Lack of concordant p53 mutations in some paired primary and metastatic mouse squamous cell carcinomas induced by chemical carcinogenesis.

We studied the frequency and pattern of p53 mutations in 16 mouse skin primary squamous carcinomas induced by chemical carcinogens and their 19 matched metastases. The molecular changes were analyzed by polymerase chain reaction-single-strand conformation polymorphism and subsequent direct sequencing analysis. Eleven mutations of the p53 gene were detected in a total of eight primary tumors, and 10 mutations were detected in nine metastases. Only four pairs had identical mutations in primary and paired metastatic tumors. Eight mutations in six pairs were detected in primary tumors but not in their metastases, and four mutations from three matched pairs were detected in metastases but not in primary tumors. The four pairs that contained the same mutations in both the primary and secondary tumors had lymph-node metastases, and all mutations occurred in exon 8. Conversely, five of six pairs with p53 mutations only in primary tumors had lung metastases, and only one of the mutations occurred in exon 8. None of the mutations found only in metastases were located in exon 8. These data indicate that p53 mutations are prevalent in lymph-node metastases and infrequent in lung metastases of mouse skin tumors and that primary tumors with exon 8 mutations may be more likely to metastasize to the lymph nodes.