Oxidative DNA damage and DNA repair gene variants in differentiated thyroid cancer patients treated with radioactive iodine.

PURPOSE

This study aimed to evaluate oxidative DNA damage and its association with polymorphisms in DNA repair enzymes among patients with differentiated thyroid cancer (DTC) treated with high-dose radioactive iodine (RAI, ≥100 mCi). Relationships between DNA damage markers, gene variants, and clinical or tumor characteristics were also explored.

METHODS

Seventy-nine patients with DTC and 59 age and sex matched controls from a Turkish population were included. Urinary 8-hydroxy-2'-deoxyguanosine (8-oxoG), a marker of oxidative DNA damage, was measured by ELISA at baseline, 2 weeks, and 3 months post-RAI. Genotyping for hOGG1 Ser326Cys and APE1 Asp148Glu polymorphisms was performed on leukocyte-derived DNA using real-time PCR and melting curve analysis.

RESULTS

Urinary 8-oxoG levels showed a non-significant upward trend over time (p = 0.252). The Cys/Cys genotype of hOGG1 was more frequent in patients than controls (13 vs. 6%, p = 0.54), while the Ser/Cys genotype was significantly less frequent in patients (36.7 vs. 57.6%; OR: 0.46, 95% CI: 0.22-0.94, p = 0.03). Cys allele frequencies were 0.32 in patients and 0.35 in controls. APE1 genotype and allele distributions did not differ significantly between groups. No associations were found between polymorphisms and 8-oxoG levels or clinical features, including DTC subtype, tumor stage, sex, smoking status, or age.

CONCLUSION

This is the first study to jointly evaluate urinary 8-oxoG and hOGG1/APE1 polymorphisms in Turkish DTC patients receiving RAI. No consistent associations were found with oxidative DNA damage or clinical characteristics. Larger studies are needed to validate these findings.