Evaluation of p53 and bcl-2 oncoprotein expression in precancerous lesions of the oral cavity.

The oral cavity is continually exposed to various traumas due to the effect of thermal, mechanical and chemical stimuli, which when accompanied by inflammatory states may promote the growth of neoplastic changes. Numerous studies have revealed a correlation between the expression of p53 and Bcl-2 proteins and the progression of neoplastic disease. It cannot be excluded that these proteins act as biomarkers of a neoplastic transformation threatening in precancerous states (including leukoplakia) or the already existing neoplastic transformation (e.g. in oral squamous cell carcinoma). The aim of the study was to evaluate the expression of p53 and Bcl-2 proteins in the proliferating epithelium in relation to leukoplakia degree and with regard to the lesions accompanied and not accompanied by squamous cell carcinomas. Fifty-five cases of proliferating changes in the oral epithelium (leukoplakia) were investigated. Group I contained 20 leukoplakias not accompanied by oral squamous cell carcinomas. Groups II, III and IV included 35 cases of changes in the vicinity of carcinomas on the lower lip (group II), in the front 2/3 of the tongue (group III) and in the oral floor (group IV). Staining was performed according to the immunohistochemical method with the use of monoclonal antibodies against human p53 protein (DAKO No M7001) and Bcl-2 (DAKO No M0887). A higher expression of p53 protein (54%) was found in leukoplakia changes coexisting with squamous cell carcinomas, compared with the non-accompanied ones (p53--45%). The results indicate a correlation between epithelial dysplasia degree and p53 and Bcl-2 protein expression--severe dysplasia occurred with an increase in the expression of both proteins. Leukoplakias situated in the vicinity of squamous cell carcinomas showed higher expression of p53 and Bcl-2 compared with the non-accompanied alterations. A correlation was also revealed between the location and p53 and Bcl-2 protein expression degree in the non-accompanied changes; no such correlations were found in proliferating epithelial changes adjacent to neoplastic tumors.