As the compromised sensitivity to chemotherapy associated with ABCG2 activity represents a pivotal factor contributing to the decreased accumulation of drugs within cancer cells, and that the ABCG2-mediated resistance to MTX-211 could pose a therapeutic challenge in the future, we evaluated whether inhibiting ABCG2 could overcome MTX-211 resistance in multidrug-resistant S1-MI-80 cancer cells. Here, ABCG2 is linked to cancer.