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.