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

Background: 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 and correlates with poor prognosis. The aims of this 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 for OSCC patients. Method: soral squamous cell carcinoma (OSCC) cell lines were treated with SOX7 small interfering RNA or SOX7 peptide, and their effects on cell proliferation, invasiveness, and colony formation were investigated by proliferation, in vitro invasion, and clonogenic assays. SOX7 protein expression in OSCC and normal oral mucosal tissues was examined by immunohistochemistry. Associations between SOX7 protein expression and clinicopathological parameters of OSCC patients were statistically analyzed. Results: 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. Expression of SOX7 protein was decreased in OSCC tissues compared with normal oral mucosal tissues (P<.001). Negative SOX7 expression in patients with OSCC was significantly associated with positive lymph node metastasis (P=.041), advanced TNM stage (P=.024), and poor prognosis (P=.017). Conclusions: 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 for patients with OSCC.