Objective: To investigate the associations of polymorphisms in the following DNA double-strand break repair (DSBR) genes with papillary thyroid carcinoma (PTC) risk (including RAD51  rs11852786, RAD51B  rs963917, BRCA1  rs12516 and rs8176318, BRCA2  rs15869, XRCC4  rs2035990 and XRCC5  rs2440).
Materials and Methods: A matched case–control study was implemented to examine associations between PTC risk and the above polymorphisms. Subsequently, we evaluated the effects of the potential PTC susceptibility-related variant rs15869 on BRCA2 mRNA secondary structure and BRCA2 expression through bioinformatics analysis and experiment validation. Additionally, luciferase assay was used to identify whether rs15869 polymorphism can substantially affect the binding of hsa-miR-1178-3p to BRCA2  mRNA. Finally, Pearson correlation analysis was performed to determine the correlation between the expression of hsa-miR-1178-3p and BRCA2 mRNA and protein in thyroid tissues harboring rs15869 different genotypes.
Results: BRCA2  rs15869 CC genotype was associated with a higher risk of PTC than its AA genotype. Subsequently, stratified analyses came to the same conclusion in the female or age< 50 population. Furthermore, we confirmed that the A-to-C substitution of rs15869 changed BRCA2 mRNA secondary structure and contributed to a decreased BRCA2 expression. Mechanistically, a significantly decreased luciferase activity verified a greater binding between hsa-miR-1178-3p and rs15869 C allele, but not the A allele, which was evidenced by the significant negative correlation between hsa-miR-1178-3p with BRCA2 mRNA and protein levels in thyroid tissues with AC and CC genotype but not AA genotype at rs15869.
Conclusion: BRCA2  rs15869 is characterized as a potential biomarker associated with PTC risk, highlighting the contribution of the hsa-miR-1178-3p via functional exploration.
Keywords: papillary thyroid carcinoma, DNA double-strand break repair, BRCA2 , rs15869 polymorphism, hsa-miR-1178-3p