Electrophoretic mobility shift assays implicate XRCC2:rs3218550C>T as a potential low-penetrant susceptibility allele for sporadic breast cancer.

Objective: A previous study undertaken at our centre to identify common genetic variants associated with sporadic breast cancer in Sri Lankan women showed that the T allele of rs3218550, located in the 3'untranslated region of X-ray repair cross-complementing gene-2 (XRCC2), increased breast cancer risk by 1.5-fold. Dual luciferase reporter assays performed in MCF-7 breast cancer cells showed a putative transcriptional repressor effect exerted mainly by the T allele. Electrophoretic mobility shift assays were conducted to further investigate the interaction of this variant with DNA-binding protein, using nuclear protein extracts derived from MCF-7 cells.

Results: An allele-specific differential binding was observed. The T allele resulted in differential DNA-protein complex binding as evidenced by the presence of multiple bands of increased intensity compared to the wild-type C allele. This implies possible alteration in binding of regulatory proteins by the variant allele. These results implicate XRCC2:rs3218550C>T as a potential low-penetrant susceptibility allele for sporadic breast cancer. XRCC2 is known to play an essential role in homologous recombination repair of DNA double-strand breaks. It is plausible that this variant may be exerting regulatory effects on XRCC2 gene expression leading to altered DNA repair capacity. Further functional studies are warranted to validate this finding.