AHRR methylation predicts smoking status and smoking intensity in both saliva and blood DNA

Abstract

Many existing DNA repositories do not have robust characterizations of smoking, while for many currently ongoing studies, the advent of vaping has rendered traditional cotinine‐based methods of determining smoking status unreliable. Previously, we have shown that methylation status at cg05575921 in whole blood DNA can reliably predict cigarette consumption. However, whether methylation status in saliva can be used similarly has yet to be established. Herein, we use DNA from 418 biochemically confirmed smokers or nonsmokers to compare and contrast the utility of cg05575921 in classifying and quantifying cigarette smoking. Using whole blood DNA, a model incorporating age, gender, and methylation status had a receiver operating characteristic (ROC) area under the curve (AUC) for predicting smoking status of 0.995 with a nonlinear demethylation response to smoking. Using saliva DNA, the ROC AUC for predicting smoking was 0.971 with the plot of the relationship of DNA methylation to daily cigarette consumption being very similar to that seen for whole blood DNA. The addition of information from another methylation marker designed to correct for cellular heterogeneity improved the AUC for saliva DNA to 0.981. Finally, in 31 subjects who reported quitting smoking 10 or more years previously, cg05575921 methylation was nonsignificantly different from controls. We conclude that DNA methylation status at cg05575921 in DNA from whole blood or saliva predicts smoking status and daily cigarette consumption. We suggest these epigenetic assessments for objectively ascertaining smoking status will find utility in research, clinical, and civil applications.

Refinement of cg05575921 demethylation response in nascent smoking

“…Still, the actual consumption of cigarettes that these cotinine levels represent may be lower. In our studies of adults who only smoked cigarettes that used this same ELISA assay, the same methylation level corresponded to~2 cigarettes per day [15]. Furthermore, the majority of the 19 W3 subjects, whose data is given in Fig.…”

“…Dozens of genome wide studies have suggested that DNA methylation approaches may address some of these limitations [13,14]. Building on these studies, we and others have shown that single assessments of blood or saliva DNA methylation status at cg05575921, a CpG residue in the aryl hydrocarbon repressor receptor (AHRR) locus, is extremely sensitive to regular adult smoking [15,16]. Furthermore, in preliminary work, we have shown that saliva DNA assessment of cg05575921 predicts adolescent smoking status [17].…”

Epigenetic Biomarkers for Environmental Exposures and Personalized Breast Cancer Prevention

“…Although DNA methylation loci associated with numerous exposures have been identified, most have not been demonstrated to be able to act as markers. The exceptions, CpG markers for current smoking and current heavy alcohol intake, were identified in cohorts that used questionnaires that assessed detailed current and previous use, including type, quantity, frequency, and duration of use, age when first started using, and age when quitting (if applicable) [37,40,59,60]. Identification of epigenetic markers for additional personal exposures that may be associated with breast cancer risk would also require a robust characterization of the exposure and data analysis for potential associations with the peripheral blood epigenome.…”

“…These findings suggest that epigenetic signatures can represent a biological memory of past exposures and that such signatures may be retained in the exposed stem and progenitor cells [29]. More recently, AHRR hypomethylation in saliva was also shown to predict smoking with an AUC of 0.971 [40]. Thus, salivary DNA methylation may also serve as biomarkers of environmental exposures.…”

AHRR cg05575921 methylation in relation to smoking and PM2.5 exposure among Taiwanese men and women

“…In addition to being a predictor of smoking habits [52], AHRR cg05575921 methylation from whole blood or saliva DNA is a validated predictor of smokingrelated morbidity and mortality [35,49]. For instance, AHRR cg05575921 hypomethylation has been associated with enhanced carcinogenesis especially in the lungs [10,31,35,38].…”