ABCG2 and colonic neoplasm: The phenylfurocoumarin derivative (R)-9-(3,4-dimethoxyphenyl)-4-((3,3-dimethyloxiran-2-yl)methoxy)-7H-furo [3,2-g]chromen-7-one (PFC) in HCT-116/BCRP colon cancer cells, drastically lowers the IC50 of SN-38 while inhibiting ABCG2/BCRP-mediated drug transport function.