Background: The prognosis of squamous cell carcinoma of the oral tongue is poor and it would be beneficial to find prognostic markers to better adjust treatment. Bmi-1 controls cell cycle and self-renewal of tissue stem cells, transcription factor c-myc affects cell proliferation and apoptosis, and Snail regulates epithelial–mesenchymal transition. The expression of these markers has been connected to prognosis in many cancer types. Methods: Bmi-1, c-myc, and Snail expressions were studied in our material consisting of 73 primarily T1N0M0 oral tongue carcinoma patients. We compared the immunoexpressions of Bmi1, c-myc, and Snail with clinical parameters including the degree of histological differentiation, tumour size, TNM classification, depth of invasion, and resection margins. In addition, survival analyses were performed, comparing disease-free survival time with the registered protein expression of the markers mentioned above. Results: A significant correlation between Bmi-1 protein expression and recurrence (log-rank test, P =0.005) was detected. Snail and c-myc expression did not correlate with prognosis. Snail expression correlated with histopathological grade (Fisher's exact test, P =0.007) and with the invasion depth of tumours ( χ 2 -test, P =0.037). Conclusion: Negative Bmi-1 immunoexpression might serve as a marker of poor prognosis in oral tongue carcinoma patients.

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Our results suggest that especially MMP-13 may be regarded as a prognostic biomarker in OTSCC.