p53 expression in oral cancer: observations of a South Indian study

Oral cancers constitute a significant proportion of hospital admissions among cancer patients in India. The aim of this study was to elucidate the role of tumour suppressor gene p53 in the pathogenesis of oral squamous cell carcinoma by immunohistochemistry. Though extensive studies on p53 alterations in oral cancers have been done in Western countries and some Asian countries, only a few studies have emerged from India, especially the Southern states. This study would therefore be helpful in providing an Indian perspective, with particular reference to South Indian states. A total of 110 cases of oral squamous cell carcinoma, 35 dysplastic lesions, 15 hyperplastic lesions, and 50 samples of normal mucosa were assessed for p53 expression. Out of 110 cases of oral carcinoma, 40 (36%) were p53 positive. Among 35 cases of dysplastic lesions studied, 6 (17%) showed p53 positive staining. None of the hyperplastic lesions and normal oral lesions showed any evidence of p53 positivity. However, in 9 out of 40 (23%) cases of positive infiltrating squamous cell carcinomas, the adjacent or overlying non-tumourous epithelium demonstrated focal areas of p53 positive staining in the basal and parabasal layers of the epithelium. In addition, in 7 out of 110 (6%) cases, cytoplasmic staining was observed. In these samples, nuclei were not stained. Our results indicate that p53 over-expression may be involved in only a certain proportion of oral carcinomas. The fact that 6% of the dysplastic lesions were p53 positive, and adjacent non-tumourous epithelium of 23% infiltrating squamous cell carcinomas showed positive staining for p53 in the progenitor compartment of the epithelium indicates that p53 immunoreactivity could be used to detect early tumours as well.