One major multidrug-resistance (MDR) mechanism is the increased expression of P-glycoprotein (P-gp), also known as MDR protein 1 (MDR-1), which functions as a drug efflux agent on the cancer cell membrane and exports substances, including therapeutic drugs, from the intracellular milieu to the extracellular matrix [27,28]. This evidence concerns the gene ABCB1 and cancer.