Mutations in the p53 gene and human papillomavirus infection as significant prognostic factors in squamous cell carcinomas of the oral cavity.

Abstract

The p53 gene has been indicated to be a tumour suppressor gene that is found in mutated form in common human cancers. Human papillomavirus (HPV) has oncogenic activity in cervical and oral squamous cell carcinomas (SCCs). The E6 protein of HPV is known to bind with p53 protein and inactive the tumor suppressor activity by promoting p53 degradation. Because of this background, we examined 38 primary, resected specimens of oral SCCs for detection of p53 mutations and HPV DNAs. Exons 5 through 8 of the p53 Mutations were observed in nine cases (24%). HPV-DNA detection and typing were performed using PCR with ¿high risk group' HPV-specified primers. HPV DNA sequences were detected in eight cases (21%). The AvaII digestion pattern of PCR-amplified HPV DNA showed that HPV-16 was present in all eight cases. Seven cases were p53 mutation-positive/HPV-negative, six cases were p53 mutation-negative/HPV-positive, and two intraosseus SCC cases were p53 mutation-positive/ HPV-positive. Thus, 15/38 (40%) cases had inactivation of the p53 protein. Interestingly, p53 mutation-negative/ HPV-negative cases had a poorer prognosis than p53 mutation positive or HPV-positive cases (P < 0.01). We conclude that (1) mutation in the p53 gene and/or HPV infection are frequent (40%) in oral SCC; (2) inactivation of p53 function by mutation and HPV infection are important genetic events in the development of 40% integral of oral SCCs; (3) p53 mutation and HPV infection are not mutually exclusive events and (4) other oncogenes or tumor suppressor genes may be crucial in the development of oral SCC if the prognosis is poor.