ABCG2 and lung carcinoma: For ABCG2 the pairs were: (1) the parental H460 human lung carcinoma cell line and its mitoxantrone-selected, ABCG2-overexpressing sub-line H460 MX20; and (2) the same HEK pcDNA parent cell line as a comparator for the ABCG2-transfected HEK cell line, R-5.