cell fate.

Tunstall-Pedoe O, Roy A, Karadimitris A, de la Fuente J, Fisk NM, Bennett P, Norton A, Vyas P, Roberts I. 2008. Abnormalities in the myeloid progenitor compartment in Down syndrome fetal liver precede acquisition of GATA1 mutations. Blood, 112 (12), pp. 4507-4511. | Show Abstract | Read more

Down syndrome (DS) children have a high frequency of acute megakaryoblastic leukemia (AMKL) in early childhood. At least 2 in utero genetic events are required, although not sufficient, for DS-AMKL: trisomy 21 (T21) and N-terminal-truncating GATA1 mutations. To investigate the role of T21 in DS-AMKL, we compared second trimester hemopoiesis in DS without GATA1 mutations to gestation-matched normal controls. In all DS fetal livers (FLs), but not marrows, megakaryocyte-erythroid progenitor frequency was increased (55.9% +/- 4% vs 17.1% +/- 3%, CD34(+)CD38(+) cells; P < .001) with common myeloid progenitors (19.6% +/- 2% vs 44.0% +/- 7%) and granulocyte-monocyte (GM) progenitors (15.8% +/- 4% vs 34.5% +/- 9%) commensurately reduced. Clonogenicity of DS-FL versus normal FL CD34(+) cells was markedly increased (78% +/- 7% vs 15% +/- 3%) affecting megakaryocyte-erythroid ( approximately 7-fold higher) and GM and colony-forming unit-granulocyte, erythrocyte macrophage, megakaryocyte (CFU-GEMM) progenitors. Replating efficiency of CFU-GEMM was also markedly increased. These data indicate that T21 itself profoundly disturbs FL hemopoiesis and they provide a testable hypothesis to explain the increased susceptibility to GATA1 mutations in DS-AMKL and DS-associated transient myeloproliferative disorder.

Hamlett I, Draper J, Strouboulis J, Iborra F, Porcher C, Vyas P. 2008. Characterization of megakaryocyte GATA1-interacting proteins: the corepressor ETO2 and GATA1 interact to regulate terminal megakaryocyte maturation. Blood, 112 (7), pp. 2738-2749. | Show Abstract | Read more

The transcription factor GATA1 coordinates timely activation and repression of megakaryocyte gene expression. Loss of GATA1 function results in excessive megakaryocyte proliferation and disordered terminal platelet maturation, leading to thrombocytopenia and leukemia in patients. The mechanisms by which GATA1 does this are unclear. We have used in vivo biotinylated GATA1 to isolate megakaryocyte GATA1-partner proteins. Here, several independent approaches show that GATA1 interacts with several proteins in the megakaryocyte cell line L8057 and in primary megakaryocytes. They include FOG1, the NURD complex, the pentameric complex containing SCL/TAL-1, the zinc-finger regulators GFI1B and ZFP143, and the corepressor ETO2. Knockdown of ETO2 expression promotes megakaryocyte differentiation and enhances expression of select genes expressed in terminal megakaryocyte maturation, eg, platelet factor 4 (Pf4). ETO2-dependent direct repression of the Pf4 proximal promoter is mediated by GATA-binding sites and an E-Box motif. Consistent with this, endogenous ETO2, GATA1, and the SCL pentameric complex all specifically bind the promoter in vivo. Finally, as ETO2 expression is restricted to immature megakaryocytes, these data suggest that ETO2 directly represses inappropriate early expression of a subset of terminally expressed megakaryocyte genes by binding to GATA1 and SCL.

Kassouf MT, Chagraoui H, Vyas P, Porcher C. 2008. Differential use of SCL/TAL-1 DNA-binding domain in developmental hematopoiesis. Blood, 112 (4), pp. 1056-1067. | Show Abstract | Read more

Dissecting the molecular mechanisms used by developmental regulators is essential to understand tissue specification/differentiation. SCL/TAL-1 is a basic helix-loop-helix transcription factor absolutely critical for hematopoietic stem/progenitor cell specification and lineage maturation. Using in vitro and forced expression experimental systems, we previously suggested that SCL might have DNA-binding-independent functions. Here, to assess the requirements for SCL DNA-binding activity in vivo, we examined hematopoietic development in mice carrying a germline DNA-binding mutation. Remarkably, in contrast to complete absence of hematopoiesis and early lethality in scl-null embryos, specification of hematopoietic cells occurred in homozygous mutant embryos, indicating that direct DNA binding is dispensable for this process. Lethality was forestalled to later in development, although some mice survived to adulthood. Anemia was documented throughout development and in adulthood. Cellular and molecular studies showed requirements for SCL direct DNA binding in red cell maturation and indicated that scl expression is positively autoregulated in terminally differentiating erythroid cells. Thus, different mechanisms of SCL's action predominate depending on the developmental/cellular context: indirect DNA binding activities and/or sequestration of other nuclear regulators are sufficient in specification processes, whereas direct DNA binding functions with transcriptional autoregulation are critically required in terminal maturation processes.

Hasle H, Abrahamsson J, Arola M, Karow A, O'Marcaigh A, Reinhardt D, Webb DK, van Wering E, Zeller B, Zwaan CM, Vyas P. 2008. Myeloid leukemia in children 4 years or older with Down syndrome often lacks GATA1 mutation and cytogenetics and risk of relapse are more akin to sporadic AML. Leukemia, 22 (7), pp. 1428-1430. | Read more

Thomson D, Vyas P, Hammersley MS. 2008. Cerebral venous sinus thrombosis in polycythaemia. Br J Hosp Med (Lond), 69 (3), pp. 170. | Read more

Vyas P, Crispino J. 2008. JAK mutations in Down syndrome - associated transient myeloproliferative disorder and acute megakaryocytic leukemia BLOOD, 111 (4), pp. 2493-2493. | Read more

Zwaan MC, Reinhardt D, Hitzler J, Vyas P. 2008. Acute leukemias in children with Down syndrome. Pediatr Clin North Am, 55 (1), pp. 53-x. | Show Abstract | Read more

Children with Down syndrome have an increased risk for developing both acute myeloid as well as lymphoblastic leukemia. These leukemias differ in presenting characteristics and underlying biology when compared with leukemias occurring in non-Down syndrome children. Myeloid leukemia in children with Down syndrome is preceded by a preleukemic clone (transient leukemia or transient myeloproliferative disorder), which may disappear spontaneously, but may also need treatment in case of severe symptoms. Twenty percent of children with transient leukemia subsequently develop myeloid leukemia. This transition offers a unique model to study the stepwise development of leukemia, and of gene dosage effects mediated by aneuploidy.

Webb D, Roberts I, Vyas P. 2007. Haematology of Down syndrome. Arch Dis Child Fetal Neonatal Ed, 92 (6), pp. F503-F507. | Show Abstract | Read more

Down syndrome is a common congenital disorder affecting approximately 1/1000 live births. Newborns and children with Down syndrome may present with many haematological problems. In addition, benign abnormalities of the blood count and blood film, which may manifest at any age, population-based and cancer-based registries and clinical trials suggest there is a approximately 12-fold increased risk of acute lymphoblastic leukaemia in the age group of 5-30 years that rises to approximately 40-fold in children younger than 5 years, and that there is a approximately 150-fold increased risk of acute myeloid leukaemia in children younger than 5 years. There is also a virtually unique predisposition to a transient neonatal leukaemia, known as transient abnormal myelopoiesis. Deaths from leukaemia, in part, account for the excess mortality associated with Down syndrome. This article reviews the clinical presentation and the progress made in the management of these disorders over the past decade. It also briefly considers the recent exciting scientific advances that have potential to transform management of leukaemia in children with Down syndrome and also have implications for management of childhood leukaemia more generally.

Norton A, Fisher C, Liu H, Wen Q, Mundschau G, Fuster JL, Hasle H, Zeller B, Webb DK, O'Marcaigh A et al. 2007. Analysis of JAK3, JAK2, and C-MPL mutations in transient myeloproliferative disorder and myeloid leukemia of Down syndrome blasts in children with Down syndrome. Blood, 110 (3), pp. 1077-1079. | Read more

Heald B, Hilden JM, Zbuk K, Norton A, Vyas P, Theil KS, Eng C. 2007. Severe TMD/AMKL with GATA1 mutation in a stillborn fetus with Down syndrome. Nat Clin Pract Oncol, 4 (7), pp. 433-438. | Show Abstract | Read more

BACKGROUND: A 34-year-old woman was referred for evaluation of a recent stillborn male fetus, gestational age 27 6/7 weeks, found to have congenital myeloid leukemia at autopsy. Autopsy findings included high weight for gestational age, hepatomegaly, and extensive intravascular leukemic infiltrates in the placenta, heart, liver, thymus, lung, kidneys, and brain. Genetic consultation and examination of photographs of the fetus revealed dysmorphic features. INVESTIGATIONS: Immunoperoxidase staining of placental tissue, fluorescence in situ hybridization of paraffin-embedded sections of the placenta using probes for t(12;21)(p13;q22), t(8;21)(q22;q22) and t/del(11q23), cytogenetic analysis of fetal tissue (tendon), sequence analysis of GATA1 in placental leukemic cells, and parental chromosome studies. DIAGNOSIS: Down syndrome with in utero onset of GATA1 mutation-positive severe transient myeloproliferative disorder/acute megakaryoblastic leukemia. MANAGEMENT: Genetic counseling for the recurrence risk of Down syndrome on the basis of maternal age.

Gyan E, Sternberg A, Leclercq-Cardus S, Willems L, Cagnard N, Frisan E, Dreyfus F, Lacombe C, Vyas P, Fontenay M. 2007. Endoplasmic reticulum gene expression profile of erythroid progenitors in low risk myelodysplastic syndromes LEUKEMIA RESEARCH, 31 pp. S78-S79. | Read more

Halsey C, Fisher C, Strathdee G, Gibson B, Holyoake T, Vyas P, Graham G. 2007. GATA1 mutational analysis in chronic myeloid leukaemia. Br J Haematol, 137 (4), pp. 375-376. | Read more

Vyas P, Crispino JD. 2007. Molecular insights into Down syndrome-associated leukemia. Curr Opin Pediatr, 19 (1), pp. 9-14. | Show Abstract | Read more

PURPOSE OF REVIEW: Four years ago it was discovered that nearly all cases of transient myeloproliferative disorder and acute megakaryocytic leukemia in children with Down syndrome acquire mutations in the hematopoietic transcription factor gene GATA1. Studies within the past year, described within this review, have provided tremendous insights into the role of GATA1 mutations in these malignancies. RECENT FINDINGS: In the past year, our understanding of the molecular and cellular consequences of GATA1 mutations has been greatly enhanced. Most importantly, we have learned that these mutations, which result in the exclusive production of the short GATA1 isoform named GATA1s, have a distinct effect on fetal liver progenitors. In addition, multiple studies have shown that GATA1s can substitute for GATA1 in many aspects of megakaryocytic maturation. Finally, an important clinical study has revealed that GATA1 mutations alone are insufficient for leukemia. SUMMARY: Leukemia in children with Down syndrome requires at least three cooperating events--trisomy 21, a GATA1 mutation, and a third, as yet undefined, genetic alteration. Recent studies have provided tremendous insights into the GATA1 side of the story. Future experiments with human patient samples and mouse models will likely increase our awareness of the role of trisomy 21 in transient myeloproliferative disorder and acute megakaryocytic leukemia.

Vyas P, Roberts I. 2006. Down myeloid disorders: a paradigm for childhood preleukaemia and leukaemia and insights into normal megakaryopoiesis. Early Hum Dev, 82 (12), pp. 767-773. | Show Abstract | Read more

Newborns and children with Down Syndrome are predisposed to a range of blood disorders, which include acute lymphoblastic leukaemia and acute megakaryocytic leukaemia (AMKL). Over the last four years there has been considerable progress in our understanding of DS AMKL. Like other childhood leukaemias DS AMKL is initiated in utero and can present in the neonatal period as a clinically overt preleukaemic condition, transient myeloproliferative disorder (TMD). In addition to trisomy 21, fetal haemopoietic progenitors acquire N-terminal truncating mutations in the key megakaryocyte-erythroid transcription factor GATA1. These are the minimum required events for TMD to develop. In approximately 30% of TMD patients, additional as yet unidentified (epi)genetic mutations are required for progression to AMKL. Thus, DS TMD and AMKL provide a unique model of childhood leukaemia where the preleukaemic and leukaemic phases are ascertainable and separable allowing distinct steps in leukaemogenesis to be studied individually. These findings also have implications for the clinical management of DS TMD and AMKL specifically and also of childhood leukaemia more generally.

Ahmed MR, Chehal A, Zahed L, Taher A, Haidar J, Shamseddine A, O'Hea AM, Bienz N, Dgany O, Avidan N et al. 2006. Linkage and mutational analysis of the CDAN1 gene reveals genetic heterogeneity in congenital dyserythropoietic anemia type I. Blood, 107 (12), pp. 4968-4969. | Read more

Purbhoo MA, Sutton DH, Brewer JE, Mullings RE, Hill ME, Mahon TM, Karbach J, Jäger E, Cameron BJ, Lissin N et al. 2006. Quantifying and imaging NY-ESO-1/LAGE-1-derived epitopes on tumor cells using high affinity T cell receptors. J Immunol, 176 (12), pp. 7308-7316. | Show Abstract

Presentation of intracellular tumor-associated Ags (TAAs) in the context of HLA class I molecules offers unique cancer-specific cell surface markers for the identification and targeting of tumor cells. For most peptide Ags, the levels of and variations in cell surface presentation remain unknown, yet these parameters are of crucial importance when considering specific TAAs as targets for anticancer therapy. Here we use a soluble TCR with picomolar affinity for the HLA-A2-restricted 157-165 epitope of the NY-ESO-1 and LAGE-1 TAAs to investigate presentation of this immunodominant epitope on the surface of a variety of cancer cells. By single molecule fluorescence microscopy, we directly visualize HLA-peptide presentation for the first time, demonstrating that NY-ESO-1/LAGE-1-positive tumor cells present 10-50 NY-ESO-1/LAGE-1(157-165) epitopes per cell.

Guyot B, Murai K, Fujiwara Y, Valverde-Garduno V, Hammett M, Wells S, Dear N, Orkin SH, Porcher C, Vyas P. 2006. Characterization of a megakaryocyte-specific enhancer of the key hemopoietic transcription factor GATA1. J Biol Chem, 281 (19), pp. 13733-13742. | Show Abstract | Read more

Specification and differentiation of the megakaryocyte and erythroid lineages from a common bipotential progenitor provides a well studied model to dissect binary cell fate decisions. To understand how the distinct megakaryocyte- and erythroid-specific gene programs arise, we have examined the transcriptional regulation of the megakaryocyte erythroid transcription factor GATA1. Hemopoietic-specific mouse (m)GATA1 expression requires the mGata1 enhancer mHS-3.5. Within mHS-3.5, the 3' 179 bp of mHS-3.5 are required for megakaryocyte but not red cell expression. Here, we show mHS-3.5 binds key hemopoietic transcription factors in vivo and is required to maintain histone acetylation at the mGata1 locus in primary megakaryocytes. Analysis of GATA1-LacZ reporter gene expression in transgenic mice shows that a 25-bp element within the 3'-179 bp in mHS-3.5 is critical for megakaryocyte expression. In vitro three DNA binding activities A, B, and C bind to the core of the 25-bp element, and these binding sites are conserved through evolution. Activity A is the zinc finger transcription factor ZBP89 that also binds to other cis elements in the mGata1 locus. Activity B is of particular interest as it is present in primary megakaryocytes but not red cells. Furthermore, mutation analysis in transgenic mice reveals activity B is required for megakaryocyte-specific enhancer function. Bioinformatic analysis shows sequence corresponding to the binding site for activity B is a previously unrecognized motif, present in the cis elements of the Fli1 gene, another important megakaryocyte-specific transcription factor. In summary, we have identified a motif and a DNA binding activity likely to be important in directing a megakaryocyte gene expression program that is distinct from that in red cells.

Ahmed MR, Zaki M, Sabry MA, Higgs D, Vyas P, Wood W, Wickramasinghe SN. 2006. Evidence of genetic heterogeneity in congenital dyserythropoietic anaemia type I. Br J Haematol, 133 (4), pp. 444-445. | Read more

Bourquin JP, Subramanian A, Langebrake C, Reinhardt D, Bernard O, Ballerini P, Baruchel A, Cavé H, Dastugue N, Hasle H et al. 2006. Identification of distinct molecular phenotypes in acute megakaryoblastic leukemia by gene expression profiling. Proc Natl Acad Sci U S A, 103 (9), pp. 3339-3344. | Show Abstract | Read more

Individuals with Down syndrome (DS) are predisposed to develop acute megakaryoblastic leukemia (AMKL), characterized by expression of truncated GATA1 transcription factor protein (GATA1s) due to somatic mutation. The treatment outcome for DS-AMKL is more favorable than for AMKL in non-DS patients. To gain insight into gene expression differences in AMKL, we compared 24 DS and 39 non-DS AMKL samples. We found that non-DS-AMKL samples cluster in two groups, characterized by differences in expression of HOX/TALE family members. Both of these groups are distinct from DS-AMKL, independent of chromosome 21 gene expression. To explore alterations of the GATA1 transcriptome, we used cross-species comparison with genes regulated by GATA1 expression in murine erythroid precursors. Genes repressed after GATA1 induction in the murine system, most notably GATA-2, MYC, and KIT, show increased expression in DS-AMKL, suggesting that GATA1s fail to repress this class of genes. Only a subset of genes that are up-regulated upon GATA1 induction in the murine system show increased expression in DS-AMKL, including GATA1 and BACH1, a probable negative regulator of megakaryocytic differentiation located on chromosome 21. Surprisingly, expression of the chromosome 21 gene RUNX1, a known regulator of megakaryopoiesis, was not elevated in DS-AMKL. Our results identify relevant signatures for distinct AMKL entities and provide insight into gene expression changes associated with these related leukemias.

Vyas P, Sternberg A. 2006. Characterization of the hemopoietic defect in early stages of the myelodysplastic syndromes. Adv Enzyme Regul, 46 (1), pp. 98-112. | Show Abstract | Read more

Myelodysplasia (MDS) is a heterogeneous disorder characterised by bone marrow failure and progression to acute myeloid leukaemia where the molecular and cellular haematopoietic defects are poorly understood. To gain insight into this the pathogenesis of this condition, we analyzed gene expression profiles of bone marrow CD34+ stem/progenitor cells from patients with MDS at a early stage in the disease and compared them with profiles from CD34+ cells from age-matched controls and patients with non-MDS anaemia. Given the heterogeneity of early MDS, a surprisingly consistent finding was decreased expression of B-cell lineage affiliated genes in MDS patients compared to normal controls and samples with non-MDS anaemia. These findings were then confirmed in the original samples and further samples from a new MDS patient group by Taqman Real Time PCR. Flow cytometry on unfractionated marrow from independent samples also demonstrated reduced B-cell progenitors in MDS patients compared to normal controls. These novel findings suggest a common perturbation in early MDS haematopoiesis. They also provide the rationale for a larger study to evaluate the diagnostic utility of reduced B-cell progenitor number as a diagnostic biomarker of early low risk MDS which can pose a diagnostic challenge.

Schuh AH, Tipping AJ, Clark AJ, Hamlett I, Guyot B, Iborra FJ, Rodriguez P, Strouboulis J, Enver T, Vyas P, Porcher C. 2005. ETO-2 associates with SCL in erythroid cells and megakaryocytes and provides repressor functions in erythropoiesis. Mol Cell Biol, 25 (23), pp. 10235-10250. | Show Abstract | Read more

Lineage specification and cellular maturation require coordinated regulation of gene expression programs. In large part, this is dependent on the activator and repressor functions of protein complexes associated with tissue-specific transcriptional regulators. In this study, we have used a proteomic approach to characterize multiprotein complexes containing the key hematopoietic regulator SCL in erythroid and megakaryocytic cell lines. One of the novel SCL-interacting proteins identified in both cell types is the transcriptional corepressor ETO-2. Interaction between endogenous proteins was confirmed in primary cells. We then showed that SCL complexes are shared but also significantly differ in the two cell types. Importantly, SCL/ETO-2 interacts with another corepressor, Gfi-1b, in red cells but not megakaryocytes. The SCL/ETO-2/Gfi-1b association is lost during erythroid differentiation of primary fetal liver cells. Genetic studies of erythroid cells show that ETO-2 exerts a repressor effect on SCL target genes. We suggest that, through its association with SCL, ETO-2 represses gene expression in the early stages of erythroid differentiation and that alleviation/modulation of the repressive state is then required for expression of genes necessary for terminal erythroid maturation to proceed.

Sternberg A, Killick S, Littlewood T, Hatton C, Peniket A, Seidl T, Soneji S, Leach J, Bowen D, Chapman C et al. 2005. Evidence for reduced B-cell progenitors in early (low-risk) myelodysplastic syndrome. Blood, 106 (9), pp. 2982-2991. | Show Abstract | Read more

Early, low-risk International Prognostic Scoring System (IPSS) myelodysplastic syndrome (MDS) is a heterogeneous disorder where the molecular and cellular hematopoietic defects are poorly understood. To gain insight into this condition, we analyzed gene expression profiles of marrow CD34+ progenitor cells from normal-karyotype, low-blast-count MDS patients, age-matched controls, and patients with non-MDS anemia. Given the heterogeneity of early MDS, a surprisingly consistent finding was decreased expression of B-cell lineage-affiliated genes in MDS patients compared with healthy controls and 3 of 5 samples with non-MDS anemia. Both patients with non-MDS anemia with reduced B-cell gene expression were on chemotherapy. In 25 of 27 of the original samples and 9 further MDS samples, Taqman real-time polymerase chain reaction (PCR) confirmed these data. Flow cytometry on unfractionated marrow from independent samples also demonstrated reduced B-cell progenitors in MDS patients compared with healthy controls. These novel findings suggest a common perturbation in early MDS hematopoiesis. They also provide the rationale for a larger study to evaluate the diagnostic utility of reduced B-cell progenitor number as a diagnostic biomarker of early low-risk MDS, which can pose a diagnostic challenge.

Kuhl C, Atzberger A, Iborra F, Nieswandt B, Porcher C, Vyas P. 2005. GATA1-mediated megakaryocyte differentiation and growth control can be uncoupled and mapped to different domains in GATA1. Mol Cell Biol, 25 (19), pp. 8592-8606. | Show Abstract | Read more

The DNA-binding hemopoietic zinc finger transcription factor GATA1 promotes terminal megakaryocyte differentiation and restrains abnormal immature megakaryocyte expansion. How GATA1 coordinates these fundamental processes is unclear. Previous studies of synthetic and naturally occurring mutant GATA1 molecules demonstrate that DNA-binding and interaction with the essential GATA1 cofactor FOG-1 (via the N-terminal finger) are required for gene expression in terminally differentiating megakaryocytes and for platelet production. Moreover, acquired mutations deleting the N-terminal 84 amino acids are specifically detected in megakaryocytic leukemia in human Down syndrome patients. In this study, we have systematically dissected GATA1 domains required for platelet release and control of megakaryocyte growth by ectopically expressing modified GATA1 molecules in primary GATA1-deficient fetal megakaryocyte progenitors. In addition to DNA binding, distinct N-terminal regions, including residues in the first 84 amino acids, promote platelet release and restrict megakaryocyte growth. In contrast, abrogation of GATA1-FOG-1 interaction leads to loss of differentiation, but growth of blocked immature megakaryocytes is controlled. Thus, distinct GATA1 domains regulate terminal megakaryocyte gene expression leading to platelet release and restrain megakaryocyte growth, and these processes can be uncoupled.

Rodrigues NP, Janzen V, Forkert R, Dombkowski DM, Boyd AS, Orkin SH, Enver T, Vyas P, Scadden DT. 2005. Haploinsufficiency of GATA-2 perturbs adult hematopoietic stem-cell homeostasis. Blood, 106 (2), pp. 477-484. | Show Abstract | Read more

The zinc finger transcription factor GATA-2 plays a fundamental role in generating hematopoietic stem-cells in mammalian development. Less well defined is whether GATA-2 participates in adult stem-cell regulation, an issue we addressed using GATA-2 heterozygote mice that express reduced levels of GATA-2 in hematopoietic cells. While GATA-2+/- mice demonstrated decreases in some colony-forming progenitors, the most prominent changes were observed within the stem-cell compartment. Heterozygote bone marrow had a lower abundance of Lin(-)c-kit(+)Sca-1(+)CD34- cells and performed poorly in competitive transplantation and quantitative week-5 cobblestone area-forming cell (CAFC) assays. Furthermore, a stem-cell-enriched population from GATA1+/- marrow was more quiescent and exhibited a greater frequency of apoptotic cells associated with decreased expression of the anti-apoptotic gene Bcl-xL. Yet the self-renewal potential of the +/- stem-cell compartment, as judged by serial transplantations, was unchanged. These data indicate compromised primitive cell proliferation and survival in the setting of a lower GATA-2 gene dose without a change in the differentiation or self-renewal capacity of the stem-cells that remain. Thus, GATA-2 dose regulates adult stem-cell homeostasis by affecting select aspects of stem cell function.

Rodriguez P, Bonte E, Krijgsveld J, Kolodziej KE, Guyot B, Heck AJ, Vyas P, de Boer E, Grosveld F, Strouboulis J. 2005. GATA-1 forms distinct activating and repressive complexes in erythroid cells. EMBO J, 24 (13), pp. 2354-2366. | Show Abstract | Read more

GATA-1 is essential for the generation of the erythroid, megakaryocytic, eosinophilic and mast cell lineages. It acts as an activator and repressor of different target genes, for example, in erythroid cells it represses cell proliferation and early hematopoietic genes while activating erythroid genes, yet it is not clear how both of these functions are mediated. Using a biotinylation tagging/proteomics approach in erythroid cells, we describe distinct GATA-1 interactions with the essential hematopoietic factor Gfi-1b, the repressive MeCP1 complex and the chromatin remodeling ACF/WCRF complex, in addition to the known GATA-1/FOG-1 and GATA-1/TAL-1 complexes. Importantly, we show that FOG-1 mediates GATA-1 interactions with the MeCP1 complex, thus providing an explanation for the overlapping functions of these two factors in erythropoiesis. We also show that subsets of GATA-1 gene targets are bound in vivo by distinct complexes, thus linking specific GATA-1 partners to distinct aspects of its functions. Based on these findings, we suggest a model for the different roles of GATA-1 in erythroid differentiation.

Hellebostad M, Carpenter E, Hasle H, Mitchell C, Vyas P. 2005. GATA1 mutation analysis demonstrates two distinct primary leukemias in a child with down syndrome; implications for leukemogenesis. J Pediatr Hematol Oncol, 27 (7), pp. 408-409. | Read more

Hughan SC, Senis Y, Best D, Thomas A, Frampton J, Vyas P, Watson SP. 2005. Selective impairment of platelet activation to collagen in the absence of GATA1. Blood, 105 (11), pp. 4369-4376. | Show Abstract | Read more

Defects in the X-linked DNA-binding megakaryocyte transcription factor GATA1 cause thrombocytopenia and abnormal platelet function. However, detailed studies of GATA1 function in platelet activation are lacking. Here, we studied platelets from GATA1-deficient mice and from a male patient (S14) with a bleeding diathesis attributed to a single amino acid substitution (R216Q) in the N-terminal GATA1 zinc finger that alters binding to DNA. In both cases there was inhibition of aggregation to collagen and decreased tyrosine phosphorylation of glycoprotein VI (GPVI)-signaling proteins. This effect was more marked in GATA1-deficient murine platelets, where it was associated with a significant reduction in surface GPVI expression. Moreover, both human and murine GATA1-mutant platelets showed reduced adhesion and aggregate formation on a collagen matrix at an intermediate rate of shear, although this could not be accounted solely by the thrombocytopenia and altered GPVI expression, indicating that GATA1 regulates additional factors important for platelet activation under shear. In contrast, there was no inhibition of responses to G protein-coupled receptor agonists in GATA1-perturbed platelets. Our results are consistent with GATA1 regulating some but not all pathways of platelet activation, leading to an impairment of aggregate formation under flow, which cannot be attributed solely to the thrombocytopenia.

Carpenter E, Valverde-Garduno V, Sternberg A, Mitchell C, Roberts I, Vyas P, Vora A. 2005. GATA1 mutation and trisomy 21 are required only in haematopoietic cells for development of transient myeloproliferative disorder. Br J Haematol, 128 (4), pp. 548-551. | Show Abstract | Read more

Trisomy 21 [Down's syndrome (DS)] and mutations in transcription factor GATA1 predispose neonates to a transient myeloproliferative disorder (TMD) and/or acute megakaryocytic leukaemia (AMKL). The role of trisomy 21 in their pathogenesis is unclear. We previously reported two rare neonates without DS who had TMD, one of whom progressed to AMKL. Trisomy 21 was detected only in blood cells at presentation with TMD/AMKL and disappeared with disease resolution. We now show that the blood cells at presentation of TMD harboured GATA1 genomic DNA mutations, suggesting a requirement for trisomy 21 in haematopoietic cells, rather than other cell types, for development of TMD/AMKL.

Valverde-Garduno V, Guyot B, Anguita E, Hamlett I, Porcher C, Vyas P. 2004. Differences in the chromatin structure and cis-element organization of the human and mouse GATA1 loci: implications for cis-element identification. Blood, 104 (10), pp. 3106-3116. | Show Abstract | Read more

Cis-element identification is a prerequisite to understand transcriptional regulation of gene loci. From analysis of a limited number of conserved gene loci, sequence comparison has proved a robust and efficient way to locate cis-elements. Human and mouse GATA1 genes encode a critical hematopoietic transcription factor conserved in expression and function. Proper control of GATA1 transcription is critical in regulating myeloid lineage specification and maturation. Here, we compared sequence and systematically mapped position of DNase I hypersensitive sites, acetylation status of histone H3/H4, and in vivo binding of transcription factors over approximately 120 kilobases flanking the human GATA1 gene and the corresponding region in mice. Despite lying in approximately 10 megabase (Mb) conserved syntenic segment, the chromatin structures of the 2 homologous loci are strikingly different. The 2 previously unidentified hematopoietic cis-elements, one in each species, are not conserved in position and sequence and have enhancer activity in erythroid cells. In vivo, they both bind the transcription factors GATA1, SCL, LMO2, and Ldb1. More broadly, there are both species- and regulatory element-specific patterns of transcription factor binding. These findings suggest that some cis-elements regulating human and mouse GATA1 genes differ. More generally, mouse human sequence comparison may fail to identify all cis-elements.

Fisher C, Steensma D, Janmohamed R, Kaczmarski R, Reilly JT, Vyas P. 2004. Absence of mutations in the key megakaryocyte transcriptional regulator FOG-1 in patients with idiopathic myelofibrosis. Br J Haematol, 126 (5), pp. 750-752. | Read more

Schlaeger TM, Schuh A, Flitter S, Fisher A, Mikkola H, Orkin SH, Vyas P, Porcher C. 2004. Decoding hematopoietic specificity in the helix-loop-helix domain of the transcription factor SCL/Tal-1. Mol Cell Biol, 24 (17), pp. 7491-7502. | Show Abstract | Read more

The helix-loop-helix (HLH) domain is employed by many transcription factors that control cell fate choice in multiple developmental settings. Previously, we demonstrated that the HLH domain of the class II basic HLH (bHLH) protein SCL/Tal-1 is critical for hematopoietic specification. We have now identified residues in this domain that are essential for restoring hematopoietic development to SCL-/- embryonic stem cells and sufficient to convert a muscle-specific HLH domain to one able to rescue hematopoiesis. Most of these critical residues are distributed in the loop of SCL, with one in helix 2. This is in contrast to the case for MyoD, the prototype of class II bHLH proteins, where the loop seems to serve mainly as a linker between the two helices. Among the identified residues, some promote heterodimerization with the bHLH partners of SCL (E12/E47), while others, unimportant for this property, are still crucial for the biological function of SCL. Importantly, the residue in helix 2 specifically promotes interaction with a known partner of SCL, the LIM-only protein LMO2, a finding that strengthens genetic evidence that these proteins interact. Our data highlight the functional complexity of bHLH proteins, provide mechanistic insight into SCL function, and strongly support the existence of an active SCL/LMO2-containing multiprotein complex in early hematopoietic cells.

Guyot B, Valverde-Garduno V, Porcher C, Vyas P. 2004. Deletion of the major GATA1 enhancer HS 1 does not affect eosinophil GATA1 expression and eosinophil differentiation. Blood, 104 (1), pp. 89-91. | Show Abstract | Read more

Expression of the myeloid transcription factor GATA1 is required for early stages of eosinophil differentiation. Defining mechanisms regulating eosinophil GATA1 expression will be important to understand development of this lineage. However, the cis-elements required for eosinophil GATA1 expression are not fully characterized. Previous work identified HS 1 as a major GATA1 enhancer, but its role in eosinophil GATA1 expression is unclear. Here, we show that mouse HS 1 deletion leaves eosinophil GATA1 mRNA expression and eosinophil differentiation unaffected. Chromatin isolated from eosinophils and encompassing HS 1 is weakly enriched for acetylated histones H3/H4. HS 1 deletion does not alter eosinophil GATA1 locus histone acetylation. In eosinophils, GATA1 and CCAAT/enhancer binding protein epsilon (C/EBP epsilon) do not bind HS 1 but bind selectively a cis-element in the first GATA1 intron. Thus, HS 1 is not required for eosinophil GATA1 expression. Instead, this study suggests a previously unsuspected role for the GATA1 intron element for this function.

Ahmed M, Sternberg A, Hall G, Thomas A, Smith O, O'Marcaigh A, Wynn R, Stevens R, Addison M, King D et al. 2004. Natural history of GATA1 mutations in Down syndrome. Blood, 103 (7), pp. 2480-2489. | Show Abstract | Read more

Acquired mutations in megakaryocyte transcription factor GATA1 have recently been reported in Down syndrome (DS), transient myeloproliferative disorder (TMD), and acute megakaryoblastic leukemia (AMKL). To provide novel insight into GATA1 mutations in DS, genomic DNA was assayed from 12 AMKL and 4 TMD cases (including neonatal, prediagnosis samples in 4 of 16), neonatal blood spots from 21 DS children without clinically evident TMD or AMKL, and 62 non-DS cord blood samples, using techniques not previously employed with such samples. GATA1 mutations were present in all TMD and AMKL cases and at birth in 3 of 4 children without known clinical TMD, who later developed AMKL. They were present at birth in 2 of 21 DS neonates, who have not yet, but could still, develop AMKL (now 26 and 31 months). GATA1 mutations were not detected in 62 non-DS cord blood samples. In 4 AMKL patients multiple independent GATA1 mutations were observed. These data show GATA1 mutations occur in utero in most DS TMD and AMKL, that they may occur without clinical signs of disease, and that multiple separate GATA1 mutant clones can occur in an individual. The findings have implications for pathogenesis of DS TMD and AMKL and highlight parallels between DS AMKL and other childhood leukemias.

Gurbuxani S, Vyas P, Crispino JD. 2004. Recent insights into the mechanisms of myeloid leukemogenesis in Down syndrome. Blood, 103 (2), pp. 399-406. | Show Abstract | Read more

GATA-1 is the founding member of a transcription factor family that regulates growth and maturation of a diverse set of tissues. GATA-1 is expressed primarily in hematopoietic cells and is essential for proper development of erythroid cells, megakaryocytes, eosinophils, and mast cells. Although loss of GATA-1 leads to differentiation arrest and apoptosis of erythroid progenitors, absence of GATA-1 promotes accumulation of immature megakaryocytes. Recently, we and others have reported that mutagenesis of GATA1 is an early event in Down syndrome (DS) leukemogenesis. Acquired mutations in GATA1 were detected in the vast majority of patients with acute megakaryoblastic leukemia (DS-AMKL) and in nearly every patient with transient myeloproliferative disorder (TMD), a "preleukemia" that may be present in as many as 10% of infants with DS. Although the precise pathway by which mutagenesis of GATA1 contributes to leukemia is unknown, these findings confirm that GATA1 plays an important role in both normal and malignant hematopoiesis. Future studies to define the mechanism that results in the high frequency of GATA1 mutations in DS and the role of altered GATA1 in TMD and DS-AMKL will shed light on the multistep pathway in human leukemia and may lead to an increased understanding of why children with DS are markedly predisposed to leukemia.

Vyas P, Norris FA, Joseph R, Majerus PW, Orkin SH. 2000. Inositol polyphosphate 4-phosphatase type I regulates cell growth downstream of transcription factor GATA-1. Proc Natl Acad Sci U S A, 97 (25), pp. 13696-13701. | Show Abstract | Read more

Megakaryocytes lacking transcription factor GATA-1 fail to complete maturation in vivo and hyperproliferate. To define how GATA-1 regulates megakaryocyte cell growth we searched for mRNA transcripts expressed in primary wild-type, but not GATA-1(-), megakaryocytes. One differentially expressed transcript encodes inositol polyphosphate 4-phosphatase type I (4-Ptase I). This enzyme hydrolyses phosphatidylinositol 3,4-bisphosphate and also has lesser activity against soluble analogues of this lipid, inositol 3, 4-bisphosphate and inositol 1,3,4-triphosphate. Reintroduction of 4-Ptase I into both primary GATA-1(-) and wild-type megakaryocytes significantly retards cell growth, suggesting that absence of 4-Ptase I may contribute to the hyperproliferative phenotype of GATA-1(-) megakaryocytes. Overexpression of 4-Ptase I also markedly reduces growth of NIH 3T3 fibroblasts. Taken together, these data indicate that 4-Ptase I is a regulator of cell proliferation.

Vyas P, Norris A, Majerus P, Orkin S. 1999. Type 1 inositol polyphosphate-4-phosphatase influences growth of primary megakaryocytes and other cell types and is differentially expressed in the absence of GATA-1. BLOOD, 94 (10), pp. 685A-685A.

Vyas P, Vickers MA, Picketts DJ, Higgs DR. 1995. Conservation of position and sequence of a novel, widely expressed gene containing the major human alpha-globin regulatory element. Genomics, 29 (3), pp. 679-689. | Show Abstract | Read more

We have determined the cDNA and genomic structure of a gene (-14 gene) that lies adjacent to the human alpha-globin cluster. Although it is expressed in a wide range of cell lines and tissues, a previously described erythroid-specific regulatory element that controls expression of the alpha-globin genes lies within intron 5 of this gene. Analysis of the -14 gene promoter shows that it is GC rich and associated with a constitutively expressed DNase 1 hypersensitive site; unlike the alpha-globin promoter, it does not contain a TATA or CCAAT box. These and other differences in promoter structure may explain why the erythroid regulatory element interacts specifically with the alpha-globin promoters and not the -14 gene promoter, which lies between the alpha promoters and their regulatory element. Interspecies comparisons demonstrate that the sequence and location of the -14 gene adjacent to the alpha cluster have been maintained since the bird/mammal divergence, 270 million years ago.

Craddock CF, Vyas P, Sharpe JA, Ayyub H, Wood WG, Higgs DR. 1995. Contrasting effects of alpha and beta globin regulatory elements on chromatin structure may be related to their different chromosomal environments. EMBO J, 14 (8), pp. 1718-1726. | Show Abstract

Expression of the human alpha and beta globin gene clusters is regulated by remote sequences, referred to as HS -40 and the beta-locus control region (beta-LCR) that lie 5-40 kb upstream of the genes they activate. Because of their common ancestry, similar organization and coordinate expression it has often been assumed that regulation of the globin gene clusters by HS -40 and the beta-LCR occurs via similar mechanisms. Using interspecific hybrids containing chromosomes with naturally occurring deletions of HS -40 we have shown that, in contrast to the beta-LCR, this element exerts no discernible effect on long-range chromatin structure and in addition does not influence formation of DNase I hypersensitive sites at the alpha globin promoters. These differences in the behaviour of HS -40 and the beta-LCR may reflect their contrasting influence on gene expression in transgenic mice and may result from the differing requirements of these elements in their radically different, natural chromosomal environments; the alpha cluster lying within a region of constitutively 'open' chromatin and the beta cluster in a segment of chromatin which opens in a tissue-specific manner. Differences in the hierarchical control of the alpha and beta globin clusters may exemplify more general differences in the regulation of eukaryotic genes which lie in similar open or closed chromosomal regions.

Sharpe JA, Wells DJ, Whitelaw E, Vyas P, Higgs DR, Wood WG. 1993. Analysis of the human alpha-globin gene cluster in transgenic mice. Proc Natl Acad Sci U S A, 90 (23), pp. 11262-11266. | Show Abstract | Read more

A 350-bp segment of DNA associated with an erythroid-specific DNase I-hypersensitive site (HS-40), upstream of the alpha-globin gene cluster, has been identified as the major tissue-specific regulator of the alpha-globin genes. However, this element does not direct copy number-dependent or developmentally stable expression of the human genes in transgenic mice. To determine whether additional upstream hypersensitive sites could provide more complete regulation of alpha gene expression we have studied 17 lines of transgenic mice bearing various DNA fragments containing HSs -33, -10, -8, and -4, in addition to HS -40. Position-independent, high-level expression of the human zeta- and alpha-globin genes was consistently observed in embryonic erythroid cells. However, the additional HSs did not confer copy-number dependence, alter the level of expression, or prevent the variable down-regulation of expression in adults. These results suggest that the region upstream of the human alpha-globin genes is not equivalent to that upstream of the beta locus and that although the two clusters are coordinately expressed, there may be differences in their regulation.

Sharpe JA, Summerhill RJ, Vyas P, Gourdon G, Higgs DR, Wood WG. 1993. Role of upstream DNase I hypersensitive sites in the regulation of human alpha globin gene expression. Blood, 82 (5), pp. 1666-1671. | Show Abstract

Erythroid-specific DNase 1 hypersensitive sites have been identified at the promoters of the human alpha-like genes and within the region from 4 to 40 kb upstream of the gene cluster. One of these sites, HS-40, has been shown previously to be the major regulator of tissue-specific alpha-globin gene expression. We have now examined the function of other hypersensitive sites by studying the expression in mouse erythroleukemia (MEL) cells of various fragments containing these sites attached to HS-40 and an alpha-globin gene. High level expression of the alpha gene was observed in all cases. When clones of MEL cells bearing a single copy of the alpha-globin gene fragments were examined, expression levels were similar to those of the endogenous mouse alpha genes and similar to MEL cells bearing beta gene constructs under the control of the beta-globin locus control region. However, there was no evidence that the additional hypersensitive sites increased the level of expression or conferred copy number dependence on the expression of a linked alpha gene in MEL cells.

Vickers MA, Vyas P, Harris PC, Simmons DL, Higgs DR. 1993. Structure of the human 3-methyladenine DNA glycosylase gene and localization close to the 16p telomere. Proc Natl Acad Sci U S A, 90 (8), pp. 3437-3441. | Show Abstract | Read more

We recently reported the presence of four genes lying between the human alpha-globin gene cluster and the telomere of the short arm of chromosome 16 (16p). We now report that one of these genes encodes 3-methyladenine DNA glycosylase, an enzyme important in the repair of DNA after damage by alkylating agents. The gene comprises five exons, representation of which differs in independently isolated cDNA clones. Although the gene is widely expressed, the abundance of its mRNA is considerably higher in a colon adenocarcinoma cell line (HT29) than in other cell lines that were tested. The major positive erythroid-specific regulatory element controlling alpha-globin gene expression lies equidistant between the promoters of the alpha-globin genes and the 3-methyladenine DNA glycosylase gene. Interestingly, in contrast to the alpha-globin genes, expression of the 3-methyladenine DNA glycosylase gene is not influenced by the regulatory element in the human erythroleukemia cell line K562.

Vyas P, Sharpe JA, Watt P, Higgs DR, Wood WG. 1992. Regulation of human embryonic globin genes zeta 2 and epsilon in stably transformed mouse erythroleukemia cells. Blood, 80 (7), pp. 1832-1837. | Show Abstract

Previous work has suggested that the promoter regions of the human embryonic zeta 2 and epsilon globin genes contain negative regulatory regions that could play a role in the repression of these genes in postembryonic erythroblasts. We have examined this possibility by studying the expression of these genes in mouse erythroleukemia cells, an adult erythroid cell line that might be expected to contain repressor molecules that would bind to the putative negative regulatory regions. When attached to appropriate upstream regulatory elements (alpha HS-40 and beta HS1,2) both the zeta and epsilon genes were expressed in these cells at a low level, but no increase in expression was observed when similar constructs lacking the proposed negative regulatory sequences were introduced into these cells. These results cast doubt on the possibility that these sequences play a major role in the developmental repression of the embryonic globin genes, unless they function only in a normal chromosomal organization.

Vyas P, Vickers MA, Simmons DL, Ayyub H, Craddock CF, Higgs DR. 1992. Cis-acting sequences regulating expression of the human alpha-globin cluster lie within constitutively open chromatin. Cell, 69 (5), pp. 781-793. | Show Abstract | Read more

Current models suggest that tissue-specific genes are arranged in discrete, independently controlled segments of chromatin referred to as regulatory domains. Transition from a closed to open chromatin structure may be an important step in the regulation of gene expression. To determine whether the human alpha-globin cluster, like the beta-globin cluster, lies within a discrete, erythroid-specific domain, we have examined the long-range genomic organization and chromatin structure around this region. The alpha genes lie adjacent to at least four widely expressed genes. The major alpha-globin regulatory element lies 40 kb away from the cluster within an intron of one of these genes. Therefore, unlike the beta cluster, cis-acting sequences controlling alpha gene expression are dispersed within a region of chromatin that is open in both erythroid and nonerythroid cells. This implies a difference in the hierarchical control of alpha- and beta-globin expression.

HIGGS D, WOOD W, JARMAN A, VICKERS M, WILKIE A, LAMB J, VYAS P, BENNETT J. 1990. THE ALPHA-THALASSEMIAS ANNALS OF THE NEW YORK ACADEMY OF SCIENCES, 612 pp. 15-22.

Vyas P, Goldstone AH. 1990. Bone marrow transplantation. Practitioner, 234 (1492), pp. 732-734.

Higgs DR, Wood WG, Jarman AP, Vickers MA, Wilkie AO, Lamb J, Vyas P, Bennett JP. 1990. The alpha-thalassemias. Ann N Y Acad Sci, 612 pp. 15-22.

Vyas P, Higgs DR, Weatherall DJ, Dunn D, Serjeant BE, Serjeant GR. 1988. The interaction of alpha thalassaemia and sickle cell-beta zero thalassaemia. Br J Haematol, 70 (4), pp. 449-454. | Show Abstract | Read more

The effects of alpha thalassaemia on sickle cell-beta zero thalassaemia have been studied by comparing haematological and clinical features in four subjects homozygous for alpha thalassaemia 2 (2-gene group), 27 heterozygotes (3-gene group), and 55 with a normal alpha globin gene complement (4-gene group). Alpha thalassaemia was associated with significantly higher haemoglobin levels and lower reticulocyte counts independent of the presence of splenomegaly. Contrary to expectation, alpha thalassaemia was associated with small but significant increases in mean cell volume and mean corpuscular haemoglobin concentration. Splenomegaly at age 5 years and episodes of acute splenic sequestration were significantly more frequent in the 4-gene group. There were no significant differences in painful crises, acute chest syndrome, or other clinical features.

Mettananda S, Fisher CA, Hay D, Badat M, Quek L, Clark K, Hublitz P, Downes D, Kerry J, Gosden M et al. 2017. Editing an α-globin enhancer in primary human hematopoietic stem cells as a treatment for β-thalassemia. Nat Commun, 8 (1), pp. 424. | Show Abstract | Read more

β-Thalassemia is one of the most common inherited anemias, with no effective cure for most patients. The pathophysiology reflects an imbalance between α- and β-globin chains with an excess of free α-globin chains causing ineffective erythropoiesis and hemolysis. When α-thalassemia is co-inherited with β-thalassemia, excess free α-globin chains are reduced significantly ameliorating the clinical severity. Here we demonstrate the use of CRISPR/Cas9 genome editing of primary human hematopoietic stem/progenitor (CD34+) cells to emulate a natural mutation, which deletes the MCS-R2 α-globin enhancer and causes α-thalassemia. When edited CD34+ cells are differentiated into erythroid cells, we observe the expected reduction in α-globin expression and a correction of the pathologic globin chain imbalance in cells from patients with β-thalassemia. Xenograft assays show that a proportion of the edited CD34+ cells are long-term repopulating hematopoietic stem cells, demonstrating the potential of this approach for translation into a therapy for β-thalassemia.β-thalassemia is characterised by the presence of an excess of α-globin chains, which contribute to erythrocyte pathology. Here the authors use CRISP/Cas9 to reduce α-globin expression in hematopoietic precursors, and show effectiveness in xenograft assays in mice.

Khan N, Hills RK, Knapper S, Steadman L, Qureshi U, Rector JL, Bradbury C, Russell NH, Vyas P, Burnett AK et al. 2016. Normal Hematopoietic Progenitor Subsets Have Distinct Reactive Oxygen Species, BCL2 and Cell-Cycle Profiles That Are Decoupled from Maturation in Acute Myeloid Leukemia. PLoS One, 11 (9), pp. e0163291. | Show Abstract | Read more

In acute myeloid leukemia (AML) quiescence and low oxidative state, linked to BCL2 mitochondrial regulation, endow leukemic stem cells (LSC) with treatment-resistance. LSC in CD34+ and more mature CD34- AML have heterogeneous immunophenotypes overlapping with normal stem/progenitor cells (SPC) but may be differentiated by functional markers. We therefore investigated the oxidative/reactive oxygen species (ROS) profile, its relationship with cell-cycle/BCL2 for normal SPC, and whether altered in AML and myelodysplasia (MDS). In control BM (n = 24), ROS levels were highest in granulocyte-macrophage progenitors (GMP) and CD34- myeloid precursors but megakaryocyte-erythroid progenitors had equivalent levels to CD34+CD38low immature-SPC although they were ki67high. BCL2 upregulation was specific to GMPs. This profile was also observed for CD34+SPC in MDS-without-excess-blasts (MDS-noEB, n = 12). Erythroid CD34- precursors were, however, abnormally ROS-high in MDS-noEB, potentially linking oxidative stress to cell loss. In pre-treatment AML (n = 93) and MDS-with-excess-blasts (MDS-RAEB) (n = 14), immunophenotypic mature-SPC had similar ROS levels to co-existing immature-SPC. However ROS levels varied between AMLs; Flt3ITD+/NPM1wild-type CD34+SPC had higher ROS than NPM1mutated CD34+ or CD34- SPC. An aberrant ki67lowBCL2high immunophenotype was observed in CD34+AML (most prominent in Flt3ITD AMLs) but also in CD34- AMLs and MDS-RAEB, suggesting a shared redox/pro-survival adaptation. Some patients had BCL2 overexpression in CD34+ ROS-high as well as ROS-low fractions which may be indicative of poor early response to standard chemotherapy. Thus normal SPC subsets have distinct ROS, cell-cycle, BCL2 profiles that in AML /MDS-RAEB are decoupled from maturation. The combined profile of these functional properties in AML subpopulations may be relevant to differential treatment resistance.

Craddock C, Houlton AE, Quek LS, Ferguson P, Gbandi E, Roberts C, Metzner M, Garcia-Martin N, Kennedy A, Hamblin A et al. 2017. Outcome of Azacitidine Therapy in Acute Myeloid Leukemia is not Improved by Concurrent Vorinostat Therapy but is Predicted by a Diagnostic Molecular Signature. Clin Cancer Res, | Show Abstract | Read more

Purpose: Azacitidine (AZA) is a novel therapeutic option in older patients with acute myeloid leukemia (AML) but its rational utilization is compromised by the fact that neither the determinants of clinical response nor its mechanism of action are defined. Co-administration of histone deacetylase inhibitors, such as vorinostat (VOR), is reported to improve the clinical activity of AZA but this has not been prospectively studied in AML. Experimental Design: We compared outcomes in 259 adults with AML (n=217) and MDS (n=42) randomized to receive either AZA monotherapy (75 mg/m(2) × seven days every 28 days) or AZA combined with VOR 300 mg bd on days 3-9 po. Next generation sequencing was performed in 250 patients on 41 genes commonly mutated in AML. Serial immunophenotyping of progenitor cells was performed in 47 patients. Results: Co-administration of VOR did not increase the overall response rate (P=0.84) or overall survival (OS) (P=0.32). Specifically, no benefit was identified in either de novo or relapsed AML. Mutations in the genes CDKN2A (P=0.0001), IDH1 (P=0.004) and TP53 (P=0.003) was associated with reduced OS. Lymphoid multi-potential progenitor populations were greatly expanded at diagnosis and although reduced in size in responding patients remained detectable throughout treatment. Conclusion: This study demonstrates no benefit of concurrent administration of VOR with AZA but identifies a mutational signature predictive of outcome after AZA based therapy. The correlation between heterozygous loss of function CDKN2A mutations and decreased OS implicates induction of cell cycle arrest as a mechanism by which AZA exerts its clinical activity.

Amatangelo MD, Quek L, Shih A, Stein EM, Roshal M, David MD, Marteyn B, Farnoud NR, de Botton S, Bernard OA et al. 2017. Enasidenib induces acute myeloid leukemia cell differentiation to promote clinical response. Blood, 130 (6), pp. 732-741. | Show Abstract | Read more

Recurrent mutations at R140 and R172 in isocitrate dehydrogenase 2 (IDH2) occur in many cancers, including ∼12% of acute myeloid leukemia (AML). In preclinical models these mutations cause accumulation of the oncogenic metabolite R-2-hydroxyglutarate (2-HG) and induce hematopoietic differentiation block. Single-agent enasidenib (AG-221/CC-90007), a selective mutant IDH2 (mIDH2) inhibitor, produced an overall response rate of 40.3% in relapsed/refractory AML (rrAML) patients with mIDH2 in a phase 1 trial. However, its mechanism of action and biomarkers associated with response remain unclear. Here, we measured 2-HG, mIDH2 allele burden, and co-occurring somatic mutations in sequential patient samples from the clinical trial and correlated these with clinical response. Furthermore, we used flow cytometry to assess inhibition of mIDH2 on hematopoietic differentiation. We observed potent 2-HG suppression in both R140 and R172 mIDH2 AML subtypes, with different kinetics, which preceded clinical response. Suppression of 2-HG alone did not predict response, because most nonresponding patients also exhibited 2-HG suppression. Complete remission (CR) with persistence of mIDH2 and normalization of hematopoietic stem and progenitor compartments with emergence of functional mIDH2 neutrophils were observed. In a subset of CR patients, mIDH2 allele burden was reduced and remained undetectable with response. Co-occurring mutations in NRAS and other MAPK pathway effectors were enriched in nonresponding patients, consistent with RAS signaling contributing to primary therapeutic resistance. Together, these data support differentiation as the main mechanism of enasidenib efficacy in relapsed/refractory AML patients and provide insight into resistance mechanisms to inform future mechanism-based combination treatment studies.

Stein EM, DiNardo CD, Pollyea DA, Fathi AT, Roboz GJ, Altman JK, Stone RM, DeAngelo DJ, Levine RL, Flinn IW et al. 2017. Enasidenib in mutant IDH2 relapsed or refractory acute myeloid leukemia. Blood, 130 (6), pp. 722-731. | Show Abstract | Read more

Recurrent mutations in isocitrate dehydrogenase 2 (IDH2) occur in ∼12% of patients with acute myeloid leukemia (AML). Mutated IDH2 proteins neomorphically synthesize 2-hydroxyglutarate resulting in DNA and histone hypermethylation, which leads to blocked cellular differentiation. Enasidenib (AG-221/CC-90007) is a first-in-class, oral, selective inhibitor of mutant-IDH2 enzymes. This first-in-human phase 1/2 study assessed the maximum tolerated dose (MTD), pharmacokinetic and pharmacodynamic profiles, safety, and clinical activity of enasidenib in patients with mutant-IDH2 advanced myeloid malignancies. We assessed safety outcomes for all patients and clinical efficacy in the largest patient subgroup, those with relapsed or refractory AML, from the phase 1 dose-escalation and expansion phases of the study. In the dose-escalation phase, an MTD was not reached at doses ranging from 50 to 650 mg per day. Enasidenib 100 mg once daily was selected for the expansion phase on the basis of pharmacokinetic and pharmacodynamic profiles and demonstrated efficacy. Grade 3 to 4 enasidenib-related adverse events included indirect hyperbilirubinemia (12%) and IDH-inhibitor-associated differentiation syndrome (7%). Among patients with relapsed or refractory AML, overall response rate was 40.3%, with a median response duration of 5.8 months. Responses were associated with cellular differentiation and maturation, typically without evidence of aplasia. Median overall survival among relapsed/refractory patients was 9.3 months, and for the 34 patients (19.3%) who attained complete remission, overall survival was 19.7 months. Continuous daily enasidenib treatment was generally well tolerated and induced hematologic responses in patients for whom prior AML therapy had failed. Inducing differentiation of myeloblasts, not cytotoxicity, seems to drive the clinical efficacy of enasidenib. This trial was registered at www.clinicaltrials.gov as #NCT01915498.

Quek L, Otto GW, Garnett C, Lhermitte L, Karamitros D, Stoilova B, Lau IJ, Doondeea J, Usukhbayar B, Kennedy A et al. 2016. Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage. J Exp Med, 213 (8), pp. 1513-1535. | Show Abstract | Read more

Our understanding of the perturbation of normal cellular differentiation hierarchies to create tumor-propagating stem cell populations is incomplete. In human acute myeloid leukemia (AML), current models suggest transformation creates leukemic stem cell (LSC) populations arrested at a progenitor-like stage expressing cell surface CD34. We show that in ∼25% of AML, with a distinct genetic mutation pattern where >98% of cells are CD34(-), there are multiple, nonhierarchically arranged CD34(+) and CD34(-) LSC populations. Within CD34(-) and CD34(+) LSC-containing populations, LSC frequencies are similar; there are shared clonal structures and near-identical transcriptional signatures. CD34(-) LSCs have disordered global transcription profiles, but these profiles are enriched for transcriptional signatures of normal CD34(-) mature granulocyte-macrophage precursors, downstream of progenitors. But unlike mature precursors, LSCs express multiple normal stem cell transcriptional regulators previously implicated in LSC function. This suggests a new refined model of the relationship between LSCs and normal hemopoiesis in which the nature of genetic/epigenetic changes determines the disordered transcriptional program, resulting in LSC differentiation arrest at stages that are most like either progenitor or precursor stages of hemopoiesis.

Ivey A, Hills RK, Simpson MA, Jovanovic JV, Gilkes A, Grech A, Patel Y, Bhudia N, Farah H, Mason J et al. 2016. Assessment of Minimal Residual Disease in Standard-Risk AML. N Engl J Med, 374 (5), pp. 422-433. | Show Abstract | Read more

BACKGROUND: Despite the molecular heterogeneity of standard-risk acute myeloid leukemia (AML), treatment decisions are based on a limited number of molecular genetic markers and morphology-based assessment of remission. Sensitive detection of a leukemia-specific marker (e.g., a mutation in the gene encoding nucleophosmin [NPM1]) could improve prognostication by identifying submicroscopic disease during remission. METHODS: We used a reverse-transcriptase quantitative polymerase-chain-reaction assay to detect minimal residual disease in 2569 samples obtained from 346 patients with NPM1-mutated AML who had undergone intensive treatment in the National Cancer Research Institute AML17 trial. We used a custom 51-gene panel to perform targeted sequencing of 223 samples obtained at the time of diagnosis and 49 samples obtained at the time of relapse. Mutations associated with preleukemic clones were tracked by means of digital polymerase chain reaction. RESULTS: Molecular profiling highlighted the complexity of NPM1-mutated AML, with segregation of patients into more than 150 subgroups, thus precluding reliable outcome prediction. The determination of minimal-residual-disease status was more informative. Persistence of NPM1-mutated transcripts in blood was present in 15% of the patients after the second chemotherapy cycle and was associated with a greater risk of relapse after 3 years of follow-up than was an absence of such transcripts (82% vs. 30%; hazard ratio, 4.80; 95% confidence interval [CI], 2.95 to 7.80; P<0.001) and a lower rate of survival (24% vs. 75%; hazard ratio for death, 4.38; 95% CI, 2.57 to 7.47; P<0.001). The presence of minimal residual disease was the only independent prognostic factor for death in multivariate analysis (hazard ratio, 4.84; 95% CI, 2.57 to 9.15; P<0.001). These results were validated in an independent cohort. On sequential monitoring of minimal residual disease, relapse was reliably predicted by a rising level of NPM1-mutated transcripts. Although mutations associated with preleukemic clones remained detectable during ongoing remission after chemotherapy, NPM1 mutations were detected in 69 of 70 patients at the time of relapse and provided a better marker of disease status. CONCLUSIONS: The presence of minimal residual disease, as determined by quantitation of NPM1-mutated transcripts, provided powerful prognostic information independent of other risk factors. (Funded by Bloodwise and the National Institute for Health Research; Current Controlled Trials number, ISRCTN55675535.).

Mussai F, De Santo C, Abu-Dayyeh I, Booth S, Quek L, McEwen-Smith RM, Qureshi A, Dazzi F, Vyas P, Cerundolo V. 2013. Acute myeloid leukemia creates an arginase-dependent immunosuppressive microenvironment. Blood, 122 (5), pp. 749-758. | Show Abstract | Read more

Acute myeloid leukemia (AML) is the most common acute leukemia in adults and the second most common frequent leukemia of childhood. Patients may present with lymphopenia or pancytopenia at diagnosis. We investigated the mechanisms by which AML causes pancytopenia and suppresses patients' immune response. This study identified for the first time that AML blasts alter the immune microenvironment through enhanced arginine metabolism. Arginase II is expressed and released from AML blasts and is present at high concentrations in the plasma of patients with AML, resulting in suppression of T-cell proliferation. We extended these results by demonstrating an arginase-dependent ability of AML blasts to polarize surrounding monocytes into a suppressive M2-like phenotype in vitro and in engrafted nonobese diabetic-severe combined immunodeficiency mice. In addition, AML blasts can suppress the proliferation and differentiation of murine granulocyte-monocyte progenitors and human CD34(+) progenitors. Finally, the study showed that the immunosuppressive activity of AML blasts can be modulated through small-molecule inhibitors of arginase and inducible nitric oxide synthase, suggesting a novel therapeutic target in AML. The results strongly support the hypothesis that AML creates an immunosuppressive microenvironment that contributes to the pancytopenia observed at diagnosis.

Leung A, Ciau-Uitz A, Pinheiro P, Monteiro R, Zuo J, Vyas P, Patient R, Porcher C. 2013. Uncoupling VEGFA functions in arteriogenesis and hematopoietic stem cell specification. Dev Cell, 24 (2), pp. 144-158. | Show Abstract | Read more

VEGFA signaling is critical for endothelial and hematopoietic stem cell (HSC) specification. However, blood defects resulting from perturbation of the VEGFA pathway are always accompanied by impaired vascular/arterial development. Because HSCs derive from arterial cells, it is unclear whether VEGFA directly contributes to HSC specification. This is an important question for our understanding of how HSCs are formed and for developing their production in vitro. Through knockdown of the regulator ETO2 in embryogenesis, we report a specific decrease in expression of medium/long Vegfa isoforms in somites. This leads to absence of Notch1 expression and failure of HSC specification in the dorsal aorta (DA), independently of vessel formation and arterial specification. Vegfa hypomorphs and isoform-specific (medium/long) morphants not only recapitulate this phenotype but also demonstrate that VEGFA short isoform is sufficient for DA development. Therefore, sequential, isoform-specific VEGFA signaling successively induces the endothelial, arterial, and HSC programs in the DA.

Roy A, Cowan G, Mead AJ, Filippi S, Bohn G, Chaidos A, Tunstall O, Chan JK, Choolani M, Bennett P et al. 2012. Perturbation of fetal liver hematopoietic stem and progenitor cell development by trisomy 21. Proc Natl Acad Sci U S A, 109 (43), pp. 17579-17584. | Show Abstract | Read more

The 40-fold increase in childhood megakaryocyte-erythroid and B-cell leukemia in Down syndrome implicates trisomy 21 (T21) in perturbing fetal hematopoiesis. Here, we show that compared with primary disomic controls, primary T21 fetal liver (FL) hematopoietic stem cells (HSC) and megakaryocyte-erythroid progenitors are markedly increased, whereas granulocyte-macrophage progenitors are reduced. Commensurately, HSC and megakaryocyte-erythroid progenitors show higher clonogenicity, with increased megakaryocyte, megakaryocyte-erythroid, and replatable blast colonies. Biased megakaryocyte-erythroid-primed gene expression was detected as early as the HSC compartment. In lymphopoiesis, T21 FL lymphoid-primed multipotential progenitors and early lymphoid progenitor numbers are maintained, but there was a 10-fold reduction in committed PreproB-lymphoid progenitors and the functional B-cell potential of HSC and early lymphoid progenitor is severely impaired, in tandem with reduced early lymphoid gene expression. The same pattern was seen in all T21 FL samples and no samples had GATA1 mutations. Therefore, T21 itself causes multiple distinct defects in FL myelo- and lymphopoiesis.

Jan M, Snyder TM, Corces-Zimmerman MR, Vyas P, Weissman IL, Quake SR, Majeti R. 2012. Clonal evolution of preleukemic hematopoietic stem cells precedes human acute myeloid leukemia. Sci Transl Med, 4 (149), pp. 149ra118. | Show Abstract | Read more

Given that most bone marrow cells are short-lived, the accumulation of multiple leukemogenic mutations in a single clonal lineage has been difficult to explain. We propose that serial acquisition of mutations occurs in self-renewing hematopoietic stem cells (HSCs). We investigated this model through genomic analysis of HSCs from six patients with de novo acute myeloid leukemia (AML). Using exome sequencing, we identified mutations present in individual AML patients harboring the FLT3-ITD (internal tandem duplication) mutation. We then screened the residual HSCs and detected some of these mutations including mutations in the NPM1, TET2, and SMC1A genes. Finally, through single-cell analysis, we determined that a clonal progression of multiple mutations occurred in the HSCs of some AML patients. These preleukemic HSCs suggest the clonal evolution of AML genomes from founder mutations, revealing a potential mechanism contributing to relapse. Such preleukemic HSCs may constitute a cellular reservoir that should be targeted therapeutically for more durable remissions.

Vyas P, Jacobsen SE. 2011. Clever leukemic stem cells branch out. Cell Stem Cell, 8 (3), pp. 242-244. | Show Abstract | Read more

Individual tumors harbor heterogeneous populations of genetically distinct subclones. Two recent papers in Nature by Notta et al. (2011) and Anderson et al. (2011) reveal genetic heterogeneity in functional leukemic stem cells, which has important implications for how both cancer and normal stem cell populations may adapt to selective pressure.

Goardon N, Marchi E, Atzberger A, Quek L, Schuh A, Soneji S, Woll P, Mead A, Alford KA, Rout R et al. 2011. Coexistence of LMPP-like and GMP-like leukemia stem cells in acute myeloid leukemia. Cancer Cell, 19 (1), pp. 138-152. | Show Abstract | Read more

The relationships between normal and leukemic stem/progenitor cells are unclear. We show that in ∼80% of primary human CD34+ acute myeloid leukemia (AML), two expanded populations with hemopoietic progenitor immunophenotype coexist in most patients. Both populations have leukemic stem cell (LSC) activity and are hierarchically ordered; one LSC population gives rise to the other. Global gene expression profiling shows the LSC populations are molecularly distinct and resemble normal progenitors but not stem cells. The more mature LSC population most closely mirrors normal granulocyte-macrophage progenitors (GMP) and the immature LSC population a previously uncharacterized progenitor functionally similar to lymphoid-primed multipotential progenitors (LMPPs). This suggests that in most cases primary CD34+ AML is a progenitor disease where LSCs acquire abnormal self-renewal potential.

Papaemmanuil E, Cazzola M, Boultwood J, Malcovati L, Vyas P, Bowen D, Pellagatti A, Wainscoat JS, Hellstrom-Lindberg E, Gambacorti-Passerini C et al. 2011. Somatic SF3B1 mutation in myelodysplasia with ring sideroblasts. N Engl J Med, 365 (15), pp. 1384-1395. | Show Abstract | Read more

BACKGROUND: Myelodysplastic syndromes are a diverse and common group of chronic hematologic cancers. The identification of new genetic lesions could facilitate new diagnostic and therapeutic strategies. METHODS: We used massively parallel sequencing technology to identify somatically acquired point mutations across all protein-coding exons in the genome in 9 patients with low-grade myelodysplasia. Targeted resequencing of the gene encoding RNA splicing factor 3B, subunit 1 (SF3B1), was also performed in a cohort of 2087 patients with myeloid or other cancers. RESULTS: We identified 64 point mutations in the 9 patients. Recurrent somatically acquired mutations were identified in SF3B1. Follow-up revealed SF3B1 mutations in 72 of 354 patients (20%) with myelodysplastic syndromes, with particularly high frequency among patients whose disease was characterized by ring sideroblasts (53 of 82 [65%]). The gene was also mutated in 1 to 5% of patients with a variety of other tumor types. The observed mutations were less deleterious than was expected on the basis of chance, suggesting that the mutated protein retains structural integrity with altered function. SF3B1 mutations were associated with down-regulation of key gene networks, including core mitochondrial pathways. Clinically, patients with SF3B1 mutations had fewer cytopenias and longer event-free survival than patients without SF3B1 mutations. CONCLUSIONS: Mutations in SF3B1 implicate abnormalities of messenger RNA splicing in the pathogenesis of myelodysplastic syndromes. (Funded by the Wellcome Trust and others.).

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