Inhibition of autophagy by 3-MA promotes hypoxia-induced apoptosis in human colorectal cancer cells.

OBJECTIVE: Cell autophagy reduces the sensitivity of cancer cells to therapeutic reagents in various types of human cancer. Therefore, the aim of our study was to use human colorectal cancer HCT116 cells to explore whether inhibition of autophagy by 3-Methyladenine (3-MA, an autophagy inhibitor) is able to enhance hypoxia-induced apoptosis in vitro. MATERIALS AND METHODS: HCT116 cells were treated with 3-MA, hypoxia, or 3-MA plus hypoxia, and the autophagy, apoptosis and proliferation of the HCT116 cells were investigated. Western blot analysis was used to detect autophagy specificity protein microtubule-associated protein light chain 3 (LC3) expression. Effects on apoptosis were evaluated by using flow cytometry (JC-1 staining to measure mitochondrial membrane potential) and annexin V-propidium iodide (PI) staining. RESULTS: The results showed that the treatment of HCT116 cells in vitro with hypoxia alone increased autophagy as well as apoptosis, whereas combination treatment with 3-MA and hypoxia markedly inhibited hypoxia-induced autophagy, but increased hypoxia-induced cell apoptosis. CONCLUSIONS: Autophagy might play a role as a self-defense mechanism in hypoxia-treated colon cancer cells, and its inhibition could be a promising strategy for the adjuvant chemotherapy of colon cancer.