First, the Abcb1a and Abcb1b genes, members of the ATP‐binding cassette, encoding the multidrug resistance protein (MDR1 or P‐gp) involved in resistance of BRCA1/2‐deficient breast and ovarian cancer patients to PARP inhibitors, are upregulated.35, 36. Here, BRCA1 is linked to ovarian carcinoma.