Highly penetrant, but rare, mutations in genes involved in double-strand break repair (i.e., BRCA1 and BRCA2) are associated with a risk for breast cancer of 40% to 65% by age 70 years (1, 2). Polymorphisms in other double-strand break repair genes are thought to contribute to the risk for the disease, either independently or through modifying the risk associated with rare mutations.

This study focuses on polymorphisms in three genes involved in the homologous recombination of double-strand breaks: RAD51 5′ untranslated region 135 G>C (rs1801320), X-ray repair cross-complementing group 2 (XRCC2) Arg188His (rs3218536), and XRCC3 Thr241Met (rs861539) in relation to breast cancer risk in the New York University Women's Health Study cohort.

The New York University Women's Health Study cohort collected questionnaires and blood samples from 14,274 healthy women ages 35 to 65 years in 1985 to 1991 (3). The current nested case-control study is matched for age and date at blood donation and includes incident cases of invasive breast cancer diagnosed before March 1998, with further methodologic details described by Shore et al. (4).

DNA was isolated using Qiagen QIAamp Blood Mini Kits (Qiagen, Inc.; ref. 4). Genotyping was done using PCR-RFLP methods described previously (ref. 4; see Appendix 1 for gene-specific PCR conditions and primer sequences). Blood clots and/or cell aggregates were available for 48% of the women. For the remaining women, serum specimens were used. Genotype results from clots/red cells and serum showed excellent concordance between repeated samples (n = 73) in pilot studies (97% for RAD51 135 G>C, 99% for XRCC2 Arg188His, and 98% for XRCC3 Thr241Met). Quality control duplicates showed 100% concordance for all three polymorphisms.

Statistical Methods

Deviation from Hardy-Weinberg equilibrium was assessed in controls using the χ2 goodness-of-fit test. The relationship between genotype and breast cancer risk was evaluated using conditional logistic regression and the additive coding model. The dominant model was also assessed for RAD51 and XRCC2 because of the small number of individuals with the homozygous variant genotype. Tests for interaction between genotype and ethnicity, family history, body mass index, and smoking were planned a priori.

Given our sample size (612 cases and 612 controls) and the allelic frequencies in our population, we had sufficient power (99% for RAD51 135 G>C, 99% for XRCC2 Arg188His, and 88% for XRCC3 Thr241Met) to detect associations of the magnitude observed by Kadouri et al. (5) for RAD51 135 G>C and Kuschel et al. (6) for XRCC2 Arg188His and XRCC3 Thr241Met.

Genotype frequencies did not deviate from Hardy-Weinberg equilibrium (P > 0.5). Variant allele frequencies were comparable with those previously reported for populations of Caucasians of European descent for XRCC2 Arg188His (8%; refs. 6-9) and XRCC3 Thr241Met (36%; refs. 8-14), but the variant allele frequency for RAD51 135 G>C of 9% was somewhat lower than previous reports (5, 6, 9).

Table 1 describes study subject characteristics. As expected, significant differences in body mass index and parity/age at first full-term pregnancy were observed between cases and controls. However, these variables were not associated with genotype. Ethnicity was significantly associated with breast cancer risk and genotype. Asian and Hispanic women had a lower risk for breast cancer than non-Jewish White women (odds ratio, 0.49; 95% confidence interval, 0.29-0.81); this association is as expected (15). Ethnicity was significantly related to genotype for RAD51 GC/CC (P < 0.0001) and XRCC3 CT/TT (P < 0.0001) genotypes. Among Black women, 37.4% had at least one copy of the RAD51 135 G>C variant allele (non-Jewish White, 15.9%; Jewish White, 9.6%; others, 17.3%). The XRCC3 Thr241Met variant was most common (67.3%) among Jewish White women (non-Jewish White, 60.3%; Black, 38.4%; others, 40.8%). XRCC2 Arg188His variant was not significantly related to ethnicity.

Table 1.

Characteristics of cases and controls

VariablesCases (n = 612)Controls (n = 612)Odds ratio (95% confidence interval)*P*
Age at diagnosis (y)     
    Median (25th, 75th percentile) 60.3 (51.8, 66.6) 60.3 (51.8, 66.6) Matched  
Body mass index (kg/m2),     
    Median (25th, 75th percentile)     
    Age ≤52 y 22.8 (20.9, 25.4) 23.1 (21.4, 25.0) 0.56 (0.11-2.75) 0.47 
    Age >52 y 25.2 (22.5, 28.4) 24.2 (22.0, 27.6) 2.20 (1.00-4.82) 0.05 
Height (cm)     
    Median (25th, 75th percentile) 163 (157, 168) 163 (157, 168) 1.00 (0.99-1.02) 0.72 
Ethnicity, n (%)     
    Caucasian     
        Non-Jewish 222 (39.7) 202 (36.9) 1.00 0.02 
        Jewish 254 (45.4) 232 (42.4) 1.02 (0.77-1.35)  
    Black 50 (8.9) 59 (10.8) 0.77 (0.49-1.21)  
    Others (including Hispanic and Asian) 33 (5.9) 54 (9.9) 0.49 (0.29-0.81)  
    Unknown 53 65   
Family history, n (%)     
    None 468 (76.5) 475 (77.6) 1.00 0.31§ 
    1 affected relative, >45 y 76 (12.4) 85 (13.9) 0.91 (0.66-1.27)  
    1 affected relative, age unknown 15 (2.5) 12 (2.0) 1.24 (0.58-2.65)  
    >1 affected relative or 1 age <45 y 53 (8.7) 40 (6.5) 1.33 (0.87-2.04)  
Age at menarche (y), n (%)     
    <13 309 (50.5) 286 (46.7) 1.00  
    ≥13 303 (49.5) 326 (53.3) 0.87 (0.70-1.08) 0.20 
Number of pregnancies, n (%)     
    Nulliparous 201 (37.2) 180 (32.1) 1.00 0.19§ 
    1 62 (11.5) 81 (14.5) 0.73 (0.48-1.10)  
    2 153 (28.3) 173 (30.9) 0.77 (0.56-1.06)  
    ≥3 125 (23.1) 126 (22.5) 0.82 (0.58-1.15)  
    Unknown 71 52   
Age at first term pregnancy (y), n (%)     
    <25 142 (23.2) 183 (29.9) 1.00 0.0002§ 
    25-29 168 (27.5) 180 (29.4) 1.21 (0.88-1.66)  
    Nulliparous 201 (32.8) 180 (29.4) 1.47 (1.08-1.99)  
    >30 101 (16.5) 69 (11.3) 1.96 (1.32-2.89)  
Smoking status, n (%)     
    Never 253 (47.7) 253 (48.8) 1.00 0.35 
    Ever 278 (52.4) 265 (51.2) 0.99 (0.76-1.29)  
    Unknown 81 94   
VariablesCases (n = 612)Controls (n = 612)Odds ratio (95% confidence interval)*P*
Age at diagnosis (y)     
    Median (25th, 75th percentile) 60.3 (51.8, 66.6) 60.3 (51.8, 66.6) Matched  
Body mass index (kg/m2),     
    Median (25th, 75th percentile)     
    Age ≤52 y 22.8 (20.9, 25.4) 23.1 (21.4, 25.0) 0.56 (0.11-2.75) 0.47 
    Age >52 y 25.2 (22.5, 28.4) 24.2 (22.0, 27.6) 2.20 (1.00-4.82) 0.05 
Height (cm)     
    Median (25th, 75th percentile) 163 (157, 168) 163 (157, 168) 1.00 (0.99-1.02) 0.72 
Ethnicity, n (%)     
    Caucasian     
        Non-Jewish 222 (39.7) 202 (36.9) 1.00 0.02 
        Jewish 254 (45.4) 232 (42.4) 1.02 (0.77-1.35)  
    Black 50 (8.9) 59 (10.8) 0.77 (0.49-1.21)  
    Others (including Hispanic and Asian) 33 (5.9) 54 (9.9) 0.49 (0.29-0.81)  
    Unknown 53 65   
Family history, n (%)     
    None 468 (76.5) 475 (77.6) 1.00 0.31§ 
    1 affected relative, >45 y 76 (12.4) 85 (13.9) 0.91 (0.66-1.27)  
    1 affected relative, age unknown 15 (2.5) 12 (2.0) 1.24 (0.58-2.65)  
    >1 affected relative or 1 age <45 y 53 (8.7) 40 (6.5) 1.33 (0.87-2.04)  
Age at menarche (y), n (%)     
    <13 309 (50.5) 286 (46.7) 1.00  
    ≥13 303 (49.5) 326 (53.3) 0.87 (0.70-1.08) 0.20 
Number of pregnancies, n (%)     
    Nulliparous 201 (37.2) 180 (32.1) 1.00 0.19§ 
    1 62 (11.5) 81 (14.5) 0.73 (0.48-1.10)  
    2 153 (28.3) 173 (30.9) 0.77 (0.56-1.06)  
    ≥3 125 (23.1) 126 (22.5) 0.82 (0.58-1.15)  
    Unknown 71 52   
Age at first term pregnancy (y), n (%)     
    <25 142 (23.2) 183 (29.9) 1.00 0.0002§ 
    25-29 168 (27.5) 180 (29.4) 1.21 (0.88-1.66)  
    Nulliparous 201 (32.8) 180 (29.4) 1.47 (1.08-1.99)  
    >30 101 (16.5) 69 (11.3) 1.96 (1.32-2.89)  
Smoking status, n (%)     
    Never 253 (47.7) 253 (48.8) 1.00 0.35 
    Ever 278 (52.4) 265 (51.2) 0.99 (0.76-1.29)  
    Unknown 81 94   
*

Odds ratios and P values are for conditional univariate regression analysis.

Using ln of body mass index (at baseline) as a continuous variable.

A division at the age of 52 y was decided upon a priori as a surrogate for menopausal status.

§

P for trend using ordered categories shown in this table.

Unadjusted and ethnicity-adjusted odds ratios and 95% confidence intervals are presented in Table 2. Although ethnicity was found to be related to genotype and risk, adjusting for ethnicity altered the odds ratios only slightly. In this population, none of the polymorphisms was found to influence breast cancer risk. The sum of variant alleles was also not related to risk (data not shown). Similar results were obtained when the analysis was restricted to Caucasians (data not shown). No significant interaction was found between genotype and ethnicity, body mass index, smoking, parity, or family history.

Table 2.

DNA repair polymorphisms and breast cancer risk

Genotype*Cases
Controls
Unadjusted
Ethnicity adjusted
n (%)n (%)Odds ratio (95% confidence interval)POdds ratio (95% confidence interval)P
Rad51 (n = 1,222)       
    GG 516 (84.5) 513 (84.0) 1.00 0.67 1.00 0.91 
    GC 88 (14.4) 88 (14.4) 0.99 (0.72-1.36)  1.05 (0.76-1.45)  
    CC 7 (1.1) 10 (1.6) 0.67 (0.24-1.87)  0.68 (0.24-1.94)  
    GG vs GC/CC   1.04 (0.76-1.41) 0.82 1.02 (0.74-1.39) 0.92 
XRCC2 (n = 1,204)       
    GG 515 (85.5) 519 (86.2) 1.00 0.82 1.00 0.77 
    GA 83 (13.8) 78 (13.0) 1.07 (0.77-1.50)  1.08 (0.77-1.52)  
    AA 4 (0.7) 5 (0.8) 0.81 (0.22-3.01)  0.83 (0.22-3.12)  
    GG vs GA/AA   1.06 (0.76-1.47) 0.74 1.07 (0.77-1.48) 0.71 
XRCC3 (n = 1,222)       
    CC 254 (41.6) 249 (40.8) 1.00 0.47 1.00 0.77 
    CT 259 (42.4) 286 (46.8) 0.88 (0.68-1.13)  0.83 (0.64-1.08)  
    TT 98 (16.0) 76 (12.4) 1.28 (0.89-1.83)  1.20 (0.83-1.72)  
Genotype*Cases
Controls
Unadjusted
Ethnicity adjusted
n (%)n (%)Odds ratio (95% confidence interval)POdds ratio (95% confidence interval)P
Rad51 (n = 1,222)       
    GG 516 (84.5) 513 (84.0) 1.00 0.67 1.00 0.91 
    GC 88 (14.4) 88 (14.4) 0.99 (0.72-1.36)  1.05 (0.76-1.45)  
    CC 7 (1.1) 10 (1.6) 0.67 (0.24-1.87)  0.68 (0.24-1.94)  
    GG vs GC/CC   1.04 (0.76-1.41) 0.82 1.02 (0.74-1.39) 0.92 
XRCC2 (n = 1,204)       
    GG 515 (85.5) 519 (86.2) 1.00 0.82 1.00 0.77 
    GA 83 (13.8) 78 (13.0) 1.07 (0.77-1.50)  1.08 (0.77-1.52)  
    AA 4 (0.7) 5 (0.8) 0.81 (0.22-3.01)  0.83 (0.22-3.12)  
    GG vs GA/AA   1.06 (0.76-1.47) 0.74 1.07 (0.77-1.48) 0.71 
XRCC3 (n = 1,222)       
    CC 254 (41.6) 249 (40.8) 1.00 0.47 1.00 0.77 
    CT 259 (42.4) 286 (46.8) 0.88 (0.68-1.13)  0.83 (0.64-1.08)  
    TT 98 (16.0) 76 (12.4) 1.28 (0.89-1.83)  1.20 (0.83-1.72)  
*

Using the χ2 test, no significant difference in genotype frequencies was observed between cases and controls.

Matched pairs were excluded if either member of the pair could not be definitively genotyped.

P for trend.

Genetic instability acquired through inefficient double-strand break repair is believed to be a component of breast cancer susceptibility. RAD51 plays a central role in homologous recombination, through direct interaction with XRCC2, XRCC3, BRCA1, BRCA2, etc., to form a complex essential for the repair of double-strand breaks and DNA cross-links (especially XRCC2 and XRCC3) and for the maintenance of chromosome stability (16).

Studies have suggested that RAD51 135 G>C modifies the breast cancer risk of women with a family history of breast cancer (17, 18) or carriers of BRCA2 mutations (5, 18-21). However, results have been inconsistent (22-24). Studies of non–BRCA2 mutation carriers or women without a family history have found no association between RAD51 135 G>C and breast cancer risk (5, 6).

Results for XRCC2 Arg188His have been similarly mixed (6-8, 23). It is thought that this polymorphism has only a small effect on gene activity (7), although it may modify risk in those with low levels of plasma α-carotene (25) or plasma folate (26).

XRCC3 Thr241Met has been found to be associated with increased DNA adducts (27), chromosomal deletions (28), and sensitivity to ionizing radiation and cross-linking agents (29, 30). Some (6, 17, 31) but not all (10, 23, 25, 32, 33) studies have found XRCC3 Thr241Met to be related to an increased risk for breast cancer. Pooled analyses and meta-analyses show a small but significant increase in risk (8, 14, 22, 34).

Disruption of double-strand break repair is thought to contribute to carcinogenesis through the accumulation of genetic errors and genetic instability (35). However, in this study, the RAD51, XRCC2, and XRCC3 variants were found not to be associated with breast cancer risk. Unlike other reports, no relationship was found between RAD51 135 G>C and family history of breast cancer, perhaps because the participants in the study were not selected for having a family history of disease or being BRCA1/2 mutation carriers.

Grant support: National Cancer Institute Center grant CA 16087 and National Cancer Institute grant CA091892, Department of Defense grant DAMD17-01-1-0578, and Komen Foundation grant BCTR 2000 685.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1
Begg CB, Haile RW, Borg A, et al. Variation of breast cancer risk among BRCA1/2 carriers.
JAMA
2008
;
299
:
194
-201.
2
Antoniou A, Pharoah P, Narod S, et al. Average risks of breast and ovarian cancer associated with BRCA1 or BRCA2 mutations detected in case series unselected for family history: a combined analysis of 22 studies.
Am J Hum Genet
2003
;
72
:
1117
–30.
3
Zeleniuch-Jacquotte A, Shore R, Koenig K, et al. Postmenopausal levels of oestrogen, androgen, and SHBG and breast cancer: long-term results of a prospective study.
Br J Cancer
2004
;
90
:
153
–9.
4
Shore R, Zeleniuch-Jacquotte A, Currie D, et al. Polymorphisms in XPC and ERCC2 genes, smoking and breast cancer risk. Int J Cancer 2008;122:2101–5.
5
Kadouri L, Kote-Jarai Z, Hubert A, et al. A single-nucleotide polymorphism in the RAD51 gene modifies breast cancer risk in BRCA2 carriers, but not in BRCA1 carriers or noncarriers.
Br J Cancer
2004
;
90
:
2002
–5.
6
Kuschel B, Auranen A, McBride S, et al. Variants in DNA double-strand break repair genes and breast cancer susceptibility.
Hum Mol Genet
2002
;
11
:
1399
–407.
7
Rafii S, O'Regan P, Xinarianos G, et al. A potential role for the XRCC2 R188H polymorphic site in DNA-damage repair and breast cancer.
Hum Mol Genet
2002
;
11
:
1433
–8.
8
García-Closas M, Egan KM, Newcomb PA, et al. Polymorphisms in DNA double-strand break repair genes and risk of breast cancer: two population-based studies in USA and Poland, and meta-analyses.
Hum Genet
2006
;
V119
:
376
–88.
9
Packer B, Yeager M, Burdett L, et al. SNP500Cancer: a public resource for sequence validation, assay development, and frequency analysis for genetic variation in candidate genes.
Nucleic Acids Res
2006
;
34
:
D617
–21.
10
Manuguerra M, Saletta F, Karagas MR, et al. XRCC3 and XPD/ERCC2 single nucleotide polymorphisms and the risk of cancer: a HuGE review.
Am J Epidemiol
2006
;
164
:
297
-302.
11
Smith TR, Miller MS, Lohman K, et al. Polymorphisms of XRCC1 and XRCC3 genes and susceptibility to breast cancer.
Cancer Lett
2003b
;
190
:
183
–90.
12
Jacobsen NR, Nexo BA, Olsen A, et al. No Association between the DNA repair gene XRCC3 T241M polymorphism and risk of skin cancer and breast cancer.
Cancer Epidemiol Biomarkers Prev
2003
;
12
:
584
–5.
13
Goode EL, Ulrich CM, Potter JD. Polymorphisms in DNA repair genes and associations with cancer risk.
Cancer Epidemiol Biomarkers Prev
2002
;
11
:
1513
–30.
14
Han S, Zhang H-T, Wang Z, et al. DNA repair gene XRCC3 polymorphisms and cancer risk: a meta-analysis of 48 case-control studies.
Eur J Hum Genet
2006
;
14
:
1136
–44.
15
Ries L, Melbert D, Krapcho M, et al., editors. SEER cancer statistics review, 1975-2004. Bethesda, MD: National Cancer Institute; 2006.
16
Thacker J. The RAD51 gene family, genetic instability and cancer.
Cancer Lett
2005
;
219
:
125
–35.
17
Costa S, Pinto D, Pereira D, et al. DNA repair polymorphisms might contribute differentially on familial and sporadic breast cancer susceptibility: a study on a Portuguese population.
Breast Cancer Res Treat
2007
;
103
:
209
–17.
18
Jara L, Acevedo ML, Blanco R, et al. RAD51 135G>C polymorphism and risk of familial breast cancer in a South American population.
Cancer Genet Cytogenet
2007
;
178
:
65
–9.
19
Levy-Lahad E, Lahad A, Eisenberg S, et al. A single nucleotide polymorphism in the RAD51 gene modifies cancer risk in BRCA2 but not BRCA1 carriers.
Proc Natl Acad Sci U S A
2001
;
98
:
3232
–6.
20
Wang WW, Spurdle AB, Kolachana P, et al. A single nucleotide polymorphism in the 5′ untranslated region of RAD51 and risk of cancer among BRCA1/2 mutation carriers.
Cancer Epidemiol Biomarkers Prev
2001
;
10
:
955
–60.
21
Antoniou A, Sinilnikova O, Simard J, et al. RAD51 135G→C modifies breast cancer risk among BRCA2 mutation carriers: results from a combined analysis of 19 studies.
Am J Hum Genet
2007
;
81
:
1186
–200.
22
Lee K-M, Choi J-Y, Kang C, et al. Genetic polymorphisms of selected DNA repair genes, estrogen and progesterone receptor status, and breast cancer risk.
Clin Cancer Res
2005
;
11
:
4620
–6.
23
Webb PM, Hopper JL, Newman B, et al. Double-strand break repair gene polymorphisms and risk of breast or ovarian cancer.
Cancer Epidemiol Biomarkers Prev
2005
;
14
:
319
–23.
24
Jakubowska A, Gronwald J, Menkiszak J, et al. The RAD51 135 G>C polymorphism modifies breast cancer and ovarian cancer risk in Polish BRCA1 mutation carriers.
Cancer Epidemiol Biomarkers Prev
2007
;
16
:
270
–5.
25
Han J, Hankinson SE, Ranu H, et al. Polymorphisms in DNA double-strand break repair genes and breast cancer risk in the Nurses' Health Study.
Carcinogenesis
2004
;
25
:
189
–95.
26
Han J, Hankinson SE, Zhang SM, et al. Interaction between genetic variations in DNA repair genes and plasma folate on breast cancer risk.
Cancer Epidemiol Biomarkers Prev
2004
;
13
:
520
–4.
27
Matullo G, Palli D, Peluso M, et al. XRCC1, XRCC3, XPD gene polymorphisms, smoking and 32P-DNA adducts in a sample of healthy subjects.
Carcinogenesis
2001
;
22
:
1437
–45.
28
Au W, Salama S, Sierra-Torres C. Functional characterization of polymorphisms in DNA repair genes using cytogenetic challenge assays.
Environ Health Perspect
2003
;
111
:
1843
–50.
29
Fuller L, Painter R. A Chinese hamster ovary cell line hypersensitive to ionizing radiation and deficient in repair replication.
Mutat Res
1988
;
193
:
109
–21.
30
Caldecott K, Jeggo P. Cross-sensitivity of gamma-ray-sensitive hamster mutants to cross-linking agents.
Mutat Res
1991
;
255
:
111
–21.
31
Sangrajrang S, Schmezer P, Burkholder I, et al. The XRCC3 Thr241Met polymorphism and breast cancer risk: a case control study in a Thai population.
Biomarkers
2007
;
12
:
523
–32.
32
Smith TR, Levine EA, Perrier ND, et al. DNA-repair genetic polymorphisms and breast cancer risk.
Cancer Epidemiol Biomarkers Prev
2003a
;
12
:
1200
–4.
33
Thyagarajan B, Anderson KE, Folsom AR, et al. No association between XRCC1 and XRCC3 gene polymorphisms and breast cancer risk: Iowa Women's Health Study.
Cancer Detect Prev
2006
;
30
:
313
–21.
34
The Breast Cancer Association Consortium. Commonly studied single-nucleotide polymorphisms and breast cancer: results from the Breast Cancer Association Consortium.
J Natl Cancer Inst
2006
;
98
:
1382
–96.
35
Reliene R, Bishop AJR, Schiestl RH, et al. Involvement of homologous recombination in carcinogenesis.
Adv Genet
2007
;
58
:
67
–87.