ABCB1 and cancer: It has been reported that some of these transporters, mainly, ABCB1 (P-glycoprotein or multidrug-resistant protein, MDR1), ABCG2 (breast cancer resistance protein, BCRP), and ABCC1 (Multidrug resistance-associated protein 1 (MRP1)), are strongly related to the development of multidrug resistance in cancer.