Background: MicroRNAs (miRNAs) play key roles in the development and progression of various cancers. However, the precise functions and regulation mechanisms of miRNAs in human tumors remain elusive.
Methods: Quantitative real time-PCR (qRT-PCR) was performed to detect the level of miR-32-5p in colorectal cancer tissues. The relationships between miR-32-5p level with clinicopathological characteristics and prognosis were analyzed. The miR-32-5p inhibitor was employed to knock down the expression of miR-32-5p. The overexpression plasmid and si-RNA targeting TOB1 were generated. Clone formation assays under radiant exposure were used to evaluate the radiosensitization. Transwell migration and invasion were employed to test the ability of cell migration and invasion. Luciferase reporter assays were used to confirm the regulation of miR-32-5p on the expression of TOB1. Rescue experiments were conducted to investigate the effects of TOB1 on the functions of miR-32-5p.
Results: In this study, we found that miR-32-5p was significantly upregulated in colorectal cancer tissues compared with adjacent normal tissues. The level of miR-32-5p was positively correlated with tumor differentiation and metastasis. Log-rank tests showed that high level of miR-32-5p was significantly correlated with poor overall survival and disease-free survival. Anti-miR-32-5p remarkably enhanced the radiosensitivity and inhibited migration and invasion of colorectal cancer cells. In addition, overexpression of TOB1 obviously increased the radiosensitivity and inhibited migration and invasion of colorectal cancer cells. Moreover, bioinformatics analysis and luciferase reporter assays demonstrated that miR-32-5p suppressed the expression of TOB1 through directly binding to the 3ʹ-UTR of TOB1 mRNA. Rescue experiments indicated that miR-32-5p regulated the radiosensitivity, migration and invasion of colorectal cancer cells through inhibiting TOB1 expression.
Conclusion: This study suggested that miR-32-5p may serve as a prognostic and therapeutic target for colorectal cancer, and downregulation of miR-32-5p enhanced the radiosensitivity and inhibited migration and invasion through promoting TOB1 expression.
Keywords: miR-32-5p, TOB1, radiosensitivity, migration and invasion, colorectal cancer