Drug-efflux transporter genes (ABCB1a, ABCB1b, and ABCB2) encoding multidrug resistance protein 1 (MDR1) were found to be highly expressed and exhibited epithelial-to-mesenchymal transition phenotypes in a PARPi resistant cohort in a murine model of BRCA1-mutated breast tumors (81). The gene discussed is BRCA1; the disease is breast neoplasm.