The AUCs based on methylation (<i>AHRR</i> and <i>F2RL3</i>) and urine cotinine in predicting current smoker from never-smoker status.

<p>The AUCs based on methylation (<i>AHRR</i> and <i>F2RL3</i>) and urine cotinine in predicting current smoker from never-smoker status.</p

Performance of urine cotinine and hypomethylation of <i>AHRR</i> and <i>F2RL3</i> as biomarkers for smoking exposure in a population-based cohort - Fig 1

<p>Box plots of distribution showing methylation of <i>AHRR</i> (a) and <i>F2RL3</i> (b) genes in never-, former- and current smokers.</p

Box plots of distribution showing methylation of <i>AHRR</i> gene in never-, former- and current smokers according to gender.

<p>Box plots of distribution showing methylation of <i>AHRR</i> gene in never-, former- and current smokers according to gender.</p

Odds ratios of lung cancer risk for <i>AHRR</i> and <i>F2RL3</i> methylation in multivariate analysis.

<p>Odds ratios of lung cancer risk for <i>AHRR</i> and <i>F2RL3</i> methylation in multivariate analysis.</p

ROC analysis for predicting current smoking status.

<p>Cotinine levels above the cutoff of 201.0 ng/ml were associated with current smoking status, with high predictive value for current smokers compared to never-smokers (left, AUC = 0.974). Using a cut-off level for <i>AHRR</i> gene methylation of 60.2%, <i>AHRR</i> gene methylation also showed high performance for predicting current smokers (right, AUC = 0.942) with a sensitivity of 84.0% and specificity of 95.4%.</p

PCR and pyrosequeincing primers for <i>AHRR</i> and <i>F2RL3</i>.

<p>PCR and pyrosequeincing primers for <i>AHRR</i> and <i>F2RL3</i>.</p

The correlation between methylation and urine continine concentration (ng/ml).

<p>The methylation (x-axis) of <i>AHRR</i> (left) and <i>F2RL3</i> (right) inversely correlated with urine cotinine concentration (y-axis).</p

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

<div><p>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 (<i>AHRR</i> and <i>F2RL3</i>) and urine cotinine as well as self-reported smoking status. DNA methylation levels of <i>AHRR</i> and <i>F2RL3</i> 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 <i>AHRR</i> and <i>F2RL3</i> associated with smoking exposure. The lung cancer risk associated with DNA methylation and urine cotinine was analyzed using logistic regression analysis. The <i>AHRR</i> and <i>F2RL3</i> 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 <i>AHRR</i> and <i>F2RL3</i> distinguished current smokers from never-smokers with high accuracy. Logistic multivariate analysis showed that <i>AHRR</i> methylation is significantly associated with the risk of lung cancer (OR = 0.96, <i>P</i> = 0.011). Our study validated the smoking-associated DNA methylation markers reported in a Korean population-based cohort. In conclusion, DNA methylation of <i>AHRR</i> and <i>F2RL3</i> 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.</p></div

Characteristics of the study population.

<p>Characteristics of the study population.</p

The AUCs based on methylation (<i>AHRR</i> and <i>F2RL3</i>) in predicting current and former smoker from never-smoker status.

<p>The AUCs based on methylation (<i>AHRR</i> and <i>F2RL3</i>) in predicting current and former smoker from never-smoker status.</p