RESUMO
Despite their known transforming properties, the effects of leukemogenic FLT3-ITD mutations on hematopoietic stem and multipotent progenitor cells and on hematopoietic differentiation are not well understood. We report a mouse model harboring an ITD in the murine Flt3 locus that develops myeloproliferative disease resembling CMML and further identified FLT3-ITD mutations in a subset of human CMML. These findings correlated with an increase in number, cell cycling, and survival of multipotent stem and progenitor cells in an ITD dose-dependent manner in animals that exhibited alterations within their myeloid progenitor compartments and a block in normal B cell development. This model provides insights into the consequences of constitutive signaling by an oncogenic tyrosine kinase on hematopoietic progenitor quiescence, function, and cell fate.
Assuntos
Proliferação de Células , Células-Tronco Hematopoéticas/metabolismo , Leucemia Mielomonocítica Crônica/metabolismo , Células-Tronco Multipotentes/metabolismo , Mutação , Transtornos Mieloproliferativos/metabolismo , Tirosina Quinase 3 Semelhante a fms/metabolismo , Animais , Diferenciação Celular , Sobrevivência Celular , Células Cultivadas , Éxons , Regulação Neoplásica da Expressão Gênica , Genótipo , Células-Tronco Hematopoéticas/patologia , Humanos , Estimativa de Kaplan-Meier , Leucemia Experimental/metabolismo , Leucemia Experimental/patologia , Leucemia Mielomonocítica Crônica/genética , Leucemia Mielomonocítica Crônica/mortalidade , Leucemia Mielomonocítica Crônica/patologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Células-Tronco Multipotentes/patologia , Transtornos Mieloproliferativos/genética , Transtornos Mieloproliferativos/patologia , Fenótipo , Transdução de Sinais , Tirosina Quinase 3 Semelhante a fms/genéticaRESUMO
We report that TG101348, a selective small-molecule inhibitor of JAK2 with an in vitro IC50 of approximately 3 nM, shows therapeutic efficacy in a murine model of myeloproliferative disease induced by the JAK2V617F mutation. In treated animals, there was a statistically significant reduction in hematocrit and leukocyte count, a dose-dependent reduction/elimination of extramedullary hematopoiesis, and, at least in some instances, evidence for attenuation of myelofibrosis. There were no apparent toxicities and no effect on T cell number. In vivo responses were correlated with surrogate endpoints, including reduction/elimination of JAK2V617F disease burden assessed by quantitative genomic PCR, suppression of endogenous erythroid colony formation, and in vivo inhibition of JAK-STAT signal transduction as assessed by flow cytometric measurement of phosphorylated Stat5.
Assuntos
Substituição de Aminoácidos , Modelos Animais de Doenças , Janus Quinase 2/antagonistas & inibidores , Janus Quinase 2/genética , Policitemia Vera/tratamento farmacológico , Policitemia Vera/enzimologia , Inibidores de Proteínas Quinases/uso terapêutico , Pirrolidinas/uso terapêutico , Sulfonamidas/uso terapêutico , Animais , Transplante de Medula Óssea , Linhagem Celular Tumoral , Ensaio de Unidades Formadoras de Colônias , Determinação de Ponto Final , Citometria de Fluxo , Sistema Hematopoético/citologia , Sistema Hematopoético/efeitos dos fármacos , Humanos , Janus Quinase 2/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Fenilalanina/genética , Inibidores de Proteínas Quinases/farmacocinética , Inibidores de Proteínas Quinases/farmacologia , Pirrolidinas/farmacocinética , Transdução de Sinais/efeitos dos fármacos , Sulfonamidas/farmacocinética , Taxa de Sobrevida , Resultado do Tratamento , Valina/genéticaRESUMO
To understand the role of FoxO family members in hematopoiesis, we conditionally deleted FoxO1, FoxO3, and FoxO4 in the adult hematopoietic system. FoxO-deficient mice exhibited myeloid lineage expansion, lymphoid developmental abnormalities, and a marked decrease of the lineage-negative Sca-1+, c-Kit+ (LSK) compartment that contains the short- and long-term hematopoietic stem cell (HSC) populations. FoxO-deficient bone marrow had defective long-term repopulating activity that correlated with increased cell cycling and apoptosis of HSC. Notably, there was a marked context-dependent increase in reactive oxygen species (ROS) in FoxO-deficient HSC compared with wild-type HSC that correlated with changes in expression of genes that regulate ROS. Furthermore, in vivo treatment with the antioxidative agent N-acetyl-L-cysteine resulted in reversion of the FoxO-deficient HSC phenotype. Thus, FoxO proteins play essential roles in the response to physiologic oxidative stress and thereby mediate quiescence and enhanced survival in the HSC compartment, a function that is required for its long-term regenerative potential.