ABSTRACT
miR-340 can promote the proliferation and invasion of cancer cells, but how miR-340 regulates the occurrence and development of cancer in colon cancer is rarely reported. This study aims to explore the biological function and target gene regulation mechanism of miR-340 in colorectal cancer cells. Firstly, RT-qPCR was used to detect the expression level of miR-340 in different colorectal cancer cell lines, and then miR-340 was overexpressed or inhibited in COLO-205 cells. CCK-8, Transwell migration and invasion assay, and flow cytometry were performed to analyze the cell ability of proliferation, migration and invasion, as well as cell apoptosis and cell cycle. Finally, after bioinformatics prediction of miR-340 target genes, luciferase reporter gene and Western blot experiment were applied to verify those target genes. The results showed that miR-340 was downregulated in COLO-205 cells. Compared with the control group, cell proliferation, migration and invasion were significantly inhibited in the miR-340 overexpression group, but were promoted in the miR-340 suppression group (P<0. 01). The results of flow cytometry showed that the percentage of apoptosis in the miR-340 overexpression group was significantly increased, while the percentage of apoptosis in the miR-340 inhibition group was decreased (P<0. 01). The bioinformatics analysis of the overexpression miR-340 transfection group showed that the 3′UTR of glucose regulated protein 78 kD (GRP78) had a miR-340-5p binding site, and the luciferase activity was significantly reduced in the overexpression miR-340 group (P<0. 01); Western blot results also showed that overexpression of miR-340 can inhibit the expression of GRP78, while inhibiting miR-340 expression, the expression of GRP78 is relieved. In summary, miR-340 can directly target GRP78 to promote the apoptosis of COLO-205 cells and inhibit their proliferation, migration and invasion.