IMMUNOHISTOCHEMICAL EVALUATION OF BCL-2 ONCOPROTEIN IN ORAL DYSPLASIAAND CARCINOMA

The proto-oncogene bcl-2 is associated with follicular lymphoma involv ing translocation t(14;18)(q32;q21) and is also overexpressed in vario us neoplasms. We report deregulation of bcl-2 expression during progre ssion from oral epithelial dysplasia to squamous cell carcinoma. Immun ohistochemical analysis with monoclonal antibodies to bcl-2 oncoprotei n in formalin-fixed paraffin-embedded tissue sections revealed that se vere epithelial dysplasias had a higher percentage of immunoreactivity than did mild and moderate dysplasias and squamous cell carcinomas. E xpression of this oncoprotein was directly proportional to the degree of epithelial dysplasia, and nondysplastic basal cells contiguous to n eoplastic lesions also expressed bcl-2. These findings, along with dow n-regulation of bcl-2 in differentiating carcinomas, suggest a role fo r this oncoprotein in relatively early stages of oral tumor progressio n. Differentiating neoplastic cells with marginal or no bcl-2 reactivi ty showed heterogeneous cell labeling of varying intensity for differe ntiation-associated cytokeratin (CK13), indicating their inverse topog raphic relationship.