Roles of p53 and ras gene mutations in genesis of oral SCC in India

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In order to find differences of the genesis of oral squamous cell carcinomas in between India and Japan, 53 oral tumor samples obtained from Government Rajaji Hospital, Madurai were analyzed for p53 and ras mutations and another 50 uterine cervical cancer samples from Anna Cancer Hospital, Kancheepuram for p53 and HPV status. DNA was isolated form these tumors and specific regions were PCR-amplified using primers for p53, ras and HPV.The amplifications were done in the presence of 32PdCTP and the products for p53 and ras were screened for mutations by SSCP analysis. SSCP positive samples for p53 were confirmed and sequenced in Tokyo Medical Dental University by A.K.Munirajan who visitied here thrice for this purpose and to learn other techniques. The results indicated p53 mutations in 11 out of 53 (21%) oral samples. Most of these mutations were transition, which is consistent with the involvement of tabacco-related nitrosoamines in the etiology of oral squamous cell carcinoma. Ras mutations were relatively of high frequency (32%). However the p53 and ras mutations did not overlap in a sample. Moreover, most ras mutations were detected in H-ras gene. Unider conditions which detected HPV in 60-70% of cervical cancers we were unable to demosntrate the presence of HPV in the oral cancers, suggesting no significant role of this verus in genesis of Indian oral squamous cell carcinoma.