ABCG2 and colorectal carcinoma: For example, regorafenib significantly improved the sensitivity of BCRP-overexpressing S1-M1-80 CRC cells to mitoxantrone and SN-38, both substrates of BCRP, by interacting with the BCRP transmembrane domain and impairing BCRP efflux, thereby increasing intracellular drug retention [243].