MicroRNA509 acts as a tumor suppressor in tongue squamous cell carcinoma by targeting epidermal growth factor receptor

Tongue squamous cell carcinoma (TSCC) is the most frequent type of oral carcinoma, and is characterized by high metastatic and growth capabilities. Previous studies have demonstrated that aberrantly expressed cancerassociated microRNAs (miRs) may be associated with tumorigenesis and tumor development in various types of cancer, including TSCC. miR509 has been identified as a critical regulator in tumorigenesis and tumor development, via its tumorsuppressing actions in several types of human cancer. In the present study, miR509 expression in TSCC tissues and cell lines was determined by reverse transcriptionquantitative polymerase chain reaction. The effects of miR509 on TSCC cell proliferation and invasion were evaluated via MTT and invasion assays, respectively. In addition, the direct target of miR509 in TSCC was investigated. The present study demonstrated that miR509 expression was downregulated in TSCC tissue samples and cell lines, whereas its ectopic expression suppressed TSCC cell proliferation and invasion in vitro. In addition, epidermal growth factor receptor (EGFR) was identified as a direct target gene of miR509 in TSCC cells. EGFR downregulation was demonstrated to suppress the proliferation and invasion of TSCC cells, similar to miR509 overexpression. Furthermore, EGFR was significantly upregulated in TSCC tissues, and the levels of miR509 were revealed to be negatively correlated with EGFR expression in TSCC tissues. Following transfection with miR509 mimics, signaling pathways downstream of EGFR appeared to be suppressed, as phosphorylated (p)extracellular signalregulated kinase and pAkt were downregulated in TSCC cells. In conclusion, the results of the present study suggested that miR509 may inhibit the proliferation and invasion of TSCC cells via directly targeting EGFR, thus suggesting that the miR509/EGFR axis may have potential as a novel therapeutic target for the development of a treatment for patients with TSCC.