PGP and cancer: Over-expression of membraneefflux pumps as P-glycoprotein (P-gp, ABCB1) is tightly related tothe multidrug resistance (MDR) phenomenon in cancer cells,1−3 and chemotherapy failure.4 Therefore,modulating drug efflux by P-gp is, currently, still one of the mostpromising strategies to beat MDR in cancer.