---

Background and purpose: Colorectal cancer is one of the most common cancers in the world and Iran. This cancer is a multifactorial disease that is induced by interaction of various genetic and environmental factors. In this study, we investigated the interactions between different environmental factors and candidate polymorphisms of two genes in colorectal cancer X-ray repair cross-complementing-1(XRCC1) and Oxo guanine DNA-glycosylase 1 (OGG1), which play roles in the DNA repair pathway and maintaining the integrity of the genome.
Materials and methods: This case-control study was conducted in 150 patients with colorectal cancer and 150 healthy controls selected from hospitals affiliated with Ahvaz Jundishapur University of Medical Sciences. Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) was used to determine the allele of the polymorphisms. After determining the different genotypes, the interaction of these genotypes with environmental risk factors in two groups of patients and controls was analyzed and compared.
Results: The study showed that XRCC1 (Arg399Gln) polymorphism in body mass index and obesity was significantly correlated with colorectal cancer (p= 0.009). Also, the Lur race was found to be highly susceptible to developing colorectal cancer (p= 0.003), but there was no significant correlation between these items and other risk factors and OGG1 (Ser326Cys) polymorphism in colorectal cancer.
Conclusion: In this study, XRCC1 Arg399Gln gene polymorphism was significantly associated with obesity and Lur race had a high potential for developing colorectal cancer.