XRCC3 and NBS1 gene polymorphisms modulate the risk of pre-oral cancer and oral cancer in the North Indian population

Background: Oral cancer is alarming disease in the developing countries like India. DNA repair capacity may affect by genetic polymorphisms in DNA repair genes and thus may cause to cancer. XRCC3 involves in homologous recombination repair pathway and repair DNA damage and crosslinks while, NBS1 participate in repair of double strand DNA break and starts the cell-cycle checkpoint signaling. Aims and Objectives: This study was to conducted to find the association of XRCC3, NBS1 polymorphisms with oral disease. Materials and Methods: This study included 230 patients of precancerous oral lesions (Leukoplakia 70, Oral Sub mucous fibrosis 90, Lichen Planus 70), 72 oral cancer and 300 healthy control samples and genotyping was done by PCR-RFLP methods. Chi-square test was used for calculation of genotype and allele frequencies. Odds ratio and P values were calculated with Epi-Info programme (http://wwwn.cdc.gov/epiinfo/). Results: TT genotype of XRCC3 was associated with high risk of precancerous lesions and oral cancerous lesions (P value=0.0001, OR=9.68, 95% CI=2.82-33.21; and P value=0.0001, OR=13.10, 95% CI=3.38-50.73 respectively). We did not observe any interactions of XRCC3 polymorphism with demographic parameters in influencing the risk of oral diseases. Variant allele genotypes (CG, GG) of NBS1 (C>G) polymorphism showed protective association with Oral submucous fibrosis (OSMF), lichen planus as well as oral cancer (OR=0.31, OR=0.01; OR=0.39, OR=0.03; OR=0.43, OR=0.31 respectively). Particularly, tobacco chewer with CG & GG genotypes were at decrease risk of oral diseases (P value=0.02, OR=0.32, 95% CI=0.12-0.80). Compared to CC/CC combined genotype CG/CC, CG/CT, GG/CC and CG/CT genotypes decreased the risk of oral disease (OR=0.05, 0.47, 0.26 & 0.14 respectively). Conclusion: This study concludes that SNP in XRCC3, NBS1 affects susceptibility to oral disease.