BRCA2 and breast cancer: Previous data revealed that PARPi including olaparib, niraparib, and simmiparib induced mild synthetic lethality in human breast cancer, HCC1937 (BRCA1-deficient), and colorectal cancers (CRC), HCT-15 (BRCA2-deficient), cells in vitro, and the antitumor activity was limited in mouse xenograft models16–18.