Expression of p16, p53 and Ki-67 proteins in the progression of epithelial dysplasia of the oral cavity.

Abstract. Background: The overexpression of the protein products of genes associated with the cell cycle tumour protein53 (p53), cyclin-dependent kinase inhibitor 2A (p16) and antigen identified by monoclonal antibody Ki-67 (Ki-67) is apparently of great significance. This study evaluated the immunohistochemical expression of these proteins in precancerous lesions and in carcinoma of the oral cavity. Materials and Methods: The nuclear expression of p53 and Ki- 67 and nuclear and/or cytoplasmic expression of p16 protein was examined in 54 biopsy specimens from the oral cavity obtained over a period of 3 years. The samples included 18 cases of normal/hyperplastic mucosa, 25 cases of dysplasia and 11 cases of invasive squamous cell carcinoma. The specimens were grouped into three categories: 1 = no or mild dysplasia, 2 = moderate or severe dysplasia, and 3 = invasive carcinoma. Results: p16 was negative in all the group 1 specimens, while both p53 and Ki-67, when present, were limited to the cells of the basal layer. In the group 2 specimens, the number of p16-, p53-, and Ki-67-positive cells increased as the grade of dysplasia progressed. In group 3 (invasive carcinomas), p53 and p16 expression occurred respectively in 81.8% and 54.5% of cases, while Ki-67 was elevated in all the cases. Conclusion: The expression of the cell-cycle proteins p16 and p53 in the dysplastic epithelium, in association with Ki-67, may represent significant markers to recognize evolution of precancerous disease in the oral cavity and to improve identification of the degree of dysplasia.