The aim of this study was to determine whether the burden of JAK2 V617F allele correlated with major clinical outcomes in patients with polycythemia vera (PV). To this end, we determined JAK2 mutant allele levels in granulocytes of 173 PV patients at diagnosis. The mean (7s.d.) mutant allele burden was 52% (729); 32 patients (18%) had greater than 75% mutant allele. The burden of JAK2 V617F allele correlated with measurements of stimulated erythropoiesis (higher hematocrit, lower mean cell volume, serum ferritin and erythropoietin levels) and myelopoiesis (higher white cell count, neutrophil count and serum lactate dehydrogenase) and with markers of neutrophil activation (elevated leukocyte alkaline phosphatase and PRV-1 expression). As compared to those with less than 25% mutant allele, patients harboring greater than 75% JAK2 V617F allele were at higher relative risk (RR) of presenting larger spleen (RR 4.7; Po0.001) or suffering from pruritus (RR 3.1; Po0.001). In these patients, the risk of requiring chemotherapy (RR 1.8; P ¼ 0.001) or developing major cardiovascular events (RR 7.1; P ¼ 0.003) during follow up were significantly increased. We conclude that a burden of JAK2 V617F allele greater than 75% at diagnosis points to PV patients with high-risk disease.

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BackgroundFifty to sixty percent of patients with essential thrombocythemia harbor the JAK2 V617F mutation. The impact of this mutation on clinical phenotype is still debated. The aim of this study was to evaluate possible correlations between JAK2 V617F mutant allele burden and both clinical presentation and hematologic abnormalities in essential thrombocythemia patients.

Key Points• Differential gene and miRNA expression analysis in PMF granulocytes identifies new biomarkers and putative therapeutic targets.• Activation of the miR-155/ JARID2 axis in PMF CD341 cells results in overproduction of MK precursors.Primary myelofibrosis (PMF) is a myeloproliferative neoplasm characterized by megakaryocyte (MK) hyperplasia, bone marrow fibrosis, and abnormal stem cell trafficking. PMF may be associated with somatic mutations in JAK2, MPL, or CALR. Previous studies have shown that abnormal MKs play a central role in the pathophysiology of PMF. In this work, we studied both gene and microRNA (miRNA) expression profiles in CD34 1 cells from PMF patients. We identified several biomarkers and putative molecular targets such as FGR, LCN2, and OLFM4. By means of miRNA-gene expression integrative analysis, we found different regulatory networks involved in the dysregulation of transcriptional control and chromatin remodeling. In particular, we identified a network gathering several miRNAs with oncogenic potential (eg, miR-155-5p) and targeted genes whose abnormal function has been previously associated with myeloid neoplasms, including JARID2, NR4A3, CDC42, and HMGB3. Because the validation of miRNA-target interactions unveiled JARID2/miR-155-5p as the strongest relationship in the network, we studied the function of this axis in normal and PMF CD34 1 cells. We showed that JARID2 downregulation mediated by miR-155-5p overexpression leads to increased in vitro formation of CD41 1 MK precursors. These findings suggest that overexpression of miR-155-5p and the resulting downregulation of JARID2 may contribute to MK hyperplasia in PMF. (Blood. 2014;124(13):e21-e32)

Association of myeloproliferative neoplasm (MPN) with lymphoproliferative neoplasm (LPN) has been occasionally reported. The aim of this study, which included 353 patients with polycythemia vera and 467 with essential thrombocythemia, was to assess whether the risk of developing LPN is increased in MPN patients. Expected numbers of LPN incident cases were calculated based on 5-year age group, gender, and calendar time -specific cancer incidence rates in the general population of the same area. Standardized incidence ratios were computed to estimate the relative risk of developing LPN. Analyses were carried out for the whole series and then separately for essential thrombocythemia and polycythemia vera, gender, and JAK2V617F genotype. With 4,421 person-years, we found 11 patients developing LPN, including four chronic lymphocytic leukemias, five non -Hodgkin's lymphomas, and two plasma cell disorders, after a median interval time of 68 months from MPN diagnosis. Cumulative risk to develop LPN at 5 and 10 years was 0.93% (95% confidence interval, 0.39-2.22) and 2.96% (95% confidence interval, 1.52-5.72), respectively. There was a 3.44-fold increased risk of LPN compared with the general population, ranging from 2.86 for plasma cell disorder to 12.42 for chronic lymphocytic leukemia; the risk was significantly increased in JAK2V617F mutated patients (5.46-fold) and in males (4.52-fold). The JAK2V617F mutation was found in lymphoid tumor cells in two of three cases evaluated, indicating that, in some patients, LPN originated in a JAK2V617F mutated common lymphoid-myeloid hematopoietic progenitor cell. We conclude that the risk of developing LPN is significantly increased in MPN patients compared with the general population. (Cancer Epidemiol Biomarkers Prev 2009;18(7):2068 -73)