Prevalence of the JAK2V617F mutation in Chinese patients with Budd-Chiari syndrome and portal vein thrombosis: a prospective study

Background and Aim: Whether routine screening for the JAK2V617F mutation should be performed in Chinese patients with Budd‐Chiari syndrome (BCS) and portal vein thrombosis (PVT) is unclear. Therefore, we aimed to evaluate the prevalence of the JAK2V617F mutation in such patients and to explore the risk factors associated with the mutation. Methods: All consecutive patients with BCS and PVT diagnosed between September 2009 and May 2011 were prospectively enrolled in the observational study and underwent the JAK2V617F mutation detection. Results: Prevalence of the JAK2V617F mutation was 4.3% (4/92) in patients with primary BCS, 26.6% (17/64) in non‐malignant and non‐cirrhotic patients with PVT, and 1.4% (1/71) in cirrhotic patients with PVT. All BCS patients with the JAK2V617F mutation had both platelet count (PLT) of above 100 × 10⁹/L (range, 107–188 × 10⁹/L) and splenomegaly. In non‐malignant and non‐cirrhotic patients with PVT, higher PLT and older ages were the independent predictors of the JAK2V617F mutation. Further, the difference in PLT between the patients with and without the mutation displayed greater significance in the subgroup of patients with splenomegaly (P < 0.0001), but the statistical significance disappeared in the subgroup of patients with splenectomy (P = 0.1312). Conclusions: The low prevalence of the JAK2V617F mutation in patients with BCS suggests that myeloproliferative neoplasm should be an uncommon etiological factor of BCS in China. Routine screening for the JAK2V617F mutation might be recommended in non‐malignant and non‐cirrhotic patients with PVT, but not in cirrhotic patients with PVT. The coexistence of higher PLT and splenomegaly might be closely associated with the JAK2V617F mutation.     

Modulation of JAK2 V617F allele burden dynamics by hydroxycarbamide in polycythaemia vera and essential thrombocythaemia patients

The definition of primary refractory acute myeloid leukaemia is the failure to achieve a response after one or two cycles of induction. Given that there are many different strategies involving different doses of cytarabine and anthracyclines, which may or may not be equivalent, and as this is an area of unmet need with the potential for the development of new agents and strategies, uniform criteria for response have been described that need to be adhered to. The outcome of patients with chemoresistant disease is poor with only a proportion of patients salvaged by allogeneic stem cell transplantation. Progress in supportive care strategies and donor identification has enabled more of these patients to undergo unrelated donor transplantation. Novel strategies and new agents directed at the biology of the disease and the mechanisms of resistance are needed.     

JAK2 V617F mutation is rare in idiopathic erythrocytosis: a difference from polycythemia vera

A single mutation 1849G>T in the JAK2 gene (V617F) has recently been described in classical myeloproliferative disorders (MPD). To investigate the incidence and clinical significance of the JAK2 mutation, we performed allele-specific polymerase chain reaction (PCR) and enzyme-based assessment in 11 idiopathic erythrocytosis (IE) and 15 polycythemia vera (PV) patients. Aberrant bands indicating the V617F mutation were detected in only one of 11 patients with IE, whereas all of the 15 patients with PV showed the JAK2 mutation. Sequence analysis was subsequently performed in the IE patient showing aberrant bands on allele-specific PCR, and a nucleotide change corresponding to the V617F mutation was detected in four of 29 clones tested. This patient might have progressed to PV according to the new WHO diagnostic criteria proposed in 2007, since a gradual increase in platelet counts was observed 4 years after the time of diagnosis. A further longitudinal study monitoring V617F positive-cells will clarify the process of progression from IE to PV in such a patient.     

The JAK2V617F mutation and thrombosis

Since the discovery of the JAK2^V617F mutation, the clinical and pathological consequences of this acquired defect have been extensively investigated to determine whether its presence characterises a distinct subgroup of myeloproliferative disorders (MPD). MPD management remains highly dependent on the patient’s thrombotic risk. Whether the presence of the JAK2^V617F mutation modifies the thrombotic risk is currently contentious, although there is increasing clinical evidence to suggest that the mutation may be variably associated with thrombosis. These observations are further supported by laboratory parameters which suggest that the JAK2^V617F mutation may confer increased activation of leucocytes and platelets in MPD. The role of screening for the JAK2^V617F mutation in patients presenting with thrombosis without overt MPD is unclear, but appears justified in cases of idiopathic splanchnic vein thrombosis.     

A lower intensity of treatment may underlie the increased risk of thrombosis in young patients with masked polycythaemia vera

In patients who do not meet the World Health Organization (WHO) criteria for overt polycythaemia vera (PV), a diagnosis of masked PV (mPV) can be determined. A fraction of mPV patients may display thrombocytosis, thus mimicking essential thrombocythaemia (ET). No previous studies have examined clinical outcomes of mPV among young JAK2‐mutated patients. We analysed a retrospective cohort of 538 JAK2‐mutated patients younger than 40 years, after a re‐assessment of the diagnosis according to the haemoglobin threshold for mPV. In this cohort of patients, 97 (18%) met the WHO criteria for PV, 66 patients (12%) were classified as mPV and 375 (70%) as JAK2‐mutated ET. Surprisingly, a significant difference in the incidence of thrombosis was found when comparing mPV versus overt PV patients (P = 0·04). In multivariate analysis, the only factor accounting for the difference in the risk of thrombosis was the less frequent use of phlebotomies and cytoreduction in mPV patients compared to those with overt PV. Thus, we emphasize the need for the identification of mPV in young JAK2‐mutated patients in order to optimize their treatments.     

Open‐label study of oral CEP‐701 (lestaurtinib) in patients with polycythaemia vera or essential thrombocythaemia with JAK2‐V617F mutation

JAK2‐V617F is central to the pathogenesis of myeloproliferative neoplasms. We examined whether lestaurtinib decreased JAK2‐V617F allele burden and evaluated its clinical benefits and tolerability in patients with polycythaemia vera (PV) and essential thrombocythaemia (ET). This phase 2, open‐label, multicentre study was designed to detect ≥15% reduction in JAK2‐V617F allele burden in 15% of patients. Eligible patients received lestaurtinib 80 mg twice daily for 18 weeks and could participate in a 1‐year extension phase of treatment. Of 39 enrolled patients, 27 (69%) had PV; 12 (31%) had ET. While the pre‐specified responder rate of 15% was not met, lestaurtinib modestly reduced JAK2‐V617F allele burden and reduced spleen size in a subset of patients. Of 37 patients in the full efficacy analysis, 5 (14%) responded clinically. Every patient had ≥1 adverse event, most commonly gastrointestinal (95%). Fifteen patients (38%) experienced serious adverse events; 23 (59%) withdrew due to adverse events. This is the first reported study of JAK2‐inhibitor treatment in patients with PV/ET and highlights both the need for further studies to assess the role of JAK2 inhibition in treatment of PV/ET and the use of JAK2‐V617F as a biomarker for response. This trial was registered at www.clinicaltrials.gov as NCT00586651.     

骨髓增殖性肿瘤128例JAK2V617F基因突变与血栓栓塞关系研究

目的研究骨髓增殖性肿瘤(MPN)患者JAK2V617F突变与发生血栓栓塞的关系。方法回顾性分析2008年2月至2011年7月新疆地区128例不同民族MPN患者临床特征、实验室检查、JAK2V617F基因突变及血栓栓塞事件发生情况等资料。结果 MPN患者中93例(72.6%)存在JAK2V617F突变,66例(51.6%)发生血栓事件,其中突变阳性93例患者中58例有血栓形成,35例突变阴性患者中8例有血栓形成,突变阳性组与阴性组血栓发生率比较差异有统计学意义(χ2=15.893,P<0.05)。76例汉族MPN中58例为突变阳性,42例发生血栓,52例少数民族中35例突变阳性,24例发生血栓,汉族与少数民族患者JAK2基因突变总阳性率及血栓发生率比较均无统计学意义(χ2=1.261,1.026,P>0.05)。结论真性红细胞增多症、原发性血小板增多症及特发性骨髓纤维化等经典MPN患者中均有较高的JAK2V617F基因突变率,并突变阳性者血栓发生率明显高于阴性者;新疆地区汉族与维、哈、回等少数民族MPN患者JAK2V617F基因突变阳性率及血栓形成率之间差异无统计学意义。该突变阳性、年龄≥60岁、WBC≥15×109/L、合并有血管危险因素的患者血栓发生风险可能会高,应尽早予以干预治疗。     

The JAK2V617 mutation induces constitutive activation and agonist hypersensitivity in basophils from patients with polycythemia vera

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 correlations between JAK2V617F mutation and 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 those with polycythemia vera, and was correlated with the V617F burden. The burden of V617F allele was similar in neutrophils and basophils from patients with polycythemia vera, while total JAK2 mRNA content was remarkably greater in the basophils; however, the content of JAK2 protein in basophils was not increased. The number of CD63⁺ basophils was higher in patients with polycythemia vera than in healthy subjects or patients with essential thrombocythemia or primary myelofibrosis and was correlated with the V617F burden. Ultrastructurally, basophils from patients with polycythemia vera contained an increased number of granules, most of which were empty suggesting cell degranulation in vivo. Ex vivo experiments revealed that basophils from patients with polycythemia vera were hypersensitive to the priming effect of interleukin-3 and to f-MLP-induced activation; pre-treatment with a JAK2 inhibitor reduced polycythemia vera basophil activation. Finally, we found that the number of circulating CD63⁺ basophils was significantly greater in patients suffering from aquagenic pruritus, who also showed a higher V617F allele burden.

Conclusions

These data indicate that the number of constitutively activated and hypersensitive circulating basophils is increased in polycythemia vera, underscoring a role of JAK2V617F in these cells’ abnormal function and, putatively, in the pathogenesis of pruritus.     

The JAK2(V617F) tyrosine kinase mutation in myelofibrosis with myeloid metaplasia: lineage specificity and clinical correlates

An association between an activating JAK2 mutation (JAK2(V617F)) and BCR/ABL-negative myeloproliferative disorders was recently reported in multiple simultaneous publications. In the current study, mutation analysis for JAK2(V617F) was performed in peripheral blood mononuclear cells (PBMC) from 157 patients with myelofibrosis with myeloid metaplasia (MMM) including 117 with agnogenic (AMM), 22 with postpolycythaemic (PPMM), and 18 with post-thrombocythaemic (PTMM) myeloid metaplasia. The detection rate for JAK2(V617F) was significantly higher in PPMM (91%; homozygous in 18%) compared with either AMM (45.3%; homozygous in 2.6%) or PTMM (38.9%; homozygous in 11.1%). Concomitant analysis in granulocytes (n=57) and CD34(+) cells (n=25) disclosed a higher incidence of homozygous JAK2(V617F) mutation but the overall mutation rate was similar to that obtained from PBMC. JAK2(V617F) was not detected in DNA derived from T cells (n=19). In AMM, the presence of JAK2(V617F) was associated with an older age at diagnosis and a history of thrombosis or pruritus. Multivariate analysis identified only age and the Dupriez prognostic score as independent prognostic factors; JAK2(V617F) had no prognostic significance. In conclusion, JAK2(V617F) is a myeloid lineage-specific event, its incidence in MMM is significantly higher with an antecedent history of polycythaemia vera (PV), and its presence in AMM does not affect prognosis but is associated with PV-characteristic clinical features.     

The role of serum erythropoietin level and jak2 v617f allele burden in the diagnosis of polycythaemia vera

Low serum erythropoietin (EPO) is a minor criterion of Polycythaemia Vera (PV) but its diagnostic usefulness relies on studies performed before the discovery of JAK2 V617F mutation. The objective of the present study was to evaluate the diagnostic accuracy of serum EPO and JAK2 V617F allele burden as markers of PV as well as the combination of different diagnostic criteria in 287 patients (99 with PV, 137 with Essential Thrombocythaemia and 51 with non‐clonal erythrocytosis). Low EPO showed good diagnostic accuracy as a marker for PV, with the area under the curve (AUC) of the chemiluminescent‐enhanced enzyme immunoassay (CEIA) being better than that of radioimmunoassay (RIA) (0·87 and 0·76 for CEIA and RIA, respectively). JAK2 V617F quantification displayed an excellent diagnostic accuracy, with an AUC of 0·95. A haematocrit >52% (males) or >48% (females) plus the presence of the JAK2 V617F mutation had a sensitivity and specificity of 79% and 97%, respectively. Adding low EPO or the JAK2 V617F allele burden did not improve the diagnostic accuracy for PV whereas the inclusion of both improved the sensitivity up to 83% and maintaining 96% specificity. Haematocrit and qualitative JAK2 V617F mutation allow a reliable diagnosis of PV. Incorporation of EPO and/or JAK2 V617F mutant load does not improve the diagnostic accuracy.