ABCG2 promotes the extracellular efflux of various carcinogens, including 2-amino-1-methyl-6-phenylimidazo [4, 5-b] pyridine, so the risk of cancer may be increased by intracellular accumulation of carcinogens if ABCG2 activity is inhibited [26,27]. This evidence concerns the gene ABCG2 and cancer.