Prolactin-dependent up-regulation of BRCA1 expression in human breast cancer cell lines

We report experimental evidence that BRCA1, a breast and ovarian cancer sus ceptibility gene, is up-regulated in response to prolactin (PRL) stimulatio n. Expression of the BRCA1 gene was monitored in 2 human breast cancer cell lines (MCF-7 and T-47D) and in the normal mammary epithelial cell line MCF 10a. Using competitive RT-PCR, we have shown that PRL induced an increase i n BRCA1 mRNA level in MCF-7 and T-47D cell Lines at a dose resulting in the maximal enhancement of cell proliferation. The up-regulation was 12-fold i n MCF-7 cells and 2-fold in T-47D cells. No increase in BRCA1 mRNA level wa s observed in the MCF10a cell line. The level of BRCA1 protein was quantifi ed using an affinity chromatography strategy. At the protein level, PRL tre atment induced a 4-fold increase of BRCA1 protein-expression in MCF-7 and a 6-fold increase in T-47D cells, whereas BRCA1 protein expression was not a ffected by PRL in MCF10a. (C) 1999 Academic Press.