ABCB1 and cancer: Multidrug resistance (MDR) is a manifestation of cancer cells that involves resistance to various chemotherapeutic drugs due to the intrinsic and acquired expression of the ABC transporter known as p-glycoprotein (P-gp), multidrug resistance protein 1 (MDR1) or ATP-binding cassette sub-family B member 1 (ABCB1) [3].