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Haploid loss of bax leads to accelerated mammary tumor development in C3(1)/SV40‐TAg transgenic mice: reduction in protective apoptotic response at the preneoplastic stage
Author(s) -
Shibata MasaAki,
Liu MinLing,
Knudson Michael C.,
Shibata Eiko,
Yoshidome Katsuhide,
Bandey Tabassum,
Korsmeyer Stanley J.,
Green Jeffrey E.
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.10.2692
Subject(s) - biology , apoptosis , transgene , genetically modified mouse , microbiology and biotechnology , ploidy , cancer research , gene , genetics
The dramatic increase in apoptosis observed during the development of preneoplastic mammary lesions is associated with a significant elevation in Bax expression in C3(1)/SV40 large T antigen (TAg) transgenic mice. The significance of Bax expression during tumor progression in vivo was studied by generating double‐transgenic mice carrying the C3(1)/TAg transgene and mutant alleles for bax . C3(1)/TAg transgenic mice carrying mutant bax alleles exhibited accelerated rates of tumor growth, increased tumor numbers, larger tumor mass and decreased survival rates compared with mice carrying wild‐type bax . Accelerated tumorigenesis associated with the bax +/− genotype did not require the loss of function of the second bax allele. Thus, haploid insufficiency of bax is enough to accelerate tumor progression, suggesting that the protective effect of Bax is dose‐dependent. While levels of apoptosis in the preneoplastic lesions, but not carcinomas, were reduced in bax +/− or bax −/− mice compared with bax +/+ mice, rates of cellular proliferation in mammary lesions were similar among all bax genotypes. These data demonstrate that bax is a critical suppressor of mammary tumor progression at the stage of preneoplastic mammary lesion development through the upregulation of apoptosis, but that this protective effect is lost during the transition from preneoplasia to invasive carcinoma.