Progesterone Induces BRCA1 mRNA Decrease, Cell Cycle Alterations and Apoptosis in the MCF7 Breast Cancer Cell Line

Background: Inherited mutations of the BRCA1 gene are responsible for hereditary breast and ovarian cancer syndrome. However, little is known of how disruption of BRCA1 functions preferentially increases cancer risk in hormone-dependent organs. We aimed to study whether BRCA1 was regulated by progesterone in the MCF7 breast cancer cell line. Materials and Methods: MCF7 breast cancer cells were incubated with 10 -4 or 10 -10 M progesterone for 24 or 48 hours. BRCA1 expression, proliferation and apoptosis were analysed. Results: 10 -4 M progesterone decreased cell proliferation, cell cycle progression and induced apoptosis. In addition, BRCA1 and cyclin A mRNA decreased. In contrast, none of these effects were observed in MCF7 cells incubated with 10 -10 M progesterone. Conclusion: The down-regulation of BRCA1 in MCF7 cells incubated with 10 -4 M progesterone seems to be a consequence of cell cycle alterations rather than a direct effect of the hormone on BRCA1.