Spleen deflation and beyond: The pros and cons of Janus kinase 2 inhibitor therapy for patients with myeloproliferative neoplasms

The myeloproliferative neoplasms (MPNs) essential thrombocythemia (ET), polycythemia vera (PV), and primary myelofibrosis (MF) are malignancies that frequently harbor the recurrent somatic point mutation JAK2^V617F. The discovery of this mutation has fueled the development of Janus kinase 2 (JAK2) inhibitors. Available results have indicated that JAK2 inhibitors are particularly effective at reducing spleen size. However, the activity of these agents is multifaceted and also involves a marked improvement of systemic symptoms and, for those agents with dual JAK1 and JAK2 inhibitory activity, a marked reduction in the levels of circulating cytokines involved in the pathogenesis of the disease. Because JAK2 inhibitors are not specific for JAK2^V617F, responses have also been observed in JAK2^V617F‐negative MPNs because of the inhibition of wild‐type JAK2, which is also likely responsible for the induction of cytopenias in patients with MF and for the normalization of peripheral blood counts observed in patients with ET or PV. Given the distinct mortality and morbidity associated with ET, PV, and MF, the use of JAK2 inhibitors appears reasonable for patients with MF as well as for those with ET or PV who have become resistant or intolerant to hydroxyurea. Ongoing randomized, placebo‐controlled, phase 3 trials will further delineate the role of these agents in the management of patients with MPNs. The pros and cons of JAK2 kinase inhibitor therapy are herein discussed. Cancer 2012;. © 2011 American Cancer Society.     

Novel molecular mechanism of cellular transformation by a mutant molecular chaperone in myeloproliferative neoplasms

Deregulation of the cytokine‐receptor signaling pathway plays a significant role in tumorigenesis. Such deregulation is frequently caused by alterations in the genes involved in the signaling pathway. At the end of 2013, recurrent somatic mutations in the calreticulin (CALR) gene that encodes a molecular chaperone were identified in a subset of patients with Philadelphia‐chromosome negative myeloproliferative neoplasms (MPN). The present review focuses on the role of CALR mutations in the oncogenic transformations observed in MPN. All the CALR mutations were found to generate a + 1 frameshift in the reading frame on exon 9, which encodes the carboxy (C)‐terminus end of CALR, and thus conferred a common mutant‐specific sequence in all the CALR mutants. The mutant CALR (but not the wild‐type) constitutively activates the thrombopoietin (TPO) receptor, myeloproliferative leukemia protein (MPL), even in the absence of TPO to induce cellular transformation. Preferential interaction between the mutant CALR and MPL is achieved by a presumptive conformational change induced by the mutant‐specific C‐terminus domain, which allows N‐domain binding to MPL. Even though mutant CALR is expressed on the cell surface and is secreted out of cells, it only presents autocrine capacity for MPL activation. These findings define a novel molecular mechanism by which the mutant molecular chaperone constitutively activates the cytokine receptor to induce cellular transformation.     

Experimental therapeutics for patients with myeloproliferative neoplasias

Philadelphia chromosome (Ph)-negative myeloproliferative neoplasms (MPNs) are characterized by stem cell-derived, unrestrained clonal myeloproliferation. The World Health Organization classification system, proposed in 2008, identifies 7 distinct categories of Ph-negative MPNs including essential thrombocythemia (ET); polycythemia vera (PV); primary myelofibrosis (PMF); mastocytosis; chronic eosinophilic leukemia; chronic neutrophilic leukemia; and MPN, unclassifiable. For many years, the treatment of ET, PV, and PMF, the most frequently diagnosed Ph-negative MPNs, has been largely supportive. In recent years, that paradigm has been challenged because of the discovery of a recurrent point mutation in the Janus kinase 2 (JAK2) gene (JAK2(V617F)). This mutation can be detected in the vast majority of patients with PV and approximately half of patients with ET or PMF and serves as both a diagnostic marker as well as representing a putative molecular target for drug development. Several putative targeted agents with significant in vitro JAK2 inhibitory activity and various degrees of JAK2 specificity are currently undergoing clinical evaluation. Furthermore, other investigational non-tyrosine kinase inhibitor approaches such as immunomodulatory agents and pegylated interferon- have also shown promising results in MPNs.     

Analysis of genomic aberrations and gene expression profiling identifies novel lesions and pathways in myeloproliferative neoplasms

Polycythemia vera (PV), essential thrombocythemia and primary myelofibrosis, are myeloproliferative neoplasms (MPNs) with distinct clinical features and are associated with the JAK2V617F mutation. To identify genomic anomalies involved in the pathogenesis of these disorders, we profiled 87 MPN patients using Affymetrix 250K single-nucleotide polymorphism (SNP) arrays. Aberrations affecting chr9 were the most frequently observed and included 9pLOH (n=16), trisomy 9 (n=6) and amplifications of 9p13.3-23.3 (n=1), 9q33.1-34.13 (n=1) and 9q34.13 (n=6). Patients with trisomy 9 were associated with elevated JAK2V617F mutant allele burden, suggesting that gain of chr9 represents an alternative mechanism for increasing JAK2V617F dosage. Gene expression profiling of patients with and without chr9 abnormalities (+9, 9pLOH), identified genes potentially involved in disease pathogenesis including JAK2, STAT5B and MAPK14. We also observed recurrent gains of 1p36.31-36.33 (n=6), 17q21.2-q21.31 (n=5) and 17q25.1-25.3 (n=5) and deletions affecting 18p11.31-11.32 (n=8). Combined SNP and gene expression analysis identified aberrations affecting components of a non-canonical PRC2 complex (EZH1, SUZ12 and JARID2) and genes comprising a 'HSC signature' (MLLT3, SMARCA2 and PBX1). We show that NFIB, which is amplified in 7/87 MPN patients and upregulated in PV CD34+ cells, protects cells from apoptosis induced by cytokine withdrawal.     

412例骨髓增殖性肿瘤的JAK2V617F突变检测及其临床意义

目的 研究JAK2V617F突变在慢性骨髓增殖性肿瘤(MPN)中的发生率及其与临床表现和并发症间的相关性.方法 采用等位基因特异性PCR方法,检测MPN中JAK2V617F的发生情况.结果 412例MPN患者中,JAK2V617F突变277例.JAK2V617F在原发性血小板增多症(ET)、特发性骨髓纤维化(IMF)和不能分类的骨髓增殖性疾病(MPD-U)中发生率分别为55.9%、66.7%和52.4%(P>0.05),均低于真性红细胞增多症(PV,95.6%),差异有统计学意义(P<0.05).JAK2突变型患者的平均年龄高于野生型患者(P<0.01);JAK2突变型患者的白细胞计数和血红蛋白水平均高于野生型患者(P<0.05);JAK2突变型患者中血管事件的发生率高于野生型患者(P<0.05);JAK2突变型的MPD-U患者较野生型患者更易进展为典型MPN(P<0.05);在301例行染色体检查的患者中,未发现核型异常与JAK2V617F表达之间存在相关性.结论 检测MPD-U患者中JAK2V617F的突变情况对疾病发展有提示作用;JAK2V617F突变与MPN患者年龄、外周血细胞计数及血管事件并发症相关.     

Efficacy of NS-018, a potent and selective JAK2/Src inhibitor, in primary cells and mouse models of myeloproliferative neoplasms

Aberrant activation of Janus kinase 2 (JAK2) caused by somatic mutation of JAK2 (JAK2V617F) or the thrombopoietin receptor (MPLW515L) plays an essential role in the pathogenesis of myeloproliferative neoplasms (MPNs), suggesting that inhibition of aberrant JAK2 activation would have a therapeutic benefit. Our novel JAK2 inhibitor, NS-018, was highly active against JAK2 with a 50% inhibition (IC₅₀) of <1 n, and had 30–50-fold greater selectivity for JAK2 over other JAK-family kinases, such as JAK1, JAK3 and tyrosine kinase 2. In addition to JAK2, NS-018 inhibited Src-family kinases. NS-018 showed potent antiproliferative activity against cell lines expressing a constitutively activated JAK2 (the JAK2V617F or MPLW515L mutations or the TEL–JAK2 fusion gene; IC₅₀=11–120 n), but showed only minimal cytotoxicity against most other hematopoietic cell lines without a constitutively activated JAK2. Furthermore, NS-018 preferentially suppressed in vitro erythropoietin-independent endogenous colony formation from polycythemia vera patients. NS-018 also markedly reduced splenomegaly and prolonged the survival of mice inoculated with Ba/F3 cells harboring JAK2V617F. In addition, NS-018 significantly reduced leukocytosis, hepatosplenomegaly and extramedullary hematopoiesis, improved nutritional status, and prolonged survival in JAK2V617F transgenic mice. These results suggest that NS-018 will be a promising candidate for the treatment of MPNs.     

Epidemiology,outcome, and risk factors for infectious complications in myelofibrosis patients receiving ruxolitinib: A multicenter study on 446 patients

Infections represent one of the major concerns regarding the utilization of ruxolitinib (RUX) in patients with myelofibrosis. With the aim to investigate epidemiology, outcome and risk factors for infections in RUX‐exposed patients, we collected clinical and laboratory data of 446 myelofibrosis patients treated with RUX between June 2011 and November 2016 in 23 European Hematology Centers. After a median RUX exposure of 23.5 months (range, 1‐56), 123 patients (28%) experienced 161 infectious events (grades 3‐4 32%, fatal 9%), for an incidence rate of 17 cases per 100 pts/y. The rate of infections tended to decrease over time: 14% of patients developed the first infection within 6 months, 5% between 6 and 12 months, 3.7% between 12 and 18 months, 3.4% between 18 and 24 months, and 7.9% thereafter (P < .0001). Respiratory tract infections were more frequently observed (81 events, 50%), and bacteria were the most frequent etiological agents (68.9%). However, also viral (14.9%) and fungal infections (2.5%) were observed. In multivariate analysis, previous infectious event (HR 2.54; 95% CI, 1.51‐4.28; P = .0005) and high international prognostic score system category (IPSS) (HR 1.53; 95% CI, 1.07‐2.20; P = .021) significantly correlated with higher infectious risk. On the contrary, spleen reduction ≥50% from baseline after 3 months of treatment (P = .02) was associated with better infection‐free survival. Taken together, these findings reinforce the concept of disease severity as the most important risk factor for infections, and describe, for the first time, that a positive therapeutic effect in reducing splenomegaly may also reduce subsequent infectious complications.     

412例骨髓增殖性肿瘤的JAK2V617F突变检测及其临床意义

目的 研究JAK2V617F突变在慢性骨髓增殖性肿瘤(MPN)中的发生率及其与临床表现和并发症间的相关性.方法 采用等位基因特异性PCR方法,检测MPN中JAK2V617F的发生情况.结果 412例MPN患者中,JAK2V617F突变277例.JAK2V617F在原发性血小板增多症(ET)、特发性骨髓纤维化(IMF)和不能分类的骨髓增殖性疾病(MPD-U)中发生率分别为55.9%、66.7%和52.4%(P>0.05),均低于真性红细胞增多症(PV,95.6%),差异有统计学意义(P<0.05).JAK2突变型患者的平均年龄高于野生型患者(P<0.01);JAK2突变型患者的白细胞计数和血红蛋白水平均高于野生型患者(P<0.05);JAK2突变型患者中血管事件的发生率高于野生型患者(P<0.05);JAK2突变型的MPD-U患者较野生型患者更易进展为典型MPN(P<0.05);在301例行染色体检查的患者中,未发现核型异常与JAK2V617F表达之间存在相关性.结论 检测MPD-U患者中JAK2V617F的突变情况对疾病发展有提示作用;JAK2V617F突变与MPN患者年龄、外周血细胞计数及血管事件并发症相关.     

412例骨髓增殖性肿瘤的JAK2V617F突变检测及其临床意义

目的 研究JAK2V617F突变在慢性骨髓增殖性肿瘤(MPN)中的发生率及其与临床表现和并发症间的相关性.方法 采用等位基因特异性PCR方法,检测MPN中JAK2V617F的发生情况.结果 412例MPN患者中,JAK2V617F突变277例.JAK2V617F在原发性血小板增多症(ET)、特发性骨髓纤维化(IMF)和不能分类的骨髓增殖性疾病(MPD-U)中发生率分别为55.9%、66.7%和52.4%(P>0.05),均低于真性红细胞增多症(PV,95.6%),差异有统计学意义(P<0.05).JAK2突变型患者的平均年龄高于野生型患者(P<0.01);JAK2突变型患者的白细胞计数和血红蛋白水平均高于野生型患者(P<0.05);JAK2突变型患者中血管事件的发生率高于野生型患者(P<0.05);JAK2突变型的MPD-U患者较野生型患者更易进展为典型MPN(P<0.05);在301例行染色体检查的患者中,未发现核型异常与JAK2V617F表达之间存在相关性.结论 检测MPD-U患者中JAK2V617F的突变情况对疾病发展有提示作用;JAK2V617F突变与MPN患者年龄、外周血细胞计数及血管事件并发症相关.     

费城染色体阴性骨髓增殖性肿瘤的诊断与治疗:JAK2 V617F基因突变评价

简要回顾了近百余年人们对骨髓增殖性肿瘤(MPN)的认识过程,重点讨论这一类疾病的诊断与治疗.JAK2 V617F基因突变的发现将费城染色体阴性(Ph-)MPN带入分子生物学时代,为临床提供了重要的诊断手段和依据,指导、研发了芦可替尼(ruxolitinib)等一批靶向药物.但是,与慢性粒细胞白血病(CML)中的bcr-abl不同,JAK2 V617F突变不是MPN诊断的“金标准”,其他辅助检查和鉴别诊断仍不可少.目前,JAK抑制剂开始用于Ph-MPN患者,有一定的适应证,远期疗效正在观察,目前还不能替代有效的常规治疗,如羟基脲、阿司匹林等.     

412例骨髓增殖性肿瘤的JAK2V617F突变检测及其临床意义

目的 研究JAK2V617F突变在慢性骨髓增殖性肿瘤(MPN)中的发生率及其与临床表现和并发症间的相关性.方法 采用等位基因特异性PCR方法,检测MPN中JAK2V617F的发生情况.结果 412例MPN患者中,JAK2V617F突变277例.JAK2V617F在原发性血小板增多症(ET)、特发性骨髓纤维化(IMF)和不能分类的骨髓增殖性疾病(MPD-U)中发生率分别为55.9%、66.7%和52.4%(P>0.05),均低于真性红细胞增多症(PV,95.6%),差异有统计学意义(P<0.05).JAK2突变型患者的平均年龄高于野生型患者(P<0.01);JAK2突变型患者的白细胞计数和血红蛋白水平均高于野生型患者(P<0.05);JAK2突变型患者中血管事件的发生率高于野生型患者(P<0.05);JAK2突变型的MPD-U患者较野生型患者更易进展为典型MPN(P<0.05);在301例行染色体检查的患者中,未发现核型异常与JAK2V617F表达之间存在相关性.结论 检测MPD-U患者中JAK2V617F的突变情况对疾病发展有提示作用;JAK2V617F突变与MPN患者年龄、外周血细胞计数及血管事件并发症相关.     

412例骨髓增殖性肿瘤的JAK2V617F突变检测及其临床意义

目的 研究JAK2V617F突变在慢性骨髓增殖性肿瘤(MPN)中的发生率及其与临床表现和并发症间的相关性.方法 采用等位基因特异性PCR方法,检测MPN中JAK2V617F的发生情况.结果 412例MPN患者中,JAK2V617F突变277例.JAK2V617F在原发性血小板增多症(ET)、特发性骨髓纤维化(IMF)和不能分类的骨髓增殖性疾病(MPD-U)中发生率分别为55.9%、66.7%和52.4%(P>0.05),均低于真性红细胞增多症(PV,95.6%),差异有统计学意义(P<0.05).JAK2突变型患者的平均年龄高于野生型患者(P<0.01);JAK2突变型患者的白细胞计数和血红蛋白水平均高于野生型患者(P<0.05);JAK2突变型患者中血管事件的发生率高于野生型患者(P<0.05);JAK2突变型的MPD-U患者较野生型患者更易进展为典型MPN(P<0.05);在301例行染色体检查的患者中,未发现核型异常与JAK2V617F表达之间存在相关性.结论 检测MPD-U患者中JAK2V617F的突变情况对疾病发展有提示作用;JAK2V617F突变与MPN患者年龄、外周血细胞计数及血管事件并发症相关.     

412例骨髓增殖性肿瘤的JAK2V617F突变检测及其临床意义

目的 研究JAK2V617F突变在慢性骨髓增殖性肿瘤(MPN)中的发生率及其与临床表现和并发症间的相关性.方法 采用等位基因特异性PCR方法,检测MPN中JAK2V617F的发生情况.结果 412例MPN患者中,JAK2V617F突变277例.JAK2V617F在原发性血小板增多症(ET)、特发性骨髓纤维化(IMF)和不能分类的骨髓增殖性疾病(MPD-U)中发生率分别为55.9%、66.7%和52.4%(P>0.05),均低于真性红细胞增多症(PV,95.6%),差异有统计学意义(P<0.05).JAK2突变型患者的平均年龄高于野生型患者(P<0.01);JAK2突变型患者的白细胞计数和血红蛋白水平均高于野生型患者(P<0.05);JAK2突变型患者中血管事件的发生率高于野生型患者(P<0.05);JAK2突变型的MPD-U患者较野生型患者更易进展为典型MPN(P<0.05);在301例行染色体检查的患者中,未发现核型异常与JAK2V617F表达之间存在相关性.结论 检测MPD-U患者中JAK2V617F的突变情况对疾病发展有提示作用;JAK2V617F突变与MPN患者年龄、外周血细胞计数及血管事件并发症相关.