ABCB1 and neoplasm: ABCB1 (previously called MDR1) was the first member to be cloned (Riordan et al., 1985; Roninson et al., 1986; Ueda et al., 1987), with the encoded protein (p-glycoprotein or p-gp) being called multidrug resistance protein owing to the observation that it was overexpressed in tumor cells with resistance to multiple chemotherapeutic agents.