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)

HLA-G5 is secreted by erythroblasts in all hematopoietic organs, suggesting a role for this protein in erythropoiesis. To examine this, we analyzed whether HLA-G5 affects the proliferation of UT7/EPO and HEL erythroleukemia cells and characterized the mechanism by which HLA-G5 influences erythropoietin receptor (EPOR) signaling. We show that HLA-G5 inhibits the proliferation of UT7/EPO cells, the EPOR signaling of which is similar to that of normal erythroid progenitors. HLA-G5-mediated inhibition was associated with reduced phosphorylation of JAK2 kinase and that of the downstream signaling proteins STAT-5 and STAT-3. Involvement of JAK2 in erythroid cell proliferation has been highlighted by the role of JAK2 V617F mutation in polycythemia vera (PV), a myeloproliferative disorder characterized by erythroid lineage overproduction. We demonstrate that HLA-G5 downregulates EPOR constitutive signaling of JAK2 V617F-expressing HEL cells, leading to inhibition of cell proliferation through G1 cell cycle arrest. Combination of HLA-G5 with JAK inhibitor I further decreases HEL cell growth. Clinical relevance is provided by analysis of PV patients who carry JAK2 V617F mutation, showing that HLA-G5 inhibits the formation of erythropoietin-independent erythroid colonies. Such HLA-G5-mediated inhibition constitutes a new parameter to be considered in the design of future approaches aimed at treating JAK2 V617F-positive myeloproliferative disorders.
Leukemia 2008 Mar
PMID:HLA-G turns off erythropoietin receptor signaling through JAK2 and JAK2 V617F dephosphorylation: clinical relevance in polycythemia vera. 1805 84

We investigated the activity of ITF2357, a novel histone deacetylase inhibitor (HDACi) with antitumor activity, on cells carrying the JAK2(V617F) mutation obtained from polycythemia vera (PV) and essential thrombocythemia (ET) patients as well as the HEL cell line. The clonogenic activity of JAK2(V617F) mutated cells was inhibited by low concentrations of ITF2357 (IC(50) 0.001-0.01 microM), 100- to 250-fold lower than required to inhibit growth of normal or tumor cells lacking this mutation. Under these conditions, ITF2357 allowed a seven fold increase in the outgrowth of unmutated over mutated colonies. By western blotting we showed that in HEL cells, ITF2357 led to the disappearance of total and phosphorylated JAK2(V617F) as well as pSTAT5 and pSTAT3, but it did not affect the wild-type JAK2 or STAT proteins in the control K562 cell line. By real-time PCR, we showed that, upon exposure to ITF2357, JAK2(V617F) mRNA was not modified in granulocytes from PV patients while the expression of the PRV-1 gene, a known target of JAK2, was rapidly downmodulated. Altogether, the data presented suggest that ITF2357 inhibits proliferation of cells bearing the JAK2(V617F) mutation through a specific downmodulation of the JAK2(V617F) protein and inhibition of its downstream signaling.
Leukemia 2008 Apr
PMID:The histone deacetylase inhibitor ITF2357 selectively targets cells bearing mutated JAK2(V617F). 1807 39

Optimal clinical management of patients with primary myelofibrosis and post-essential thrombocythemia/polycythemia vera myelofibrosis is a challenge, given the typically advanced age of presentation and variability of the disease course and prognosis. Current medical therapeutic options have not demonstrated an impact on the disease course, which exceeds the palliation of disease-related extramedullary hematopoiesis and alleviation of cytopenias. In contrast, allogeneic stem cell transplantation (SCT) can lead to 'cure' but is limited due to patient's age or comorbidities. Currently, in patients, who are reasonable candidates, SCT (frequently with a reduced intensity conditioning regimen) is employed for intermediate- to high-risk disease. Current pharmaco-medical therapy is used as a bridge to transplant, or instead of transplant in poor transplant candidates. Pathogenetic insights, especially the discovery of the Janus kinase (JAK)2(V617F) mutation, have ushered in a host of new potential therapeutic agents that may augment the role of medical therapy. Similarly, the boundaries of transplantation continue to alter with strategies that decrease conditioning-related toxicity, improved antimicrobial prophylaxis and decreased graft-versus-host disease. The potential for continued improvements in both medical and transplant therapy suggests that for the immediate future the optimal choices for an individual patient will remain potentially volatile and present complex decisions.
Leukemia 2008 Mar
PMID:Choosing between stem cell therapy and drugs in myelofibrosis. 1818 25

Myelofibrosis (MF; primary or post-essential thrombocythemia/polycythemia vera) is incurable clonal myeloproliferative disorder, with no effective treatment. Epigenetic changes play an important role in cancer pathogenesis through transcriptional silencing of critical tumor suppressor genes. We conducted a phase-II study to evaluate the activity of DNA methyltransferase inhibitor, 5-azacitidine, in patients with MF. Thirty-four patients (76% previously treated) received 5-azacitidine at 75 mg/m(2) subcutaneously daily for 7 days, every 4 weeks. Twelve (35%) patients had abnormal cytogenetics and 19 (70%) of 27 evaluable patients had JAK2(V617F) mutation. Responses occurred in 8 (24%) patients after a median of 5 months (range, 3-10). Partial response occurred in 1 (3%) patient (duration 22+ months) and clinical improvement in 7 (21%) patients (median duration 4 months; range, 2-8.5). Myelosuppression was the major adverse effect, with grade 3-4 neutropenia in 10 (29%) patients. Global DNA methylation assessed by the long interspersed nucleotide element (LINE) bisulfite/pyrosequencing assay decreased from 53% pretherapy to 44% on day 14 (P=0.0014) and returned to 50% at the end of the first 28-day cycle (P=0.016). 5-azacitidine is relatively well tolerated and results in induction of global hypomethylation in patients with MF, but results in limited clinical activity.
Leukemia 2008 May
PMID:A phase II study of 5-azacitidine for patients with primary and post-essential thrombocythemia/polycythemia vera myelofibrosis. 1850 50

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder, characterized by increased proliferation of megakaryocytes and elevated platelet count that usually occurs sporadically. We report a family with seven affected individuals in three generations, including one individual with a phenotype resembling polycythemia vera, a related disorder. Megakaryocyte (CFU-MK) colony formation occurred in the absence of added cytokines in cultures of peripheral blood from affected family members. Some reports of familial ET have identified mutations in THPO and MPL, the genes for a cytokine (thrombopoietin, TPO) that regulates platelet production and its receptor (c-MPL), respectively. In this family, the MPL gene was excluded by linkage analysis. Although TPO levels were elevated in most affected family members and evidence for linkage was found between the disease and THPO (theta=0.0, Z(max)=3.0), a THPO mutation was not identified by DNA sequencing. The JAK2 V617F mutation that has been associated with 50% of sporadic cases of ET was identified as a somatic mutation, an acquired defect, in peripheral blood of the two most severely affected family members. These patients also had elevated TPO levels. Further study of familial myeloproliferative diseases will help elucidate the initiating genetic events underlying ET.
Leukemia 2008 Aug
PMID:Familial essential thrombocythemia with spontaneous megakaryocyte colony formation and acquired JAK2 mutations. 1849 61

JAK2 and MPL mutations are recurrent in myeloproliferative neoplasms (MPNs). A JAK2 mutation, primarily JAK2V617F, is almost invariably associated with polycythemia vera (PV). However, JAK2V617F also occurs in the majority of patients with essential thrombocythemia (ET) or primary myelofibrosis (PMF) as well as in a much smaller percentage of those with other MPNs. The mechanism(s) behind this one allele-multiple phenotypes phenomenon has not been fully elucidated. The issue is further confounded by the presence of marked variation in JAK2V617F allele burden among mutation-positive patients. In the current communication, we discuss potential mechanisms for phenotypic diversity among JAK2V617F-positive MPNs as well as review the current literature in regard to genotype-phenotype correlations (that is clinical correlates and prognostic significance) in the context of both the presence or absence of the mutation (ET and PMF) and its allele burden (PV, ET and PMF).
Leukemia 2008 Jul
PMID:Clinical correlates of JAK2V617F presence or allele burden in myeloproliferative neoplasms: a critical reappraisal. 1849 62

Major causes of morbidity and mortality in polycythemia vera (PV) and essential thrombocythemia (ET) are represented by thrombosis and bleeding, progression to myelofibrosis and transformation to acute leukemia. Myelosuppressive therapy, preferentially with hydroxyurea, can reduce the rate of vascular complications, but there is some concern about an increased rate of leukemic transformation with this agent. Therefore, management of these disorders poses a significant challenge, and a risk-oriented therapeutic approach should be strictly followed to avoid inappropriate exposure to cytotoxic drugs on one side or suboptimal treatment on the other. Established risk factors for cardiovascular events are represented by older age and previous thrombosis, whereas impact of novel biological factors, including leukocytosis and JAK2V617F mutational status and/or mutational burden, is under active investigation. Low-risk PV patients should be managed only with phlebotomy and aspirin, whereas high-risk patients should also receive cytotoxic therapy. Regarding the management of ET, there is no clear indication for intervention in low-risk patients, whereas high-risk patients should be managed with chemotherapy. Other therapeutic options, such as interferon-alpha or anagrelide, may find place in selected patients including those who are resistant/intolerant to hydroxyurea. Finally, there is great expectation for novel drugs targeting the constitutively active JAK2/STAT pathway.
Leukemia 2008 Aug
PMID:Evidence and expertise in the management of polycythemia vera and essential thrombocythemia. 1859 37

Although it has long been known that the myeloproliferative neoplasms (MPN) polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF) are clonal hematopoietic stem-cell disorders, for many years the genetic basis for these disorders was elusive. A new era in MPN biology began in 2005 with the discovery of a somatic point mutation in JAK2 tyrosine kinase (JAK2V617F), which was identified in a significant proportion of patients with PV, ET and PMF. Based on the hypothesis that JAK-STAT signaling is central to the pathogenesis of JAK2V617F-negative MPN, genomic studies have identified JAK2 exon 12 mutations in JAK2V617F-negative PV and activating mutations in MPL in patients with JAK2V617F-negative ET and PMF. In this review, we will discuss the role of these mutant alleles in the pathogenesis of PV, ET and PMF, the potential therapeutic implications of these discoveries, and the implications of these discoveries for genomic studies of hematopoietic malignancies.
Leukemia 2008 Oct
PMID:JAK2 and MPL mutations in myeloproliferative neoplasms: discovery and science. 1875 26

The BCR-ABL-negative myeloproliferative neoplasms (MPNs), polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF), entered the spotlight in 2005 when the unique somatic acquired JAK2 V617F mutation was described in >95% of PV and in 50% of ET and PMF patients. For the very rare PV patients who do not harbor the JAK2 V617F mutation, exon 12 JAK2 mutants were discovered also to result in activated forms of JAK2. A minority of ET and PMF patients harbor mutations that constitutively activate the thrombopoietin receptor (TpoR). In bone marrow reconstitution models based on retroviral transduction, the phenotype induced by JAK2 V617F is less severe and different from the rapid fatal myelofibrosis induced by TpoR W515L. The reasons for these differences are unknown. Exactly by which mechanism(s) one acquired somatic mutation, JAK2 V617F, can promote three different diseases remains a mystery, although gene dosage and host genetic variation might have important functions. We review the recent progress made in deciphering signaling anomalies in PV, ET and PMF, with an emphasis on the relationship between JAK2 V617F and cytokine receptor signaling and on cross-talk with several other signaling pathways.
Leukemia 2008 Oct
PMID:Aberrant signal transduction pathways in myeloproliferative neoplasms. 1876 48

Interferon (IFN) was the first cytokine discovered 50 years ago, with a wide range of biological properties, including immunomodulatory, proapoptotic and antiangiogenic activities, that rapidly raised interest in its therapeutic use in malignancies. IFN-receptor characterization was also pivotal in the discovery of the JAK/STAT signaling pathway. Among the large IFN family, mainly one of the type I IFN, IFN-alpha2, is used in therapy. Many clinical trials have shown remarkable efficacy of IFN-alpha in bcr-abl-negative myeloproliferative neoplasms (MPNs), especially polycythemia vera (PV), and essential thrombocythemia (ET). IFN-alpha induces about 80% of hematological responses in those diseases and is able to reduce splenomegaly, as well as relieve pruritus and other constitutional symptoms. Yet its use was limited by toxicity, leading to early treatment discontinuation in about 20% of the patients. However, its lack of leukemogenic potential and its possible use during pregnancy have already made IFN-alpha the drug of choice for younger MPN patients. In addition, several studies have shown a probably selective effect of IFN-alpha on PV and ET clones, as shown by cytogenetic remissions, reversions to polyclonal hematopoiesis, and more recently by induction of JAK2V617F complete molecular remissions in PV which may widen the indications of IFN-alpha in JAK2-mutated MPN.
Leukemia 2008 Nov
PMID:Interferon-alpha therapy in bcr-abl-negative myeloproliferative neoplasms. 1884 85


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