Abstract 3647: Dose-dependent alteration of CpG methylation in AHRR and GFI1 in mononuclear cell DNA of smokers.
Authors: Wang Xuting , Pittman Gary S. , Su Dan , Adamski Kelly N. , Campbell Michelle R. , Joubert Bonnie R. , Huang Zhiqing Y. , Hoyo Cathrine , Murphy Susan K. , London Stephanie A. , Bell Douglas A. 
Published: August 2014

About 45 million (∼19%) of U.S. adults smoke, 46 million are former smokers and &gt;100 million are exposed to environmental tobacco smoke. Tobacco use is associated with many types of cancer, heart disease, stroke, and respiratory disease. While hundreds of tobacco smoke constituents cause DNA damage, many adverse outcomes are not related to DNA damage and an emerging hypothesis is that exposure-induced epigenetic effects may mediate many of these outcomes. Using epigenome-wide association, Joubert et al (Env Health Perspectives, 2012) observed Bonferroni-corrected statistically significant associations (480,000 tests, p&lt;10-7) between maternal smoking and DNA methylation in cord blood at 26 CpG sites in 10 genes. We selected 21 smoking- associated CpGs in 4 genes to test as biomarkers of tobacco smoke exposure in adults. We measured methylation in peripheral blood mononuclear cell DNA of healthy adult smokers (5-70 cigarettes per day, n=43) and nonsmokers (n=19) using Illumina 450K methylation arrays. We used linear regression to assess the relationship between current smoking, pack-years, years smoked, and methylation level (log ratio beta) as the outcome. Blood from smokers and nonsmokers was also fractionated using antibody-coated magnetic beads into granulocytes, B cell, and T cell subpopulations to identify effects in specific hematopoietic lineages. Age and race were not significantly associated with methylation differences. Seven of 21 tested CpGs (AHRR, GFI1 and MYO1G) were strongly associated with both dose-dependent current smoking and years of smoking (Bonferroni, p&lt;0.0023) while 13/21 displayed nominal significance (p&lt;0.05). The greatest changes associated with current smoking were among CpGs located in the Ah Receptor Repressor gene (AHRR, cg05575921, delta beta = 27%, p= 1x10-10; cg23576855, delta beta=21%, p=1.96x10-6) and the GFI1 gene (four CpGs, p &lt;0.005). Of the 21 CpGs tested, 17 displayed methylation differences that were directionally consistent with those observed in cord blood in relation to maternal smoking in pregnancy suggesting these CpGs may be a general hematopoietic biomarker of smoking. Surprisingly CpG methylation levels in the CYP1A1 regulatory region were not influenced by smoking, contrary to the effect in cord blood. The functional meaning of these smoking-induced alterations in CpG methylation is not yet clear but in ongoing work we are examining gene expression and cellular phenotype in the blood of smokers.

Citation Format: Xuting Wang, Gary S. Pittman, Dan Su, Kelly N. Adamski, Michelle R. Campbell, Bonnie R. Joubert, Zhiqing Y. Huang, Cathrine Hoyo, Susan K. Murphy, Stephanie A. London, Douglas A. Bell. Dose-dependent alteration of CpG methylation in AHRR and GFI1 in mononuclear cell DNA of smokers. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3647. doi:10.1158/1538-7445.AM2013-3647