The Gain-of-Function JAK2 V617F Mutation Shifts the Phenotype of Essential Thrombocythemia and Chronic Idiopathic Myelofibrosis to More "Erythremic" and Less "Thrombocythemic": A Molecular, Histologic, and Clinical Study

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.

Correlations between Janus kinase 2 V617F allele burdens and clinicohematologic parameters in myeloproliferative neoplasms

BACKGROUND

This study evaluated potential correlations between the allele burden of the Janus kinase 2 (JAK2) V617F mutation and clinicohematologic characteristics in patients with myeloproliferative neoplasms (MPN).

METHODS

Clinical and hematologic features were reviewed for 103 MPN patients, including patients with polycythemia vera (PV, 22 patients), essential thrombocythemia (ET, 64 patients), and primary myelofibrosis (PMF, 17 patients). JAK2 V617F allele status and allele burdens were measured by allele-specific PCR and pyrosequencing, respectively.

RESULTS

The JAK2 V617F mutation was detected in 95.5%, 68.8%, and 52.9% of PV, ET, and PMF patients, respectively. JAK2 V617F-positive ET patients were significantly older and exhibited higher neutrophil fractions, a higher frequency of thrombotic events, and a higher myelofibrosis rate than JAK2 V617F-negative patients (P <0.05). PV patients carried the highest mean T allele burden (66.0%±24.9%) compared with ET (40.5%±25.2%) and PMF patients (31.5%±37.0%) (P =0.00). No significant correlations were detected between V617F allele burden and patient age, white blood cell count, Hb, Hct, or the platelet count for PV, ET, or PMF patients. ET patients with organomegaly had a higher JAK2 V617F allele burden (53.4%±23.7%) than patients without organomegaly (35.6%±24.3%) (P =0.03).

CONCLUSIONS

The JAK2 V617F mutational status and its allele burden correlate with the clinicohematologic phenotypes of ET patients, including older age, higher neutrophil count, and greater rates of organomegaly, thrombotic events, and myelofibrosis. For PV and PMF patients, larger-scale studies involving more MPN patients are needed.

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.

Cytogenetic abnormalities in essential thrombocythemia at presentation and transformation

Cytogenetic abnormalities in patients with essential thrombocythemia (ET) are infrequent. Their role in survival of patients and disease transformation is not extensively studied. We describe cytogenetic abnormalities in 172 patients with ET at a single institution. At presentation nine (5.2%) patients had cytogenetic abnormality and three (1.7%) additional patients acquired them during follow-up. Survival of patients with cytogenetic changes at presentation did not differ when compared to the patients with normal karyotype. The more common were abnormalities of chromosome 9 (n = 4), 20 (n = 2), 5 (n = 2), and complex abnormalities (n = 2). Forty-one patients (23.8%) had additional cytogenetic tests performed for monitoring purposes during follow-up. Five patients (2.9%) with normal karyotype transformed to myelofibrosis (MF) without developing new cytogenetic changes at transformation. Two patients (1.2%) with normal karyotypes at presentation transformed to myelodysplastic syndrome and acute myeloid leukemia, respectively. Both acquired complex cytogenetic changes at the time of transformation. There is no rationale for repeating cytogenetic tests in ET patients on follow up, unless blood cell count changes suggest possible transformation.

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.

Clinical correlates of JAK2V617F presence or allele burden in myeloproliferative neoplasms: a critical reappraisal

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).

Stat5 as a diagnostic marker for leukemia

The Jak-Stat-Socs pathway is an important component of cytokine receptor signaling. Not surprisingly, perturbation of this pathway is implicated in diseases of hematopoietic and immune origin, including leukemia, lymphoma and immune deficiencies. This review examines the role of a key component of this pathway, Stat5. This has been shown to be activated in a variety of leukemias and myeloproliferative disorders, including downstream of a range of key oncogenes where it has been shown to play an important role in mediating their effects. Therefore, Stat5 represents a useful pan-leukemia/myeloproliferative disorder diagnostic marker and key therapeutic end point, as well as representing an attractive therapeutic target for these disorders.