MicroRNA-154 functions as a tumor suppressor in bladder cancer by directly targeting ATG7

Aberrant expression of miR-154 is usually found in cancer studies; however, the role of miR-154 has seldom been reported in bladder cancer (BCa). In this study, we observed that miR-154 expression was significantly downregulated in BCa tissues and cell lines, and was associated with several clinicopathological characteristics, including advanced T stage, lymphatic invasion, and distant metastasis. Low expression level of miR-154 was associated with poor survival outcomes in BCa patients. Overexpression of miR-154 led to significant decrease in the proliferation, migration, and invasion of BCa cells, while knockdown of miR-154 yielded the opposite effect. ATG7 was identified as a direct target of miR-154. ATG7 expression was negatively correlated with miR-154 expression in BCa tissues. Silencing of ATG7 achieved a similar effect to miR-154 overexpression; overexpression of ATG7 reversed the inhibitory effect of miR-154 on BCa cell proliferation, migration and invasion. A xenograft study revealed that miR-154 inhibited BCa cell growth in vivo, and suppressed ATG7 expression. Altogether, this study demonstrated that miR-154 may function as a tumor suppressor in BCa and indicated that miR-154 may be a potential therapeutic target for BCa patients.