ABCB1 and malignant colon neoplasm: In conclusion, our results show that poziotinib reverses MDR in ABCG2- and ABCB1-overexpressing colon cancer cells to their corresponding anticancer drug substrates, It is likely that poziotinib reverses MDR in ABCG2-overexpressing cells by inhibiting the efflux activity of the ABCG2 transporter, as well as by downregulating the expression level of the ABCG2 transporter protein.