PGP and cancer: Multidrug resistance (MDR) of human tumorsreduces the clinicalefficacy of current anticancer agents.1−3 Cancer is one of theleading causes of death worldwide and despite significant therapeuticinnovations and advancements in clinical formulation, MDR is one ofthe major challenges in cancer treatment, being responsible for manycases of refractory cancer and tumor recurrence.4−7 One of the mechanisms responsiblefor MDR is the overexpression of ATP-binding cassette (ABC) drug effluxpumps, such as P-glycoprotein (P-gp), causing increased cellular drugefflux.