Objective To determine miR-497-5p expression in pancreatic cancer (PaCa) and its clinical significance, and to explore its effects and mechanisms on the proliferation of PaCa cells.

Methods The expression levels of miR-497-5p were detected by real-time quantitative PCR experiment. The relation between miR-497-5p expression and clinicopathological features, the prognosis of PaCa patients were analyzed by Chi-square test and Kaplan-Meier method. The effects of miR-497-5p overexpression on the proliferation and cell cycle of Capan-2 and PANC-1 cells were detected by cell counting kit-8 (CCK-8) experiment and flow cytometry. The relation between miR-497-5p level and the cyclin E1 (CCNE1) mRNA expression was analyzed by Spearman correlation test. The regulatory effect of miR-497-5p on CCNE1 expression was confirmed by dual luciferase reporter experiment and Western blot.

Results miR-497-5p expression in cancer tissues was significantly lower than that in adjacent normal tissues (P < 0.001), and its expression in T3+T4 stages cancer tissues were significantly lower than those in T1+T2 stages cancer tissues (P < 0.001); low expression of miR-497-5p was associated with advanced T stage (P=0.003); The 5-year overall survival rate of patients with low miR-497-5p expression was significantly lower than those with high miR-497-5p expression (P=0.036). Compared with the control group, miR-497-5p overexpression significantly reduced cell proliferation, increased the cell proportion in G₀/G₁ phase and decreased the cell proportion in S phase. The expression levels of CCNE1 mRNA in cancer tissues were significantly higher than those in adjacent normal tissues (P < 0.001), and its expression was negatively correlated with miR-497-5p expression (P < 0.001). miR-497-5p could bind directly to the 3'-UTR of CCNE1 mRNA and inhibit the expression of CCNE1 protein.

Conclusion miR-497-5p expression is downregulated in PaCa cells and associated with relatively advanced T stage and poor prognosis; the overexpression of miR-497-5p induces the cell cycle arrest to inhibit the proliferation of PaCa cells by targeting CCNE1 gene.