Decreased expression of SOX 7 induces cell proliferation and invasion and correlates with poor prognosis in oral squamous cell carcinoma

Background SOX 7, a member of the SOX family of transcription factors, acts as a tumor suppressor in multiple cancers. Downregulation of SOX 7 has been reported in advanced tumors and correlates with poor prognosis. The aims of this study were to investigate the effects of SOX 7 on cell proliferation, invasion, and colony formation in oral squamous cell carcinoma ( OSCC ) cells and to evaluate the effectiveness of SOX 7 protein as a prognostic indicator for OSCC patients. Methods oral squamous cell carcinoma ( OSCC ) cell lines were treated with SOX 7 small interfering RNA or SOX 7 peptide, and their effects on cell proliferation, invasiveness, and colony formation were investigated by proliferation, in vitro invasion, and clonogenic assays. SOX 7 protein expression in OSCC and normal oral mucosal tissues was examined by immunohistochemistry. Associations between SOX 7 protein expression and clinicopathological parameters of OSCC patients were statistically analyzed. Results SOX 7 silencing‐induced cell proliferation and invasion in SCC ‐4 cells. SOX 7 peptide treatment inhibited cell proliferation, colony formation, and invasion in SCC ‐9 and SCC ‐25 cells. Expression of SOX 7 protein was decreased in OSCC tissues compared with normal oral mucosal tissues ( P <.001). Negative SOX 7 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 SOX 7 inhibits cell proliferation, colony formation, and invasion in OSCC as a tumor suppressor and that negative SOX 7 expression could be a poor prognostic indicator for patients with OSCC .