Objectives. Several studies have demonstrated that genetic variants of certain DNA repair genes such as the RAD51 and XRCC1 increase cancer risk substantially. The results were also observed to be race-and tumor sitespecific. Hence, this study aimed to determine the possible association of XRCC1 Arg399Gln and RAD51 135G>C polymorphisms combined with risk factors of colorectal cancer (CRC) among selected Filipinos.Methods. Genomic DNA isolated from peripheral blood samples of histologically confirmed CRC patients (n=70) and their age-and sex-matched clinically healthy controls (n=70) were analyzed for polymorphisms of XRCC1 and RAD51 genes by polymerase chain reaction.Results. The genotypic distribution pattern of RAD51 135G>C (p˃0.05) was not significantly different between the CRC cases and controls. Significantly higher incidence (p=0.016) of the XRCC1 GG genotype was noted among the cases (n=34, 49%) compared with controls (n= 20, 29%). Individuals carrying the XRCC1 AG genotype have a lower risk of developing CRC (OR=0.42, 95% CI=0.21-0.85) than the XRCC1 GG genotype. XRCC1 AG genotype combined with alcohol drinking, smoking, or family history of cancer also showed a lower risk of developing CRC. There was no significant association between the genetic variants of RAD51 135G>C and CRC risk. Carriers of both XRCC1 GG and RAD51 CC genotypes showed a 5x higher risk (OR=5.02; 95%; CI=1.0429-24.1283) compared to those carrying other genotype combinations (p=0.028).
Conclusions. XRCC1Arg399Gln but not RAD51 135G>C may be associated with CRC development among Filipinos. Individuals who drink alcohol, smoke tobacco and have a family history of cancer have a lower risk of developing CRC when they are also carrying the XRCC1 AG genotype. The findings may have significant implications in designing personalized methods for screening, diagnosing, and treating CRC.