The relationship of smoking to cg05575921 methylation in blood and saliva DNA samples from several studies

Abstract

Numerous studies have shown that cg05575921 methylation decreases in response to smoking. However, secondary to methodological issues, the magnitude and dose dependency of that response is as of yet unclear. This lack of certainty is a barrier to the use of DNA methylation clinically to assess and monitor smoking status. To better define this relationship, we conducted a joint analysis of methylation sensitive PCR digital (MSdPCR) assessments of cg05575921 methylation in whole blood and/or saliva DNA to smoking using samples from 421 smokers and 423 biochemically confirmed non-smokers from 4 previously published studies. We found that cg05575921 methylation manifested a curvilinear dose dependent decrease in response to increasing cigarette consumption. In whole blood DNA, the Receiver Operating Characteristic (ROC) Area Under the Curve (AUC) of cg05575921 methylation for predicting daily smoking status was 0.98. In saliva DNA, the gross AUC was 0.91 with correction for cellular heterogeneity improving the AUC to 0.94. Methylation status was significantly associated with the Fagerstrom Test for Nicotine Dependence score, but with significant sampling heterogeneity. We conclude that MSdPCR assessments of cg05575921 methylation are a potentially powerful, clinically implementable tool for the assessment and management of smoking.

Alcohol Use Intensity Decreases in Response to Successful Smoking Cessation Therapy

“…Methodological challenges are at least partially to blame for this lack of understanding. Defining the dose response of cg05575921 methylation to daily cigarette consumption and cessation greatly benefitted from the availability of two existing, readily employable, short-term biomarkers of smoking—exhaled carbon monoxide and cotinine—to help define the set point for non-smokers and to invalidate data from subjects who falsely stated that they achieved smoking cessation [ 20 ]. This was not a trivial problem.…”

“…This was not a trivial problem. While collecting the four cohorts of subjects included in a recently published meta-analysis of the dose responsiveness of cg05575921, we found that ~4% of the subjects who enrolled and stated that they were lifetime non-users of nicotine-containing products in fact had significant serum levels of cotinine [ 20 ]. This high rate of unreliable self-report is a problem for the examination of alcohol consumption.…”

“…The DNA was prepared from whole blood using cold protein precipitation as previously described [ 15 , 20 , 21 , 23 , 24 ]. Serum cotinine levels were determined by the University of Iowa Diagnostic Laboratories under standard clinical processes.…”

“…What is more, different from CDT and PEth testing, the ATS can be assessed using DNA prepared from either blood or saliva [ 18 ]. Since a recently established biomarker for smoking [ 19 ], cg05575921 methylation, which can also be assessed using saliva [ 20 ], can be used simultaneously to measure cigarette consumption, this greater accuracy and ease of assessment makes the ATS an attractive metric for helping to decipher the relationship between forms of tobacco use and alcohol consumption. Indeed, in recent work, we used the combination of cg05575921 methylation and the ATS to show that smokers, but not vapers, have a higher rate of HAC, as compared to the general population [ 21 ].…”

The potential of DNA methylation as a biomarker for obesity and smoking

“…A droplet digital PCR (ddPCR) assay measuring methylation at cg05575921 successfully predicted smoking status in adults with varying smoking histories [151]. Also, methylation‐sensitive ddPCR assessments of the same CpG site have been shown to identify current smokers in both whole blood and saliva [152]. These examples demonstrate the effective implementation of methylation biomarkers in clinical settings to reliably assess smoking.…”