Over-expression of Bmi-1 protein in oral precancerous lesions and squamous cell carcinomas

Objective To investigate the expression and the clinicopathological significance of B-cell-specific Moloney leukemia virus insertion site-1 (Bmi-1) protein in oral precancerous lesions and oral squamous cell carcinoma (OSCC). Methods The level of Bmi-1 protein in paraffin-embeded tissue sections of 10 cases of normal oral epithelium, 31 cases of epithelium dysplasia and 61 cases of OSCC were determined by immunohistochemistry. The clinical and pathological significances of Bmi-1 over-expression in oral carcinogenesis were statistically analyzed by SPSS 11.5. Results Bmi-1 protein was not detectable in normal oral epithelium and significantly altered from mild-dysplasia to OSCC. The percentages of Bmi-1 over- expression were 29%(9 / 31) in dysplasia and 62.3%(38 / 61) in OSCC. The percentage of Bmi-1 over-expression in OSCC was significantly higher than that in normal oral epithelium and dysplasia tissues (P 0.05). Statistical analysis revealed a strong correlationship between Bmi-1 expresson and the TNM stages, as well as the lymph node metastasis in OSCC (P 0.05). Conclusions Bmi-1 up-regulation was an early event in oral carcinogenesis and was related to tumor pro- gression. Bmi-1 could be used as a marker for assessing the progression of OSCC and provided a basis for clinical therapeutic decisions.