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Mammary development fate and breast cancer risk

A full-term pregnancy or a 3-week treatment with estrogen and progestins induces a protective state against chemical carcinogen-induced mammary tumorigenesis in rats and mice. These experimental models are a paradigm for the well-established fact that an early full-term pregnancy in humans induces a life-long decreased risk for breast cancer. Up to now, this hypothesis has not been successfully tested in non-carcinogen-treated rodents. We tested the hypothesis in p53 null mouse mammary epithelium. A 2-week exposure to estrogen and progesterone reduced significantly (P < 0.05) the incidence of spontaneous breast cancer in p53 null epithelial cells. The hormone-treated cells had a unique gene expression profile at 40 weeks post hormone removal compared with untreated p53 null epithelial cells. Current experiments are examining the developmental stage specificity of the response to estrogen and progesterone. Additionally, genes specific to the hormone-treated p53 null cells are being further evaluated. These results indicate that short periods of hormone treatment can markedly delay mammary tumorigenesis in models where the initiating oncogene is relevant to human breast cancer.

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Medina, D. Mammary development fate and breast cancer risk. Breast Cancer Res 7 (Suppl 2), P2.03 (2005).

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  • Breast Cancer
  • Estrogen
  • Progesterone
  • Breast Cancer Risk
  • Progestin