The association of JAK2V617F mutation and leukocytosis with thrombotic events in essential thrombocythemia

IRF4 and IRF8 expression are associated with clinical phenotype and clinico-hematological response to hydroxyurea in essential thrombocythemia

The morbidity and mortality of myeloproliferative neoplasms (MPNs) are primarily caused by arterial and venous complications, progression to myelofibrosis, and transformation to acute leukemia. However, identifying molecular-based biomarkers for risk stratification of patients with MPNs remains a challenge. We have previously shown that interferon regulatory factor-8 (IRF8) and IRF4 serve as tumor suppressors in myeloid cells. In this study, we evaluated the expression of IRF4 and IRF8 and the JAK2V617F mutant allele burden in patients with MPNs. Patients with decreased IRF4 expression were correlated with a more developed MPN phenotype in myelofibrosis (MF) and secondary AML (sAML) transformed from MPNs versus essential thrombocythemia (ET). Negative correlations between the JAK2V617F allele burden and the expression of IRF8 (P < 0.05) and IRF4 (P < 0.001) and between white blood cell (WBC) count and IRF4 expression (P < 0.05) were found in ET patients. IRF8 expression was negatively correlated with the JAK2V617F allele burden (P < 0.05) in polycythemia vera patients. Complete response (CR), partial response (PR), and no response (NR) were observed in 67.5%,10%, and 22.5% of ET patients treated with hydroxyurea (HU), respectively, in 12 months. At 3 months, patients in the CR group showed high IRF4 and IRF8 expression compared with patients in the PR and NR groups. In the 12-month therapy period, low IRF4 and IRF8 expression were independently associated with the unfavorable response to HU and high WBC count. Our data indicate that the expression of IRF4 and IRF8 was associated with the MPN phenotype, which may serve as biomarkers for the response to HU in ET.

Data-driven analysis of JAK2V617F kinetics during interferon-alpha2 treatment of patients with polycythemia vera and related neoplasms

Treatment with PEGylated interferon-alpha2 (IFN) of patients with essential thrombocythemia and polycythemia vera induces major molecular remissions with a reduction in the JAK2V617F allele burden to undetectable levels in a subset of patients. A favorable response to IFN has been argued to depend upon the tumor burden, implying that institution of treatment with IFN should be as early as possible after the diagnosis. However, evidence for this statement is not available. We present a thorough analysis of unique serial JAK2V617F measurements in 66 IFN-treated patients and in 6 untreated patients. Without IFN treatment, the JAK2V617F allele burden increased exponentially with a period of doubling of 1.4 year. During monotherapy with IFN, the JAK2V617F allele burden decreased mono- or bi-exponentially for 33 responders of which 28 patients satisfied both descriptions. Bi-exponential description improved the fits in 19 cases being associated with late JAK2V617F responses. The decay of the JAK2V617F allele burden during IFN treatment was estimated to have half-lives of 1.6 year for the monoexponential response and 1.0 year in the long term for the bi-exponential response. In conclusion, through data-driven analysis of the JAK2V617F allele burden, we provide novel information regarding the JAK2V617F kinetics during IFN-treatment, arguing for early intervention.

Somatic Mutations and Clonal Hematopoiesis: Unexpected Potential New Drivers of Age-Related Cardiovascular Disease

Increasing evidence shows that conventional cardiovascular risk factors are incompletely predictive of cardiovascular disease, particularly in elderly individuals, suggesting that there may still be unidentified causal risk factors. Although the accumulation of somatic DNA mutations is a hallmark of aging, its relevance in cardiovascular disease or other age-related conditions has been, with the exception of cancer, largely unexplored. Here, we review recent clinical and preclinical studies that have identified acquired mutations in hematopoietic stem cells and subsequent clonal hematopoiesis as a new cardiovascular risk factor and a potential major driver of atherosclerosis. Understanding the mechanisms underlying the connection between somatic mutation-driven clonal hematopoiesis and cardiovascular disease will be highly relevant in the context of personalized medicine, as it may provide key information for the design of diagnostic, preventive, or therapeutic strategies tailored to the effects of specific somatic mutations.

Association of JAK2V617F mutation with thrombosis in Indian patients with Philadelphia negative chronic myeloproliferative neoplasms

Background

: It is still a matter of debate regarding the association of JAK2V617F mutation with thrombosis in BCR-ABL negative CMPN patients. The role of JAK2V617F mutation in increasing the thrombotic risk in CMPNs is yet unequivocal.

Aims

: To clarify the contribution of JAK2V617F mutation in thrombosis in CMPN patients.

Settings and Design

This retrospective study was done to evaluate role of JAK2V617F mutation in thrombosis in CMPNs.

Materials and Methods

65 CMPN patients (PV, ET and PMF) were analyzed for JAK2V617F mutation using ARMS-PCR and detailed history of thrombosis was recorded in these patients.

Statistical Analysis

P values were 2 tailed, and statistical significance was set at P < 0.05.

Results

: 46/65 were males and 19/65 were females [M: F: 2.4:1] with median age 46 years [range, 14-80 years]. Patients had median Hb 15.6 g/dl [range, 5.1-20.3], median TLC 10.7 × 10⁹/l [range 2.4-216] and platelet count 360 × 10⁹/l [range, 20-1859]. 32 were JAK2V617F positive and 33 were negative for this mutation. On comparing the prevalence of thrombosis in JAK2V617F positive patients with JAK2V617F negative patients, we observed that 20/32 (62.5%) JAK2V617F positive patients had thrombosis as compared to 16/33 (48%) in JAK2V617F negative patients (P = 0.04). We observed significant association of JAK2V617F mutation with thrombosis, however no association of this mutation with thrombosis was observed among the JAK2V617F negative patients.

Conclusion

Our study suggests that JAK2V617F mutation may increase the risk of thrombosis in CMPNs. This finding could lead to risk stratification, setting up the treatment strategy in CMPNs.

The impact of JAK2V617F mutation on different types of thrombosis risk in patients with essential thrombocythemia: a meta-analysis

To assess the effect of JAK2V617F on different thrombotic risks in essential thrombocythemia (ET) patients, we identified eligible studies from several databases including Pubmed, Embase, and Cochrane Central Register of Controlled Trials (up to November 2014). Twenty-two studies of 2922 ET patients were included in exploring the relationship between JAK2V617F and the risk of thrombosis. Compared to JAK2V617F-negative ET patients, JAK2V617F-positive ET patients had higher odd risks (ORs) of arterial thrombosis [OR = 2.59 (1.84-3.65)] and venous thrombosis [OR = 2.10 (1.53-2.88)]. The JAK2V617F-positive group was also more prone to increased risk of microcirculatory disturbances [OR = 1.50 (0.97-2.32)]. Moreover, JAK2V617F may indicate increased risk of either arterial [OR = 1.71 (1.22-2.39)] or venous thrombosis [OR = 2.90 (1.54-5.46)] before diagnosis of ET. During follow-up, JAK2V617F might not be related to arterial thrombosis [OR = 1.90 (0.90-2.08)], but rather venous thrombosis [OR = 1.95 (1.08-3.53)]. In conclusion, JAK2V617F increased the risk of arterial and venous thrombosis in ET patients, while understanding its role in microcirculatory disturbances will require further studies.

The role of Janus kinase 2 (JAK2) in myeloproliferative neoplasms: therapeutic implications

The acquired recurrent mutation, JAK2 V617F, is the most frequent mutation associated with myeloproliferative neoplasms (MPNs). JAK2 signaling is critical in normal hematopoiesis. Studies using genetically engineered mouse models demonstrated a central role of JAK2 V617F in the pathogenesis of MPNs. Data in animal models showed that JAK2 inhibitors target JAK2 V617F kinase and decrease disease burden. Clinical trials demonstrated that JAK1/2 inhibitors ameliorate constitutional symptoms and reduce spleen size in patients with myelofibrosis. However, JAK2 inhibitors have limited ability to reduce JAK2 V617F allele burden or bone marrow fibrosis in humans. JAK2 inhibitor-based combination therapies are being explored.

Platelet-induced thrombin generation by the calibrated automated thrombogram assay is increased in patients with essential thrombocythemia and polycythemia vera

The platelet contribution to the thrombophilic state of patients with myeloproliferative neoplasms (MPNs), i.e., essential thrombocythemia (ET) and polycythemia vera (PV), remains uncertain. In this study we aimed to characterize the thrombin generation (TG) potential expressed by platelets from these subjects, compare it to normal platelets, and identify what factors might be responsible for platelet TG. In a group of 140 MPN patients (80 ET and 60 PV) and 72 healthy subjects, we measured the global procoagulant potential of platelet-rich plasma (PRP) utilizing the TG assay by the calibrated automated thrombogram (CAT). To characterize the procoagulant contribution of platelets in PRP, the TG of both isolated platelets and platelet-poor plasma was measured, and the platelet surface expression of TF was determined. Finally, the activation status of platelets was assessed by the levels of P-selectin expressed on platelet surface. MPN patients had significantly increased PRP and isolated platelet TG potential compared to controls. This was associated to the occurrence of platelet activation. Patients carriers of the JAK2V617F mutation showed the highest values of TG and platelet surface TF and P-selectin. Platelet TG potential was significantly lower in hydroxyurea(HU) compared to non-HU-treated patients and was lowest in HU-treated JAK2V617F carriers. In subjects not receiving HU, platelet TG significantly increased by JAK2V617F allele burden increment (P < 0.05).This study demonstrates a platelet-dependent form of hypercoagulability in MPN patients, particularly in those carriers of the JAK2V617F mutation. The cytoreductive therapy with HU significantly affects this prothrombotic phenotype.

Impact of JAK2V617F mutation on thrombosis and myeloid transformation in essential thrombocythemia: a multivariate analysis by Cox regression in 141 patients

OBJECTIVE

To perform a multivariate analysis by Cox proportional hazard model of the impact of JAK2 V617F mutation on thrombosis and myeloid transformations in patients with essential thrombocythemia (ET).

PATIENTS AND METHODS

The clinicopathologic features and outcome of a cohort of Chinese ET patients were retrospectively reviewed. JAK2 V617F mutation was detected by allele-specific polymerase chain reaction. Potential risk factors including JAK2 V617F that might impact on thrombosis and outcome were studied by multivariate analysis with Cox proportional hazard model.

RESULTS

Of 141 patients studied, JAK2 V617F was found in 80 cases (57%). JAK2 V617F was positively correlated with hemoglobin and leukocyte count at diagnosis. Univariate analysis showed significant thrombotic risks to be JAK2 V617F (P=0.006), hemoglobin >13 g/dl (P=0.015), and age >55 years (P=0.011). However, in multivariate analysis, only age and hemoglobin were independent risk factors. JAK2 V617F was unrelated to survival or leukemic/myelofibrotic transformation.

CONCLUSION

In Chinese patients with ET, JAK2 V617F was positively associated with age, hemoglobin, and leukocyte count, but was not an independent risk for thrombosis.

Prevalence of MPL W515L/K mutations in Taiwanese patients with Philadelphia-negative chronic myeloproliferative neoplasms

BACKGROUND

The discovery of Janus kinase 2 (JAK2)-V617F has provided important insight into the pathogenesis of Philadelphia-negative chronic myeloproliferative neoplasms (Ph-negative MPNs); however, the etiology of JAK2(V617F)-negative Ph-negative MPN remains unidentified. MPL(W515L) and MPL(W515K) (MPL(W515L/K)) are 2 gain-of-function mutations, which have been found in some Ph-negative MPN patients from Western countries. However, little is known about the incidence of these mutations in Taiwanese Ph-negative MPN patients.

METHODS

We determined the MPL sequence of DNA samples from 105 patients, including 88 patients with Ph-negative MPNs and 17 with myelodysplastic syndrome, using polymerase chain reaction amplification of the cytokine receptor MPL exon 10 sequence.

RESULTS

All the patients were normal at codon 515 regardless of their JAK2 status.

CONCLUSION

The MPL W515L/K mutations are rare in Taiwanese patients with Ph-negative MPNs.

Prognostic utility of spontaneous erythroid colony formation and JAK2 mutational analysis for thrombotic events in essential thrombocythaemia

BACKGROUND

Thrombotic events in essential thrombocythaemia (ET) are difficult to predict with current risk stratification based on age and prior history of thrombosis.

AIMS

We aimed to assess the predictive value of the JAK2 V617F mutation (JAK2) and spontaneous erythroid colony (SEC) growth for the development of thrombotic events post diagnosis in patients with ET.

METHODS

Consecutive patients with ET were retrospectively identified, and clinical and laboratory correlates were evaluated. Thrombotic events were categorized according to their occurrence at or prior to diagnosis (prior thrombosis), and any time post diagnosis of ET (subsequent thrombosis). JAK2 analysis was performed by allele-specific PCR on whole blood or bone marrow.

RESULTS

A total of 62 patients was identified, median age 63 years; 67% (41/61) JAK2-positive and 47% (25/53) SEC-positive. Median follow-up was 33 months (range, 1 to 137). JAK2-positive patients showed a trend to increased prior thrombosis (27% vs 5%, P= 0.08), and a significant increase in the development of subsequent thrombosis (5-year event rate 31% vs 6%, P= 0.04), which persisted when stratified for a history of prior thrombosis (P= 0.04). Survival was not affected by JAK2 status. The SEC assay predicted an increased rate of baseline thrombosis (16% vs 0%, P= 0.04), but was not found to be predictive of any subsequent thrombotic events.

CONCLUSIONS

Patients with ET who are JAK2-positive by whole blood allele-specific PCR appear to be at increased risk of thrombotic complications, which is independent of a prior history of thrombosis.

Novel strategies for patients with chronic myeloproliferative disorders

PURPOSE OF REVIEW

This review focuses on new strategies for unmet clinical needs and on new targeted therapies in classical Philadelphia-negative myeloproliferative neoplasms.

RECENT FINDINGS

Meta-analyses in essential thrombocythemia documented Janus kinase 2 (JAK2) V617F as being associated with increased risk of thrombosis. New studies reinforced the evidence of leukocytosis as an independent risk factor for thrombosis in polycythemia vera and essential thrombocythemia. In a phase II trial of pegylated interferon-alpha2a in polycythemia vera patients, a decrease of JAK2 mutant expression to undetectable levels was demonstrated. New trials documented that 5-azacytidine and bortezomib have negligible effect in primary myelofibrosis, whereas thalidomide and tipifarnib produce 22 and 44% response, respectively. In primary myelofibrosis, the JAK2 inhibitor, INCB018424, resulted in a rapid and marked reduction in splenomegaly and a clinical improvement, with a modest effect on JAK2 V617F burden.

SUMMARY

Treating low-risk essential thrombocythemia and polycythemia vera patients presenting with leukocytosis or JAK2 V617F mutation in order to prevent thrombosis deserves a prospective validation. Pursuing clonal remission in polycythemia vera by interferon needs new evidence. Tipifarnib may be added to conventional therapeutic instruments for symptomatic primary myelofibrosis. The results of anti-JAK2-targeted therapies are encouraging as regards symptoms reduction but not clonal remission.

Perspectives on thrombosis in essential thrombocythemia and polycythemia vera: is leukocytosis a causative factor?

Leukocyte (WBC) count has been recently identified as an independent predictor of major thrombosis in both essential thrombocythemia (ET) and polycythemia vera (PV). However, whether leukocytosis should be simply considered a marker for vascular disease or whether elevated WBC levels actually contribute directly to causing such disorders is presently matter of many studies. By adopting epidemiologic criteria for causation, we have examined the characteristics to support this association such as (1) strength, (2) consistency, (3) specificity, (4) temporality, (5) biologic gradient, (6) plausibility, (7) experimental evidence, and (8) analogy. Our conclusion supports the notion that baseline leukocytosis in ET and PV patients adds prognostic significance to existing risk factors and that may be considered causative of vascular events. These developments could induce clinicians to incorporate WBC count into standard clinical practice. However, we need prospective clinical studies with stratification of patients according to their baseline leukocyte counts. Until such evidence is available, the decision on how to manage these patients should continue to follow conventional criteria.

JAK2 V617F mutation in essential thrombocythemia: correlation with clinical characteristics, response to therapy and long-term outcome in a cohort of 275 patients

The JAK2(V617F) mutation occurs in 50% of patients with essential thrombocythemia (ET). We investigated the correlation between the JAK2(V617F) mutation and clinical and laboratory characteristics, thrombohemorrhagic risk and incidence of disease evolution in 275 patients with ET followed for a median follow-up of 7 years. JAK2(V617F) mutation was detected in 175 patients (64%), of whom 173 were heterozygous. Patients with the mutation were older and displayed higher hemoglobin and hematocrit levels, but lower platelet count. Cytotoxic treatment requirement was similar in the two groups, but patients with the mutation showed better responses. Incidence of thrombosis and disease evolution was comparable. JAK2 mutational status assessment was valuable to distinguish two populations of patients with ET, showing distinctive hematologic and clinical features.

Long-term follow-up of 386 consecutive patients with essential thrombocythemia: safety of cytoreductive therapy

Cytotoxic agents like Hydroxyurea, Busulfan and Interferon-alpha are to date the most commonly used therapeutic approaches in Essential Thrombocythemia (ET). However, few data on the efficacy and safety of these agents in the long-term are currently available. We report a retrospective analysis of the long-term outcome of 386 consecutive ET patients, followed at single Institution for a median follow-up of 9.5 years (range, 3-28.5). Cytoreductive therapy was administered to 338 patients (88%), obtaining a response in 86% of cases. Forty-five patients (12%) experienced a thrombosis. Among baseline characteristics, only history of vascular events prior to ET diagnosis predicted a higher incidence of thrombosis. Evolution in acute leukemia/myelofibrosis occurred in 6 (1,5%) and 20 (5%) patients, and was significantly higher in patients receiving sequential cytotoxic agents. Overall survival was 38% at 19 years and was poorer for patients older than 60 years, with higher leukocytes count (>15 x 10(9)/L), hypertension and mellitus diabetes at ET diagnosis and for patients experiencing a thrombotic event during follow-up. Cytoreductive therapy was effective in decreasing platelet number with negligible toxicity; however, thrombocytosis control did not reduce the incidence of thrombosis and, for patients who received sequential therapies, the probability of disease evolution was higher and survival was poorer.

Association of V617F Jak2 mutation with the risk of thrombosis among patients with essential thrombocythaemia or idiopathic myelofibrosis: a systematic review

INTRODUCTION

Many studies evaluated the association of V617F Jak-2 with the risk of thrombosis in patients with essential thrombocythaemia, but the results of these studies were inconsistent. Few studies evaluated the association of V617F Jak-2 mutation with the risk of thrombosis in patients with idiopathic myelofibrosis. Therefore, we performed a systematic review of the studies that assessed the risk of thrombosis associated with V617F Jak-2 in patients with ET or IM.

MATERIALS AND METHODS

We searched MEDLINE and EMBASE databases and reference lists of retrieved articles. Odds ratios (ORs) and 95% confidence intervals (CI) were calculated for each trial and pooled.

RESULTS

We included 21 studies involving patients with essential thrombocythaemia and 6 studies patients with idiopathic myelofibrosis. In essential thrombocythaemia patients, V617F Jak-2 was associated with a significant increased risk of thrombosis (OR 1.92, 95% CI 1.45-2.53), both of venous (OR 2.49, 95% CI 1.71-3.61) and arterial (OR 1.77, 95% CI 1.29-2.43) vessels. In idiopathic myelofibrosis patients, the risk of thrombosis associated with V617F Jak-2 tended to be increased (OR 1.76, 95% CI 0.91-3.41).

CONCLUSIONS

Our systematic review suggests that V617F Jak-2 increases the risk of thrombosis in essential thrombocythaemia patients by about two fold while its role in idiopathic myelofibrosis patients is uncertain.

Is JAK2 V617F mutation more than a diagnostic index? A meta-analysis of clinical outcomes in essential thrombocythemia

A systematic review and meta-analysis was carried out to compare the frequency of clinically significant outcomes between JAK2 V617F positive and wild type patients with essential thrombocythemia (ET). JAK2 V617F positivity in patients with ET was associated with a clear increase in the odds of thrombosis [OR=1.83 (95% CI, 1.32-2.53), p<0.0001], and much higher odds of transformation to polycythemia vera [OR=7.67 (95% CI, 2.04-28.87), p=0.0009]. The mean difference of the white blood cell count between JAK2 positive and negative patients was associated with an increased odds ratio for thrombosis (p=0.02). The JAK2 V617F mutation in patients with ET is associated with an increased risk of adverse cardiovascular outcomes via an increase in the leukocyte count.