title: Validation of the MethylationEPIC BeadChip for fresh-frozen and formalin-fixed paraffin-embedded tumours.
abstract: DNA methylation is the most studied epigenetic modification due to its role in regulating gene expression, and its involvement in the pathogenesis of cancer and several diseases upon aberrations in methylation. The method of choice to evaluate genome-wide methylation has been the Illumina HumanMethylation450 BeadChip (450K), but it was recently replaced with the MethylationEPIC BeadChip (EPIC). We therefore sought to validate the EPIC array in comparison to the 450K array for both fresh-frozen (FF) and formalin-fixed paraffin-embedded (FFPE) tumours. We also performed analysis on the EPIC array with paired FF and FFPE samples to adapt to a clinical setting where FFPE is routinely used. Further, we compared two restoration methods, REPLI-g and Infinium, for FFPE-derived DNA on the EPIC array. The Pearson correlation of β values for common probes on the 450K and EPIC array was high for both FF (mean: 0.992) and FFPE (mean: 0.984) samples. The β values generated from the EPIC array for FFPE samples correlated well with the paired FF tumours, but varied between 0.901 and 0.987. We did note that sample pairs with lower correlation had less bimodal density distributions of β values and displayed higher noise in the copy number alteration plots (generated from the methylation array data) in the FFPE sample. Both REPLI-g and the Infinium restoration for FFPE samples performed well on the EPIC array and generated equivalent correlation scores to the paired FF sample.
authors.affiliation: Sahlgrenska Cancer Center, Department of Pathology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Box 425, 405 30, Gothenburg, Sweden.
authors.forename: Teresia
authors.initials: T
authors.lastname: Kling
authors.affiliation: Sahlgrenska Cancer Center, Department of Pathology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Box 425, 405 30, Gothenburg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Wenger
authors.affiliation: Department of Cancer Biology, UCL Cancer Institute, University College London, London, UK.
authors.forename: Stephan
authors.initials: S
authors.lastname: Beck
authors.affiliation: Sahlgrenska Cancer Center, Department of Pathology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Box 425, 405 30, Gothenburg, Sweden.
authors.forename: Helena
authors.initials: H
authors.lastname: Carén
mesh_terms: D001932:Brain Neoplasms / Q000235:genetics* / Q000473:pathology; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D016612:Paraffin Embedding; D016707:Tissue Fixation
keywords: 450K; Brain tumour; DNA methylation; DNA restoration; EPIC; Epigenetics; Formalin-fixed paraffin-embedded tissue