P53 (Pro72Arg) polymorphism associated with the risk of oral squamous cell carcinoma in gutka, niswar and manpuri addicted patients of Pakistan.
The chewing habit of paan, chhaliya, and tobacco is common in the traditional culture of Pakistan. Currently, niswar, gutka and manpuri are also commercially available in the Pakistani market. Epidemiologic evidences and increased rate of oral squamous cell carcinoma (OSCC) cases may indicate a direct relationship of these chewing habits with oral carcinogenesis. The p53 gene has been known to be a tumor suppressor gene that is found mutated in common human cancers. The p53 gene contains a single nucleotide polymorphism at codon 72 of exon 4 which encodes either proline (Pro) or arginine (Arg). The aim of the present study was to investigate association of p53 gene codon 72 polymorphism with patients of oral squamous cell carcinoma consuming these carcinogenic chewable materials. Blood and tissue samples of 260 OSCC patients were collected with informed consent from the local hospitals of Karachi. The patients were compared with controls of similar age and sex. The exon 4 of p53 gene was examined by PCR-SSCP. The tumor samples showing mobility shift were purified and sequenced. The C>G missense mutation at nucleotide position 215 of the coding sequence was identified which substitutes proline with arginine at codon 72 of p53 protein. When the data for CCC72CGC polymorphism was analyzed statistically, a significant difference was observed between OSCC and control samples. The Pro allelic frequencies were significantly higher in OSCC patients as compare to controls. The current study indicated the Pro form of p53 codon 72 increases the risk of developing OSCC in Pakistani population. The risk ratio for Pro allele was 1.5004 (95% confidence interval: 1.2559 to 1.7924) and odds ratio of Pro allele was 2.389 (95% confidence interval: 1.5591 to 2.8137) in comparison with the Arg and Pro alleles in the OSCC group. These evidences suggest that there may be specific genetic targets with these chewing ingredients that are responsible for causing OSCC. The p53 codon 72 polymorphism is associated with OSCC at somatic cell level but the polymorphism was not associated at inherited level.