title: Breast cancer risk and common single nucleotide polymorphisms in homologous recombination DNA repair pathway genes XRCC2, XRCC3, NBS1 and RAD51.
abstract: The possible role for DNA repair deficiencies in cancer development, namely in breast cancer has been the subject of increasing interest since it has been reported that breast cancer patients might be deficient in the repair of DNA damage. Exposure to ionizing radiation has been pointed out as a risk factor for breast cancer, and the type of DNA lesions induced by this carcinogen can be repaired by homologous recombination DNA repair (HRR) pathway. To evaluate the potential modifying role of some single nucleotide polymorphisms (SNP) in HRR involved genes on the individual susceptibility to breast cancer we carried out a hospital based case-control study in a Caucasian Portuguese population (289 histological confirmed breast cancer patients and 548 control individuals). We genotyped 4 SNPs in 4 different HRR pathway genes, XRCC2 (Ex3+442G>A, R188H, rs3218536), XRCC3 (Ex8-5C>T, T241M, rs861539), NBS1 (Ex5-32C>G, E185Q, rs1805794) and RAD51 5'UTR (Ex1-59G>T, rs1801321), tagging 41 SNPs in these genes. The frequency of the different polymorphisms in the Portuguese control population is similar to the ones reported for other Caucasian populations, and the deviation of the Hardy-Weinberg equilibrium was only observed for the XRCC2 (Ex3+442G>A, R188H, rs3218536) polymorphism in the control population. The results obtained, after logistic regression analysis, did not reveal a major role of these polymorphisms on breast cancer susceptibility. However, when the population was stratified according to breast feeding (women that breast fed and women that never breast fed) it is observed, in women that never breast fed, that the heterozygous individuals for the XRCC2 (Ex3+442G>A, R188H, rs3218536) polymorphism have a decreased risk for breast cancer [adjusted OR=0.45; 95% CI=0.22-0.92] (P=0.03). Additionally, after stratification according to menopausal status, our results suggest that post-menopausal women carrying at least one variant allele for the XRCC3 (Ex8-5C>T, T241M, rs861539) polymorphism have a lower risk for breast cancer [adjusted OR=0.67; 95% CI, 0.47-0.94] (P=0.03). Most of the studies suggest that breastfeeding may be responsible for 2/3 of the estimate reduction of breast cancer. The longer the duration of breastfeeding the lower the potential risk associated with breast cancer. Therefore, in our study the potential protective role of the variant allele of XRCC2 (Ex3+442G>A, R188H, rs3218536), in never breast fed women, might be related with a more efficient DNA repair activity.
authors.affiliation: Department of Genetics, Faculty of Medical Sciences, New University of Lisbon, UNL, Rua da Junqueira 96, P-1349-008 Lisboa, Portugal. snsilva.gene@fcm.unl.pt <snsilva.gene@fcm.unl.pt>
authors.forename: Susana N
authors.initials: SN
authors.lastname: Silva
authors.forename: Marta
authors.initials: M
authors.lastname: Tomar
authors.forename: Claudia
authors.initials: C
authors.lastname: Paulo
authors.forename: Bruno Costa
authors.initials: BC
authors.lastname: Gomes
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Azevedo
authors.forename: Valdemar
authors.initials: V
authors.lastname: Teixeira
authors.forename: Julieta Esperança
authors.initials: JE
authors.lastname: Pina
authors.forename: José
authors.initials: J
authors.lastname: Rueff
authors.forename: Jorge Francisco
authors.initials: JF
authors.lastname: Gaspar
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D016172:DNA Fingerprinting; D004260:DNA Repair; D049914:DNA Repair-Deficiency Disorders / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D011174:Portugal / Q000453:epidemiology; D051135:Rad51 Recombinase / Q000235:genetics* / Q000378:metabolism; D012307:Risk Factors
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C112156:NBN protein, human; D009687:Nuclear Proteins; C110901:X-ray repair cross complementing protein 3; C113187:XRCC2 protein, human; C495153:RAD51 protein, human; D051135:Rad51 Recombinase