3-MA enhances chemotherapeutic effect of 5-FU by inhibiting autophagy in colon cancer

Objective: To explore a novel adjuvant strategy of improving 5-fluorouracil (5-FU)-based chemotherapy for colorectal cancer. Methods: Human colon cancer cell (HCT 116) was used to investigate the effect of 5-FU (7.5 μmol/L), 3-methyladenine (3-MA, 5 mmol/L), or their combination on apoptotic cell death and autophagy. MTT assay was used to observe the suppression of cell survival. Hoechst plus PI staining and MDC assay was used to detect apoptosis and autophagy. Western blotting was used to explore the molecular changes. Finally, the experiment results were further examined in vivo. Results: We found that the survival of HCT116 was suppressed by 5-FU and the combination of 5-FU and 3-MA promoted the apoptosis. Autophagy was activated by 5-FU treatment and 3-MA inhibited 5-FU-induced autophagy. The suppression of cell survival increased from (51.64±4.04)% to (79.89±1.35)%, and the apoptosis increased by more than 100%. HCT116 cells were injected in the nude mouse to produce tumor. The combination treatment of 5-FU and 3-MA inhibited the growth of xenografts compared with 5-FU alone. Conclusion: 3-MA enhances 5-FU-induced apoptosis by inhibiting autophagy in HCT116, and this could be a promising strategy for colorectal cancer chemotherapy.