RESUMEN
BACKGROUND: miR-34a has an antitumor effect and can regulate the expression of multiple target genes. Therefore, it may become a new target for the treatment of tumors. OBJECTIVE: To investigate the effect of miR-34a and its target gene SIRT1 on the proliferation, apoptosis and invasion of colon cancer stem cells in vitro . METHODS: Colon cancer stem cells were enriched from human colon cancer cell line HCT116 by serum-free suspension culture. Then, the percentage of CD44+/CD133+cells was identified by flow cytometry method. Colon cancer stem cells in transfection and control groups were transfected with artificially synthesized miR-34a mimics and negative control sequences, respectively. Cells with no transfection were used as non-transfection group. Cell proliferation, apoptosis, and invasion were detected through cell counting kit-8 assay, cell apoptosis experiment, and cell invasion experiment, respectively. The expression of SIRT1 mRNA and protein was detected by qRT-PCR and western blot analysis, respectively. RESULTS AND CONCLUSION: CD44+/CD133+cells accounted for (78.3±6.7)% of the tumor stem cells enriched in the serum-free medium. The expression of miR-34a in miR-34a transfection group was higher than that of non-transfection group and miR-34a control group (P < 0.05). Compared with the non-transfection group and the miR-34a control group, the cell proliferation ability was significantly decreased (P < 0.05), the apoptotic rate increased significantly (P < 0.05), and the number of invasion cells decreased significantly (P < 0.05) in the miR-34a transfection group. The expression level of SIRT1 mRNA and protein in the miR-34a transfection group was significantly lower than that in the non-transfection group and the miR-34a control group (P < 0.05). These findings suggest that miR-34a may down-regulate the expression of SIRT1 to suppress cell growth and invasion and promote apoptosis in colon cancer stem cells.