P53 overexpression in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is a characteristic tumor displaying epidemiological, genetic and regional distribution properties and is unique by its natural behavior and therapy. Investigation of the molecular and biological changes, gene amplifications and activations that occur during carcinogenesis and progression can provide new insight into the pathology of the disease and may add biological factors that can be used as new prognostic markers. The p53 tumor suppressor gene is the most frequently mutated gene in human cancer. Although point mutations in the p53 gene are observed in nasopharyngeal cancer, the mutation rate is lower than in other tumors. Immunohistochemical studies have shown significant p53 overexpression in NPC material. In this study, p53 protein immunoreactivity was investigated in paraffin sections of primary nasopharyngeal tumors and metastatic cervical lymph nodes and association with clinical and histopathological characteristics was evaluated. Ninety-seven paraffin sections from 81 patients with NPC treated from 1990 to 1996 were examined by immunohistochemistry and were correlated with clinical features and treatment outcome. Among a total of 97 samples, positive staining for p53 protein was observed in 83 (85.5%) samples while no staining was found in 14 (14.5%) cases. Immunoreactivity was observed in 62 (81.5%) of the primary nasopharyngeal biopsy specimens. The correlation between p53 expression and histological type, stage, age and sex distributions was tested. After statistical analysis according to Chi-square test and Yates' correction, no significant difference was demonstrated (p>0.05). There was no statistically significant correlation with p53 immunoreactivity and overall and disease-free survival. Although the association between NPC and p53 is not clear, our study confirms that p53 overexpression is present in a considerable subset of patients with NPC.