While dacomitinib at concentration below 1 μM did not appreciably affect cell proliferation, it was found to significantly potentiate the anticancer activity of other ABCG2 substrate anticancer drugs in two drug-selected ABCG2-overexpressing cancer cell lines (H460/MX20 and S1-MI-80) and two ABCG2 stable transfected HEK293 cells (expressing either the wild type ABCG-482-R2 or the mutant ABCG-482-T7). This evidence concerns the gene ABCG2 and cancer.