MiR-133b regulates the proliferation, colony formation, and invasion of bladder cancer cells via inhibiting SOX4.

OBJECTIVES

Bladder cancer is one of the most common urothelial tumors with high incidence and mortality rates. Although it has been reported that microRNA (miR)-133b can regulate tumorigenesis of bladder cancer, the mechanism remains unclear. Sex-determining region Y-box transcription factor 4 (SOX4) exhibits an important role in tumorigenesis, but it is unclear whether SOX4 and miR-133b are associated with regulation of pathogenesis of bladder cancer. This study aims to determine the expressions of SOX4 and miR-133b in bladder cancer tissues and cells, investigate their effects on the proliferation, colony formation, and invasion of bladder cancer cells, and to explore the association between miR-133b and SOX4 in regulating biological featurss of bladder cancer cells.

METHODS

The bladder cancer and adjacent tissue samples of 10 patients who underwent surgical resection in the Second Xiangya Hospital of Central South Universty from Januray to June 2015 were obtained. The levels of miR-133b were tested by real-time PCR, and the protein levels of SOX4 were evaluated using Western blotting in bladder cancer tissues, matched adjacent tissues, and cell lines. The correlation between miR-133b expression and SOX4 expression in bladder cancer tissues was analyzed. Using the online database TargetScan, the relationship between SOX4 and miR-133b was predicted. MiR-133b mimics, miR-133b inhibitor, and short hairpin RNA (shRNA)-SOX4 were transfected into T24 cells by Lipofectamine 2000. The relationship between miR-133b and SOX4 was also verified by a dual-luciferase reporter assay. The proliferation of T24 cells cultured for 0, 12, 48, 72, and 96 h was evaluated by cell counting kit-8 (CCK-8) assay. The colony formation capacity of bladder cancer cells was tested after 14-day culture, and cell invasion capacity was evaluated with Transwell invasion assay.

RESULTS

Bladder cancer tissue and bladder cancer cells had low level of miR-133b but high level of SOX4, compared with matched adjacent tissues and normal bladder epithelial cells. A negative correlation between mRNA and SOX4 protein levels in bladder cancer tissues was also found (=-0.84). The results of online database TargetScan showed that miR-133b targets at SOX4, and overexpression of miR-133b significantly attenuated the expression of SOX4 in T24 cells. Both overexpression of miR-133b and knockdown of SOX4 significantly inhibited the proliferation, colony formation, and invasion capacity of bladder cancer cells in vitro. SOX4 down-regulation restored the effects of miR-133b inhibitor on the proliferation, colony formation, and invasion capacity of T24 cells.

CONCLUSIONS

The up-regulation of SOX4 contributes to the progression of bladder cancer, and miR-133b can regulate the proliferation, colony formation, and invasion of bladder cancer cells via inhibiting SOX4.