Autoregulatory feedback loop of EZH2/miR-200c/E2F3 as a driving force for prostate cancer development

The histone methyltransferase enhancer of zeste homolog 2 (EZH2) has recently attracted considerable attention because of its dysregulation in prostate cancer (PCa) and its important function in PCa development. To date, little is known about the underlying cellular function and regulatory networks of EZH2 in PCa. This study aims to determine whether or not the autoregulatory feedback loop of EZH2/miR-200c/E2F3 serves key functions in PCa development. Bioinformatics and integrative analytical approaches were employed to identify the relationships of EZH2 to specific cancer-related gene sets. Results indicated that the enrichment of gene sets about cell cycle progression was associated with EZH2 expression. The depletion of EZH2 in cell experiments inhibited PCa cell growth and blocked cell cycle accompanying the downregulation of E2F3 expression. Furthermore, miR-200c served as an important mediator between EZH2 and E2F3. Compared with scrambled control cells, sh-EZH2 cells showed lower H3K27me3 expression and higher miR-200c expression. Western blot and luciferase reporter assays showed that miR-200c inversely modulated E2F3 by directly targeting the binding site within 3'UTR. Moreover, decreased miR-200c expression largely abrogated the effect of sh-EZH2 on E2F3 expression and E2F3-induced cell cycle progression. EZH2 was positively regulated by E2F3 at the transcriptional level. Immunohistochemistry and in situ hybridization revealed a significant correlation among EZH2, miR-200c, and E2F3 expression in human PCa tissues. In conclusion, the autoregulatory feedback loop of EZH2/miR-200c/E2F3 served an important function in PCa development. Targeting this aberrantly activated feedback loop may provide a new therapeutic strategy against PCa.