Background: Increasing evidence suggests that circular RNAs play a key role in regulating bladder cancer progression. However, this remains to be fully elucidated.

Results: In this study, we reanalyzed our previous RNA sequence, and circ5912 was found to downregulate significantly in bladder cancer tissues compared with normal control. Expression of circ5912 inversely correlates with bladder cancer grade, stage, metastasis, and better patient outcomes. In vitro and in vivo, circ5912 has been shown to repress transforming growth factor β signaling, which suppresses proliferation, invasion and migration of bladder cancer induced by mesenchymal-to epithelial transition.

Conclusions: Our study firstly demonstrate that circ5912 regulates mesenchymal-to epithelial transition pathway to suppress bladder cancer progression and propose new therapeutic targets and biomarkers for bladder cancer.

Materials and Methods: Clinical values of circ5912 in human bladder cancer were examined in a cohort of 58 patients by qPCR. 2 bladder cancer cell lines, T24 and SW780, were used for biological evaluation of circ5912. CCK8, clone formation, wound healing and trans-well assays were performed to determine the in vivo effect of circ5912; a mouse subcutaneous model was designed for in vivo analysis. Western blotting, RNA pulldown assays and florescent in situ hybridization were applied for mechanistic analysis.