title: Leukocyte-adjusted epigenome-wide association studies of blood from solid tumor patients.
abstract: Epigenome-wide studies of DNA methylation using blood-derived DNA from cancer patients are complicated by the heterogeneity of cell types within blood and the associated cell lineage specification of DNA methylation signatures. Here, we applied a novel set of analytic approaches to assess the association between cancer case-status and DNA methylation adjusted for leukocyte variation using blood specimens from three case-control cancer studies (bladder: 223 cases, 205 controls; head and neck: 92 cases, 92 controls; and ovarian: 131 cases, 274 controls). Using previously published data on leukocyte-specific CpG loci and a recently described approach to deconvolute subject-specific blood composition, we performed an epigenome-wide analysis to examine the association between blood-based DNA methylation patterns and each of the three aforementioned solid tumor types adjusted for cellular heterogeneity in blood. After adjusting for leukocyte profile in our epigenome-wide analysis, the omnibus association between case-status and methylation was significant for all three studies (bladder cancer: P = 0.047; HNSCC: P = 0.013; ovarian cancer: P = 0.0002). Subsequent analyses revealed that CpG sites associated with cancer were enriched for transcription factor binding motifs involved with cancer-associated pathways. These results support the existence of cancer-associated DNA methylation profiles in the blood of solid tumor patients that are independent of alterations in normal leukocyte distributions. Adoption of the methods developed here will make it feasible to rigorously assess the influence of variability of normal leukocyte profiles when investigating cancer related changes in blood-based epigenome-wide association studies.
authors.affiliation: Department of Environmental Health; University of Cincinnati College of Medicine; Cincinnati, OH USA; Department of Epidemiology; Brown University; Providence, RI USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Langevin
authors.affiliation: Department of Biostatistics; Oregon State University College of Public Health and Human Sciences; Corvallis, OR USA.
authors.forename: E Andres
authors.initials: EA
authors.lastname: Houseman
authors.affiliation: Department of Pathology & Laboratory Medicine; Brown University; Providence, RI USA.
authors.forename: William P
authors.initials: WP
authors.lastname: Accomando
authors.affiliation: Department of Community and Family Medicine; Section of Biostatistics and Epidemiology; Dartmouth Medical School; Lebanon, NH USA.
authors.forename: Devin C
authors.initials: DC
authors.lastname: Koestler
authors.affiliation: Department of Community and Family Medicine; Section of Biostatistics and Epidemiology; Dartmouth Medical School; Lebanon, NH USA; Department of Pharmacology and Toxicology; Dartmouth Medical School; Lebanon, NH USA.
authors.forename: Brock C
authors.initials: BC
authors.lastname: Christensen
authors.affiliation: Division of Epidemiology and Community Health; University of Minnesota Masonic Cancer Center; Minneapolis, MN USA.
authors.forename: Heather H
authors.initials: HH
authors.lastname: Nelson
authors.affiliation: Department of Community and Family Medicine; Section of Biostatistics and Epidemiology; Dartmouth Medical School; Lebanon, NH USA.
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Karagas
authors.affiliation: Department of Community and Family Medicine; Section of Biostatistics and Epidemiology; Dartmouth Medical School; Lebanon, NH USA; Department of Pharmacology and Toxicology; Dartmouth Medical School; Lebanon, NH USA.
authors.forename: Carmen J
authors.initials: CJ
authors.lastname: Marsit
authors.affiliation: Department of Neurological Surgery; University of California San Francisco; San Francisco, CA USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Wiencke
authors.affiliation: Department of Epidemiology; Brown University; Providence, RI USA; Department of Pathology & Laboratory Medicine; Brown University; Providence, RI USA.
authors.forename: Karl T
authors.initials: KT
authors.lastname: Kelsey
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005260:Female; D055106:Genome-Wide Association Study; D006258:Head and Neck Neoplasms / Q000097:blood* / Q000235:genetics; D006801:Humans; D007962:Leukocytes / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000097:blood* / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D001749:Urinary Bladder Neoplasms / Q000097:blood* / Q000235:genetics
keywords: EWAS; HNSCC; bladder cancer; epigenomics; ovarian cancer