miR-204 Negatively Regulates Cell Growth And Metastasis By Targeting ROBO4 In Human Bladder Cancer.

BACKGROUND: MicroRNAs (miRNAs) are well characterized for their important roles in human cancers by influencing various aspects of malignancy. Till now, the function and mechanism of miR-204, a tumor suppressor in several cancers, remain unclear in bladder cancer (BC). Here, we intend to explore its roles in BC progression. METHODS: qRT-PCR was applied to determine miR-204 and ROBO4 expression in BC tissues and cell lines. miR-204 expression with clinicopathological features was analyzed. The impacts of miR-204 on BC cell growth and metastasis in vitro were evaluated by both loss-of-function and gain-of-function assays (CCK-8, crystal violet staining, wound healing and transwell assays). Furthermore, qRT-PCR, Western blot and luciferase reporter assays were used to validate the targeting of ROBO4 by miR-204. Finally, linear regression was performed to analyze the correlation of miR-204 and ROBO4 in BC tissues. RESULTS: Expression of miR-204 was markedly decreased in BC tissues and cell lines were compared with respective controls. Low miR-204 expression was associated with positive advanced T stage and lymph node metastasis. Cellular function studies revealed that miR-204 inhibited BC cell growth, migration and invasion. Mechanistic exploration found that miR-204 directly targeted ROBO4. Rescue assays indicated that ROBO4 restoration could reverse the antitumor effects of miR-204 in BC. Finally, ROBO4 was significantly correlated with miR-204 levels inversely. CONCLUSION: miR-204 might serve as a tumor suppressor in BC by targeting ROBO4.