ABCG2 and colorectal cancer: In this study, we found that ataxia-telangiectasia mutated (ATM) kinase inhibitor AZ32 was a potent inhibitor of ABCG2 and could sensitize ABCG2-overexpressing colorectal cancer cells to chemotherapeutic drugs mitoxantrone and doxorubicin by increasing their intracellular concentrations.