title: Patterns of DNA methylation in the normal colon vary by anatomical location, gender, and age.
abstract: Alterations in DNA methylation have been proposed to create a field cancerization state in the colon, where molecular alterations that predispose cells to transformation occur in histologically normal tissue. However, our understanding of the role of DNA methylation in field cancerization is limited by an incomplete characterization of the methylation state of the normal colon. In order to determine the colon's normal methylation state, we extracted DNA from normal colon biopsies from the rectum, sigmoid, transverse, and ascending colon and assessed the methylation status of the DNA by pyrosequencing candidate loci as well as with HumanMethylation450 arrays. We found that methylation levels of repetitive elements LINE-1 and SAT-α showed minimal variability throughout the colon in contrast to other loci. Promoter methylation of EVL was highest in the rectum and progressively lower in the proximal segments, whereas ESR1 methylation was higher in older individuals. Genome-wide methylation analysis of normal DNA revealed 8388, 82, and 93 differentially methylated loci that distinguished right from left colon, males from females, and older vs. younger individuals, respectively. Although variability in methylation between biopsies and among different colon segments was minimal for repetitive elements, analyses of specific cancer-related genes as well as a genome-wide methylation analysis demonstrated differential methylation based on colon location, individual age, and gender. These studies advance our knowledge regarding the variation of DNA methylation in the normal colon, a prerequisite for future studies aimed at understanding methylation differences indicative of a colon field effect.
authors.affiliation: Division of Clinical Research; Fred Hutchinson Cancer Research Center; Seattle, WA USA; Research and Development Service; VA Puget Sound Health Care System; Seattle, WA USA; Department of Medicine; University of Washington School of Medicine; Seattle, WA USA.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Kaz
authors.affiliation: Division of Clinical Research; Fred Hutchinson Cancer Research Center; Seattle, WA USA.
authors.forename: Chao-Jen
authors.initials: CJ
authors.lastname: Wong
authors.affiliation: Division of Clinical Research; Fred Hutchinson Cancer Research Center; Seattle, WA USA.
authors.forename: Slavomir
authors.initials: S
authors.lastname: Dzieciatkowski
authors.affiliation: Division of Clinical Research; Fred Hutchinson Cancer Research Center; Seattle, WA USA; Department of Colorectal Surgery; the Sixth Affiliated Hospital; Sun Yat-Sen University; Guangzhou, PR China; Gastrointestinal Institute; Sun Yat-Sen University; Guangzhou, PR China.
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Medicine; University of Pittsburgh Medical Center; Pittsburgh, PA USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Schoen
authors.affiliation: Division of Clinical Research; Fred Hutchinson Cancer Research Center; Seattle, WA USA; Department of Medicine; University of Washington School of Medicine; Seattle, WA USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Grady
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D003106:Colon / Q000033:anatomy & histology* / Q000378:metabolism*; D018899:CpG Islands; D019175:DNA Methylation; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005260:Female; D015894:Genome, Human; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D008297:Male; D008875:Middle Aged; D011401:Promoter Regions, Genetic; D012007:Rectum / Q000378:metabolism; D012737:Sex Factors
chemical_list: D015815:Cell Adhesion Molecules; C506487:ESR1 protein, human; C484449:EVL protein, human; D047628:Estrogen Receptor alpha
keywords: DNA methylation; colorectal cancer; field effect; methylation microarray; normal colon methylation