MicroRNA-199a Inhibits Cell Proliferation, Migration, and Invasion and Activates AKT/mTOR Signaling Pathway by Targeting B7-H3 in Cervical Cancer

Cervical cancer is a deadly disease. Some microRNAs are involved in tumor invasion and metastasis. Decreased expression of microRNA-199a has been correlated with tumorigenesis. In our study, the quantitative real-time polymerase chain reaction results indicated that microRNA-199a was expressed at lower levels in cervical cancer tissues, and the expression level of B7-H3 was significantly increased compared with that in the adjacent normal tissues, and the expression levels of B7-H3 and microRNA-199a in cervical cancer tissues and in adjacent normal tissues were inversely correlated. We also found that the expression of microRNA-199a was downregulated in cervical cancer cell lines when compared to immortalized cells. In this study, B7-H3 was identified as a novel target of microRNA-199a in cervical cancer. TargetScan (http://www.targetscan.org/) bioinformatics analysis was used to predict that the 3′-untranslated region of B7-H3 is a direct target of microRNA-199a. The result was also verified by the luciferase reporter assay. MicroRNA-199a could directly target the 3′-untranslated region of B7-H3, but the specific signaling pathways that were involved in regulating B7-H3 expression remained unclear. To clarify whether the suppressive effect of microRNA-199a was mediated through B7-H3, a series of experiments were performed. We found that the overexpression of microRNA-199a inhibited cell proliferation, migration, and invasion via direct binding to B7-H3. Epithelial–mesenchymal transition is a major factor involved in cervical cancer metastasis. Quantitative real-time polymerase chain reaction and western blot results indicated that microRNA-199a inhibits tumor progression in cervical cancer by targeting B7-H3. The microRNAs regulatory network is quite complex. We further examined the effect of microRNA-199a on the AKT/mTOR signaling pathway. We explored the regulatory role of microRNA-199a and first demonstrated that highly expressed microRNA-199a inhibits tumor growth and activates the AKT/mTOR signaling pathway by targeting B7-H3 in vivo and in vitro. Our findings not only provide a better understanding of the pathogenesis of cervical cancer but also provide novel findings and theoretical support for potential targeted therapeutic tools for cervical cancer.