JAK2V617F基因突变与骨髓增殖性肿瘤关系

长期以来,除慢性髓系白血病的发病与BCR-ABL融合基因有关外,其他骨髓增殖性肿瘤(MPNs)的发病机制仍不清楚,近年来大量研究证实,在多种MPNs中存在较高的JAK2基因突变率,并认为该突变可能是BCR-ABL阴性MPNs所特有的分子标志.该文就近年来对JAK2基因突变、MPNs的最新诊断和靶向治疗等方面的研究进展进行综述.     

JAK2V617F allele burden in patients with myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal malignant diseases that represent a group of conditions including polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). The JAK2-V617F mutation is prevalent in almost all patients with MPNs and has become a valuable biomarker for diagnosis of MPNs. A different allele burden in these entities has long been noticed. The aim of our study was to assess the JAK2 allele burden in our JAK2V617F positive cases and its association with phenotype if any and to select a simple, sensitive assay for use in our clinical molecular diagnostic laboratory. Methodologies reported in this literature include amplification refractory mutation system–polymerase chain reaction (ARMS-PCR) and real-time quantitative polymerase chain reaction (RQ-PCR). We analyzed 174 cases by RQ-PCR for the quantification of JAK2V617F were initially screened by ARMS-PCR. We found that V617F allele burden in the entire population of patients was 73 % ranging from 0.97 to 95 %. The median V617F allele burden in PV patients was 40 %, MF was 95 %, and ET was 25 %. ARMS-PCR and RQ-PCR were proven to be sensitive since ARMS-PCR is a qualitative method; it can be used to screen JAK2V617F mutation and RQ-PCR was used to quantify the V617F cells. Our study suggests that JAK2V617F positivity is associated with MPNs, and its allele burden is an excellent diagnostic marker for disease subtypes, prognosis, disease phenotype and complication, and evolution. The data indicates that ARMS-PCR is simple and can be easily performed for the primary screening of JAK2V617F mutation, and RQ-PCR is sensitive enough to detect low mutant allele levels (>10 %), specific enough not to produce false positive results, and can be performed for the JAK2V617F allele burden quantification.     

JAK2 V617F: implications for thrombosis in myeloproliferative diseases

PURPOSE OF REVIEW: A major cause of morbidity in myeloproliferative disorders is thrombosis, although the pathophysiology of this process remains poorly understood. The review will explore the relationship between thrombosis and the recently identified gain-of-function mutation in Janus kinase 2, found in the majority of patients with myeloproliferative disorders. RECENT FINDINGS: In 2005, several groups described an acquired point mutation in the pseudokinase domain of Janus kinase 2 (JAK2 V617F). Subsequently, interest has focused on the utility of JAK2 V617F as both a diagnostic and prognostic tool, and as a potential therapeutic target. Retrospective data have identified JAK2 V617F as a risk factor for thrombosis in essential thrombocythemia, and have also shown a tight association between JAK2 V617F and abdominal vein thrombosis. SUMMARY: A general theme is that JAK2 V617F is variably associated with thrombosis and, more consistently, associated with elevations in blood counts relative to mutation-negative myeloproliferative disorders; future preclinical research should focus on the pathophysiology of thrombosis in myeloproliferative disorders, particularly in terms of the relationship between dysregulated Janus kinase 2 and elevated blood counts. A better understanding of this causal pathway will inform clinical studies, lead to improved risk stratification and, ideally, a reduction in thrombotic episodes.     

Widespread occurrence of the JAK2 V617F mutation in chronic myeloproliferative disorders

The analysis of rare chromosomal translocations in myeloproliferative disorders has highlighted the importance of aberrant tyrosine kinase signaling in the pathogenesis of these diseases. Here we have investigated samples from 679 patients and controls for the nonreceptor tyrosine kinase JAK2 V617F mutation. Of the 480 myeloproliferative disorder (MPD) samples, the proportion of positive cases per disease subtype was 30 (20%) of 152 for atypical or unclassified MPD, 2 of 134 (2%) for idiopathic hypereosinophilic syndrome, 58 of 72 (81%) for polycythemia vera, 24 of 59 (41%) essential thrombocythemia (ET), and 15 of 35 (43%) for idiopathic myelofibrosis. V617F was not identified in patients with systemic mastocytosis (n = 28), chronic or acute myeloid leukemia (n = 35), secondary erythrocytosis (n = 4), or healthy controls (n = 160). Homozygosity for V617F was seen in 43% of mutant samples and was closely correlated with chromosome 9p uniparental disomy. Homozygosity was significantly less common in ET compared with other MPD subtypes. In 53 cases analyzed, the median level of PRV1 expression was significantly higher in V617F-positive cases compared with cases without the mutation. We conclude that V617F is widespread in MPDs. Detection of this acquired mutation is likely to have a major impact on the way patients with MPD are diagnosed, as well as serving as an obvious target for signal transduction therapy.     

Regulation of Ruxolitinib on matrix metalloproteinase in JAK2V617F positive myeloproliferative neoplasms cells

正Objective To investigate the regulation of JAK2tyrosine kinase inhibitor ruxolitinib on extracellular matrix metalloproteinase(MMP in JAK2V61F positive myeloproliferative neoplasms(MPN)cells.Methods(1)Forty cases of newly diagnosed JAK2V617F positive MPN patients and 15 healthy volunteers as control in Baoding NO.1 Hospital between January 2012 and December     

JAK2V617F mutation status and allele burden in classical Ph-negative myeloproliferative neoplasms in Japan

JAK2V617F, a gain-of-function mutation in the tyrosine kinase JAK2, is frequently detected in classical myeloproliferative neoplasms (MPNs). In the present study, we determined the JAK2V617F allele burden in Japanese MPN patients using alternately binding probe competitive-polymerase chain reaction, a highly quantitative method recently developed by our group. Although we observed strong similarities in terms of epidemiological parameters associated with the JAK2V617F allele burden between our cohort and others, we found a higher JAK2V617F allele burden in Japanese polycythemia vera (PV) patients and lower frequencies of thrombosis in Japanese MPN patients compared with previous reports. In addition, despite the presence of high red blood cell counts, some patients bearing the JAK2V617F mutation were not diagnosed as PV, as their hemoglobin values were lower than the WHO PV criterion. In these patients, the JAK2V617F allele burden was strikingly similar to that in PV patients fulfilling the 2008 WHO criteria, suggesting that these patients can be classified as PV. Although isotopic measurement of red cell mass (RCM) is required for definitive diagnosis of PV, our data suggest that precise measurement of the JAK2V617F allele burden may improve the diagnosis of PV when RCM has not been determined.     

JAK2V617F突变背景下骨髓增殖性肿瘤临床表型异质性的研究进展

［摘要］　费城染色体阴性骨髓增殖性肿瘤(MPNs)是一组以造血干细胞克隆性增殖为主要特征的慢性血液肿瘤。JAK2V617F突变常见于MPNs,是诊断标准之一,其通过突变频率影响MPNs表型异质性。此外,信号通路、表观遗传学修饰、免疫异常、生活方式和其他一些因素也参与JAK2V617F相关的MPNs的异质性。该文对JAK2V617F影响MPNs表型的研究进展作一综述。     

JAK2 V617F and beyond: role of genetics and aberrant signaling in the pathogenesis of myeloproliferative neoplasms

Dysregulated signaling is a hallmark of chronic myeloproliferative neoplasms (MPNs), as evidenced by the identification of the activating JAK2 V617F somatic mutation in almost all patients with polycythemia vera (PV) and 50-60% of essential thrombocythemia and primary myelofibrosis patients. These disorders are clinically distinct, raising the question of how a single mutation can result in such phenotypic diversity. Mouse models have demonstrated that the level of JAK2 V617F expression can modulate the phenotype, and clinical studies of JAK2 V617F allele burden have reported similar findings. It has also been hypothesized that one or more pre-JAK2 V617F events may modify the MPN phenotype. However, the molecular basis of JAK2 V617F-negative essential thrombocythemia and primary myelofibrosis remains largely unexplained. Mutations in the TET2 gene have been identified in both JAK2 V617F-positive and -negative MPNs and other myeloid neoplasms, but their functional and clinical significance have yet to be clarified. In addition, recent reports have identified a specific germline haplotype that increases the predisposition to MPNs. The role of inhibitory pathways (e.g., SOCS and LNK) in regulating JAK-STAT signaling in MPNs is being increasingly recognized. The implications of these findings and their clinical relevance are the focus of this article.     

Renovascular hypertension associated with JAK2 V617F positive myeloproliferative neoplasms treated with angioplasty: 2 cases and literature review

Myeloproliferative neoplasms (MPNs) with Janus kinase 2 (JAK2) mutation are associated with a high risk for occlusive vascular diseases. We report 2 cases of renovascular hypertension associated with JAK2 V617F mutation‐positive MPNs and provide a literature review. In Case 1, a 63‐year‐old woman had resistant hypertension, massive proteinuria, and erythrocytosis. Evaluations revealed right renal artery stenosis causing renovascular hypertension and polycythemia vera with JAK2 V617F mutation. Renin‐angiotensin system inhibitors and subsequent angioplasty controlled the blood pressure and the proteinuria resolved. In Case 2, a 74‐year‐old woman had resistant hypertension and thrombocytosis. Evaluations confirmed left renal artery stenosis and essential thrombocythemia with JAK2 V617F. Angioplasty cured the hypertension. A literature review of 18 cases revealed the following as the most common characteristics of MPN‐associated renovascular hypertension: manifests primarily in women; is associated with untreated polycythemia vera and essential thrombocythemia, concomitant leukocytosis, and JAK2 mutation positivity; and is responsive to angioplasty. This report demonstrates that JAK2 mutation‐positive MPNs are a less common but important underlying cause of adult renovascular hypertension.     

Prevalence of overt myeloproliferative neoplasms and JAK2 V617F mutation in Korean patients with splanchnic vein thrombosis

Introduction: Myeloproliferative neoplasm (MPN) is known to be a major risk factor of splanchnic vein thrombosis (SVT). Recent studies revealed that a significant proportion of patients with SVT harbor a gain‐of‐function mutation in the JAK2 gene (V617F) with or without MPN. In this study, the authors investigated the prevalence of MPN and JAK2 V617F mutation in Korean patients with SVT. Methods: The study subjects were 26 patients diagnosed as having SVT based on Doppler ultrasound and/or computed tomography from January 2008 to January 2010 (16 men and 10 women; mean age 44 years, range 15–75 years). The clinical and laboratory data were reviewed. The JAK2 V617F mutation was detected by allele‐specific polymerase chain reaction and direct sequencing analyses using DNA from peripheral blood leukocytes. Results: Among 26 study patients, 12 had portal vein thrombosis, five had hepatic vein thrombosis, three had mesenteric, and two had splenic vein thrombosis. Four patients had thrombosis involving more than one splanchnic vein. Two patients (7.7%; 2/26) had overt MPN (essential thrombocythemia). JAK2 V617F was detected in three patients (11.5%) including the two patients with overt MPN. Thus, the prevalence of the JAK2 V617F mutation in patients with SVT but without overt MPN was 4.2% (1/24). Conclusion: The prevalence of overt MPN and that of JAK2 V617F were lower in Korean patients with SVT than in previous reports. Data from a larger number of patients with long‐term follow‐up are needed to reveal the clinical relevancy of JAK2 V617F in Korean patients with SVT.     

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。     

Relationship between JAK2V617F mutation,allele burden and coagulation function in Ph-negative myeloproliferative neoplasms

Objectives: Our aim was to explore the relationship between JAK2V617F mutation allele burden and hematological parameters especially in coagulation function in Chinese population.

Methods: This study included 133 Ph-negative myeloproliferative neoplasms (MPNs) patients between 2013 and 2016. All the clinical and experimental data of patients were collected at the time of the diagnosis without any prior treatment, including blood parameters, coagulation function, splenomegaly, vascular events and chromosome karyotype. PCR and qPCR were used to detect JAK2V617F mutation and JAK2V617F mutation allele burden.

Results: In polycythemia vera patients, a positive correlation between the allele burden of JAK2V617F mutation and PLT counts was found; in essential thrombocythemia (ET) patients, WBC counts, RBC counts, HB, and HCT were higher in mutated patients than in wild-type patients. Furthermore, PT-INR was higher in ET and PMF mutated patients. In addition, a positive correlation between the allele burden of JAK2V617F mutation and activated partial thromboplastin time (APTT) was observed in JAK2V617F mutated ET patients.

Conclusions: Higher hematologic parameters including counts of WBC, RBC, and PLT are closely associated with JAK2V617F mutation and its burden in Ph-negative MPNs; importantly, PT-INR, APTT are also related to JAK2V617F mutation and allele burden. Thus, our data indicate that JAK2V617F mutation allele burden might not only represent the burden of MPN but also alter the coagulation function.     

JAK2 46/1 haplotype is associated with JAK2 V617F-positive myeloproliferative neoplasms in Japanese patients

Myeloproliferative neoplasms (MPNs) constitute a group of phenotypically diverse chronic myeloid malignancies, characterized by clonal hematopoiesis and excessive production of terminally differentiated myeloid blood cells. The MPNs include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), most of which are characterized by a somatic point mutation, V617F, in the janus kinase 2 (JAK2) gene. This mutation was recently shown to occur more frequently in a specific JAK2 haplotype, JAK2 46/1, in North American and European MPN patients. Little is known, however, about JAK2 haplotypes in Japanese MPN patients. Therefore, we examined 108 Japanese patients with MPN, including 19 with PV, 61 with ET, 10 with PMF, and 17 with unclassifiable MPN, as well as 104 control individuals for the JAK2 rs10974944(C/G) single nucleotide polymorphism, in which the G allele indicates the 46/1 haplotype. We found that the JAK2 46/1 haplotype was significantly more frequent in patients with V617F-positive MPN than in controls (odds ratio [OR], 3.6; 95 % confidence interval [CI], 2.2–5.8, p < 0.001), and in PV patients than in controls (OR, 6.3; 95 % CI, 3.0–29.4, p < 0.001). In conclusion, we demonstrated that the JAK2 46/1 haplotype is associated with JAK2 V617F-positive MPNs in Japanese patients.     

JAK2V617F-positive endothelial cells contribute to clotting abnormalities in myeloproliferative neoplasms

The Janus kinase 2 (JAK2) V₆₁₇F mutation is the primary pathogenic mutation in patients with Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs). Although thrombohemorrhagic incidents are the most common causes of morbidity and mortality in patients with MPNs, the events causing these clotting abnormalities remain unclear. To identify the cells responsible for the dysfunctional hemostasis, we used transgenic mice expressing JAK2V₆₁₇F in specific lineages involved in thrombosis and hemostasis. When JAK2V₆₁₇F was expressed in both hematopoietic and endothelial cells (ECs), the mice developed a significant MPN, characterized by thrombocytosis, neutrophilia, and splenomegaly. However, despite having significantly higher platelet counts than controls, these mice showed severely attenuated thrombosis following injury. Interestingly, platelet activation and aggregation in response to agonists was unaltered by JAK2V₆₁₇F expression. Subsequent bone marrow transplants revealed the contribution of both endothelial and hematopoietic compartments to the attenuated thrombosis. Furthermore, we identified a potential mechanism for this phenotype through JAK2V₆₁₇F-regulated inhibition of von Willebrand factor (VWF) function and/or secretion. JAK2V₆₁₇F⁺ mice display a condition similar to acquired von Willebrand syndrome, exhibiting significantly less high molecular weight VWF and reduced agglutination to ristocetin. These findings greatly advance our understanding of thrombohemorrhagic events in MPNs and highlight the critical role of ECs in the pathology of hematopoietic malignancies.Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders, characterized by significant increases in one or more myeloid-cell lineages. Mutations in the Janus kinase 2 (JAK2) and MPL genes are common in the majority of Philadelphia chromosome-negative (Ph⁻) MPNs, which include polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). By far the most frequent mutation in MPNs is JAK2V₆₁₇F (1–4), which occurs in the highly conserved autoinhibitory JAK homology (JH) 2 domain, causing hyperactive kinase activity and hyperproliferation of myeloid progenitor cells, leading to overproduction of red blood cells (RBCs), platelets, and leukocytes. Although ET and PV have a relatively benign clinical course, patients’ life expectancy can be severely reduced by bleeding or thrombosis, the manifestations of which are significantly more common than other MPN-related complications such as myelofibrosis and acute leukemic transformation (5). The frequency and nature of thrombotic and hemorrhagic events vary greatly depending on disease phenotype and patient history. Data taken from a number of previous studies indicate that the probability of major thrombosis ranges between 8–29% (ET) and 11–39% (PV) whereas the incidence of bleeding at initial presentation is less frequent than thrombosis, ranging between 3–18% (ET) and 3–8% (PV) (6–8).A number of abnormalities that could potentially contribute to this prothrombotic phenotype have been identified in the blood and vascular cells of JAK2V₆₁₇F⁺ MPN patients. Much work has focused on defining platelet abnormalities, including increased expression of membrane proteins such as P-selectin and tissue factor (TF), which would prime platelets for activation and increase levels of platelet-activation markers and platelet factor 4 (PF4) in the plasma (9–12). Interestingly, however, aggregation studies show a decreased response to ADP and epinephrine in platelets isolated from patients with ET and PV compared with controls (10). Furthermore, no correlation has been made between severity of thrombocytosis in ET patients and increased risk of thrombosis (6, 13). In contrast, extreme thrombocytosis (platelets >1,500 × 10⁹/L) is thought to contribute to a hemorrhagic phenotype in ET patients, and is commonly attributed to the development of acquired von Willebrand syndrome (AVWS) (11, 12, 14), where the increased platelets bind to highly prothrombotic, ultralarge von Willebrand factor (VWF) multimers, removing them from the plasma (15).Recent studies suggest that leukocytosis is a potential thrombotic risk factor in young PV and ET patients, possibly through the interactions of leukocytes, especially neutrophils, with platelets and endothelial cells (ECs) (16, 17) or the production of prothrombotic molecules such as TF. Increased basal activation of neutrophils has been shown in PV and ET patients, including elevated expression of CD11b and levels of neutrophil proteases in the plasma, both of which are prothrombotic (9, 18, 19). Studies have also shown increased activation of vascular ECs in JAK2V₆₁₇F⁺ MPN patients. Increased P- and E-selectin levels in the plasma, coupled with decreased levels of nitric oxide (NO), could conceivably contribute to a prothrombotic phenotype. Furthermore, JAK2V₆₁₇F⁺ ECs have recently been reported in a subpopulation of MPN patients, and EC expression was coupled with an increased risk of thrombosis (20, 21). Taken together, previous studies describe physiological abnormalities in a number of cell types in JAK2V₆₁₇F⁺ MPN patients, all of which could contribute toward increased thrombosis and/or bleeding. However, these data are often contradictory and fail to definitively explain the mechanism/s responsible for the development of thrombohemorrhagic disease.Here, we used FF1 transgenic mice (22) to express human JAK2V₆₁₇F in specific lineages to determine which cells are responsible for the thrombohemorrhagic manifestations seen in patients with MPNs. FF1 mice were crossed with Pf4-Cre or Tie2-Cre mice to express JAK2V₆₁₇F specifically in platelets alone, or in hematopoietic cells and ECs, respectively (23–28). These models have provided us with an unparalleled opportunity to determine the specific role/s of JAK2V₆₁₇F in pathological thrombosis and hemostasis.     

Transgenic expression of JAK2V617F causes myeloproliferative disorders in mice

The JAK2^V617F mutation was found in most patients with myeloproliferative disorders (MPDs), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We have generated transgenic mice expressing the mutated enzyme in the hematopoietic system driven by a vav gene promoter. The mice are viable and fertile. One line of the transgenic mice, which expressed a lower level of JAK2^V617F, showed moderate elevations of blood cell counts, whereas another line with a higher level of JAK2^V617F expression displayed marked increases in blood counts and developed phenotypes that closely resembled human essential thrombocythemia and polycythemia vera. The latter line of mice also developed primary myelofibrosis-like symptoms as they aged. The transgenic mice showed erythroid, megakaryocytic, and granulocytic hyperplasia in the bone marrow and spleen, displayed splenomegaly, and had reduced levels of plasma erythropoietin and thrombopoietin. They possessed an increased number of hematopoietic progenitor cells in peripheral blood, spleen, and bone marrow, and these cells formed autonomous colonies in the absence of growth factors and cytokines. The data show that JAK2^V617F can cause MPDs in mice. Our study thus provides a mouse model to study the pathologic role of JAK2^V617F and to develop treatment for MPDs.