Objective  To investigate the expression of miR-182-5p and FOXO3 in bladder carcinoma and decipher the mechanism of it.

  Methods  The expression of miR-182-5p and FOXO3 in bladder carcinoma and adjacent tissues samples from 64 bladder cancer patients at People’s Hospital of Zhengzhou, from June 2017 to June 2019 and in cell lines were detected by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR). Based on the expression of miR-182-5p or FOXO3, the patients were assigned into miR-182-5p high and miR-182-5p low groups or FOXO3 high and FOXO3 low groups, respectively. The expression of FOXO3 protein was detected by Western blot. Kaplan-Meier survival curve was used to analyze the correlation between miR-182-5p or FOXO3 and the prognosis of bladder carcinoma patients. Dual luciferase reporter assays were used to validate the targeting of FOXO3 by miR-182-5p. Further, the effect of the miR-182-5p inhibitor on the expression of FOXO3 in bladder carcinoma cells was assessed by RT-qPCR and Western blot. The role of miR-182-5p on bladder carcinoma was determined by transfecting the T24 cells with miR-182-5p inhibitor and assessing the effect on cell proliferation, invasion, and apoptosis using the CCK-8 assay, the Transwell invasion assay, and flow cytometry, respectively.

  Results  The expression of miR-182-5p in bladder cancer tissues was higher (2.27±0.66) than that in adjacent tissues (1.04±0.36), and this difference was statistically significant (P<0.001). The expression of miR-182 was linked to tumor size, TNM stage, and lymph node metastasis. On the contrary, the expression of FOXO3 in bladder cancer tissues was downregulated and was closely associated with tumor size, degree of differentiation, TNM stage, and lymph node metastasis (P<0.05). The survival rates of bladder carcinoma patients in miR-182-5p high or FOXO3 low groups were significantly lower than those in the miR-182-5p low or FOXO3 high groups (P=0.038, P=0.004), respectively. The expression of miR-182-5p in T24 cells was significantly increased. Furthermore, the miR-182-5p inhibitor upregulated the expression of FOXO3 in T24 bladder carcinoma cells. However, the downregulation of miR-182-5p inhibited proliferation and invasion and promoted apoptosis in T24 cells (P<0.05).

  Conclusion  miR-182-5p expression is upregulated and FOXO3 expression is downregulated in bladder carcinoma tissues. miR-182-5p promotes cell proliferation and invasion and inhibits apoptosis in bladder carcinoma cells, which may be attributed to the negative regulation of FOXO3, an established tumor suppressor in bladder cancer.