Immunohistochemical expression of Bcl-2 in oral epithelial dysplasia and oral squamous cell carcinoma

BACKGROUND: The B cell lymphoma-2 gene is a proto-oncogene whose protein product inhibits apoptosis. Its role is associated with keeping cells alive, but not by stimulating them to proliferation, as other proto-oncogenes do. Increased expression of protein product of Bcl-2 gene appears in the early phase of carcinogenesis leading to apoptosis impairment and in consequence to the progression of neoplastic changes. OBJECTIVE: To evaluate and compare the expression of Bcl-2 protein in oral epithelial dysplasia and oral squamous cell carcinoma (OSCC). MATERIALS AND METHODS: Sixty cases of formalin-fixed paraffin-embedded archival specimens comprising of 30 cases of leukoplakia with oral epithelial dysplasia and 30 cases of OSCC were taken for immunohistochemical analysis using monoclonal antibody against anti-human Bcl-2 oncoprotein. RESULTS: Immunostaining for Bcl-2 protein was identified in basal and parabasal layers as granular cytoplasmic staining in oral epithelial dysplasia. In OSCC, Bcl-2 immunoreactivity was most prominent in the peripheral cells of the infiltrating tumor islands which diminished toward the center in well-differentiated and moderately differentiated OSCC, whereas stronger and more diffuse expression of Bcl-2 oncoprotein was seen in poorly differentiated OSCC. Overall positivity of 26.7% (8/30) was observed in oral epithelial dysplasia and 30% (9/30) in OSCC in this study. INTERPRETATION AND CONCLUSION: Altered expression of Bcl-2 oncoprotein may be an early molecular event which leads to prolonged cell survival, increased chances of accumulation of genetic alterations, and subsequent increase in malignant transformation potential.