ABCG2 and malignant colon neoplasm: The cell lines used in this study were NSCLC NCI-H460 and its drug-selected subline, NCI-H460/MX20, which overexpresses wild-type (WT) ABCG2 and colon cancer cell line S1, as well as its drug-selected subline, S1-M1-80, which overexpresses R482G mutant ABCG2.