ABCB1 and cancer: To elucidate the mechanism how MUC1 regulates ABCB1, we directed our attention to the EGFR pathway because the latter is not only implicated in ABCB1 regulation37, 38 but also associated with MUC1.35, 36 Recent studies showed that EGFR was involved in chemoresistance in many cancers via regulating ABCB1 and ABCG2.37, 38, 48, 49 A dynamic interaction between MUC1-C and EGFR has been reported under various contexts with a general trend of mutual functional augmentation.