BRCA1 and breast cancer: A previous study showed that gene mutations of BRCA1 and BRCA2 are related to a high risk of BC occurrence (Antoniou et al., 2003); however, BRCA1- and BRCA2-deficient tumors are sensitive to PARP1 inhibitors, and patients with these types of tumors gain more benefit from this treatment (D’Andrea, 2018).