Overexpression of p53 protein in betel- and tobacco-related human oral dysplasia and squamous-cell carcinoma in India.

The aetiological factors for oral cancer are not the same in India and in Western countries. Epidemiological studies have shown a correlation between high incidence of oral cancer and heavy consumption of betel and/or tobacco in the Indian population, while this study indicates an association with a genetic change. The p53 tumour-suppressor gene is the most commonly identified mutated gene in human malignancies. Expression of p53 protein was examined in premalignant and malignant oral lesions from Indian patients who were consumers of betel, areca nut and/or tobacco, using anti-p53 monoclonal antibodies PAb 1801 and PAb 421. Cryosections from normal, premalignant or malignant oral mucosa were used for immunostaining and the observations were confirmed by immunoprecipitation. p53 protein was detected in 55% (15/27) premalignant oral lesions (leukoplakia). Strong p53-positive staining was detected in 75% (24/32) of oral squamous-cell carcinomas. Normal oral mucosa did not show positive p53 staining (0/24). The detection of p53 protein in premalignant oral lesions suggests that p53 aberrations are an early event in the development of oral cancer in India. The high incidence of p53 positivity in leukoplakia may be due to differences in aetiological factors. p53 overexpression in premalignant oral lesions is important in view of the significantly earlier onset of leukoplakia in the Indian population compared to the development of oral malignancy, and may be helpful in identifying lesions that are more likely to progress to malignancy. The frequency of p53 protein overexpression was high in premalignant and malignant oral lesions of patients who were heavy consumers of betel, areca nut and tobacco.