Immunohistochemical analysis of PCNA, Ki-67 and p53 expression in benign, dysplastic and malignant lesions of oral mucosa

The aim of the present study was to assess the expression of proliferating cell nuclear antigens PCNA and Ki-67, as well as of tumour suppressor gene p53 in normal, hyperplastic, atrophic oral epithelium, leucoplakias without and with dysplasia, tissues adjacent to the primary tumour and in squamous cell carcinomas. A correlation was observed between p53 overexpression and proliferating activity in cases of mild, moderate and severe dysplasia, as well as in tissues adjacent to the epithelia of primary squamous carcinoma, suggesting the involvement of a p53 mutated form in cell cycle regulation. It is tentatively concluded that the appearance of p53 immunpositive cells in cases of leucoplakias without dysplasia, in tissues of lichen ruber planus and in cases of mild dysplasias can be explained by inactivation of wild type p53 and the involvement of morphologically normal cells in an abnormal proliferating activity. The p53 mutated form tended to localize focally in basal layer in cases of mild dysplasia, diffuse in some epithelial rate processes or throughout the entire basal layer in cases of moderate dysplasia, and basal in cases of severe dysplasia including entire basal and parabasal layers. Our studies indicate that it is important to study PCNA expression in close association with p53 immune expression.