ABCG2 and cancer: Indeed, the incubation of the ABCG2 overexpressing cancer cells lines with 1 μM of MK-2206 decreased the IC50 values (i.e., significantly increased the efficacy) of mitoxantrone, SN-38 and topotecan (78- and 86-fold, 23.7- and 38.1-fold, 49- and 53-fold, respectively) to a magnitude that was not significantly different from the non-resistant parental cell lines.