P53 GENE ALTERATIONS AND P53 PROTEIN IN ORAL EPITHELIAL DYSPLASIA ANDSQUAMOUS-CELL CARCINOMA

To examine the expression of p53 protein and gene alterations in oral epithelial lesions including epithelial dysplasias and primary squamou s cell carcinomas, immunohistochemical and temperature gradient gel el ectrophoresis (TGGE) methods were applied to formalin-fixed and paraff in-embedded tissues. Morphologically normal mucosal epithelium stained negatively for p53 protein. Three out of 11 (27.3 per cent) epithelia l dysplasias and 19 out of 57 (33.3 per cent) primary squamous cell ca rcinomas stained positively for p53 protein, Although more than half o f the cases were positive for p53 protein in stage I, the positive can cer cases were found at other stages with variable frequency. Immunore active products were localized in the nucleus, especially in the basal and suprabasal layers, The analysis by TGGE revealed gene alterations in exons 5-8 in 3 out of 3 epithelial dysplasias and 17 out of 19 (89 .5 per cent) primary squamous cell carcinomas which were immunohistoch emically positive for p53 protein. These results suggest that p53 gene mutation may be involved in carcinogenesis in the oral squamous epith elium even in the early stage of the dysplasia-carcinoma sequence.