RESUMO
Deregulated overexpression of MYC is implicated in the development and malignant progression of most (â¼70%) human tumors. MYC drives cell growth and proliferation, but also, at high levels, promotes apoptosis. Here, we report that the proliferative capacity of MYC-driven normal and neoplastic B lymphoid cells depends on MNT, a MYC-related transcriptional repressor. Our genetic data establish that MNT synergizes with MYC by suppressing MYC-driven apoptosis, and that it does so primarily by reducing the level of pro-apoptotic BIM. In Eµ-Myc mice, which model the MYC/IGH chromosome translocation in Burkitt's lymphoma, homozygous Mnt deletion greatly reduced lymphoma incidence by enhancing apoptosis and markedly decreasing premalignant B lymphoid cell populations. Strikingly, by inducing Mnt deletion within transplanted fully malignant Eµ-Myc lymphoma cells, we significantly extended transplant recipient survival. The dependency of lymphomas on MNT for survival suggests that drugs inhibiting MNT could significantly boost therapy of MYC-driven tumors by enhancing intrinsic MYC-driven apoptosis.
Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Apoptose/genética , Transformação Celular Neoplásica/genética , Linfoma/genética , Linfoma/mortalidade , Proteínas Proto-Oncogênicas c-myc/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-myc/genética , Animais , Antineoplásicos/uso terapêutico , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Medula Óssea/metabolismo , Medula Óssea/patologia , Linhagem Celular Tumoral , Modelos Animais de Doenças , Deleção de Genes , Regulação Neoplásica da Expressão Gênica , Humanos , Estimativa de Kaplan-Meier , Linfoma/tratamento farmacológico , Linfoma/patologia , Linfoma de Células B/genética , Camundongos , Camundongos Transgênicos , Proteínas Repressoras/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The importance of c-MYC in regulating lymphopoiesis and promoting lymphomagenesis is well-established. Far less appreciated is the vital supporting role of MYC's relative MNT. Using Rag1Cre-mediated Mnt deletion in lymphoid progenitor cells, we show here that, during normal T cell development, MNT loss enhances apoptosis, at least in part by elevating expression of the pro-apoptotic BH3-only protein BIM. Moreover, using T lymphoma-prone VavP-MYC transgenic mice, we show that Mnt deletion reduces the pool of pre-malignant MYC-driven T lymphoid cells and abrogates thymic T lymphomagenesis. In addition, we establish that Mnt deletion prevents T lymphoma development in γ-irradiated mice, most likely by enhancing apoptosis of T lymphoid cells repopulating the depleted thymus. Taken together with our recent demonstration that MNT is vital for the survival of MYC-driven pre-malignant and malignant B lymphoid cells, these results suggest that MNT represents an important new drug target for both T and B lymphoid malignancies.