Decreased expression of SOX7 induces cell proliferation and invasion, and correlates with poor prognosis in oral squamous cell carcinomas

Abstract

SOX7, a member of the SOX family of transcription factors, acts as a tumor suppressor in multiple cancers. Downregulation of SOX7 has been reported in advanced tumors, correlating with poor prognosis. The aims of the present study were to investigate the effects of SOX7 on cell proliferation, invasion, and colony formation in oral squamous cell carcinoma (OSCC) cells and to evaluate the effectiveness of SOX7 protein as a prognostic indicator in OSCC patients. OSCC cell lines were treated with SOX7 small interfering RNA (siRNA) or SOX7 peptide, and their effects on cell proliferation, invasiveness, and colony formation were investigated by WST-1, Matrigel invasion, and clonogenic assays. In addition, SOX7 protein expression in OSCC and normal oral mucosal tissues was examined by immunohistochemistry. The association between SOX7 protein expression and clinicopathological parameters of OSCC patients was statistically analyzed. SOX7 silencing induced cell proliferation and invasion in SCC-4 cells. SOX7 peptide treatment inhibited cell proliferation, colony formation, and invasion in SCC-9 and SCC-25 cells. The expression level of SOX7 protein was decreased in OSCC tissues, compared with normal oral mucosal tissues (P < 0.001). Negative SOX7 expression in OSCC patients was significantly associated with positive lymph node metastasis (P = 0.041), advanced TNM stage (P = 0.024), and poor prognosis (P = 0.017). These results suggest that SOX7 inhibits cell proliferation, colony formation, and invasion in OSCC as a tumor suppressor and that negative SOX7 expression could be a poor prognostic indicator in OSCC patients.