As shown in Figure 4, imperatorin at 10 μM notably inhibited the function of ABCG2 and restored the intracellular accumulation of PhA in ABCG2-overexpressing S1-MI-80 (Figure 4a) and H460-MX20 (Figure 4b) cancer cells, and ABCG2-transfected R482-HEK293 (Figure 4c) cells. This evidence concerns the gene ABCG2 and cancer.