SOME ORAL CARCINOMAS FROM SRI-LANKAN BETEL TOBACCO CHEWERS OVEREXPRESS P53 ONCOPROTEIN BUT LACK MUTATIONS IN EXONS 5-9/

We reported a low prevalence (11%) of p53 expression detected by immun ohistochemistry in oral squamous cell carcinomas associated with betel /tobacco chewing Sri Lankans (23). Five neoplasms which over-expressed p53 protein were used in the present study of mutations. Despite exte nsive sequence analysis no mutations were detected in exons 5 through 9 of the p53 gene in all the DNA samples of these neoplasms. Thus, ove r-expression of p53 is nor necessarily synonymous with mutations in th e exons studied, although mutations of this gene have been reported in oral and head and neck cancer from Japan and USA. The absence of muta tions in betel/tobacco related carcinomas in this population may deriv e from differences in aetiology, carcinogen metabolism and susceptibil ity, DNA repair mechanisms and/or genetic predisposition.