ABCB1 and neoplasm: Overexpression of members of the adenosine triphosphate binding cassette (ABC) transporters, including P-glycoprotein (MDR1 or ABCB1), the multidrug resistance associated protein (MRP1 or ABCC1) and the breast cancer resistance protein (BCRP1 or ABCG2), are implied in the genesis of multidrug resistance (MDR) in various tumor models [1].