The penetrance of breast cancer in BRCA1 mutation carriers appears to vary considerably. The cumulative risk of breast cancer by age 70 for a BRCA1 mutation carrier has been estimated at anywhere from 44% to 80%. Variable penetrance and age of onset of breast cancer among related BRCA1 carriers sharing the same deleterious mutations has been observed and differences in breast cancer risk between population-based families and high-risk clinic-based families with the same mutations have also been detected. These and other observations strongly suggest the existence of common genetic variants that modify the risk of cancer in BRCA1 mutation carriers. Our goal in this study is to identify genetic modifiers of breast cancer risk in BRCA1 carriers through a genome wide association study with the intent of substantially improving understanding of the etiology of these tumors as well as pathologically related triple negative breast tumors. These modifiers should also prove useful for improved risk assessment of BRCA1 mutation carriers. We propose to accomplish this through a multi-stage approach using DNA samples from BRCA1 mutation carriers that have been collected through an international consortium. In stage 1 we aim to genotype 1,500 BRCA1 carriers with young onset breast cancer and 1,500 older unaffected BRCA1 carriers on 550,000 common variants and identify variants associated with risk of breast cancer. In stage 2 we will evaluate the 13,180 variants most significantly associated with breast cancer risk in 2,000 affected and 2,000 unaffected carriers and combine the data with stage 1 to increase statistical power. In stage 3 the 384 most significant variants will be further evaluated in 2,000 affected and 2,000 unaffected BRCA1 carriers and the data will be combined with data from stages 1 and 2. In parallel, because most BRCA1 mutant tumors are triple negative tumors, we will evaluate associations between the variants in stage 3 and risk of triple negative breast cancer using 1,500 basal breast cancer patients and 1,500 matching controls provided by the Breast Cancer Association Consortium. In stage 4 fine mapping of the genomic regions containing the most significantly associated variants will be conducted to identify the variants that likely account for the modification of breast cancer risk in BRCA1 carriers.

Public Health Relevance

The identification of genetic modifiers of breast cancer risk in BRCA1 carriers will be useful for understanding the etiology of BRCA1 mutant breast cancer and triple negative breast cancer and for developing novel therapeutic targets. The modifiers may also lead to development of improved risk assessment models that better discriminate between high and lower risk BRCA1 mutation carriers.

National Institute of Health (NIH)
National Cancer Institute (NCI)
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Epidemiology of Cancer Study Section (EPIC)
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Seminara, Daniela
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Mayo Clinic, Rochester
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Barrdahl, Myrto; Rudolph, Anja; Hopper, John L et al. (2017) Gene-environment interactions involving functional variants: Results from the Breast Cancer Association Consortium. Int J Cancer 141:1830-1840
Michailidou, Kyriaki (see original citation for additional authors) (2017) Association analysis identifies 65 new breast cancer risk loci. Nature 551:92-94
Glubb, Dylan M; Johnatty, Sharon E; Quinn, Michael C J et al. (2017) Analyses of germline variants associated with ovarian cancer survival identify functional candidates at the 1q22 and 19p12 outcome loci. Oncotarget 8:64670-64684
Zuber, Verena; Bettella, Francesco; Witoelar, Aree et al. (2017) Bromodomain protein 4 discriminates tissue-specific super-enhancers containing disease-specific susceptibility loci in prostate and breast cancer. BMC Genomics 18:270
Milne, Roger L (see original citation for additional authors) (2017) Identification of ten variants associated with risk of estrogen-receptor-negative breast cancer. Nat Genet 49:1767-1778
Shimelis, Hermela; Mesman, Romy L S; Von Nicolai, Catharina et al. (2017) BRCA2 Hypomorphic Missense Variants Confer Moderate Risks of Breast Cancer. Cancer Res 77:2789-2799
Muranen, Taru A; Greco, Dario; Blomqvist, Carl et al. (2017) Genetic modifiers of CHEK2*1100delC-associated breast cancer risk. Genet Med 19:599-603
Ugalde-Morales, Emilio; Li, Jingmei; Humphreys, Keith et al. (2017) Common shared genetic variation behind decreased risk of breast cancer in celiac disease. Sci Rep 7:5942
Lecarpentier, Julie; Silvestri, Valentina; Kuchenbaecker, Karoline B et al. (2017) Prediction of Breast and Prostate Cancer Risks in Male BRCA1 and BRCA2 Mutation Carriers Using Polygenic Risk Scores. J Clin Oncol 35:2240-2250
Burgess, Stephen; Thompson, Deborah J; Rees, Jessica M B et al. (2017) Dissecting Causal Pathways Using Mendelian Randomization with Summarized Genetic Data: Application to Age at Menarche and Risk of Breast Cancer. Genetics 207:481-487

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