Population Stratification Effect on Cancer Susceptibility in an Admixed Population from Brazilian Amazon

Background/Aim: Many efforts have been made to identify candidate genes involved in cancer susceptibility. The present study aimed to investigate the association between Arg194Trp (XRCC1), Ala222Val (MTHFR) and Arg521Lys (EGFR) polymorphisms (SNPs) and their susceptibility to gastric and breast carcinoma cancer in patients from Brazilian Amazon, controlling population structure interference. Materials and Methods: The SNPs were genotyped by TaqMan (R) SNP Genotyping Assays. Ancestry was estimated by analysis of a panel with 48 ancestry informative markers. Results: Logistic regression analysis showed an inverse association with a 10% increase in African and European ancestry and cancer risk (odds ratio (OR)=1.919 and 0.676, respectively). In a preliminary Chi-square analysis a positive association between Arg521Lys (EGFR) polymorphism and carcinoma susceptibility was found (p=0.037); however, when two different methodologies to control population structure bias were utilized, this association was lost (p=0.064 and p=0.256). Conclusion: Genetic ancestry influence gastric and breast cancer risk and highlight the importance of population structure inference in association studies in highly admixed populations, such as those from Brazilian Amazon.