Oncogenic gene expression and epigenetic remodeling of cis-regulatory elements in ASXL1-mutant chronic myelomonocytic leukemia

Myeloid neoplasms are clonal hematopoietic stem cell disorders driven by the sequential acquisition of recurrent genetic lesions. Truncating mutations in the chromatin remodeler ASXL1 (ASXL1MT) are associated with a high-risk disease phenotype with increased proliferation, epigenetic therapeutic resistance, and poor survival outcomes. We performed a multi-omics interrogation to define gene expression and chromatin remodeling associated with ASXL1MT in chronic myelomonocytic leukemia (CMML). ASXL1MT are associated with a loss of repressive histone methylation and increase in permissive histone methylation and acetylation in promoter regions. ASXL1MT are further associated with de novo accessibility of distal enhancers binding ETS transcription factors, targeting important leukemogenic driver genes. Chromatin remodeling of promoters and enhancers is strongly associated with gene expression and heterogenous among overexpressed genes. These results provide a comprehensive map of the transcriptome and chromatin landscape of ASXL1MT CMML, forming an important framework for the development of novel therapeutic strategies targeting oncogenic cis interactions

Host genetic variation contributes to phenotypic diversity in myeloproliferative disorders

JAK2V617F is an acquired mutation associated with polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). We tested the hypothesis that the paradox of a single disease allele associated with 3 distinctive clinical phenotypes could be explained in part by host-modifying influences. We screened for genetic variation within 4 candidate genes involved in JAK-STAT signaling, including receptors for erythropoietin (EPOR), thrombopoietin (MPL), and granulocyte colony-stimulating factor (GCSFR), and JAK2. We genotyped 32 linkage disequilibrium tag single nucleotide polymorphism (SNP) loci in 179 white patients: 84 had PV, 58 had PMF, and 37 had ET. Genotype-phenotype analysis showed 3 JAK2 SNPs (rs7046736, rs10815148, and rs12342421) to be significantly but reciprocally associated with PV (P \u3c .001 for all; odds ratio = 0.16, 2.72, and 2.46, respectively) and ET (P \u3c .001 for all; odds ratio = 3.05, 0.29, and 0.30, respectively) but not with PMF. Three additional JAK2 SNPs (rs10758669, rs3808850, and rs10974947) and a single EPOR SNP (rs318699) were also significantly associated with PV but not with ET or PMF. Finally, intragene haplotypes in JAK2 were significantly associated with PV only. Thus, host genetic variation may contribute to phenotypic diversity among myeloproliferative disorders, including in the presence of a shared disease allele

Pruritus in polycythemia vera is associated with a lower risk of arterial thrombosis

Among 418 patients with polycythemia vera seen at our institution and in whom pruritus history was recorded, the presence of pruritus at diagnosis was documented in 131 (31%) and its absence in 287 (69%). Pruritus was less frequently reported by smokers (12% vs. 24%; P = 0.004) and diabetics (5% vs. 11%; P = 0.04). The presence of pruritus was associated with a lower rate of arterial thrombosis, both at diagnosis (8% vs. 17%; P = 0.01) and during follow-up (16% vs. 30%; P = 0.003). Multivariable analysis revealed that these associations were independent of other risk factors for thrombosis. High JAK2V617F allele burden clustered with pruritus (P = 0.002) but did not affect thrombosis rates

JAK2V617F mutation and spontaneous megakaryocytic or erythroid colony formation in patients with essential thrombocythaemia (ET) or polycythaemia vera (PV)

The in vitro cultures of erythroid (BFU-E) and megakaryocytic (CFU-Meg) progenitors have been useful diagnostic tools in myeloproliferative disorders (MPD). However, after the discovery of the JAK2V617F mutation, their diagnostic role has been uncertain. In this single-centre retrospective study we analyzed JAK2V617F mutation in 58 ET and 42 PV patients diagnosed according to WHO criteria and compared the results with those of colony forming assays with special emphasis on CFU-Meg growth. 91% of PV and 57% of ET patients had JAK2V617F mutation and they all showed spontaneous BFU-E growth. However, endogenous BFU-E formation was also seen in nine JAK2V617F mutation negative patients displaying also a normal JAK2 exon 12 allele. Endogeneous CFU-Meg colony formation was found in 59% of PV and 53% of the ET patients. A subgroup of ET patients (n=7) displayed sole spontaneous CFU-Meg growth without spontaneous BFU-E growth. They all were JAK2 mutation negative, but one of them had MPL mutation. In conclusion, in vitro cultures of haematopoietic progenitors are sensitive diagnostic tools in the present group of 100 MPD patients revealing also JAK2 mutation negative ET and PV patients displaying sole spontaneous CFU-Meg or BFU-E growth

The presence of JAK2V617F in primary myelofibrosis or its allele burden in polycythemia vera predicts chemosensitivity to hydroxyurea

JAK2V617F-positive patients with essential thrombocythemia, as opposed to their mutation-negative counterparts, require lower doses of hydroxyurea (HU) for control of their platelet count. In the current study, we looked for predictors of HU response in 69 patients with primary myelofibrosis (PMF) and 56 with polycythemia vera (PV). JAK2V617F analysis was performed on bone marrow-derived DNA obtained at or near the time of diagnosis. HU response in PMF was associated with a shorter disease duration (P = 0.008), absence of previous therapy (P = 0.01), older age at diagnosis (P = 0.009), and presence of JAK2V617F (P = 0.02). On multivariable analysis, only the latter retained its significance (48% vs. 8% response in mutation positive vs. negative cases). In PV, JAK2V617F allele burden correlated directly with HU response (P = 0.05) and inversely with daily HU dose in responding patients (P = 0.02). The current study suggests that JAK2V617F presence identifies PMF patients who are likely to respond to HU therapy, and information on its allele burden helps in assigning the optimal starting dose in individual patients with PV

JAK2V617F mutation screening as part of the hypercoagulable work-up in the absence of splanchnic venous thrombosis or overt myeloproliferative neoplasm: assessment of value in a series of 664 consecutive patients

The JAK2V617F mutation is recurrent in polycythemia vera and essential thrombocythemia, which are myeloproliferative neoplasms (MPNs) frequently associated with arterial and/or venous thromboembolism. More recently, the JAK2V617F mutation has been identified as a surrogate marker for subclinical or occult clonal myeloproliferation in patients with splanchnic venous thrombosis. However, information is limited regarding JAK2V617F-associated thrombosis outside the splanchnic district in patients without overt MPN. To address this issue, we retrospectively studied a consecutive series of 664 such patients who experienced thrombotic events characteristic of an MPN (500 with venous thromboembolism, 136 with stroke, and 28 with myocardial infarction at a young age). The JAK2V617F mutation was detected in only 6 (\u3c1.0%) patients (5 with recurrent venous thromboembolism and 1 with stroke), and the mutant allele burden was low in all instances (range, 2.2%-7.5%). None of these 6 patients developed either overt MPN or recurrent thrombosis after a median follow-up of 40 months. We conclude that the prevalence of the JAK2V617F mutation in patients with nonsplanchnic venous thrombosis in the absence of MPN is too low to warrant mutation screening as part of the hypercoagulable work-up. Our study also suggests that the natural history of a JAK2V617F-positive occult MPN might be different from that of a typical MPN