Overexpression of p53 protein and p53 mutations in oral carcinoma

Background. Alterations of the tumour suppressor gene p53 are frequently present in different types of cancer and correlate to aetiological factors or prognosis in tumours of several sites. We have examined the frequency of p53 alterations in oral carcinoma and correlated these events with aetiological factors. Methods. A total of 46 cases of oral carcinoma were studied for both the presence of p53 mutations by screening with temperature gradient gel electrophoresis (TGGE) and direct sequencing of the exons 5-8 and immunohistochemically detectable p53 accumulation. Results. Mutations of the p53 gene were detected in 19 out of 46 carcinomas (41.3%) by screening with TGGE. By direct sequencing mutations were identified in 27 cases. A p53 accumulation was present in 28 out of 46 tumours (60.9%). The rate of p53-positive tumour cells correlated with the tumour grade. Of 19 tumours with mutations 15 revealed p53 accumulation. In addition 13 nonmutated tumours were p53 immunoreactive, probably due to epigenetical influence on protein processing. Smoking related G to T transversions were found in four out of 46 oral carcinomas. Conclusions. Alterations of the tumour suppressor gene p53 are frequently present in oral carcinomas. Smoking-related mutations are less frequent than in lung cancer.