[Analysis of expression of p53 tumor suppressor gene in human oral squamous cell carcinoma]

Expression of p53 tumor suppressor gene was examined in oral squamous cell carcinomas (OSCC), the precancerous lesions (leukoplakia) and cell lines established from OSCC, to investigate (1) whether or not all p53 mutations can be detected immunohistochemically and (2) when the alterations of the p53 gene and/or protein occur during the genesis of OSCC from leukoplakia. Over-expression was detected in 11 out of 16 cell lines with the anti-p53 monoclonal antibody PAb1801, although the remaining 5 cell lines have previously been reported to have mutations, thus suggesting that the immunohistochemical method has a limitation. To answer the second question, the ZA case was chosen as this case of OSCC with a point mutation at codon 279 had a history of leukoplakias which showed a malignant progression. The polymerase chain reaction/single strand conformation polymorphism (PCR/SSCP) method was employed to determine the presence of the mutation. Immunohistochemistry showed over-expression of the p53 protein in all 5 biopsy materials of leukoplakia, while the mutation was detected in 2 materials. In other 15 cases of leukoplakia, over-expression has a relation to epithelial dysplasia. These results indicate alterations of p53 gene and/or protein are observed not only in OSCC but also in leukoplakia and play an important role in the genesis of OSCC.