ABCB1 and cancer: To further determine whether olmutinib in the above cell lines reverses the multi-drug resistance (MDR) mediated by ABC transporters, the drug-induced resistant human cancer cell line (KB-C2, NCI-H460/MX20, and KB-CV60) and the transfected resistant cell line (HEK293/ABCB1, HEK293/G2, and HEK293/MRP1) and their corresponding parental cell lines (KB-3-1, NCI-H460, and HEK293/pcDNA3.1) were used to perform the cytotoxicity assay.