ABCG2 and neoplasm: Inhibition of the proper transport function of these ABC proteins has been reported to be responsible for drug–drug interactions.4 In addition, P‐gp and BCRP are also known for their involvement in multidrug resistance (MDR).5 As efflux transporters for different anticancer agents, including anthracyclines, kinase inhibitors (imatinib), and alkaloids (e.g. topotecan),6 P‐gp and/or BCRP overexpression increases the transport of these agents out of the tumor cells resulting in decreased drug response.5