Haplotype Based Analysis of XRCC3 Gene Polymorphisms in Thyroid Cancer

In mammalian cells, XRCC3 plays an important role in the DNA double-strand breaks (DSBs) repair by homologous recombination. Genetic polymorphisms in XRCC3 gene may potentially affect the repair of DSBs and thus confer susceptibility to thyroid cancer. In this study, we used a haplotype-based approach to investigate whether 5 selected SNPs i.e. rs1799796, rs1799794, rs861539, rs709399 and rs861530 of XRCC3 gene are associated with thyroid cancer risk in 456 cancer patients and 400 cancer-free controls.

Genotyping was performed using Allele-specific PCR followed by sequencing. Statistical analysis was performed to analyse gene and haplotype association.

After analysis, frequency of mutant genotype/alleles of SNPs (rs1799796, p<0.0001; rs1799794, p<0.0001; rs861539, p<0.001; rs709399, p <0.0001; rs861530, p<0.002) was found significantly higher in thyroid cancer patients compared to controls. Significant associations were found for most of the variant genotypes in SNPs of rs1799794, rs1799796, rs861539, rs861530 and rs709399 in papillary thyroid and follicular cancer patients compared to other histologic subtypes of thyroid carcinoma. Additionally, haplotype analysis revealed that haplotypes, AACGA (p= 0.0005), AGTAA (p= 0.008), GATAA (p= 0.001), GGCAA (p= 0.001) were linked with significant increase in thyroid cancer risk. However, haplotype AGCGG (p= 0.0009) was associated with a significant reduced thyroid cancer risk.

Our results suggest that common genetic variants in the XRCC3 gene of DSBR pathway may modulate thyroid cancer risk.