To investigate the role of Bmi1 in the initiation and development of tongue squamous cell carcinoma (TSCC) .

The immunohistochemistry analysis was performed to analysis the expression level of Bmi1 in 77 TSCC cases, 22 leukoplakia cases and 12 normal tongue biopsies. The data were analyzed using SPSS 17.0. One-Way ANOVA and Student′s t-test were used to compare the differences between groups. Pearson and Spearman correlation coefficients were used to assess correlations among the Bmi1 gene expression and clinical and histopathological parameters of TSCC patients. Bmi1 Survival curves of TSCC patients were plotted using the Kaplan-Meier method and compared using the log-rank test. For all statistical analyses, P<0.05 was considered statistically significant.

Bmi1 expression was significantly higher in LP and TSCC than in normal tongue tissue (P= 0.014; P= 0.036) . For LP cases, Bmi1 expression was also significantly higher in moderate and severe ones than in light ones (P= 0.014) . For TSCC cases, the expression level of Bmi1 was significantly higher in the patients with positive node metastasis status than those with negative status (P= 0.006) , and in late-stage (stages Ⅲ and Ⅳ) than in early-stage disease (stages Ⅰ and Ⅱ) (P= 0.004) . There was no significant correlation between the expression of Bmi1 and age, gender, or pT stage in the present study. However, strong positive correlations were observed between the expression of Bmi1 and pN and the clinical stages (P<0.05) . Significant positive correlation was also observed among Bmi1 expression, SOD2 expression and Ki67 expression (P<0.05) . There was a significantly higher 5-year survival rate in low Bmi1 expression group than in high Bmi1 expression group (P<0.001) .

Bmi1 expression was significantly higher in TSCC and LP tissues. Bmi1 expression began at the early stage of TSCC, and played an important role in the initiation and progression of TSCC.