TNF-alpha polymorphism in oral cancer and oral potentially malignant disorders: meta-analysis and investigation as a potential tool to determine individual susceptibility and the prognosis.

There is increasing evidence that tumour necrosis factor alpha (TNF-alpha) gene polymorphisms may promote development and spread of cancer through transitions at different loci that lead to its altered expression. However, data on TNF-alpha gene polymorphisms in oral cancer remain highly controversial. This meta-analysis was performed to determine the impact of TNF-alpha gene polymorphisms on oral squamous cell carcinoma (OSCC) and oral potentially malignant disorders (OPMD). An electronic search was conducted in the PubMed, Cochrane Library, Google Scholar, and Web of Science databases to identify original articles reporting TNF-alpha polymorphism in OSCC and OPMD. The articles were examined by two independent authors. Data from the included articles were compiled and tabulated. Risk of bias was analysed. Overall, 11 eligible articles that included 1070 cases of OSCC and 641 cases of OPMD in which TNF-alpha polymorphism was studied, were included for quantitative analysis. It was found that both TNF-alpha -308 and -238 polymorphisms were significantly associated with the development of oral cancer. TNF-alpha polymorphism was significantly associated with OSCC and OPMD. Moreover, in polymorphisms of TNF-alpha at both -308 and -238, the G allele, especially the homozygous form (GG), was found to be associated with oral cancer.