miR-4262 Targets Anti-Apoptotic Gene B-Cell Lymphoma-2 to Induce Cell Apoptosis and Inhibit Cell Proliferation in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC), a frequently happened cancer, is still an important threaten to human with unsatisfactory prognosis. Increasing evidence indicated that abnormal miRNA expressions were related to the development of OSCC. microRNA (miR)-4262 has been considered to be a cancer suppressor in various tumors, however its exact role in OSCC remains to be clarified. During the current research, we proposed to probe the biological activity and fundamental mechanism of miR-4262 in OSCC. The expression levels of miR-4262 in SCC9 and HOK cells were analyzed using quantitative real time polymerase chain reaction (qRT-PCR). TargetScan and luciferase reporter assay were carried out to quest the possible target gene of miR-4262. qRT-PCR and Western blotting analysis were employed to measure the expressions of B-cell lymphoma-2 (Bcl-2) in OSCC tissues, adjacent non-cancerous tissues, SCC9 and HOK cells. Cell proliferation and apoptosis of SCC9 cells were detected by Thiazolyl Blue Tetrazolium Bromide (MTT) and flow cytometry (FCM) analysis. The expressions of apoptosis-related proteins Bcl-2 and Bcl2-associated X protein (Bax) were checked by Western blotting analysis. Firstly, we found that miR-4262 expressed lower level in OSCC cells than that in the control. Results from TargetScan and luciferase reporter analysis showed that miR-4262 directly targeted Bcl-2. Then, up-regulated Bcl-2 was detected in OSCC tissues and cells compared with controls. Subsequently, Bcl-2-siRNA was found to be able to decrease cell viability while promote cell apoptosis in SCC9 cells, accompanied with the reduction of Bcl-2 and promotion of Bax. The Bcl-2/Bax ratio was reduced in Bcl-2-siRNA transfected group. In addition, miR-4262 mimic significantly suppressed the Bcl-2 expression, whereas the suppression was reversed by Bcl-2-plasmid. Furthermore, our results presented that miR-4262 mimic notably reduced cell viability and promoted cell apoptosis in SCC9 cell lines. Up-regulated miR-4262 could also downregulate Bcl-2 expression, upregulate the expression of Bax and decrease the Bcl-2/Bax ratio in SCC9 cells. However, Bcl-2-plasmid attenuated all these effects of miR-4262 mimic. Taken together, our findings indicated that miR-4262 exerted tumor-suppressive effects through targeting Bcl-2, resulting in promotion of cell apoptosis and inhibition of cell viability in OSCC cell lines. Therefore, miR-4262 might be a promising prognostic biomarker and novel therapeutic target during the therapy of OSCC.