Decreased expression of Beclin-1 is significantly associated with a poor prognosis in oral tongue squamous cell carcinoma

The autophagy-related gene Beclin-1 is critical in the regulation of tumourigenesis and progression, but its role in oral tongue squamous cell carcinoma (OTSCC) has not yet been reported. This study aimed to investigate Beclin-1 expression and its significance in OTSCC. Beclin-1 expression was assessed by reverse transcription-quantitative polymerase chain reaction or western blot analysis in 14 OTSCC tissues and matched adjacent noncancerous tissues as well as in 5 OTSCC cell lines and a normal tongue epithelial cell line. Beclin-1 protein expression was examined by immunohistochemistry in 133 OTSCC specimens, and the correlation between Beclin-1 expression and clinicopathological features was investigated. Furthermore, MTT and colony formation assays were performed to investigate the effect of Beclin-1 on the proliferation and clonogenicity of OTSCC cells. It was demonstrated that Beclin-1 expression was significantly decreased in the majority of the 14 OTSCC tissues and the 5 OTSCC cell lines relative to the matched non-cancerous tissues and the normal tongue epithelial cell line, respectively. Immunohistochemistry analysis revealed that decreased Beclin-1 expression was significantly correlated with poor differentiation, lymph node metastasis, advanced clinical tumour-node-metastasis stage, and a poor prognosis in patients with OTSCC. The in vitro assays indicated that the overexpression of Beclin-1 significantly inhibits the proliferation and clonogenicity of OTSCC cells. These results demonstrate that Beclin-1 acts as a tumour suppressor in the development or progression of OTSCC and that Beclin-1 may represent a novel prognostic marker for patients with OTSCC.