Presentation Authors: Zhenyu Ou*, Yongjie Wang, Longxiang Wu, Mengda Zhang, Long Wang, Changsha, China, People's Republic of
Introduction: The epidemiological studies show obvious gender difference in bladder cancer (BCa): the incidence and mobility of BCa is around 4 folds higher in men than that in women. This sex disparity implies that the potential involvement of sex steroid pathways in bladder cancer development and progression. Recent researches suggest that estrogen receptor alpha (ERÎ±) plays a protective role in BCa. However, it remains to be futher elucidated the mechanisms how ERÎ± mediates BCa progression. As a novel class of non-coding RNAs, circular RNAs (circRNAs) could affect the development of BCa. In the present study, we tried to explore the mechanisms how ERÎ± inhibit BCa invasion through modulating circRNAs.
Methods: We identified 20 BCa related circRNAs through analyzing datasets and literature. Real-time PCR analysis was applied to detect the expression change of the 20 cicRNAs after manipulating ERÎ± in BCa cell lines. In vitro invasion assay and in vivo orthotopic mouse BCa model were used to illustrate ERÎ± affect BCa invsion and metastasis through regulating circRNA expression. Luciferase reporter assay, chromatin immunoprecipitation assay and biotin-coupled probe pull down assay were applied to dissect the mechanisms.
Results: Human clinical data implied lower ERÎ± expression might be associated with worse prognosis in BCa patients. The BCa related circRNA circ_0023642 was significantly decreased when ERÎ± was over expressed while significantly increased when ERÎ± was knocked down in BCa cells. In vitro invasion experiments using various BCa cells demonstrate that ERÎ± can decrease the BCa cell invasion via suppression of circ_0023642. ERÎ± suppressed circ_0023642 then led to increased miR-490-5p, which reduced epidermal growth factor receptor (EGFR) expression and decreased BCa cell invasion. In the orthotopic mouse BCa model, decreasing ERÎ± with shRNA promoted BCa metastasis, while adding circ_0023642 partly reversed this effect. Further mechanism dissection showed that ERÎ± reduced circ_002364 expression via modulating its host gene UVRAG through binding to the estrogen-response-element on the 5'-promoter of UVRAG. Circ_002364 was observed to directly bind to miR-490-5p. MiR-490-5p could regulate the EGFR expression via binding to the miR-490-5p binding site located on the EGFR mRNA 3' UTR.
Conclusions: Together, these results suggest that ERÎ± acts as a BCa suppressor by altering the ERÎ±/ circ_0023642/miR-490-5p/EGFR signals. This newly identified pathway may serve as basis to develop novel therapeutic strategies to treat BCa.