Epigenetic portraits of human breast cancers (expression data)

Breast cancer is a molecularly, biologically and clinically heterogeneous group of disorders. Understanding this diversity is essential to improving diagnosis and optimising treatment. Both genetic and acquired epigenetic abnormalities participate in cancer, but information is scant on the involvement of the epigenome in breast cancer and its contribution to the complexity of the disease. Here we used the Infinium Methylation Platform to profile at single-CpG resolution (over 14,000 genes interrogated) the methylomes of 119 breast tumours. It emerges that many genes whose expression is linked to the ER status are epigenetically controlled (or/ we show that the two major phenotypes of breast cancers determined by ER status are widely involving epigenetic regulatory mechanisms), offering the prospect of a novel approach to treating ER-positive tumours. We have distinguished methylation-profile-based tumour clusters, some coinciding with known expression subtypes but also new entities that may provide a meaningful basis for refining breast tumour typology. We show that methylation patterns may reflect the cellular origins of tumours. Having highlighted an unexpectedly strong epigenetic component in the regulation of key immune pathways, we show that a set of immune genes have high prognostic value in specific tumour categories. By laying the ground for better understanding of breast cancer heterogeneity and improved tumour taxonomy, the precise epigenetic portraits drawn here should contribute to better management of breast cancer patients.

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Dedeurwaerder S, Desmedt C, Calonne E, Singhal SK, Haibe-Kains B, Defrance M, Michiels S, Volkmar M, Deplus R, Luciani J, Lallemand F, Larsimont D, Toussaint J, Haussy S, Rothé F, Rouas G, Metzger O, Majjaj S, Saini K, Putmans P, Hames G, van Baren N, Coulie PG, Piccart M, Sotiriou C, Fuks F