Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.2 (focal adhesion kinase)
44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chromosomal aberrations in polycythemia vera (PV) are heterogenous and nonrandom. A prognostic predictive value of these aberrations has not been established. The V617F mutation in the JAK2 gene on chromosome 9p24.1 was identified recently in peripheral blood leukocytes in the majority of patients with PV and in approximately half of patients with essential thrombocythemia and idiopathic myelofibrosis. Within the JAK2 V617F-positive PV patients, however, clinical presentation and degree of myeloproliferation varies to a great extent. Here we report four cases of chronic myeloproliferative disorders [two with PV, one with PV in transformation to idiopathic myelofibrosis (IMF) and one IMF patient], with the distinct karyotypic abberations der(18) t(9;18) (p13;p11) and der(9;18)(p10;q10). Two patients had hyperproliferative PV and two had "transitional PV" and IMF, respectively. All four patients harbored the JAK2 V617F mutation. Our data, together with previously published data, clearly indicate an association of these chromosomal abnormalities with a highly proliferative PV phenotype with a propensity to transform into postpolycythemic myelofibrosis. Cytogenetic analysis seems to identify a subgroup of patients with a distinct prognostic profile, and should be performed in conjunction with a JAK2 mutation analysis in patients suspected of a chronic myeloproliferative disease.
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PMID:A der(18)t(9;18)(p13;p11) and a der(9;18)(p10;q10) in polycythemia vera associated with a hyperproliferative phenotype in transformation to postpolycythemic myelofibrosis. 1721 18

The Philadelphia chromosome (Ph)-negative myeloproliferative disorders (MPDs) include essential thrombocythemia (ET), idiopathic myelofibrosis (IMF), and polycythemia vera (PV). All of these disorders are clonal hematologic malignancies originating at the level of the pluripotent hematopoietic stem cell. Recently, activating mutations of the intracellular cytokine-signaling molecule JAK2 have been identified in > 90% of patients with PV and in 50% of those with IMF and ET. In addition, a mutation of the thrombopoietin receptor, MPLW515L, has been documented in some patients with IMF. Both mutations activate JAK-STAT signaling pathways and likely play a role in disease progression. Both ET and PV are associated with prolonged clinical courses associated with frequent thrombotic and hemorrhagic events, and progression to myelofibrosis and acute leukemia. IMF has a much poorer prognosis and is associated with cytopenias, splenomegaly, extramedullary hematopoiesis, and bone marrow fibrosis. Stratification of risk for the development of complications from Ph-negative MPDs has guided the identification of appropriate therapies for this population. Intermediate/high-risk IMF or myelofibrosis after ET or PV is associated with a sufficiently poor prognosis to justify the use of allogeneic stem cell transplantation, which is capable of curing such patients. Reduced-intensity conditioning in preparation for allogeneic stem cell transplantation has permitted older patients with IMF to undergo transplantation with increasing success.
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PMID:Philadelphia chromosome-negative myeloproliferative disorders: biology and treatment. 1722 72

We compared the laboratory and clinical findings of 179 patients with essential thrombocythemia (ET) and 77 with polycythemia vera (PV) classified according to the presence of the JAK2 V617F mutation. A gradient was observed in laboratory values between patients with JAK2 wild-type ET, JAK2 V617F ET and PV (all of whom carried the JAK2 mutation). The rate of thrombotic complications in JAK2-positive ET patients was significantly higher than that in wild-type ET patients and not statistically different from that in PV patients.
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PMID:Risk of thrombosis in patients with essential thrombocythemia and polycythemia vera according to JAK2 V617F mutation status. 1722 51

Achieving a specific diagnosis of polycythemia vera (PV) and other myeloproliferative disorders (MPDs) is often costly and complex. However, the recent identification of a V617F mutation in the JH2 domain of the JAK2 gene in a high proportion of patients suffering from MPDs may provide confirmation of a diagnosis. This is an acquired mutation and, as such, may only be present in a small number of cells within a sample. There is therefore a clinical need for highly sensitive detection techniques. We have developed a sensitive real-time polymerase chain reaction (PCR)-based approach for both detection and quantification of the JAK2 V671F mutation load, which allows determination of mutation status without the need for prior purification of granulocytes. We have performed a comparison of this assay with two previously published detection methods. Although an amplification refractory mutation system (ARMS) was shown to be slightly superior in terms of sensitivity, our real-time PCR method provides the potential for quantification of the JAK2 V617F mutation, having potential future applications in the monitoring of minimal residual disease or predicting outcome of disease severity.
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PMID:Development of a quantitative real-time polymerase chain reaction assay for the detection of the JAK2 V617F mutation. 1725 34

The recently described JAK2 V617F mutation, present in a substantial proportion of nonchronic myelogenous leukemia chronic myeloproliferative disorders (non-CML CMPDs), is changing the way we conceptualize and diagnose these diseases. We hypothesized that the activation of this tyrosine kinase might result in activation of downstream mediators such as STAT5, which would be detectable in bone marrow biopsies. We examined the expression of activated STAT5 (nuclear phospho-STAT5) in 73 bone marrow biopsies from patients with CMPDs [20 essential thrombocythemia (ET), 26 chronic idiopathic myelofibrosis (CIMF), and 27 polycythemia vera] and 39 controls. We compared the results with the JAK2 mutational status and clinical parameters. The frequency of the JAK2 V617F was 73% (85% in PV, 65% in ET, and 65% in CIMF). All patients with the JAK2 V617F showed abnormal nuclear megakaryocytic phospho-STAT5 (nMEG pSTAT5) expression. In the JAK2 wild-type group, nMEG pSTAT5 was observed in 2/7 ET, and 3/9 CIMF patients. nMEG pSTAT5 staining was 100% sensitive and 88% specific for JAK2 V617F. Clinically, nMEG pSTAT5+ patients seemed to require cytoreductive therapy more often than those without nMEG p-STAT expression. pSTAT5 immunohistochemistry is a useful diagnostic test in bone marrow biopsies from suspected non-CML CMPD patients. It identifies most of the patients with the JAK2 V617F but also other JAK2 wild-type CMPD patients. The presence of nMEG pSTAT5 in a subset of CMPD patients lacking the mutation suggests that alternate tyrosine kinase/phosphatase pathways may be involved and warrant further investigation. Phosphoprotein detection represents a new area for diagnostic pathology that exploits specific functional characteristics of cells within the context of a tissue section.
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PMID:Bone marrow phospho-STAT5 expression in non-CML chronic myeloproliferative disorders correlates with JAK2 V617F mutation and provides evidence of in vivo JAK2 activation. 1725 68

Atypical megakaryocytes provide the histomorphological hallmark of all Philadelphia-chromosome negative chronic myeloproliferative disorder (Ph(-) CMPD) subtypes and have not been studied so far for the JAK2(V617F) mutation. The mutant gene dosage was determined in isolated megakaryocytes from 68 cases of JAK2(+)/Ph(-) CMPD by a pyrosequencing assay. Megakaryocytes from essential thrombocythemia (ET) showed significantly lower levels of mutated JAK2 alleles compared to patients with chronic idiopathic myelofibrosis (cIMF) with manifest fibrosis and polycythemia vera (PV) but not to prefibrotic cIMF. Solely, ET JAK2V617F in megakaryocytes is associated with a PV-like phenotype, and at least in one patient, the JAK2 mutation was exclusively acquired within the megakaryocytic lineage. The overt differences between prefibrotic and fibrotic cIMF suggested a causative role of the gene dosage of mutant JAK2 in fibrotic progression. Megakaryocyte analysis of a follow-up of eight individual cases with sequential biopsies, however, showed that progression to homozygosity of V617F mutated JAK2 and onset of manifest fibrosis appeared to be independent events. We conclude that megakaryocytes might be the predominant or even the exclusive lineage that acquires the JAK2(V617F) mutation in ET and that the JAK2(V617F) evolution to higher gene dosages represents a dynamic and complex process substantially involving megakaryocytes.
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PMID:Different involvement of the megakaryocytic lineage by the JAK2 V617F mutation in Polycythemia vera, essential thrombocythemia and chronic idiopathic myelofibrosis. 1726 92

The clinical course of polycythemia vera (PV) is marked by a high incidence of thrombotic complications; fibrotic and leukemic disease transformations are additional causes of morbidity and mortality. Major predictors of vascular events are increasing age and previous thrombosis; leukocytosis and high JAK2 V617F allele burden are currently being investigated for additional prognostic value in this regard. Myelosuppressive drugs can reduce the rate of thrombosis, but there is concern that their use raises the risk of transformation into acute leukemia. To tackle this dilemma, a risk-oriented management strategy is recommended. Low-risk patients should be treated with phlebotomy and low-dose aspirin. Cytotoxic therapy is indicated in high-risk patients, and the drug of choice is hydroxyurea because of its efficacy in preventing thrombosis and low leukemogenicity. Interferon-alpha should be reserved for selected categories of patients due to high cost and toxicity. The demonstration of JAK2 V617F mutation in the vast majority of PV patients opens the avenue for the development of promising new molecularly targeted drugs.
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PMID:How I treat patients with polycythemia vera. 1726 1

It is now well-recognized that the activating JAK2(V617F) mutation occurs in the majority of patients with polycythemia vera (PV) and approximately half of those with either essential thrombocythemia (ET) or myelofibrosis with myeloid metaplasia (MMM). Here we analyzed JAK2(V617F) mutation in 137 Chinese patients with myeloproliferative disorders by allele-specific polymerase chain reaction (PCR). DNA was extracted from methanol/acetic acid-fixed cells that had been routinely prepared for cytogenetic analysis. A single point mutation (Val617Phe) was identified in JAK2 in 42 (73.7%) of 57 patients with PV, 40 (58.8%) of 68 with ET, and eight (66.7%) of 12 with MMM.
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PMID:Analysis of JAK2(V617F) mutation in Chinese patients with myeloproliferative disorders. 1726 61

The JAK2 V617F mutation is a frequent genetic event in the three classical Philadelphia-chromosome negative chronic myeloproliferative disorders (Ph(neg.)-CMPD), polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF). Its occurrence varies in frequency in regards to phenotype. The mutation is found in the majority of patients with PV and about half of the patients with ET and IMF. These diseases are clonal stem cell disorders arising in an early stem cell progenitor. The level in the stem cell hierarchy on which the initiating genetic events and the JAK2 V617F mutation occurs is not known. The mutation has so far been detected in all cells of the myeloid lineage, whereas the potential clonal involvement of the lymphoid lineage is controversial. In this study, we detected the JAK2 V617F mutation by real-time quantitative PCR (qPCR) in both B-lymphocytes and T-lymphocytes in a subgroup of patients with Ph(neg.)-CMPDs. These results demonstrate the origin of the JAK2 V617F positive disorders in an early stem cell with both lymphoid and myeloid differentiation potential.
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PMID:The JAK2 V617F mutation involves B- and T-lymphocyte lineages in a subgroup of patients with Philadelphia-chromosome negative chronic myeloproliferative disorders. 1731 77

The Val617Phe point mutation of Janus kinase 2 gene is believed to participate in the pathogenesis of myeloproliferative syndrome characterised by the clonal alteration of hematopoietic stem cells. According to current results, the frequency of Val617Phe activating mutation is around 80% in polycythaemia vera, 35% in essential thrombocythemia, and 50% in chronic idiopathic myelofibrosis. The diagnoses of polycythemia vera, essential thrombocythemia and idiopathic myelofibrosis were so far based on the exclusion of secondary factors as well as bone marrow biopsy histology. The goal of the present work was to establish simple molecular genetic techniques for the routine testing of Janus kinase 2 gene Val617Phe mutation, and to compare the clinical phenotypes of Val617Phe mutation positive and negative myeloproliferative syndromes. We employed the allele specific polymerase chain technique for detection of Val617Phe mutation in 252 patients with myeloproliferative syndrome. We measured Val617Phe frequency as 85,4% (117/137) in polycythemia vera, 56,6% (56/99) in essential thrombocythemia, and 87,5% (14/16) in idiopathic myelofibrosis. We found significantly elevated hemoglobin levels and white blood cell counts (measured at the time of diagnosis) in Val617Phe-positive polycythemia vera and essential thrombocythemia patient groups compared to Val617Phe-negative patients. However, the frequencies of splenomegaly and other complications (thrombosis, bleeding, transformation to acute leukemia) were not significantly different between the mutation-positive and negative groups. In conclusion, the non-invasive mutation analysis of the Janus kinase 2 Val617Phe is suitable for routine laboratory application and helps the differential diagnosis of myeloproliferative syndrome. Although the exact role of Val617Phe mutation testing has not yet been identified on the basis of a broad professional consensus, the testing is suggested in cases of erythrocytoses and thrombocytoses of unknown origin.
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PMID:[Role of the activating mutation Val617Phe of Janus kinase 2 gene in myeloproliferative diseases and significance of its detection]. 1734 40


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