JAK2V617F 点突变与骨髓增殖性疾病的临床相关性研究

目的:研究JAK2V617F点突变与骨髓增殖性疾病(myeloproliferative disease,MPD)的临床相关性,为MPD的基因学诊断及靶向治疗提供理论依据。方法:应用等位基因特异性聚合酶链反应(AS-PCR)检测JAK2V617F点突变。结果:102例的MPD患者中包括慢性粒细胞白血病(CML)患者9例、真性红细胞增多症(PV)患者21例、原发性血小板增多症(ET)患者37例、特发性骨髓纤维化(IMF)患者16例和分类不明的骨髓增殖性疾病(uMPD)患者19例,JAK2V617F突变阳性率依次为11%、71.4%、51.4%、75.0%、78.9%。结论:JAK2V617F点突变有助于不同类型MPD的诊断,在MPD疾病的诊断中起重要作用。     

Curcumin induces apoptosis in JAK2‐mutated cells by the inhibition of JAK2/STAT and mTORC1 pathways

Myeloproliferative neoplasms are chronic myeloid cancers divided in Philadelphia positive and negative. The JAK2 V617F is the most common mutation in Philadelphia negative patients and results in a constitutive activation of the JAK/STAT pathway, conferring a proliferative advantage and apoptosis inhibition. Recent studies identified a functional crosstalk between the JAK/STAT and mTOR pathways. The identification of an effective therapy is often difficult, so the availability of new therapeutic approaches might be attractive. Previous studies showed that curcumin, the active principle of the Curcuma longa, can suppress JAK2/STAT pathways in different type of cancer and injuries. In this study, we investigated the anti‐proliferative and pro‐apoptotic effects of curcumin in JAK2 V617F‐mutated cells. HEL cell line and cells from patients JAK2 V617F mutated have been incubated with increasing concentrations of curcumin for different time. Apoptosis and proliferation were evaluated. Subsequently, JAK2/STAT and AKT/mTOR pathways were investigated at both RNA and protein levels. We found that curcumin induces apoptosis and inhibition of proliferation in HEL cells. Furthermore, we showed that curcumin inhibits JAK2/STAT and mTORC1 pathways in JAK2 V617F‐mutated cells. This inhibition suggests that curcumin could represent an alternative strategy to be explored for the treatment of patients with myeloproliferative neoplasms.     

Activation of JAK2-V617F by Components of Heterodimeric Cytokine Receptors

The JAK2-V617F mutation is an important etiologic factor for the development of myeloproliferative neoplasms. The mechanism by which this mutated tyrosine kinase initiates deregulated signals in cells is not completely understood. It is believed that JAK2-V617F requires interactions with homodimeric cytokine receptors to elicit its transforming signal. In this study, we demonstrate that components of heterodimeric cytokine receptors can also activate JAK2-V617F. Expression of IL27Ra, a heterodimeric receptor component, enhanced the activation of JAK2-V617F and subsequent downstream signaling to activation of STAT5 and ERK. In addition, expression of components of the interleukin-3 receptor, IL3Ra and the common β chain, activated JAK2-V617F as well as STAT5 and ERK. Importantly, expression of IL27Ra functionally replaced the requirement of a homodimeric cytokine receptor to promote the activation and transforming activity of JAK2-V617F in BaF3 cells. Tyrosine phosphorylation of IL27Ra was not required to induce activation of JAK2-V617F or STAT5, or to enhance the transforming activity of JAK2-V617F. Expression of IL3Ra or the common β chain in BaF3 cells also enhanced the ability of JAK2-V617F to transform these hematopoietic cells. However, the heterodimeric receptor component IL12RB1 did not enhance the activation or transforming signals of JAK2-V617F in BaF3 cells. IL27Ra also activated the K539L and R683G JAK2 mutants. Together our data demonstrate that in addition to homodimeric receptors, some heterodimeric receptor components can support the activation and transforming signals of JAK2-V617F and other JAK2 mutants. Therefore, heterodimeric receptors may play unappreciated roles in JAK2 activation in the development of hematopoietic diseases including myeloproliferative neoplasms.     

Molecular analysis of V617F mutation in Janus kinase 2 gene of breast cancer patients

BackgroundBreast cancer is a multifactorial disease with the highest frequency in females. Genetic and environmental factors can cause mutation in several genes like tyrosine kinase, JAK2 gene which may initiate cancer. Molecular analysis of mutations in the JAK2 gene along with determination of environmental, clinical and haematological risk factors associated with breast cancer patients is need of hour to improve patient's healthcare. Somatic JAK2 valine-to-phenylalanine (617 codon) mutation is one of the widely prevalent mutations.MethodsBlood was collected from seventy breast cancer patients after their consent. The questionnaire included risk factors, age group, locality, number of children, tumor type, family history, time of initial diagnosis, no of cycles/month, water conditions and exposure to radiations. Molecular analysis were carried out from genomic DNA using Sanger sequencing and allele-specific PCR to check the V617F point mutation.ResultsThe breast cancer risk factors includes unfiltered water (68.57%), urban (58.57%), menopause (55.71%), family history of cancer (18.57%), tumor grades (II, 37.14% and III, 35.71%), consanguineous marriages (44.28%) and having more than 3–4 children (45.71%). Prevalence of breast cancer was higher after the age of 35 and maximum at 35–50. In allele-specific PCR of 70 patients, 25 patients were wild type (229 bp), 25 patients were with partially deleted gene (200 bp), and 20 patient had shown no or less than 40 bp size fragments. In Sanger's sequencing of 70 BC cases, 18% were found to be positive for V617F point mutation, including 6 homozygous (T/T) and 7 heterozygous (G/T) mutations at nucleotide position 1849 in exon 14 of the JAK2 gene.ConclusionsEnvironmental and clinical risk factors were associated with breast cancer which can be overcome by improving awareness of associated risks, health facilities and reducing stress.     

The discovery of 2,5-isomers of triazole-pyrrolopyrimidine as selective Janus kinase 2 (JAK2) inhibitors versus JAK1 and JAK3

Members of the Janus kinase (JAK) family are potential therapeutic targets. Abnormal signaling by mutant JAK2 is related to hematological malignancy, such as myeloproliferative neoplasms (MPNs), and tyrosine kinase inhibitor (TKI)-resistance in non-small cell lung cancer (NSCLC). We discovered a potent and highly selective inhibitor of JAK2 over JAK1 and -3 based on the structure of 4-(2,5-triazole)-pyrrolopyrimidine. Among all triazole compounds tested, 2,5-triazole regioisomers more effectively inhibited JAK2 kinase activity than isomers with substitutions of various alkyl groups at the R₂ position, except for methyl-substituted 1,5-triazole, which was more potent than the corresponding 1,4- and 2,5-triazoles. None of the synthesized 1,4-isomers inhibited all three JAK family members. Compounds with phenyl or tolyl group substituents at the R₁ position were completely inactive compared with the corresponding analogues with a methyl substituted at the R₁ position. As a result of this structure–activity relationship, 54, which is substituted with a cyclopropylmethyl moiety, exhibited significant inhibitory activity and selectivity (IC₅₀ = 41.9 nM, fold selectivity JAK1/2 10.6 and JAK3/2 58.1). Compound 54 also exhibited an equivalent inhibition of wild type JAK2 and the V617F mutant. Moreover, 54 inhibited the proliferation of HEL 92.1.7 cells, which carry JAK2 V617F, and gefitinib-resistant HCC827 cells. Compound 54 also suppressed STAT3 phosphorylation at Y705.     

The JH2 domain and SH2-JH2 linker regulate JAK2 activity: A detailed kinetic analysis of wild type and V617F mutant kinase domains

JAK2 tyrosine kinase regulates many cellular functions. Its activity is controlled by the pseudokinase (JH2) domain by still poorly understood mechanisms. The V617F mutation in the pseudokinase domain activates JAK2 and causes myeloproliferative neoplasms. We conducted a detailed kinetic analysis of recombinant JAK2 tyrosine kinase domain (JH1) and wild-type and V617F tandem kinase (JH1JH2) domains using peptide microarrays to define the functions of the kinase domains. The results show that i) JAK2 follows a random Bi–Bi reaction mechanism ii) JH2 domain restrains the activity of the JH1 domain by reducing the affinity for ATP and ATP competitive inhibitors iii) V617F decreases affinity for ATP but increases catalytic activity compared to wild-type and iv) the SH2–JH2 linker region participates in controlling activity by reducing the affinity for ATP.     

Stimulation of the amino acid transporter SLC6A19 by JAK2

JAK2 (Janus kinase-2) is expressed in a wide variety of cells including tumor cells and contributes to the proliferation and survival of those cells. The gain of function mutation ^V617FJAK2 mutant is found in the majority of myeloproliferative diseases. Cell proliferation depends on the availability of amino acids. Concentrative cellular amino acid uptake is in part accomplished by Na⁺ coupled amino acid transport through SLC6A19 (B(0)AT). The present study thus explored whether JAK2 activates SLC6A19. To this end, SLC6A19 was expressed in Xenopus oocytes with or without wild type JAK2, ^V617FJAK2 or inactive ^K882EJAK2 and electrogenic amino acid transport determined by dual electrode voltage clamp. In SLC6A19-expressing oocytes but not in oocytes injected with water or JAK2 alone, the addition of leucine (2 mM) to the bath generated a current (I_le), which was significantly increased following coexpression of JAK2 or ^V617FJAK2, but not by coexpression of ^K882EJAK2. Coexpression of JAK2 enhanced the maximal transport rate without significantly modifying the affinity of the carrier. Exposure of the oocytes to the JAK2 inhibitor AG490 (40 μM) resulted in a gradual decline of I_le. According to chemiluminescence JAK2 enhanced the carrier protein abundance in the cell membrane. The decline of I_le following inhibition of carrier insertion by brefeldin A (5 μM) was similar in the absence and presence of JAK2 indicating that JAK2 stimulates carrier insertion into rather than inhibiting carrier retrival from the cell membrane. In conclusion, JAK2 up-regulates SLC6A19 activity which may foster amino acid uptake into JAK2 expressing cells.     

Cooperative effects of Janus and Aurora kinase inhibition by CEP701 in cells expressing Jak2V617F

The Janus kinase 2 mutant V617F occurs with high frequency in myeloproliferative neoplasms. Further mutations affecting the Janus kinase family have been discovered mostly in leukaemias and in myeloproliferative neoplasms. Owing to their involvement in neoplasia, inflammatory diseases and in the immune response, Janus kinases are promising targets for kinase inhibitor therapy in these disease settings. Various quantitative assays including two newly developed screening assays were used to characterize the function of different small‐molecule compounds in cells expressing Jak2V617F. A detailed comparative analysis of different Janus kinase inhibitors in our quantitative assays and the subsequent characterization of additional activities demonstrated for the first time that the most potent Jak2 inhibitor in our study, CEP701, also targets Aurora kinases. CEP701 shows a unique combination of both activities which is not found in other compounds also targeting Jak2. Furthermore, colony forming cell assays showed that Janus kinase 2 inhibitors preferentially suppressed the growth of erythroid colonies, whereas inhibitors of Aurora kinases preferentially blocked myeloid colony growth. CEP701 demonstrated a combined suppression of both colony types. Moreover, we show that combined application of a Janus and an Aurora kinase inhibitor recapitulated the effect observed for CEP701 but might allow for more flexibility in combining both activities in clinical settings, e.g. in the treatment of myeloproliferative neoplasms. The newly developed screening assays are high throughput compatible and allow an easy detection of new compounds with Janus kinase 2 inhibitory activity.     

A tetra-primer polymerase chain reaction approach for the detection of JAK2 V617F mutation

Recently, an acquired somatic point mutation (p.V617F) in a highly conserved residue of the pseudokinase domain of the JAK2 tyrosine kinase was shown to be associated with myeloproliferative disorders. Because of the clinical importance of this mutation in diagnosing myeloproliferative disorders and its relevance for disease progression, we have developed a tetra-primer polymerase chain reaction (PCR) assay to detect JAK2 p.V617F. Titration studies showed that the assay could reliably detect one copy of the mutant allele in a mix of 50 wild-type alleles suggesting that the lower detection limit of this assay is estimated to be 2%. This study demonstrates that genotyping and quantifying of the JAK2 V617F mutation can be performed by tetra-primer PCR using both freshly isolated and formalin-fixed tissues. Our tetra-primer PCR assay is sensitive, low-cost, and easy to use method for the detection of JAK2 p.V617F, which could be used even in low-tech laboratories.     

Abdominal venous thrombosis presenting in myeloproliferative neoplasm with JAK2 V617F mutation: a case report

Introduction

An unprovoked thombotic event in a patient is cause for further evaluation of an underlying hypercoaguable state. The investigation should include a thorough search, including checking for a variety of known inherited and acquired hypercoaguble states (protein C or S deficiency, anti-phospholipid antibodies, and anti-thrombin III deficiency) and gene mutations that predispose patients to an increased risk of clotting (for example, prothrombin gene 20210 mutation, factor V Leiden, and the JAK2 V617F mutation).

Case presentation

We report the case of a 38-year-old Caucasian woman with spontaneous, unprovoked abdominal venous thrombosis and demonstrate how testing for the JAK2 V617F mutation was useful in unmasking an underlying hypercoaguable state.

Conclusions

JAK2 V617F-positive myeloproliferative neoplasm was diagnosed. This case illustrates the importance of testing for JAK2 V617F in patients presenting with Budd-Chiari syndrome, even in the absence of overt hematologic abnormalities, in order to establish a diagnosis of underlying myeloproliferative neoplasm.     

Evaluation of clinical and laboratory findings with JAK2 V617F mutation as an independent variable in essential thrombocytosis

Essential thrombocythemia (ET) is an entity of classic Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), characterized by thrombocytosis with megakaryocytic hyperplasia and thrombocytes are increased with abnormal functions. Discovery of the protein tyrosine kinase JAK2 V617F allele contributed to better understanding of the pathogenetic mechanisms of MPNs. Acquired single point mutation in the JAK2 V617F was determined approximately 50–60 % of patients with ET. In this study we aimed to investigate the relationship between JAK2 V617F gene mutation, hematologic, biochemical markers and the complications in the ET patients. A total of 268 patients diagnosed with ET and 219 of those studied for JAK2 gene mutation were followed at the hematology clinics of three major hospitals between 2008 and 2013 were screened retrospectively. Laboratory, clinical and hematologic parameters were compared for JAK2 V617F positive and JAK2 V617F negative patients with ET. 102 (46 %) patients were positive with the JAK2 V617F mutation. The complications were observed in 61 (28 %) patients and 38 (62 %) of them had JAK2 V617F mutation. The levels of white blood cells, neutrophil, basophil, red blood cells, hemoglobin, hematocrit, mean platelet volume, thrombocytes, eosinophil; urea, creatinine were significantly different in patients with the JAK2 V617F mutation (P < 0.05). Presence of the JAK2 V617F mutation supports the diagnosis of ET. It would be useful to investigate the JAK2 V617F mutation and the hematologic and biochemical markers at diagnosis with respect to consider the risk of developing complications and to take the precautions against these complications.     

Identification of CYP4V2 mutation in 21 families and overview of mutation spectrum in Bietti crystalline corneoretinal dystrophy

Bietti crystalline corneoretinal dystrophy (BCD, MIM 210370) is a common form of hereditary retinal degeneration in the Chinese population. BCD is caused by CYP4V2 mutations. Understanding the CYP4V2 mutational spectrum and associated phenotypes is of value for clinical practice. In this study, nine CYP4V2 mutations, including four novel ones (c.215-2A>G, c.761A>G, c.958C>T, and c.1169G>A), were detected in all 21 families with BCD. All patients with CYP4V2 mutations had phenotypes typical for BCD. As of now, 34 CYP4V2 mutations have been identified in 104 of 109 families (95.4%), affecting 204 of the 218 alleles (93.6%). Of the 34 mutations, c.802-8_810del17insGC, c.992A>C, and c.1091-2A>G are the most common mutations, accounting for 62.7%, 7.4%, and 6.4% of the 204 mutant alleles, respectively. The remaining 31 mutations were only detected in 1–6 alleles. Mutations in exons 7, 8, and 9 account for 83.3% of mutant alleles (64.7%, 9.3%, and 10.3%, respectively). Our results expand the mutation spectrum of CYP4V2 and demonstrate an overview of the CYP4V2 mutation spectrum and its frequency in families with BCD. BCD is a clinically and genetically homogenous disease.