Performance of urine cotinine and hypomethylation of AHRR and F2RL3 as biomarkers for smoking exposure in a population-based cohort

Do-Hoon Lee,E Hwa Yun,Min Kyung Lim,Da Young Song,Eun Young Park,Sang-Hyun Hwang,Jin-Kyoung Oh,Max Costa

doi:10.1371/journal.pone.0176783

Abstract

There is a growing body of evidence demonstrating an association between smoking and DNA methylation. Accordingly, DNA methylation is now considered a promising biomarker of smoking exposure. We evaluated the relationship between methylation markers (AHRR and F2RL3) and urine cotinine as well as self-reported smoking status. DNA methylation levels of AHRR and F2RL3 in blood as well as urine cotinine were measured in 330 adults (46 to 87 years of age). Pyrosequencing was performed to measure DNA methylation of AHRR and F2RL3 associated with smoking exposure. The lung cancer risk associated with DNA methylation and urine cotinine was analyzed using logistic regression analysis. The AHRR and F2RL3 genes were significantly hypomethylated in current smokers compared to in individuals who have never smoked. An inverse relationship was observed between urine cotinine and methylation levels. Methylation of AHRR and F2RL3 distinguished current smokers from never-smokers with high accuracy. Logistic multivariate analysis showed that AHRR methylation is significantly associated with the risk of lung cancer (OR = 0.96, P = 0.011). Our study validated the smoking-associated DNA methylation markers reported in a Korean population-based cohort. In conclusion, DNA methylation of AHRR and F2RL3 provided accurate measures for smoking exposure. Methylation markers reflecting the long-term effect of smoking on the risk of lung cancer showed better performance in distinguishing former smokers from never-smokers.

Highlights

Self-reported exposure to smoke has been widely used to assess the health effects of smoking
We validated studies showing that methylation of aryl hydrocarbon receptor repressor (AHRR) and F2RL3 showed inverse relationships with self-reported smoking status
We identified an inverse relationship between urine cotinine and methylation markers (AHRR and F2RL3)

Summary

Introduction

Self-reported exposure to smoke has been widely used to assess the health effects of smoking. Serum cotinine is a better measure of smoking exposure than self-reporting methods [3]. It only reflects short-term exposure (half-life of cotinine in plasma has been estimated to be about 15–20 hr)[4]. Estimation of long-term smoking exposure is useful for assessing health risks accumulated through tobacco smoking[5]. Long-term smoking exposure may have effects on DNA methylation patterns, which could lead to changes in gene expression and may occur in a broader context to the development or progression of various diseases [6, 7]. A recent study of multi-prospective cohorts demonstrated that hypomethylation of smoking-related genes was associated with lung cancer risk [8]

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