Mechanism of miR-32-5p targeting TOB1 gene in regulating radiosensitization, migration and invasion of colorectal cancer cells

Objection: To investigate the effect of miR-32-5p on the radiosensitivity, migration and invasion of colorectal cancer cells and the underlying mechanism. Methods: Human colorectal cancer SW480 cells and normal colonic epithelial NCM460 cells were cultured. The colorectal cancer cells were divided into the non-transfected and transfected groups (transfected with anti-miR-NC, anti-miR-32-5p, pcDNA, pcDNA-TOB1, anti-miR-32-5p+si-NC and anti-miR-32-5p+si-TOB1, respectively). The expression of miR-32-5p and TOB1 at the mRNA and protein levels was detected by RT-qPCR and Western blot. The radiosensitivity of the transfected cells was determined by colony formation assay. The migration and invasion ability of the transfected cells were detected by Transwell assay. Whether miR-32-5p targeted TOB1 was validated by dual luciferase reporter gene assay and Western blot. Results: Compared with human colonic epithelial cells, the expression of miR-32-5p was significantly up-regulated, whereas the expression of TOB1 mRNA and protein was remarkably down-regulated in the colon cancer cells (all P < 0.05). Compared with the anti-miR-NC, the quantity of cell migration and invasion was significantly decreased (both P < 0.05) and the radiosensitivity ratio was 1. 801 in the anti-miR-32-5p group. Compared with the pcDNA group, the quantity of cell migration and invasion was significantly decreased (both P < 0.05) and the radiosensitivity ratio was 1.764 in the pcDNA-TOB1 group. Dual luciferase reporter gene assay and Western blot confirmed that miR-32-5p negatively regulated the expression of TOB1 protein. Compared with the anti-miR-32-5p+si-NC group, the quantity of cell migration and invasion was significantly increased (both P < 0.05) and the radiosensitivity ratio was 0.591 in the anti-miR-32-5p+si-TOB1 group. Conclusions: Inhibition of miR-32-5p expression can significantly enhance the radiosensitivity of colorectal cancer cells and suppress cell migration and invasion. The underlying mechanism might be related to the targeted up-regulation of TOB1 expression. (authors)