Abstract
Since the risks of development of salivary mucoepidermoid carcinoma and Warthin tumor have been significantly greater among atomic bomb survivors in a dose-dependent manner, the p53 gene, an important proto-oncogene whose mutation has been related to radiation, was analyzed by DNA sequencing and immunohistochemistry in 37 cases of mucoepidermoid carcinoma collected from Niigata and Nagasaki and in 33 cases of Warthin tumor collected from Niigata. Immunohistochemically, p53 gene products were heavily demonstrated in most of the tumor cell nuclei of mucoepidermoid carcinomas but not in Warthin tumors. Mucoepidermoid carcinomas had some point mutations (codons 136-137, 144, 232, 234, and 241) but their incidences among the samples were not significantly high (2.7%-10.8%). In contrast, three point mutations (codons 143, 151, and 229) were commonly found in the Warthin tumor cases (80%-87%), but the former two mutations did not alter their amino acid composition. Thus, there were no p53 mutations which were shared by the two tumors. However, the mutations at exon 5 of mucoepidermoid carcinomas were significantly higher in the cases from Nagasaki than those from Niigata, although their highest frequencies at most were around 10%. The results suggest that point mutations of p53 gene, as far as exons 5-7 were concerned, do not play any obviously important roles in the radiation-based tumorigenetic processes shared by mucoepidermoid carcinoma and Warthin tumor.
