DLL1 and malignant colon neoplasm: Indeed, low levels of the negative Notch regulator miR-34a were associated with a worse response of colon cancer patients to 5-FU, and its overexpression overcame ABCG2-mediated resistance of a stem cell-like subpopulation of colon cancer cells to 5-FU through downregulation of DLL1/Notch signaling.