Introduction & Objective: One candidate gene for colorectal cancer susceptibility is exonuclease1 (EXO1) .It is a member of RAD2 nuclease family. It plays a main role in mismatch repair. EXO1 acts also in DNA replication and recombination. Single nucleotide polymorphisms (SNPs) are shown to be related with cancer incidence. The aim of the present study was to examine the association between P757L polymorphism at exon 13 of the EXO1 gene and the risk of colorectal cancer in an Iranian population.

Materials & Methods: In this case-control study, 81cases and 86 healthy controls were selected from among individuals who were referred toTehran Taleghani hospital during 2008-2009. The individuals were divided into two groups, case and control, based on their colonoscopy and pathology results. Genotype analysis was performed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method and MNII restriction enzyme. Totally 167 samples were analyzed.

Results: Based on our findings when Pro/Pro genotype was reference for the Leu/Leu (TT) genotype (OR=0.168, 95%CI 0.034-0.816), it showed a reverse association with colorectal cancer. While Pro/Leu (CT) genotype did not revealed a significant association with colorectal cancer at the same status. (OR=0.663, 95%CI 0.340-1.294).

Conclusion: The results of this study were compatible with other investigations which convey Leu/Leu (TT) genotype of EXO1 has reverse association with colorectal cancer. Therefore TT genotype has a protective effect against colorectal cancer.