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

为了发现印度和日本口腔鳞状细胞癌发生的差异，我们分析了来自马杜莱Rajaji政府医院的53份口腔肿瘤样本的p53和ras突变，以及来自坎奇普拉姆Anna癌症医院的50份宫颈癌样本的p53和HPV状态。从这些肿瘤中分离DNA，并使用p53， ras和HPV引物对特定区域进行pcr扩增。扩增在32PdCTP存在的情况下进行，p53和ras的产物通过SSCP分析筛选突变。SSCP p53阳性样本由A.K.Munirajan在东京医科牙科大学确认并测序，他为此目的访问了这里三次并学习了其他技术。结果显示，53个口腔样本中有11个（21%）出现p53突变。这些突变大多是转移性的，这与烟草相关的亚硝基胺参与口腔鳞状细胞癌的病因一致。Ras突变频率较高（32%）。然而，p53和ras突变在样本中没有重叠。ras突变以H-ras基因居多。在60-70%的宫颈癌中检测到HPV的情况下，我们无法证明口腔癌中存在HPV，这表明这种病毒在印度口腔鳞状细胞癌的发生中没有显著作用。

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.