RESUMO
Oncogenic c-Myc is known to balance excessive proliferation by apoptosis that can be triggered by p53-dependent and p53-independent signaling networks. Here, we provide evidence that the BH3-only proapoptotic Bcl-2 family members Bcl-2 modifying factor (Bmf) and Bcl-2 antagonist of cell death (Bad) are potent antagonists of c-Myc-driven B-cell lymphomagenesis. Tumor formation was preceded by the accumulation of preneoplastic pre-B and immature immunoglobulin M-positive (IgM(+)) B cells in hematopoietic organs of Emu-myc/bmf(-/-) mice, whereas Emu-myc/bad(-/-) mice showed an increase of pre-B cells limited to the spleen. Although the loss of Bad had no impact on the tumor immunophenotype, Bmf deficiency favored the development of IgM(+) B cell over pre-B cell tumors. This phenomenon was caused by a strong protection of immature IgM(+) B cells from oncogene-driven apoptosis caused by loss of bmf and c-Myc-induced repression of Bmf expression in premalignant pre-B cells. Steady-state levels of B-cell apoptosis also were reduced in the absence of Bad, in support of its role as a sentinel for trophic factor-deprivation. Loss of Bmf reduced the pressure to inactivate p53, whereas Bad deficiency did not, identifying Bmf as a novel component of the p53-independent tumor suppressor pathway triggered by c-Myc.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Linfócitos B/metabolismo , Linfoma/metabolismo , Proteína de Morte Celular Associada a bcl/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Apoptose , Linfócitos B/patologia , Western Blotting , Feminino , Linfoma/genética , Linfoma/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Lesões Pré-Cancerosas/genética , Lesões Pré-Cancerosas/metabolismo , Lesões Pré-Cancerosas/patologia , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , Baço/metabolismo , Baço/patologia , Análise de Sobrevida , Fatores de Tempo , Carga Tumoral , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Proteína de Morte Celular Associada a bcl/genéticaRESUMO
Deregulation of Bcl2 family members is a frequent feature of human malignant diseases and causal for therapy resistance. A number of studies have recently shed light onto the role of pro- and anti-apoptotic Bcl2 family members in tumour-pathogenesis and in mediating the effects of classical as well as novel front-line anticancer agents, allowing the development of more efficient and more precisely targeted treatment regimens. Most excitingly, recent progress in our understanding of how Bcl2-like proteins maintain or perturb mitochondrial integrity has finally enabled the development of rational-design based anticancer therapies that directly target Bcl2 regulated events at the level of mitochondria. This review aims to give an overview on the most recent findings on the role of the Bcl2 family in tumour development in model systems of cancer, to relate these findings with observations made in human pathologies and drug-action.