Bim is a suppressor of Myc-induced mouse B cell leukemia.
Impaired apoptosis is now recognized to be central to tumor development. Bcl2, activated by chromosomal translocation in human follicular lymphoma, promotes oncogenesis by inhibiting apoptosis. Bim, a distant proapoptotic relative, is emerging as a major physiologic antagonist of Bcl2. Here, we show that loss of Bim is oncogenic. Bim protein levels were elevated in the apoptosis-prone B lymphoid cells of Emicro-Myc-transgenic mice, and Bim-mutant Emicro-Myc mice had increased numbers of IgM-bearing B cells. Emicro-Myc- expressing B lymphoid cells deficient in Bim were refractory to apoptosis induced in vitro by cytokine deprivation or antigen receptor cross-linking. Thus, Bim is induced by Myc in B cells and mediates apoptosis. Remarkably, inactivation of even a single allele of Bim accelerated Myc-induced development of tumors, particularly acute B cell leukemia. None of the primary tumors from Bim(+/-) Emicro-Myc mice displayed loss of the second allele of Bim. These findings indicate that Bim is a tumor suppressor, at least in B lymphocytes, and is haploinsufficient. Whereas the p19Arf/ p53 pathway is frequently mutated in tumors arising in Bim(+/+) Emicro-Myc mice, it was unaffected in most Bim-deficient tumors, indicating that Bim reduction is an effective alternative to loss of p53 function.[1]References
- Bim is a suppressor of Myc-induced mouse B cell leukemia. Egle, A., Harris, A.W., Bouillet, P., Cory, S. Proc. Natl. Acad. Sci. U.S.A. (2004) [Pubmed]
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