Evaluation of immunohistochemical expression of p16 and presence of human papillomavirus in oral and oropharyngeal carcinoma.

Carcinogenesis concerns several changes that eventually result in the inactivation of tumor suppressor genes and activation of protooncogenes, leading to loss of cell cycle control. Inactivation of p16 seems to be an early event in this process and occurs in approximately 80% of squamous cell carcinoma cases. The aims of this study were to evaluate the immunohistochemical expression of p16 protein in oral and oropharyngeal squamous cell carcinoma cases, with both the tumoral area itself and its surgical margin being analyzed (dysplastic areas and histologically normal epithelium adjacent to carcinoma), and to verify the presence of human papillomavirus (HPV) and its relation to p16 expression. Paraffin-embedded biopsy tissues from 26 patients, 13 with oral squamous cell carcinoma and 13 with oropharyngeal squamous cell carcinoma, comprised the analyzed samples. To detect HPV, a nested polymerase chain reaction test using PGMY 09/11 and GP5*/GP6* primers and visualization of the product on a 2% agarose gel was performed. Demographic data were obtained from medical records. The results showed low expression of p16 in the tumor area (38.46%), compared with surgical margins in the histologically normal epithelium (84.6%) and dysplastic areas (57.7%). These findings indicate the inactivation of p16 in the process of malignant transformation. The association described in the literature between expression of p16 and presence of HPV could not be verified in this study, because none of the cases was HPV positive.