Prevention of Brca1-mediated mammary tumorigenesis in mice by a progesterone antagonist by Poole Aleksandra Jovanovic, Li Ying, Kim Yoon, Lin Suh-Chin J, Lee Wen-Hwa, Lee Eva Y-H P in Science (New York, N.Y.) (2006).

[PMID: 17138902] PubMed


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. Progesterone receptors, but not estrogen receptors, are overexpressed in the mutant mammary epithelial cells because of a defect in their degradation by the proteasome pathway. Treatment of Brca1/p53-deficient mice with the progesterone antagonist mifepristone (RU 486) prevented mammary tumorigenesis. These findings reveal a tissue-specific function for the BRCA1 protein and raise the possibility that antiprogesterone treatment may be useful for breast cancer prevention in individuals with BRCA1 mutations.

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