A specific RAD51 haplotype increases breast cancer risk in Jewish non-Ashkenazi high-risk women

Association of Rad51 polymorphism with DNA repair in BRCA1 mutation carriers and sporadic breast cancer risk

BACKGROUND

Inter-individual variation in DNA repair capacity is thought to modulate breast cancer risk. The phenotypic mutagen sensitivity assay (MSA) measures DNA strand breaks in lymphocytes; women with familial and sporadic breast cancers have a higher mean number of breaks per cell (MBPC) than women without breast cancer. Here, we explore the relationships between the MSA and the Rad51 gene, which encodes a DNA repair enzyme that interacts with BRCA1 and BRCA2, in BRCA1 mutation carriers and women with sporadic breast cancer.

METHODS

Peripheral blood lymphoblasts from women with known BRCA1 mutations underwent the MSA (n = 138 among 20 families). BRCA1 and Rad51 genotyping and sequencing were performed to identify SNPs and haplotypes associated with the MSA. Positive associations from the study in high-risk families were subsequently examined in a population-based case-control study of breast cancer (n = 1170 cases and 2115 controls).

RESULTS

Breast cancer diagnosis was significantly associated with the MSA among women from BRCA1 families (OR = 3.2 95%CI: 1.5-6.7; p = 0.004). The Rad51 5'UTR 135 C>G genotype (OR = 3.64; 95% CI: 1.38, 9.54; p = 0.02), one BRCA1 haplotype (p = 0.03) and in a polygenic model, the E1038G and Q356R BRCA1 SNPs were significantly associated with MBPC (p = 0.009 and 0.002, respectively). The Rad51 5'UTR 135C genotype was not associated with breast cancer risk in the population-based study.

CONCLUSIONS

Mutagen sensitivity might be a useful biomarker of penetrance among women with BRCA1 mutations because the MSA phenotype is partially explained by genetic variants in BRCA1 and Rad51.

RAD51 135G>C polymorphism and breast cancer risk: a meta-analysis

Mutations in RAD51 gene are believed to be associated with elevated breast cancer risk. However, several case-control studies focusing on the association between RAD51 135G>C and breast cancer risk failed to achieve consensus. To clarify the effect of RAD51 135G>C polymorphism on breast cancer, a meta-analysis was performed. By searching PubMed and EMBASE, a total of 14 case-control studies, containing 12,183 cases and 10,183 controls, were included. The strength of association between RAD51 135G>C polymorphism and breast cancer risk was assessed by odds ratio (OR) with the corresponding 95% confidence interval (95% CI). When all the eligible studies were pooled into the meta-analysis, an elevated cancer risk was revealed in additive model (OR, 1.34; 95% CI, 1.01-1.78; P = 0.044) and recessive model (OR, 1.37; 95% CI, 1.03-1.82; P = 0.032). In subgroup analyses by ethnicity, BRCA1/2 mutation status, and family history, a significant association was found only among BRCA2 mutation carriers (additive model: OR, 4.92; 95% CI, 1.11-21.83; P = 0.036; recessive model: OR, 4.88; 95% CI, 1.10-21.67; P = 0.037). Sensitivity analysis did not perturb the results. In conclusion, this meta-analysis suggests that RAD51 variant 135C homozygote is associated with elevated breast cancer risk among BRCA2 mutation carriers.