Prevention of Brca1-mediated mammary tumorigenesis in mice by a progesterone antagonist.

Women with mutations in the breast cancer susceptibility gene BRCA1 are predisposed to breast and ovarian cancers. Why the BRCA1 protein suppresses tumor development specifically in ovarian hormone-sensitive tissues remains unclear. We demonstrate that mammary glands of nulliparous Brca1/p53-deficient mice accumulate lateral branches and undergo extensive alveologenesis, a phenotype that occurs only during pregnancy in wild-type mice.

Tumor suppressor functions for the Cdk inhibitor p21 in the mouse colon.

The Cdk inhibitor p21 regulates p53-mediated growth arrest following DNA damage. It is expressed during epithelial differentiation in a variety of organs including colon. We investigated susceptibility of p21-deficient mice to the colon carcinogen azoxymethane (AOM).