Background: Epigenetic information can be used to identify clinically relevant genomic variants single nucleotide polymorphisms (SNPs) of functional importance in cancer development. Super-enhancers are cell-specific DNA elements, acting to determine tissue or cell identity and driving tumor progression. Although previous approaches have been tried to explain risk associated with SNPs in regulatory DNA elements, so far epigenetic readers such as bromodomain containing protein 4 (BRD4) and super-enhancers have not been used to annotate SNPs. In prostate cancer (PC), androgen receptor (AR) binding sites to chromatin have been used to inform functional annotations of SNPs.
Results: Here we establish criteria for enhancer mapping which are applicable to other diseases and traits to achieve the optimal tissue-specific enrichment of PC risk SNPs. We used stratified Q-Q plots and Fisher test to assess the differential enrichment of SNPs mapping to specific categories of enhancers. We find that BRD4 is the key discriminant of tissue-specific enhancers, showing that it is more powerful than AR binding information to capture PC specific risk loci, and can be used with similar effect in breast cancer (BC) and applied to other diseases such as schizophrenia.
Conclusions: This is the first study to evaluate the enrichment of epigenetic readers in genome-wide associations studies for SNPs within enhancers, and provides a powerful tool for enriching and prioritizing PC and BC genetic risk loci. Our study represents a proof of principle applicable to other diseases and traits that can be used to redefine molecular mechanisms of human phenotypic variation.A.U. is supported by the South-East Norway Health Authorities (Helse Sor-Ost grant ID 2014040) at the Oslo University Hospital, and the Norwegian Centre for Molecular Medicine. I.G.M. is supported by funding from the Research Council of Norway (RCN), South East Norway Health Authority (SENHA) and the University of Oslo through the Centre for Molecular Medicine (Norway), which is part of the Nordic EMBL (European Molecular Biology Laboratory) partnership and also supported by Oslo University Hospitals. I.G.M. is also supported by the Norwegian Cancer Society and by EU FP7 funding. I.G.M. holds a visiting scientist position with Cancer Research UK through the Cambridge Research Institute and a Senior Visiting Research Fellowship with Cambridge University through the Department of Oncology. A.U. is funded by the SENHA at the Oslo University Hospital. V. Z. is supported by the Centre for Molecular Medicine (Norway) and together with A.W., F.B and O.A.A. supported by the Norwegian Centre of Research in Mental Disorders (NORMENT) with funding from the RCN, SENHA, Norwegian Health Association and KG Jebsen Foundation. This work was supported by the Kristian Gerhard Jebsen Foundation, Centre for Molecular Medicine Norway, Research Council of Norway (213837, 223273), South-East Norway Health Authorities (2013–123), National Institutes of Health (R01AG031224, R01EB000790 and RC2DA29475). I.G.M. and group members participate in the NIH Genetic Associations and Mechanisms in Oncology (GAME-ON): A Network of Consortia for Post-Genome Wide Association (Post-GWA) Research (prostate: 1U19CA148537-01). This work was also supported by Cancer Research UK Grant C5047/A3354. We would also like to thank the following for funding support: the Institute of Cancer Research and the Everyman Campaign, the Prostate Cancer Research Foundation, Prostate Research Campaign UK (now known as Prostate Cancer UK), the National Cancer Research Network UK and the National Cancer Research Institute (NCRI) UK. The ProtecT study is ongoing and is funded by the Health Technology Assessment Programme (projects 96/20/06, 96/20/99). The ProtecT trial and its linked ProMPT and CAP (Comparison Arm for ProtecT) studies are supported by Department of Health, UK, Cancer Research UK grant number C522/A8649, Medical Research Council (UK) grant number G0500966, ID 75466 and the NCRI, UK. The epidemiological data for ProtecT were generated through funding from the Southwest National Health Service Research and Development
