['5-fluorouracil-(5-FU)-based adjuvant chemotherapy is widely used for the treatment of colorectal cancer. However, 5-FU resistance in the course of treatment has become more common. Therefore, new therapeutic strategies and/or new adjuvant drugs still need to be explored.', 'Two colon-cancer-derived cell lines, colon26 and HT29, were used to investigate the effect of 5-FU, 3-methyladenine (3-MA, an autophagy inhibitor), or their combination on apoptotic cell death and autophagy. MTT assay, Hochest plus propidium iodide (PI) staining, and DNA fragmentation assay were used to observe apoptosis. Meanwhile, monodansylcadaverine (MDC) was used to detect autophagy. Finally, immunoblotting assay was used to explore the molecular change that occurred.', 'We observed the apoptosis induced by 5-FU in colon cancer cells. Meanwhile, autophagy was also stimulated. The combination treatment of 3-MA and 5-FU significantly increased the apoptotic cell death. By isolating the subcellular fractions of mitochondria and cytosol, we observed that the release of cytochrome c was increased in combination-treated cells. Cytochrome c resulted in the activation of caspase-3, thus activating PARP. Moreover, the anti-apoptotic protein, Bcl-xL, was significantly downregulated by 3-MA.'] Does inhibition of autophagy by 3-MA enhance the effect of 5-FU-induced apoptosis in colon cancer cells?