Genetic Susceptibility to Oral Cancer due to Combined Effects of GSTT1, GSTM1 and CYP1A1 Gene Variants in Tobacco Addicted Patients of Pashtun Ethnicity of Khyber Pakhtunkhwa Province of Pakistan

Associations of GSTT1, GSTM1 and CYP1A1 gene variants with risk of developing oral cancer were evaluatedin this study. A case-control study was conducted in Pashtun population of Khyber Pakhtunkhwa province ofPakistan in which 200 hospital based oral cancer cases and 151 population based healthy controls exposed tosimilar environmental conditions were included. Sociodemographic data were obtained and blood samples werecollected with informed consent for analysis. GSTM1 and GSTT1 were analysed through conventional PCRmethod while specific RT-PCR method was used to detect CYP1A1 polymorphisms. Results were analyzed forconditional logistic regression model by SPSS version 20. The study shows that patients with either GSTM1 orGSTT1 null genotypes have significantly higher risk of oral cancer (adjusted odds (OR): (3.019 (1.861-4.898)and 3.011(1.865-4.862), respectively), which further increased when either one or both null genes were present incombination (adjusted odds (OR): (3.627 (1.981-6.642 and 9.261 (4.495-19.079), respectively). CYP1A1 rs4646903gene variants individually showed weak association OR: 1.121 (0.717-1.752); however, in the presence of GSTM1and/or GSTT1 null genotypes further increasing the association (adjusted odds (ORs): 4.576 (2.038-10.273), 5.593(2.530-12.362) and 16.10 (3.854-67.260 for GSTM/GSTT null and CYP1A1 wild type, GSTM/GSTT either nulland CYP1A1 variant alleles, and all 3 gene polymorphisms combinations, respectively). Our findings suggestthat presence of GSTM1 and/or GSTT1 null genotypes along with variant alleles of CYP1A1 may be the riskalleles for oral cancer susceptibility in Pashtun population.