ABCG2 and cancer: Nevertheless, as both ABCG2 (53, 54, 55) and SLC1A5 (14, 15, 16) have been found overexpressed in various cancers, and anti-cancer drugs targeting SLC1A5/glutamine metabolism have been in development (56), it is feasible that further studies may inform novel combination therapies for tumors overexpressing these two membrane proteins.