RESUMO
BACKGROUND: Mastocytosis is characterized by the accumulation of mast cells (MCs) associated with activating mutations of KIT. Tumor necrosis factor-related apoptosis-inducing ligand receptors (TRAIL-Rs) are preferentially expressed on neoplastic cells and induce the extrinsic apoptotic pathway. Recent studies reported on the expression of TRAIL-Rs and TRAIL-induced apoptosis in cultured human MCs, which depend on stem cell factor (SCF)-induced or constitutive KIT activation. MATERIAL AND METHODS: We sought to further define the impact of TRAIL-Rs on MCs in vivo and in vitro. Using Cre/loxP recombination, we generated mice with MC-specific and ubiquitous knockout of TRAIL-R. In these mice, anaphylaxis and numbers of MCs were investigated. We also explored the expression and function of TRAIL-Rs in cultured murine and human MCs upon activation of KIT. By conducting immunofluorescence staining, we analyzed the expression of TRAIL-Rs in MCs infiltrating the bone marrow of patients with mastocytosis. RESULTS: MC-specific deletion of TRAIL-R was associated with a slight, but significant increase in anaphylaxis. Numbers of MCs in MC-specific knockouts of TRAIL-R were comparable to controls. Whereas cultured IL-3-dependent murine MCs from wild-type mice were resistant to TRAIL-induced apoptosis, SCF-stimulated MCs underwent apoptosis in response to TRAIL. Interestingly, activating KIT mutations also promoted sensitivity to TRAIL-mediated apoptosis in human MCs. In line with these findings, MCs infiltrating the bone marrow of patients with mastocytosis expressed TRAIL-R1. CONCLUSIONS: Activation of KIT regulates the function of TRAIL-Rs in MCs. TRAIL-R1 may represent an attractive diagnostic and therapeutic target in diseases associated with KIT mutations, such as mastocytosis.
Assuntos
Mastócitos/imunologia , Mastócitos/metabolismo , Proteínas Proto-Oncogênicas c-kit/metabolismo , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/metabolismo , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Medula Óssea/imunologia , Medula Óssea/metabolismo , Medula Óssea/patologia , Contagem de Células , Sobrevivência Celular/efeitos dos fármacos , Modelos Animais de Doenças , Regulação da Expressão Gênica , Humanos , Mastocitose/genética , Mastocitose/imunologia , Mastocitose/metabolismo , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Mutação , Proteínas Proto-Oncogênicas c-kit/genética , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/genética , Fator de Células-Tronco/metabolismo , Fator de Células-Tronco/farmacologia , Ligante Indutor de Apoptose Relacionado a TNF/metabolismo , Ligante Indutor de Apoptose Relacionado a TNF/farmacologiaRESUMO
Mutation of KIT receptor tyrosine kinase at residue D816 results in ligand-independent constitutive kinase activity. This mutation occurs in most patients with mastocytosis, a myeloproliferative neoplasm, and is detected at lower frequencies in acute myeloid leukemia and in germ cell tumors. Other KIT mutations occur in gastrointestinal stromal tumors (GIST) and mucosal melanoma. KIT is considered as a bona fide therapeutic target as c-kit mutations are driving oncogenes in these pathologies. However, several evidences suggest that KIT-D816V mutant is not as aggressive as other KIT mutants. Here, we show that an intracellular docking site in the juxtamembrane region of KIT maintains a negative regulation on KIT-D816V transforming potential. Sixteen signaling proteins were shown to interact with this motif. We further demonstrate that mutation of this site results in signaling modifications, altered gene expression profile and increased transforming activity of KIT-D816V mutant. This result was unexpected as mutations of the homologous sites on wild-type (WT) KIT, or on the related oncogenic FLT3-ITD receptor, impair their function. Our results support the hypothesis that, KIT-D816V mutation is a mild oncogenic event that is sufficient to confer partial transforming properties, but requires additional mutations to acquire its full transforming potential.
