Effect of venetoclax on the efflux of mitoxantrone[3H] in parental and ABCG2-overexpressing cells. Time course (0/30/60/120 min) versus the percentage of remaining intracellular mitoxantrone[3H] was plotted to illustrate the effect of venetoclax on mitoxantrone[3H] efflux in (A) HEK293/pcDNA3.1, (B) HEK293/ABCG2-R482, (C) HEK293/ABCG2-R482G, (D) HEK293/ABCG2-R482T, (E) NCI-H460, (F) NCI-H460/MX20, (G) S1 and (H) S1-M1-80 cells. Points with error bars represent mean ± SD from 3 independent duplicate experiments. Asterisks (*) indicate p < 0.05 versus control group (untreated resistant cells).