Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038002 (splenomegaly)
 9,873 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Activating FMS-like tyrosine kinase 3 (FLT3) mutations have been identified in approximately 30% of patients with acute myelogenous leukemia (AML), and recently in a smaller subset of patients with acute lymphoblastic leukemia (ALL). To explore the in vivo consequences of an activating FLT3 internal tandem duplication mutation (FLT3-ITD), we created a transgenic mouse model in which FLT3-ITD was expressed under the control of the vav hematopoietic promoter. Five independent lines of vav-FLT3-ITD transgenic mice developed a myeloproliferative disease with high penetrance and a disease latency of 6-12 months. The phenotype was characterized by splenomegaly, megakaryocytic hyperplasia, and marked thrombocythemia, but without leukocytosis, polycythemia, or marrow fibrosis, displaying features reminiscent of the human disease essential thrombocythemia (ET). Clonal immature B- or T-lymphoid disease was observed in two additional founder mice, respectively, that could be secondarily transplanted to recipient mice that rapidly developed lymphoid disease. Treatment of these mice with the FLT3 tyrosine kinase inhibitor, PKC412, resulted in suppression of disease and a statistically significant prolongation of survival. These results demonstrate that FLT3-ITD is capable of inducing myeloproliferative as well as lymphoid disease, and indicate that small-molecule tyrosine kinase inhibitors may be an effective treatment for lymphoid malignancies in humans that are associated with activating mutations in FLT3.
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PMID:FLT3 internal tandem duplication mutations induce myeloproliferative or lymphoid disease in a transgenic mouse model. 1611 83

The JAK2(V617F) mutation was found in most patients with myeloproliferative disorders (MPDs), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We have generated transgenic mice expressing the mutated enzyme in the hematopoietic system driven by a vav gene promoter. The mice are viable and fertile. One line of the transgenic mice, which expressed a lower level of JAK2(V617F), showed moderate elevations of blood cell counts, whereas another line with a higher level of JAK2(V617F) expression displayed marked increases in blood counts and developed phenotypes that closely resembled human essential thrombocythemia and polycythemia vera. The latter line of mice also developed primary myelofibrosis-like symptoms as they aged. The transgenic mice showed erythroid, megakaryocytic, and granulocytic hyperplasia in the bone marrow and spleen, displayed splenomegaly, and had reduced levels of plasma erythropoietin and thrombopoietin. They possessed an increased number of hematopoietic progenitor cells in peripheral blood, spleen, and bone marrow, and these cells formed autonomous colonies in the absence of growth factors and cytokines. The data show that JAK2(V617F) can cause MPDs in mice. Our study thus provides a mouse model to study the pathologic role of JAK2(V617F) and to develop treatment for MPDs.
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PMID:Transgenic expression of JAK2V617F causes myeloproliferative disorders in mice. 1833 77

To elucidate whether caspase activation is involved in megakaryopoiesis, we characterized megakaryocytes (MKs) in vav-bcl-2 transgenic (Tg) mice, in which Bcl-2 is overexpressed in hematopoietic cells. To exclude the effect of splenomegaly in Tg mice on megakaryopoiesis, splenectomy was performed. After splenectomy, basal platelet counts in peripheral blood were not significantly different between Tg and wild-type (WT) mice. However, when experimental thrombocytopenia was induced by injecting 5-fluorouracil into splenectomized mice, overshoot of platelet counts during the recovery phase was hardly observed in Tg mice. Analyses of MK ploidy during the recovery phase showed that MKs less than 16 N ploidy were significantly decreased in Tg mice, suggesting that MK supply from progenitors is impaired. Supporting this, differentiation of CD34-/c-kit+/Sca-1+/Lineage- stem cells into MKs was significantly hampered in Tg mice, whereas megakaryocyte-erythroid progenitors (MEPs) normally differentiated into MKs. It suggests that differentiation into MKs is impaired in Tg mice before the stage of MEP. Furthermore, MK colony formation in WT cells was dose-dependently inhibited in the presence of a caspase inhibitor. Contrary, Bcl-2-overexpressing MKs showed normal ability for in vitro platelet production. We thus believe that caspase activation is involved in the differentiation of progenitors into megakaryocytic lineage but not in platelet production.
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PMID:Caspase activation is involved in early megakaryocyte differentiation but not in platelet production from megakaryocytes. 1921 31

Philadelphia chromosome-negative myeloproliferative neoplasms, including polycythemia vera, essential thrombocytosis, and myelofibrosis, are disorders characterized by abnormal hematopoiesis. Among these myeloproliferative neoplasms, myelofibrosis has the most unfavorable prognosis. Furthermore, currently available therapies for myelofibrosis have little to no efficacy in the bone marrow and hence, are palliative. We recently developed a Janus kinase 2 (Jak2) small molecule inhibitor called G6 and found that it exhibits marked efficacy in a xenograft model of Jak2-V617F-mediated hyperplasia and a transgenic mouse model of Jak2-V617F-mediated polycythemia vera/essential thrombocytosis. However, its efficacy in Jak2-mediated myelofibrosis has not previously been examined. Here, we hypothesized that G6 would be efficacious in Jak2-V617F-mediated myelofibrosis. To test this, mice expressing the human Jak2-V617F cDNA under the control of the vav promoter were administered G6 or vehicle control solution, and efficacy was determined by measuring parameters within the peripheral blood, liver, spleen, and bone marrow. We found that G6 significantly reduced extramedullary hematopoiesis in the liver and splenomegaly. In the bone marrow, G6 significantly reduced pathogenic Jak/STAT signaling by 53%, megakaryocytic hyperplasia by 70%, and the Jak2 mutant burden by 68%. Furthermore, G6 significantly improved the myeloid to erythroid ratio and significantly reversed the myelofibrosis. Collectively, these results indicate that G6 is efficacious in Jak2-V617F-mediated myelofibrosis, and given its bone marrow efficacy, it may alter the natural history of this disease.
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PMID:The small molecule inhibitor G6 significantly reduces bone marrow fibrosis and the mutant burden in a mouse model of Jak2-mediated myelofibrosis. 2279 37