The OGG1 Ser326Cys polymorphism and its association with DNA damage and DNA repair in papillary thyroid cancer

Aim: Hydrogen peroxide, locally produced during thyroid hormone synthesis, leads to oxida- tive stress in the thyroid gland. Defective repair of oxidative DNA lesions contributes to tumor development. This study aimed to understand the importance of DNA damage and repair on thyroid cancer development through the impact of the DNA repair gene OGG1 Ser326Cys polymorphism that has clinical significance in untreated patients with papillary thyroid can- cer. Methods: The study was performed with 70 patients with papillary thyroid cancer and 73 vol- unteers as control. In lymphocytes, endogenous DNA damage, H2O2-induced DNA damage, and DNA damage after repair were determined by comet assay. The polymerase chain reac- tion-restriction fragment length polymorphism method was performed for OGG1 genotyping. Results: Endogenous DNA damage, H2O2-induced DNA damage, and DNA damage after re- pair were higher in patients with thyroid cancer than in the controls (P<0.001). An association was determined between the OGG1 Cys326 allele and increased risk for the development of papillary thyroid cancer. No significant difference was determined between cases carrying different OGG1 genotypes for endogenous DNA damage, H2O2-induced DNA damage, and DNA damage after repair in the study groups. Conclusions: Endogenous DNA damage and cell susceptibility to oxidation increase, and DNA repair is impaired in patients with papillary thyroid cancer. However, the OGG1 Ser - 326Cys polymorphism is not responsible for the DNA repair defect.