Abstract: Background The JAK2V617F mutation has been associated with constitutive and enhanced activation of neutrophils, while no information is available concerning other leukocyte subtypes. DESIGN AND METHODS: We evaluated correlation of JAK2V617F mutation with the count of circulating basophils, the number of activated CD63(+) basophils, their response in vitro to agonists as well as the effects of a JAK2 inhibitor. RESULTS: We found that basophil count was increased in patients with JAK2V617F -positive myeloproliferative neoplasms, particularly in polycythemia vera (PV), and was correlated to the V617F burden. The burden of V617F allele was similar in PV neutrophils and basophils, while total JAK2 mRNA content was remarkably greater in the latter; however, the content of JAK2 protein in basophils was not increased. Higher number of CD63(+) basophils was found in PV patients compared to healthy subjects and patients with ET or PMF and was correlated to the V617F burden. Ultrastructurally, PV basophils contained an increased number of granules, most of which were empty suggesting cell degranulation in vivo. Ex-vivo experiments revealed that PV basophils were hypersensitive to the priming effect of IL-3 and to f-MLP-induced activation; pre-treatment with a JAK2 inhibitor reduced PV basophil activation. Finally, we found that the number of circulating CD63(+) basophils was significantly greater in patients suffering from aquagenic pruritus, who also showed higher V617F allele burden. Conclusions These data indicate that constitutively activated and hypersensitive basophils circulate at increased number in PV, underscoring a role of JAK2V617F in their abnormal function and, putatively, in pathogenesis of pruritus.
Abstract: ABSTRACT The classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), that include polycythemia vera, essential thrombocythemia and primary myelofibrosis, originate from a stem cell-derived clonal myeloproliferation that manifests itself with variable hematopoietic cell lineage involvement; they are characterized by a high degree of similarities and the chance to transform each to the other and to evolve into acute leukemia. Their molecular pathogenesis has been associated with recurrent acquired mutations in JAK2 and MPL. These discoveries have simplified the diagnostic approach and provided a number of clues to understanding the phenotypic expression of MPNs; furthermore, they represented a framework for developing and/or testing in clinical trials small molecules acting as tyrosine kinase inhibitors. On the other hand, evidence of abnormal epigenetic gene regulation as a mechanism potentially contributing to the pathogenesis and the phenotypic diversity of MPNs is still scanty; however, study of epigenetics in MPNs represents an active field of research. The first clinical trials with epigenetic drugs have been completed recently, while others are still ongoing; results have been variable and at present do not allow any firm conclusion. Novel basic and translational information concerning epigenetic gene regulation in MPNs and the perspectives for therapy will be critically addressed in this review.
Abstract: According to the 2008 World Health Organization classification system for hematologic malignancies, the myeloproliferative neoplasms (MPN) include chronic myelogenous leukemia, polycythemia vera, essential thrombocythemia, primary myelofibrosis, mastocytosis, chronic eosinophilic leukemia-not otherwise specified, chronic neutrophilic leukemia, and "MPN, unclassifiable." All of these clinicopathologic entities are characterized by stem cell-derived clonal myeloproliferation, and their phenotypic diversity is ascribed to the occurrence of distinct oncogenic events. In the last 4 years, new JAK2 and MPL mutations have been added to previously described ABL and KIT mutations as molecular markers of disease in MPN. These discoveries have markedly simplified the approach to clinical diagnosis and have also provided molecular targets for the development of small-molecule drugs. In the current article, the authors provide a clinically oriented overview of MPNs in terms of their molecular pathogenesis, classification, diagnosis, and management.
Abstract: 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.
Abstract: OBJECTIVE: A direct comparison of the incidence and risk factors of major thrombosis in essential thrombocythemia (ET) and polycythemia vera (PV) according to their respective JAK2V617F allele burden is the object of this study. MATERIALS AND METHODS: We compared the rate (%/patients/year) of major thrombosis in 867 ET patients (57% JAK2V617F) with that of 415 PV patients (all JAK2V617F) and examined risk factors. RESULTS: Patients with ET wild-type, ET V617F, and PV showed a rate of thrombosis of 1.4%, 2.1%, and 2.7%/patients/year, respectively. The latter was found to progressively increase according to time of diagnosis. Actuarial probability of arterial and venous thrombosis in the first 5 years of diagnosis was roughly similar in the three groups. While in the subsequent periods, the curves of mutated ET patients diverged from wild-type, and after 10 to 15 years the ET-mutated arm approached PV. CONCLUSION: These findings support the concept of a continuum between ET JAK2 mutated and PV, not only in reference to the hematological phenotype, but also in terms of vascular events.
Abstract: A total of 186 patients with primary myelofibrosis (PMF) were genotyped for JAK2V617F at diagnosis aimed at analyzing the correlation of mutational status and mutated allele burden with outcome variables, including time to anemia, leukocytosis, leukopenia, thrombocytopenia, massive splenomegaly, leukemia, and with overall survival. A total of 127 JAK2V617F-mutated patients (68% of whole series) were divided in quartiles of V617F allele burden. After a median follow-up of 17.2 months, 23 patients died, 15 because of leukemia. A JAK2V617F mutated status did not impact on the rate of leukemia transformation or overall survival. Patients in the lower quartile had shorter time to anemia and leukopenia and did not progress to large splenomegaly. Furthermore, survival was significantly reduced in the lower quartile compared with upper quartiles and JAK2 wild-type patients. In multivariate analysis, factors associated with reduced survival were age, a blast count more than 1%, and a JAK2V617F burden within first quartile. Causes of death in the lower quartile were represented mainly by systemic infections. We conclude that a low JAK2V617F allele burden at diagnosis is preferentially associated with a myelodepletive rather than myeloproliferative phenotype and represents an independent factor associated with shortened survival in patients with PMF.
Abstract: Evidence suggests that the JAK2 V617F mutation is associated with an increased risk of first thrombosis in patients with essential thrombocythemia (ET). Whether this mutation is also a risk factor for recurrent thrombosis is currently unknown. To investigate the impact of the JAK2 V617F mutation on the risk of recurrent thrombosis in patients with ET, we carried out a multicentre retrospective cohort study. We recruited 143 patients with previous arterial (64.4%) or venous major thrombosis (34.8%) or both (0.8%); 98 of them (68.5%) carried the mutation. Thrombosis recurred in 43 of the patients (30%); overall, after adjustment for sex, age, presence of vascular risk factors, and treatment after the first thrombosis, the presence of the JAK2 mutation did not predict recurrence (multivariable hazard ratio, HR, 0.88, 95% CI 0.46-1.68). Indeed, the individuals homozygous for the JAK2 V617F (allele burden >50%) mutation had an increased risk of recurrence in comparison with wild-type patients (HR 6.15, 95% CI 1.51-24.92). In conclusion, a homozygous JAK2 V617F mutation is an independent risk factor for recurrent thrombosis in patients with ET.
Abstract: BACKGROUND: Fifty 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. DESIGN AND METHODS: In this single-center retrospective study, JAK2(V617F) allele load was measured by sensitive quantitative reverse transcriptase polymerase chain reaction (RT-PCR) in the granulocytes of 260 patients diagnosed as having essential thrombocythemia according to WHO criteria. RESULTS: Median V617F allele burden in patients with the mutation (n=165, 63.4%) was 24%, ranging from 1% to 87%; an allele burden greater than 51% was found in 5% of the patients. Older patients presented progressively higher percentages of the V617F allele. Signs of stimulated erythropoiesis and myelopoiesis, as well as higher PRV-1 levels, were found in patients with the mutation, but no linear correlation with load of mutant allele could be ascertained; on the other hand, the frequency of patients with erythropoietin-independent erythroid colonies progressively increased depending on mutant allele load. Splenomegaly and microvessel symptoms were significantly more represented among patients with greater than 50% and 25% JAK2(V617F) allele burden, respectively. Increasing mutant allele load correlated with higher frequency of arterial thrombosis at diagnosis, as confirmed also in multivariate analysis; the relative risk was 3.0 (95% CI 1.3-6.8; p=0.01) in patients having a greater than 25% mutant allele burden. CONCLUSIONS: The JAK2(V617F) mutant allele burden contributes to determining the clinical phenotype in patients with essential thrombocythemia.
Abstract: BACKGROUND: Prior thrombosis is a well-established risk factor for re-thrombosis in polycythemia vera and essential thrombocythemia but scarce data are available on the rate of re-thrombosis and the optimal strategy for prevention of recurrence. DESIGN AND METHODS: We retrospectively estimated the rate of recurrence in a multicenter cohort of 494 patients (poly-cythemia vera/essential thrombocythemia 235/259) with previous arterial (67.6%) or venous thrombosis (31%) or both (1.4%). First thrombosis was cerebrovascular disease in 191 cases, acute coronary syndrome in 106, peripheral arterial thrombosis in 44, and venous thromboembolism in 160. Microcirculatory events were not computed. RESULTS: Thrombosis recurred in 166 patients (33.6%), with an incidence of 7.6% patient-years. Sex, diagnosis (polycythemia vera or essential thrombocythemia), and presence of vascular risk factors did not predict recurrence, whereas age >60 years did (multivariable hazard ratio [HR], 1.67; 95% confidence interval [CI] 1.19-2.32). Increased leukocyte count at the time of the first thrombosis was a risk factor for recurrence in patients <60 years old (HR 3.55; 95% CI 1.02-12.25). Cytoreduction halved the risk in the overall cohort (HR 0.53; 95% CI 0.38-0.73) and the combination with antiplatelet agents or oral anticoagulants was more effective than administration of single drugs. Significant prevention of rethrombosis was independently achieved in patients with venous thromboembolism by both oral anticoagulants (HR 0.32; 95% CI 0.15-0.64) and antiplatelet agents (HR 0.42; 95% CI 0.22-0.77), in those with acute coronary syndrome by cytoreduction (HR 0.30; 95% CI 0.13-0.68), and in those with cerebrovascular disease by antiplatelet agents (HR 0.33; 95% CI 0.16-0.66). The overall incidence of major bleeding was 0.9% patient-years and rose to 2.8% in patients receiving both antiplatelet and anti-vitamin K agents. CONCLUSIONS: In patients with polycythemia vera and essential thrombocythemia, cytoreduction protects against recurrent thrombosis, particularly after acute coronary syndrome. The contemporary use of oral anticoagulants (after venous thromboembolism) or antiplatelet agents (after cerebrovascular disease or venous thromboembolism) further improves the protective effect. Such findings call for prospective studies aimed at investigating whether strategies tailored according to the type of first thrombosis could improve prevention of recurrences.
Abstract: PURPOSE: Established risk factors for thrombosis in essential thrombocythemia (ET) include age and previous vascular events. We aimed to refine this risk stratification by adding baseline leukocytosis. PATIENTS AND METHODS: We enrolled 657 patients with ET followed for a median of 4.5 years who developed 72 major thrombosis. Cox proportional hazard model was performed to analyze the thrombotic risk and to discriminate ET patients with or without thrombosis, multivariable C statistic index was used. We searched for leukocytes cutoff with the best sensitivity and specificity by a receiver operating characteristic curve. RESULTS: Results confirmed that age and prior events are independent risk factors for thrombosis and showed a gradient between baseline leukocytosis and thrombosis. On the contrary, no significant association was found either for JAK2(V617F) allele burden and for other laboratory parameters, including platelet number. In the model with conventional risk factors alone, C statistic ratio for total thrombosis was 0.63 and when leukocytosis was added, the change was small (C = 0.67). In contrast, in younger and asymptomatic patients (low-risk category), C statistic value indicated an high risk for thrombosis in patients with leukocytosis, similar to that calculated in conventionally defined high-risk group (C = 0.65). The best leukocyte cutoff values for predicting the events was found to be 9.4 (x 10(9)/L). CONCLUSION: We suggest to include baseline leukocytosis in the risk stratification of ET patients enrolled in clinical trials.
Abstract: Among 994 patients with essential thrombocythemia (ET) who were genotyped for the MPLW515L/K mutation, 30 patients carrying the mutation were identified (3.0%), 8 of whom also displayed the JAK2V671F mutation. MPLW515L/K patients presented lower hemoglobin levels and higher platelet counts than did wild type (wt) MPL; these differences were highly significant compared with MPLwt/JAK2V617F-positive patients. Reduced hemoglobin and increased platelet levels were preferentially associated with the W515L and W515K alleles, respectively. MPL mutation was a significant risk factor for microvessel disturbances, suggesting platelet hyperreactivity associated with constitutively active MPL; arterial thromboses were increased only in comparison to MPLwt/JAK2wt patients. MPLW515L/K patients presented reduced total and erythroid bone marrow cellularity, whereas the numbers of megakaryocytes, megakaryocytic clusters, and small-sized megakaryocytes were all significantly increased. These data indicate that MPLW515L/K mutations do not define a distinct phenotype in ET, although some differences depended on the JAK2V617F mutational status of the counterpart.
Abstract: Acquired mutations in the juxtamembrane region of MPL (W515K or W515L), the receptor for thrombopoietin, have been described in patients with primary myelofibrosis or essential thrombocythemia, which are chronic myeloproliferative disorders. We have developed a real-time polymerase chain reaction assay for the detection and quantification of MPL mutations that is based on locked nucleic acid fluorescent probes. Mutational analysis was performed using DNA from granulocytes. Reference curves were obtained using cloned fragments of MPL containing either the wild-type or mutated sequence; the predicted sensitivity level was at least 0.1% mutant allele in a wild-type background. None of the 60 control subjects presented with a MPLW515L/K mutation. Of 217 patients with myelofibrosis, 19 (8.7%) harbored the MPLW515 mutation, 10 (52.6%) with the W515L allele. In one case, both the W515L and W515K alleles were detected by real-time polymerase chain reaction. By comparing results obtained with conventional sequencing, no erroneous genotype attribution using real-time polymerase chain reaction was found, whereas one patient considered wild type according to sequence analysis actually harbored a low W515L allele burden. This is a simple, sensitive, and cost-effective procedure for large-scale screening of the MPLW515L/K mutation in patients suspected to have a myeloproliferative disorder. It can also provide a quantitative estimate of mutant allele burden that might be useful for both patient prognosis and monitoring response to therapy.
Abstract: JAK2 and MPL mutations are recurrent in myeloproliferative neoplasms (MPNs). A JAK2 mutation, primarily JAK2V617F, is almost invariably associated with polycythemia vera (PV). However, JAK2V617F also occurs in the majority of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) as well as in a much smaller percentage of those with other MPNs. The mechanism(s) behind this one allele-multiple phenotypes phenomenon has not been fully elucidated. The issue is further confounded by the presence of marked variation in JAK2V617F allele burden among mutation-positive patients. In the current communication, we discuss potential mechanisms for phenotypic diversity among JAK2V617F-positive MPNs as well as review the current literature in regard to genotype-phenotype correlations (that is clinical correlates and prognostic significance) in the context of both the presence or absence of the mutation (ET and PMF) and its allele burden (PV, ET and PMF).
Abstract: To elucidate the role of thrombocytosis, alone or in combination with standard (age, previous cardiovascular events) and novel (leukocytosis, JAK2(V617F) mutational status) risk factors, in the cardiovascular events of essential thrombocythemia (ET), we analyzed a cohort of 1063 patients. We found that a platelet count at diagnosis greater than 1000 x 10(9)/L was associated with significantly lower rate of thrombosis in multivariable analysis and, if combined with leukocytes less than 11 x 10(9)/L, pointed to a "low-risk" category with a rate of thrombosis of 1.59% of patients/year. On the contrary, the highest risk category (thrombosis rate, 2.95% of patients/year) was constituted of patients with leukocytosis, lower platelet count, and a JAK2(V617F) mutated genotype in most cases (77% vs 26% in the low-risk group), independently from standard risk factors. These data challenge the theory that elevated platelet count increases thrombosis risk in ET and suggest prospective clinical trials to support this hypothesis.
Abstract: Constitutive mobilization of CD34(+) cells in patients with primary myelofibrosis (PMF) has been attributed to proteolytic disruption of the CXCR4/SDF-1 axis and reduced CXCR4 expression. We document here that the number of circulating CD34(+)/CXCR4(+) cells in PMF patients, as well as the cellular CXCR4 expression, was directly related to CXCR4 mRNA level and that reduced CXCR4 mRNA level was not due to SDF-1-induced downregulation. To address whether epigenetic regulation contributes to defective CXCR4 expression, we studied the methylation status of the CXCR4 promoter using methylation-specific polymerase chain reaction and methylation-specific sequencing in the JAK2V617F-positive HEL cell line and in CD34(+) cells. We found that CD34(+) cells from PMF patients, unlike those from normal subjects, presented hypermethylation of CXCR4 promoter CpG island 1. Following incubation with the demethylating agent 5-Aza-2'-deoxycytidine (5-AzaD), the percentage of PMF CD34(+) cells expressing CXCR4 increased 3-10 times, whereas CXCR4 mRNA level increased approximately 4 times. 5-AzaD-treated PMF CD34(+) cells displayed almost complete reversal of CpG1 island 1 hypermethylation and showed enhanced migration in vitro in response to SDF-1. These data point to abnormal methylation of the CXCR4 promoter as a mechanism contributing to constitutive migration of CD34(+) cells in PMF. Disclosure of potential conflicts of interest is found at the end of this article.
Abstract: JAK2 617V>F mutation occurs in a homozygous state in 25% to 30% of patients with polycythemia vera (PV) and 2% to 4% with essential thrombocythemia (ET). Whether homozygosity associates with distinct clinical phenotypes is still under debate. This retrospective multicenter study considered 118 JAK2 617V>F homozygous patients (104 PV, 14 ET) whose clinical characteristics were compared with those of 587 heterozygous and 257 wild-type patients. Irrespective of their clinical diagnosis, homozygous patients were older, displayed a higher leukocyte count and hematocrit value at diagnosis, and presented larger spleen volume. Aquagenic pruritus was significantly more common among homozygous PV patients. JAK2 617V>F homozygosity associated with more frequent evolution into secondary myelofibrosis in both PV and ET. After adjustment for sex, age, leukocyte count, and previous thrombosis in a multivariate analysis, homozygous ET patients displayed a significantly higher risk of cardiovascular events (hazard ratio [HR] 3.97, 95% confidence interval [CI] 1.34-11.7; P = .013) than wild-type (HR = 1.0) or heterozygous patients (HR = 1.49). No significant association of JAK2 617V>F homozygosity with thrombosis risk was observed in PV. Finally, JAK2 617V>F homozygous patients were more likely to receive chemotherapy for control of disease. We conclude that JAK2 617V>F homozygosity identifies PV or ET patients with a more symptomatic myeloproliferative disorder and is associated with a higher risk of major cardiovascular events in patients with ET.
Abstract: The clinical and haematological phenotype of patients with myelofibrosis harbouring MPL(W515L/K) mutation has not been thoroughly investigated. Of 217 myelofibrosis subjects, 18 (8.2%) had an MPL mutation, four of which (22%) co-existed with JAK2(V617F) mutation. When compared with MPL wild-type patients, irrespective of JAK2(V617F) status, those with MPL(W515L/K), were more frequently female, were older (61 years vs. 57 years; P = 0.02), presented with more severe anaemia (haemoglobin, 101 g/l vs. 121 g/l; P = 0.002) and were more likely to require regular transfusional support (P = 0.012). These data indicate that MPL mutation in myelofibrosis characterises patients with more severe anaemic phenotype.
Abstract: PURPOSE: We studied the expression of the chemokine receptor CXCR4 on circulating CD34+ cells of patients with myelofibrosis with myeloid metaplasia (MMM), and examined its relationship to the severity of disease. PATIENTS AND METHODS: Surface and intracellular CXCR4 expression were measured flow cytometrically in 84 consecutive MMM patients, 16 patients with polycythemia vera (PV), and 20 healthy subjects. In 23 MMM patients, CXCR4 gene expression level was also quantitated by real time-RT-PCR in CD34+ cells. RESULTS: The expression of CXCR4 on circulating CD34+ cells was significantly reduced in patients with MMM (P<0.001) as compared to normal controls and patients with PV (P=0.01). The levels of CXCR4 mRNA in CD34+ cells were lower in patients with MMM as compared with normal subjects, and were directly correlated with the degree of CXCR4 surface expression, demonstrating that transcriptional defects were the major cause for receptor down-regulation. No statistical association was found between JAK2V617F mutational status and the extent of CXCR4 down-regulation. CXCR4 expression on CD34+ cells inversely correlated with the number of circulating CD34+ cells (R=-0.55; P<0.001), and was severely down-regulated in high risk patients and patients with a high "myelodepletion severity index". CXCR4 down-regulation was associated with advanced patient age, the presence of severe anemia, thrombocytopenia, and degree of bone marrow fibrosis. CONCLUSIONS: Reduced expression of CXCR4 by CD34+ cells is a characteristic of MMM which is associated with the constitutive mobilization of CD34+ cells and occurs in patients with advanced forms of the disease.
Abstract: An acquired JAK2 (V617F)mutation has been found in myeloid cells from most patients with chronic idiopathic myelofibrosis (IM), but whether it occurs in a common myelo-lymphoid, rather than a myeloid-restricted, progenitor cell is still debated. Using a sensitive ARMS assay for the quantitative assessment of JAK2 (V617F)cDNA, we detected the mutation in purified B-, T- and NK-cells from about half of 12 patients studied. These results indicate that involvement of lymphoid lineage in IM may be more frequent than previously supposed.
Abstract: This study was aimed at the characterization of a gene expression signature of the pluripotent hematopoietic CD34(+) stem cell in idiopathic myelofibrosis (IM), which would eventually provide novel pathogenetic insights and/or diagnostic/prognostic information. Aberrantly regulated genes were revealed by transcriptome comparative microarray analysis of normal and IM CD34(+) cells; selected genes were also assayed in granulocytes. One-hundred seventy four differentially expressed genes were identified and in part validated by quantitative polymerase chain reaction. Altered gene expression was corroborated by the detection of abnormally high CD9 or CD164, and low CXCR4, membrane protein expression in IM CD34(+) cells. According to class prediction analysis, a set of eight genes (CD9, GAS2, DLK1, CDH1, WT1, NFE2, HMGA2, and CXCR4) properly recognized IM from normal CD34(+) cells. These genes were aberrantly regulated also in IM granulocytes that could be reliably differentiated from control polycythemia vera and essential thrombocythemia granulocytes in 100% and 81% of cases, respectively. Abnormal expression of HMGA2 and CXCR4 in IM granulocytes was dependent on the presence and the mutational status of JAK2(V617F) mutation. The expression levels of both CD9 and DLK1 were associated with the platelet count, whereas higher WT1 expression levels identified IM patients with more active disease, as revealed by elevated CD34(+) cell count and higher severity score. In conclusion, molecular profiling of IM CD34(+) cells uncovered a limited number of genes with altered expression that, beyond their putative role in disease pathogenesis, are associated with patients' clinical characteristics and may have potential prognostic application.
Abstract: OBJECTIVE: Expression profiling of microRNA (miRNA) was performed in granulocytes isolated from patients with primary myelofibrosis (PMF), with the aim of identifying abnormally expressed miRNAs in comparison with normal subjects or patients with polycythemia vera (PV) or essential thrombocythemia (ET). PATIENTS AND METHODS: Using stem loop-primed reverse transcription and TaqMan quantitative real-time polymerase chain reaction, the expression of 156 mature miRNAs was evaluated using pooled granulocytes from PMF patients, either wild-type or JAK2(617V>F) mutant with >51% allele burden, and control subjects. Differentially expressed miRNAs were then validated on additional control and PMF samples, and also on PV or ET granulocytes. RESULTS: There was a global downregulation of miRNA expression in PMF granulocytes; 60 miRNAs, of 128 called present, displayed differential expression compared to normal samples. Twelve miRNAs, which had been selected based on statistically different expression level, were finally validated. In PMF granulocytes, levels of miR-31, -150, and -95 were significantly lower, while those of miR-190 significantly greater, than control and PV or ET samples; on the other hand, miR-34a, -342, -326, -105, -149, and -147 were similarly reduced in patients with PMF, PV, or ET compared to controls. Increased expression of miR-182 and -183 correlated with JAK2(617V>F) allele burden. Three in silico-predicted putative target genes (DTR, HMGA2, and MYB), showed deregulated expression in PMF granulocytes that correlated with expression level of regulatory miRNA. CONCLUSIONS: A defined miRNA profile distinguishes PMF granulocytes from those of normal subjects and, partially, also from PV or ET patients.
Abstract: 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 (+/-s.d.) mutant allele burden was 52% (+/-29); 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; P<0.001) or suffering from pruritus (RR 3.1; P<0.001). In these patients, the risk of requiring chemotherapy (RR 1.8; P=0.001) or developing major cardiovascular events (RR 7.1; P=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.
Abstract: Few investigators have evaluated the usefulness of the JAK2 V617F mutation for explaining the phenotypic variations and for predicting the risk of major clinical events in primary myelofibrosis (PMF). In a transversal survey we assayed by allele-specific polymerase chain reaction (PCR) the JAK2 V617F mutational status in 304 patients with PMF. Multiple DNA samples were collected prospectively from 64 patients, and a highly sensitive quantitative PCR was used as a confirmatory test. In a longitudinal prospective study we determined the progression rate to clinically relevant outcomes in 174 patients who had JAK2 mutation determined at diagnosis. JAK2 V617F was identified in 63.4% of patients. None of the V617F-negative patients who were sequentially genotyped progressed to become V617F positive, whereas progression rate from heterozygous to homozygous mutation was 10 per 100 patient-years. JAK2 V617F mutation contributed to hemoglobin, aquagenic pruritus, and platelet count variability, whereas homozygous mutation was independently associated with higher white blood cell count, larger spleen size, and greater need for cytoreductive therapies. Adjusting for conventional risk factors, V617F mutation independently predicted the evolution toward large splenomegaly, need of splenectomy, and leukemic transformation. We conclude that JAK2 V617F genotype should be considered in any future risk stratification of patients with PMF.
Abstract: Two murine bipotent erythroid/megakaryocytic cells, the progenitor (MEP) and precursor (PEM) cells, recently have been identified on the basis of the phenotypes of linnegc-kitposSca-1neg CD16/CD32lowCD34low and TER119pos4A5pos or 2D5pos, respectively. However, the functional relationship between these two subpopulations and their placement in the hemopoietic hierarchy is incompletely understood. We compared the biological properties of these subpopulations in marrow and spleen of mice with and without acute or chronic erythroid stress. MEP cells, but not PEM cells, express c-kit, respond to stem cell factor in vitro, and form spleen colonies in vivo. PEM cells comprise up to 50%-70% of the cells in BFU-E-derived colonies but are not present among the progeny of purified MEP cells cultured under erythroid and megakaryocytic permissive conditions. PEM cells increase 10- to 20-fold under acute and chronic stress, whereas MEP cell increases (21%-84%) are observed only in acutely stressed animals. These data suggest that MEP and PEM cells represent distinct cell populations that may exist in an upstream-downstream differentiation relationship under conditions of stress. Whereas the dynamics of both populations are altered by stress induction, the differential response to acute and chronic stress suggests different regulatory mechanisms. A model describing the relationship between MEP, PEM, and common myeloid progenitor cells is presented.
Abstract: A point mutation in the Janus tyrosine kinase 2 (JAK2) gene has been described in patients with chronic myeloproliferative disorders (MPD), but the clinical significance of JAK2(V617F), which may be harbored in either the heterozygote or homozyote status, is still largely undefined. There are indirect suggestions that clinical phenotype and also some biological characteristics are dependent on the mutated allele levels. We have designed and validated in 179 MPD patients an amplification-refractory mutation sequencing PCR assay that allows the relative quantitation of mutated and normal JAK2 mRNAs using dye-labelled mutation-specific primers and capillary electrophoresis. Direct sequencing confirmed the specificity of the assay, which has a detection limit congruent with1% and allowed to identify 9% more JAK2-mutated patients as compared to conventional allele-specific PCR. The mutated mRNA ratio ranged from 5 to 51% in the JAK2(V617F) heterozygote and from 45 to 100% in the homozygote patients. Expression levels of both PRV-1 and NF-E2 gene, previously found to be overexpressed in MPD patients, were significantly correlated to the amount of mutated JAK2 mRNA. We propose that this method might complement current technologies based on genomic DNA analysis, and lead prospectively to a better clinically oriented assessment of the impact of JAK2(V617F) mutation in MPD.
Abstract: Recent studies suggest that extracorporeal photochemotherapy (ECP) may be beneficial in patients with steroid-refractory chronic graft-versus-host disease (cGvHD). However, it is not yet clear whether certain conditions, such as age, mode of onset of cGvHD etc., influence clinical response and whether certain affected organs are more sensitive to ECP than others. We analysed the main clinical and laboratory parameters related to evolution of the disease in 32 steroid-refractory cGvHD patients, to identify any useful response predictors to ECP. ECP affected the course of the disease positively in 78% (25/32) of our cases.
Abstract: The abnormal megakaryocytopoiesis associated with idiopathic myelofibrosis (IM) plays a role in its pathogenesis. Because mice with defective expression of transcription factor GATA-1 (GATA-1(low) mutants) eventually develop myelofibrosis, we investigated the occurrence of GATA-1 abnormalities in IM patients. CD 34(+) cells were purified from 12 IM patients and 8 controls; erythroblasts and megakaryocytes were then obtained from unilineage cultures of CD 34(+) cells. Purified CD 61(+), GPA(+), and CD 34(+) cells from IM patients contained levels of GATA-1, GATA-2, and FOG-1 mRNA, as well as of GATA-2 protein, that were similar to controls. In contrast, CD 61(+) cells from IM patients contained significantly reduced GATA-1 protein. Furthermore, 45% of megakaryocytes in biopsies from IM patients did not stain with anti-GATA-1 antibody, as compared to controls (2%), essential thrombocythemia (4%), or polycythemia vera (11%) patients. Abnormalities in immunoreactivity for FOG-1 were not found, and no mutations in GATA-1 coding sequences were found. The presence of GATA-1(neg) megakaryocytes in bone marrow biopsies was independent of the Val 617 Phe JAK 2 mutation, making it unlikely that a downstream functional relationship exists. We conclude that megakaryocytes from IM patients have reduced GATA-1 content, possibly contributing to disease pathogenesis as in the GATA-1(low) mice and also representing a novel IM-associated marker.
Abstract: Females with the monoclonal type of essential thrombocythaemia (ET), based on the X-chromosome inactivation pattern (XCIP), have previously been shown to present a higher incidence of thrombosis than polyclonal ones. We aimed to assess correlations between XCIP, thrombosis, and three epigenetic markers of ET, namely PRV-1 overexpression, endogenous erythroid colony (EEC) formation, and reduced platelet Mpl content. Fifty-three (60%) of 88 subjects studied had monoclonal myelopoiesis and presented a 32% incidence of major thrombosis compared with 6% of polyclonal subjects (P = 0.009). The frequency of abnormalities of PRV-1, EEC, or Mpl was similar in monoclonal and polyclonal subjects (respectively, 28%, 48%, 75%, and 37%, 27%, 63%), and none of them correlated with thrombosis. We conclude that the exploited epigenetic markers constitute independent phenotypic variations and are not clustered according to monoclonality of myelopoiesis in ET; none of them could serve as a surrogate marker of thrombotic risk in male subjects with ET.
