The effect of polymorphism in DNA repair genes RAD51 and XRCC2 in colorectal cancer in Turkish population.

The genes RAD51 and XRCC2 encode proteins that are important for the repair of double-strand DNA breaks by recombination. Therefore, genetic variability in these genes may contribute to the occurrence and progression of carcinoma. We investigated the association of polymorphisms in the DNA repair genes XRCC2-A/G and RAD51-135G/C with the colorectal cancer risk. Genotypes were determined by PCR-RFLP assays in 71 patients with colorectal cancer and 86 age-matched healthy controls. After amplification, we used a restriction enzyme (RAD51; MvaI and XRCC2; HphI) and digested the PCR product. Then, this DNA fragments were passed through gel electrophoresis. By examining these images, we identified changes in the nucleotides in these specific regions. To clarify fragments polymorphisms, the PCR products were sequenced with an Applied Biosystems Automated Sequencer. We observed the Arg188His polymorphism of XRCC2 genes in 42.2%, as shown in 30 of the 71 cancer patients. Only 21 out of 86 controls showed this polymorphism (24.2%). We also observed that 21 of the 71 patients (29.5%) carried the RAD51135G/C polymorphism of this gene. The same polymorphism was observed in 11 of the 86 controls (12.7 %; p < 0.05). The obtained results indicate that the polymorphism of RAD51 and XRCC2 genes may be associated with the incidence of colon cancer in the Turkish population. Further studies, including those on a larger group of patients, are required to further clarify this point.