ABCG2 and lung carcinoma: Human ABC transporters belong to a superfamily comprised of 48 members, of which three are implicated in the majority of MDR observed in lung cancer cells: ABCG2 [breast cancer resistance protein (BCRP)], ABCB1 [P-glycoprotein (P-gp/MDR1)], and ABCC1 [multidrug resistance-associated protein 1 (MRP1)] (Chen et al., 2016; Katayama et al., 2016).