Allelic polymorphism of DNA repair gene XRCC1 in patients with thyroid cancer who were exposed to ionizing radiation as a result of the Chornobyl accident.

Objective - to determine and compare the features of DNA repair gene XRCC1 Arg399Gln polymorphisms in patients with thyroid cancer (TC), who were exposed to ionizing radiation as a result of the Chornobyl disaster, and in patients without exposure to ionizing radiation in history. Materials and methods. Determination of gene XRCC1 Arg399Gln polymorphisms was performed by polymerase chain reaction (PCR) in 102 patients with thyroid cancer: 38 people, who were exposed to ionizing radiation due to Chornobyl disaster (clean-up workers, evacuees and residents from controlled areas contaminated with radionuclides) and 64 individuals without exposure to ionizing radiation in anamnesis. The literature data on control groups of populations of Russia and Belarus were used for comparison of the data on spontaneous and radiation-associated thyroid cancer and calculation of allele frequencies differences and risk of cancer pathology. Results. Frequency of minor allele Arg399Gln XRCC1 gene and homozygous carriers of this allele in patients with thyroid cancer, who were exposed to ionizing radiation due to Chornobyl disaster was significantly higher than in patients without exposure to ionizing radiation in anamnesis (0.57 and 0.37, p = 0.006 and 34.21 % and 7.81 %, p = 0.001, respectively). Comparing to the literature data on XRCC1 Arg399Gln polymorphisms in radiation-exposed individuals without cancer pathology, the risk of thyroid cancer in homozygous minor allele XRCC1 Gln399Gln carriers, who were exposed to ionizing radiation was significantly increased: OR = 4.14, p = 0.001 (CI95 % 1.72-9.93). Conclusions. The carrying of homozygous minor allele Gln399Gln of DNA repair gene XRCC1 is a risk factor for thyroid cancer under the influence of ionizing radiation in research group of Ukrainian population.