Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0032463 (polycythemia vera)
 3,374 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The discovery of an activating tyrosine kinase mutation JAK2V617F in myeloproliferative neoplasms (MPNs), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) has resulted in the development of JAK2 inhibitors, of which several are being evaluated in phase I/II clinical studies. It is important to recognize that because the V617F mutation is localized in a region outside the adenosine triphosphate (ATP)-binding pocket of JAK2 enzyme, ATP-competitive inhibitors of JAK2 kinase (like the current JAK2 inhibitors in the clinic) are not likely to discriminate between wild-type and mutant JAK2 enzymes. Therefore, JAK2 inhibitors, by virtue of their near equipotent activity against wild-type JAK2 that is important for normal hematopoiesis, may have adverse myelosuppression as an expected side effect, if administered at doses that aim to completely inhibit the mutant JAK2 enzyme. While they may prove to be effective in controlling hyperproliferation of hematopoietic cells in PV and ET, they may not be able to eliminate mutant clones. On the other hand, JAK inhibitors may have great therapeutic benefit by controlling the disease for patients with MPNs who suffer from debilitating signs (eg, splenomegaly) or constitutional symptoms (which presumably result from high levels of circulating cytokines that signal through JAK enzymes). Indeed, the primary clinical benefits observed so far in MF patients have been significant reduction is splenomegaly, elimination of debilitating disease-related symptoms, and weight gain. Most importantly, patients with and without the JAK2V617F mutation appear to benefit to the same extent. In this review we summarize current clinical experience with JAK2 inhibitors in MPNs.
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PMID:Therapeutic potential of JAK2 inhibitors. 2000 49

The Philadelphia negative chronic myeloproliferative neoplasms are hematological disorders with several diagnostic challenges. Due to recent molecular findings, the WHO classification of Tumors of Hematopoietic and Lymphoid Tissue 2008 reorganized the field of chronic myeloproliferative diseases. Thus, specific molecular markers provide important information for current diagnostic strategies. This review highlights the important diagnostic tools in classical and atypical myeloproliferative neoplasms mainly the JAK2V617F mutation, the Mpl receptor, Polycythemia rubra vera 1 (PRV1), platelet-derived growth-factor receptor alpha (PDGFRA), platelet-derived growth-factor receptor beta (PDGFRB), fibroblast growth-factor receptor 1 (FGFR1) and c-kit tyrosine kinase. A description of the origin, clinical correlations and role in diagnosis and therapy is provided for each of these molecular markers.
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PMID:Molecular markers guide diagnosis and treatment in Philadelphia chromosome-negative myeloproliferative disorders (Review). 2012 96

The myeloproliferative disorders polycythemia vera, essential thrombocytosis, and primary myelofibrosis are clonal disorders arising in a pluripotent hematopoietic stem cell, causing an unregulated increase in the number of erythrocytes, leukocytes, or platelets, alone or in combination; eventual marrow dominance by the progeny of the involved stem cell; and a tendency to arterial or venous thrombosis, marrow fibrosis, splenomegaly, or transformation to acute leukemia, albeit at widely varying frequencies. The discovery of an activating mutation (V617F) in the gene for JAK2 (Janus kinase 2), a tyrosine kinase utilized by hematopoietic cell receptors for erythropoietin, thrombopoietin, and granulocyte colony-stimulating factor, provided an explanation for the shared clinical features of these 3 disorders. Constitutive JAK2 activation provides a growth and survival advantage to the hematopoietic cells of the affected clone. Because signaling by the mutated kinase utilizes normal pathways, the result is overproduction of morphologically normal blood cells, an often indolent course, and (in essential thrombocytosis) usually a normal life span. Because the erythropoietin, thrombopoietin, and granulocyte colony-stimulating factor receptors are all constitutively activated, polycythemia vera is the potential ultimate clinical phenotype of the JAK2 V617F mutation and, as a corollary, is the most common of the 3 disorders. The number of cells expressing the JAK2 V617F mutation (the allele burden) seems to correlate with the clinical phenotype. Preliminary results of clinical trials with agents that inhibit the mutated kinase indicate a reduction in splenomegaly and alleviation of night sweats, fatigue, and pruritus.
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PMID:Narrative review: Thrombocytosis, polycythemia vera, and JAK2 mutations: The phenotypic mimicry of chronic myeloproliferation. 2019 36

A somatic point mutation (V617F) in the JAK2 tyrosine kinase was found in a majority of patients with polycythemia vera (PV), essential thrombocythemia, and primary myelofibrosis. However, contribution of the JAK2V617F mutation in these 3 clinically distinct myeloproliferative neoplasms (MPNs) remained unclear. To investigate the role of JAK2V617F in the pathogenesis of these MPNs, we generated an inducible Jak2V617F knock-in mouse, in which the expression of Jak2V617F is under control of the endogenous Jak2 promoter. Expression of heterozygous mouse Jak2V617F evoked all major features of human polycythemia vera (PV), which included marked increase in hemoglobin and hematocrit, increased red blood cells, leukocytosis, thrombocytosis, splenomegaly, reduced serum erythropoietin (Epo) levels and Epo-independent erythroid colonies. Homozygous Jak2V617F expression also resulted in a PV-like disease associated with significantly greater reticulocytosis, leukocytosis, neutrophilia and thrombocytosis, marked expansion of erythroid progenitors and Epo-independent erythroid colonies, larger spleen size, and accelerated bone marrow fibrosis compared with heterozygous Jak2V617F expression. Biochemical analyses revealed Jak2V617F gene dosage-dependent activation of Stat5, Akt, and Erk signaling pathways. Our conditional Jak2V617F knock-in mice provide an excellent model that can be used to further understand the molecular pathogenesis of MPNs and to identify additional genetic events that cooperate with Jak2V617F in different MPNs.
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PMID:Conditional expression of heterozygous or homozygous Jak2V617F from its endogenous promoter induces a polycythemia vera-like disease. 2019 48

A common somatic point mutation has recently been identified in the Janus kinase 2 (JAK2) gene in virtually all cases of polycythemia vera and in a majority of patients with essential thrombocythemia and idiopathic myelofibrosis. This common mutation in the pseudokinase autoinhibitory domain of the enzyme results in constitutive tyrosine kinase activation, which in turn leads to cytokine hypersensitivity and factor independence in factor-dependent cell lines, and causes polycythemia in mice. This discovery has led to greater understanding of the molecular pathogenesis of the chronic myeloproliferative disorders, which may translate into targeted therapy.
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PMID:The JAK2(V617F) tyrosine kinase mutation in myeloproliferative disorders: Summary of published literature and a perspective. 2042 35

The myeloproliferative disorders (MPDs) are a spectrum of clonal disorders of the hematopoietic system. The discovery of activating mutations of the tyrosine kinase JAK2 in polycythemia vera, essential thrombocythemia, and primary myelofibrosis has lead to in vitro and animal model studies that promise to lead to therapeutic advances.
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PMID:The molecular biology of myeloproliferative disorders. 2054 3

BCR-ABL is a causative tyrosine kinase (TK) of chronic myelogenous leukemia (CML). In CML patients, although myeloid cells are remarkably proliferating, erythroid cells are rather decreased and anemia is commonly observed. This phenotype is quite different from that observed in polycythemia vera (PV) caused by JAK2 V617F, whereas both oncogenic TKs activate common downstream molecules at the level of hematopoietic stem cells (HSCs). To clarify this mechanism, we investigated the effects of BCR-ABL and JAK2 V617F on erythropoiesis. Enforced expression of BCR-ABL but not of JAK2 V617F in murine LSK (Lineage(-)Sca-1(hi)CD117(hi)) cells inhibited the development of erythroid cells. Among several signaling molecules downstream of BCR-ABL, an active mutant of N-Ras (N-RasE12) but not of STAT5 or phosphatidylinositol 3-kinase (PI3-K) inhibited erythropoiesis, while N-RasE12 enhanced the development of myeloid cells. BCR-ABL activated Ras signal more intensely than JAK2 V617F, and inhibition of Ras by manumycin A, a farnesyltransferase inhibitor, ameliorated erythroid colony formation of CML cells. As for the mechanisms of Ras-induced suppression of erythropoiesis, we found that GATA-1, an erythroid-specific transcription factor, blocked Ras-mediated mitogenic signaling at the level of MEK through the direct interaction. Furthermore, enforced expression of N-RasE12 in LSK cells derived from p53-, p16(INK4a)/p19(ARF)-, and p21(CIP1/WAF1)-null/wild-type mice revealed that suppressed erythroid cell growth by N-RasE12 was restored only by p21(CIP1/WAF1) deficiency, indicating that a cyclin-dependent kinase (CDK) inhibitor, p21(CIP1/WAF1), plays crucial roles in Ras-induced suppression of erythropoiesis. These data would, at least partly, explain why respective oncogenic TKs cause different disease phenotypes.
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PMID:BCR-ABL but not JAK2 V617F inhibits erythropoiesis through the Ras signal by inducing p21CIP1/WAF1. 2066 70

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.
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PMID:Experimental therapeutics for patients with myeloproliferative neoplasias. 2092 95

Since William Dameshek has described the concept of "myeloproliferative disorders (MPD)" by identifying common clinical characteristics (i.e. hemorrhage, thrombosis and leukemic transformation) of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), the advent of molecular biology has provided substantial molecular insight into the pathobiology of myeloproliferative neoplasia (MPN). Recently, the description of the gain-of-function mutation of JAK2 (JAK2V617F) has been identified in classical Philadelphia (Ph)-negative MPN, thus providing a rational target for novel innovative treatment strategies. In addition, molecular characterization of atypical Ph-negative MPN (e.g. the KITD816V mutation in mastocytosis and PDGF-receptor rearrangements in hypereosinophilic syndromes/chronic eosinophilic leukemia) complement the molecular knowledge of this heterogeneous disease family. Currently, clinical studies testing various JAK2-inhibitors in PV, ET as well as in primary and secondary myelofibrosis (MF) are under way. Interestingly, first data indicate that despite marked clinical activity in terms of spleen size reduction and improvement of constitutional symptoms, these inhibitors might not sufficiently reduce disease burden. Thus, alternative and well established treatment strategies, such as inhibition of thrombocyte aggregation by low dose aspirin, cytotoxics (e.g. hydroxyurea), immuno- and stroma-modifying therapy with interferon, tyrosine kinase inhibitors and, in selected cases, allogeneic stem cell transplantation are still important treatment options for patients suffering from MPN, which will be discussed in detail in this review.
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PMID:Current treatment concepts of Philadelphia-negative MPN. 2106 42

The four major entities that form the group of myeloproliferative neoplasms (MPN) are BCR-ABL positive chronic myeloid leukaemia (CML), chronic idiopathic myelofibrosis (CIMF), essential thrombocythemia (ET) and polycythemia vera (PV). All four are clonal diseases of the haematopoietic stem or precursor cell, they are of a chronic nature and potentially aggravate to myelofibrosis or transform into acute leukaemia. Several strategies are pursued in the treatment of MPN. On the one hand, targeted therapies such as tyrosine kinase inhibitors (imatinib, dasatinib, nilotinib) and JAK2-inhibitors are adopted in MPN as well as rather unspecific treatment with interferon-alpha and with the newer group of immunomodulatory drugs (IMIDs). On the other hand, cellular immunotherapeutical options as allogeneic haematopoietic stem cell transplantation (HSCT) and donor lymphocyte infusion (DLI) are exerted in patients with MPN. Evidence resulting from graft-versus-leukaemia (GvL) effect was the key to develop more specific immunotherapies for patients with haematologic malignancies. In this context, CML is a model for immunotherapeutic approaches, and therefore, vaccination trials using peptides derived from leukaemia-associated antigens (LAAs) to stimulate specific T cells are currently under investigation. But also in BCR-ABL-negative MPNs, antigens have been identified and immunomodulatory treatment strategies have been performed. All of the current immunotherapeutical options in patients with MPN will be discussed throughout this review.
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PMID:Immunotherapy for myeloproliferative neoplasms (MPN). 2106 47


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