Abstract
Background
A breast cancer polygenic risk score (PRS) comprising 313 common variants reliably predicts disease risk. We examined possible relationships between genetic variation, regulation, and expression to clarify the molecular alterations associated with these variants.
Methods
Genome-wide methylomic variation was quantified (MethylationEPIC) in Asian breast cancer patients (1152 buffy coats from peripheral whole blood). DNA methylation (DNAm) quantitative trait loci (mQTL) mapping was performed for 235 of the 313 variants with minor allele frequencies > 5%. Stability of identified mQTLs (p < 5e-8) across lifetime was examined using a public mQTL database. Identified mQTLs were also mapped to expression quantitative trait loci (eQTLs) in the Genotype-Tissue Expression Project and the eQTLGen Consortium.
Results
Breast cancer PRS was not associated with DNAm. A higher proportion of significant cis-mQTLs were observed. Of 822 significant cis-mQTLs (179 unique variants) identified in our dataset, 141 (59 unique variants) were significant (p < 5e-8) in a public mQTL database. Eighty-six percent (121/141) of the matched mQTLs were consistent at multiple time points (birth, childhood, adolescence, pregnancy, middle age, post-diagnosis, or treatment). Ninety-three variants associated with DNAm were also cis-eQTLs (35 variants not genome-wide significant). Multiple loci in the breast cancer PRS are associated with DNAm, contributing to the polygenic nature of the disease. These mQTLs are mostly stable over time.
Conclusions
Consistent results from DNAm and expression data may reveal new candidate genes not previously associated with breast cancer.
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Data availability
The data that support the findings of this study are available on request from Mikael Hartman (ephbamh@nus.edu.sg). The data are not publicly available due to privacy or ethical restrictions.
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Acknowledgements
SGBCC thanks the participants and all research coordinators for their excellent help with recruitment, data, and sample collection. The breast cancer genome-wide association analyses were supported by the Government of Canada through Genome Canada and the Canadian Institutes of Health Research, the ‘Ministère de l’Économie, de la Science et de l’Innovation du Québec’ through Genome Québec and grant PSR-SIIRI-701, The National Institutes of Health (U19 CA148065, X01HG007492), Cancer Research UK (C1287/A10118, C1287/A16563, C1287/A10710) and The European Union (HEALTH-F2-2009-223175 and H2020 633784 and 634935). All studies and funders are listed in Michailidou et al. (2017).
Funding
This study was supported by the National Research Foundation Singapore (NRF-NRFF2017-02), NUS start-up Grant, National University Cancer Institute Singapore (NCIS) Centre Grant [NMRC/CG/NCIS/2010, NMRC/CG/012/2013, CGAug16M005], Saw Swee Hock School of Public Health Research Programme of Research Seed Funding (Breast Cancer Prevention Program), Asian Breast Cancer Research Fund, and the NMRC Clinician Scientist Award (SI Category) [NMRC/CSA-SI/0015/2017]. The breast cancer genome-wide association analyses were supported by the Government of Canada through Genome Canada and the Canadian Institutes of Health Research, the ‘Ministère de l’Économie, de la Science et de l’Innovation du Québec’ through Genome Québec and grant PSR-SIIRI-701, The National Institutes of Health (U19 CA148065, X01HG007492), Cancer Research UK (C1287/A10118, C1287/A16563, C1287/A10710) and The European Union (HEALTH-F2-2009-223175 and H2020 633784 and 634935). All studies and funders are listed in Michailidou et al. (2017).
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Conceptualization: JLi, Data curation: MH, Formal Analysis: PJH, Funding acquisition: JLi, MH, Methodology: RD, JLi, PJH, Project administration: PJH, Resources: MH, Writing – original draft: JLi, PJH, Writing – review & editing: All co-authors.
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The authors declare no potential conflicts of interest.
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This study is approved by the Agency of Science, Technology and Research, Human Biomedical Research Office (Reference: 2020-005). Recruitment for the Singapore Breast Cancer Cohort is approved by the National Healthcare Group Domain Specific Review Board (Reference: 2009/000501) and the SingHealth Centralised Institutional Review Board (Reference: 2019/2246).
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Ho, P.J., Dorajoo, R., Ivanković, I. et al. DNA methylation and breast cancer-associated variants. Breast Cancer Res Treat 188, 713–727 (2021). https://doi.org/10.1007/s10549-021-06185-9
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DOI: https://doi.org/10.1007/s10549-021-06185-9