ABCB1 and ovarian cancer: The ATP binding cassette subfamily B member 1 (ABCB1) gene, also known as the multidrug resistance gene, encodes the p-glycoprotein efflux pump, which ultimately reduces the amount of PARPi drugs available to the cell, leading to reduced efficacy and PARPi resistance, especially in BRCA1 gene-deficient breast and ovarian cancer cell lines (Rottenberg et al., 2008; Vaidyanathan et al., 2016).