BRCA1 and breast cancer: For example, both the insulin-like growth factor 1 receptor[3] and epidermal growth factor receptor[14] are downstream targets for BRCA1; BRCA1 inhibits the transcriptional activity of progesterone receptor (PR) in the PR-positive breast cancer cell line T47D[15]; and ER-alpha activity can be suppressed by BRCA1 through regulating the acetylation vs. ubiquitination[16].