ABCB1 and malignant colon neoplasm: This could, in part, explain why poziotinib was more potent in reversing the resistance to the ABCB1 substrates, paclitaxel and doxorubicin, than the ABCG2 substrates, mitoxantrone and SN-38 in the colon cancer cells, although this remains to be elucidated.