Single Nucleotide Polymorphisms in Noncoding Regions of Rad51C Do Not Change the Risk of Unselected Breast Cancer but They Modulate the Level of Oxidative Stress and the DNA Damage Characteristics: A Case-Control Study Peter Gresner 1 *, Jolanta Gromadzinska 1 , Ewa Jablonska 1 , Maciej Stepnik 1 , Oscar Zambrano Quispe 2 , Ewa Twardowska 1 , Wojciech Wasowicz 1 1 Department of Toxicology and Carcinogenesis, Nofer Institute of Occupational Medicine, Lodz, Poland, 2 Department of Oncology, Herlev Hospital, Herlev, Denmark Abstract Deleterious and missense mutations of RAD51C have recently been suggested to modulate the individual susceptibility to hereditary breast and ovarian cancer and unselected ovarian cancer, but not unselected breast cancer (BrC). We enrolled 132 unselected BrC females and 189 cancer-free female subjects to investigate whether common single nucleotide polymorphisms (SNPs) in non-coding regions of RAD51C modulate the risk of BrC, and whether they affect the level of oxidative stress and the extent/characteristics of DNA damage. Neither SNPs nor reconstructed haplotypes were found to significantly affect the unselected BrC risk. Contrary to this, carriers of rs12946522, rs16943176, rs12946397 and rs17222691 rare-alleles were found to present significantly increased level of blood plasma TBARS compared to respective wild-type homozygotes (p,0.05). Furthermore, these carriers showed significantly decreased fraction of oxidatively generated DNA damage (34% of total damaged DNA) in favor of DNA strand breakage, with no effect on total DNA damage, unlike respective wild-types, among which more evenly distributed proportions between oxidatively damaged DNA (48% of total DNA damage) and DNA strand breakage was found (p,0.0005 for the difference). Such effects were found among both the BrC cases and healthy subjects, indicating that they cannot be assumed as causal factors contributing to BrC development. Citation: Gresner P, Gromadzinska J, Jablonska E, Stepnik M, Zambrano Quispe O, et al. (2014) Single Nucleotide Polymorphisms in Noncoding Regions of Rad51C Do Not Change the Risk of Unselected Breast Cancer but They Modulate the Level of Oxidative Stress and the DNA Damage Characteristics: A Case-Control Study. PLoS ONE 9(10): e110696. doi:10.1371/journal.pone.0110696 Editor: Gayle E. Woloschak, Northwestern University Feinberg School of Medicine, United States of America Received February 20, 2014; Accepted September 24, 2014; Published October 24, 2014 Copyright: ß 2014 Gresner et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The study was supported by the Nofer Institute of Occupational Medicine fund no. IMP1.5/2011. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * Email: pgresner@imp.lodz.pl Introduction Breast cancer (BrC) is the most common malignancy among women, with nearly 1.4 million new BrC cases causing nearly 460,000 deaths per year worldwide [1]. Although vast majority of BrC cases are sporadic, approximately 5–10% of them are considered familial, occurring at unusually young ages in members of families with strong history of hereditary breast and/or ovarian cancer (HBOC) [2]. Studies have shown that familial BrC is likely a polygenic disease caused by mutations in several high-, moderate- and low-penetrance susceptibility genes. Genes like BRCA1, BRCA2, TP53 and PTEN are well-known high- penetrance susceptibility genes, although nowadays it is assumed, that they account for roughly some 20% of all hereditary breast cancer cases [3–5]. Therefore, the ongoing quest to identify additional BrC-susceptibility genes resulted in identification of several moderate-penetrance BrC-susceptibilty genes, the majority of which are somewhat related to Brca1/Brca2-mediated path- ways. These include CHEK2, ATM, BRIP1, PALB2 and recently also RAD51C, all of which are involved in various steps of DNA recombination repair [5–7]. An approximately 2-fold relative risk increase among carriers of heterozygous mutations in these genes has been implied [8]. Members of the RAD51 gene family are often found among genes tested as possible BrC susceptibility genes. This family consists of RAD51, a key player in the homologous recombination (HR) double-strand breaks (DSBs) DNA damage response pathway, and its five paralogs: RAD51B, RAD51C, RAD51D, XRCC2 and XRCC3. Protein products of these five genes interact with each other to create hetero-tetrameric and hetero-dimeric complexes crucial for the HR machinery [9]. Out of all RAD51 paralogs, protein product of RAD51C (RAD51 homolog C, S. cervisiae; 17q25.1) seems to play a prominent role as it is found in both the above mentioned complexes. Indeed, RAD51C localizes to the sites of DNA DSBs in early stage of HR, which is thought to be a prerequisite for RAD51/DNA nucleoprotein filament assembly, a key event in the whole HR reaction [10]. Other identified functions of this protein include facilitating the migration and resolution of Holliday junctions in late stages of HR [11], repair of interstrand cross-links [12], distinct functions PLOS ONE | www.plosone.org 1 October 2014 | Volume 9 | Issue 10 | e110696