ABCG2 and neoplasm: Notable among these are ABCB1,also known as p-glycoprotein (p-gp),11 andABCG2, also referred to as breast cancer resistance protein (BCRP).12 The ABC transporters are responsible for theefflux of a wide range of chemotherapeutics across the plasma membrane,leading to lower intracellular drug levels and treatment resistance.Doxorubicin and its clinically used analogues (epirubicin, daunorubicin,and idarubicin) all are known substrates for ABCB1,13 and several studies have noted increased ABCB1 expressionin tumor cells in response to anthracycline chemotherapy.14