BRCA1 and breast cancer: It has been suggested that BRCA1 might regulate luminal differentiation through the transcriptional activation of ER.5 BRCA1 might also regulate mammary cell fate through transcriptional activation of Notch signalling pathway.2 In addition, BRCA1 could also interact with GATA3 at its C-terminal region to repress triple-negative and basal-like breast cancer (BLBCs) associated genes, such as FOXC1. 6