Abstract B07: Nasal epithelial gene expression profiles reflect dynamic biological response to smoking cessation
Authors: Hijazi Kahkeshan , Malyszko Bozena , Zhang Xiaohui , Liu Gang , Alekseyev Yuriy , Dumas Yves-Martine , Hertsgaard Louise , Jenson Joni , Rohde Cindy , Hatsukami Dorothy K , Hecht Stephen S. , Brooks Daniel R , O’Connor George , Lenburg Marc , Steiling Katrina , Spira Avrum 
Published: January 2014

Abstract
Rationale: There are few indicators of which cigarette smokers are at highest risk for developing lung cancer and COPD, and it is unclear why individuals remain at risk for decades after smoking-cessation. The kinetics of gene-expression alterations upon smoking-cessation might delineate distinct biological processes that are activated in response to and during recovery from tobacco smoke exposure. Furthermore, differences in this response or recovery might be associated with disease risk. We therefore sought to determine whether the kinetics of gene-expression alterations upon smoking-cessation could be detected in readily collected nasal epithelium.
Methods: Nasal epithelial brushings were obtained from 8 active smokers enrolled in smoking-cessation programs. Brushings were obtained at baseline and at 4, 8, 16, and 24-weeks after smoking-cessation. Urine cotinine or exhaled carbon monoxide was used to assess tobacco abstinence. RNA extracted from the nasal brushings was processed and hybridized to Gene 1.0 ST Arrays. Gene expression changes associated with smoking-cessation were identified with a linear mixed effects model. Functional enrichment was determined using DAVID. Gene Set Enrichment Analysis (GSEA) was used to determine the relationship of nasal epithelial gene-expression changes associated with smoking-cessation to previous cross-sectional bronchial and nasal airway gene expression datasets of current, longer-term former and never smokers and to a previous published dataset of in-vitro exposure of cultured bronchial epithelial cells (NHBE) to cigarette smoke (CS).
Results: The expression levels of 78 genes were associated with short-term smoking-cessation (FDR q&lt;0.05, FC ≥ 1.75), with 6 genes up-regulated and 72 genes down-regulated with tobacco abstinence. A majority of the changes occur within 1-2 months of quitting. These genes were enriched in functional categories including oxidoreductase activity and metabolism of xenobiotic (p&lt;0.05). Genes that decreased with smoking-cessation were enriched for genes whose expression levels in the airway datasets were higher in current smokers relative to never smokers or longer-term former smokers (FDR &lt;10−3). Genes increased in active smokers that reversed with smoking-cessation were enriched among genes that are induced followed 15 minutes in-vitro exposure of NHBE to CS (FDR &lt;5*10−3).
Conclusion: Nasal epithelial gene expression profiles reflect the host response to smoking-cessation and are concordant with reversible changes identified in an independent bronchial airway dataset. Genes that reverse rapidly after smoking-cessation are inversely related to gene expression differences induced by acute cigarette smoke exposure in-vitro; suggesting that aspects of the gene-expression response to tobacco smoke both occur and reverse with rapid kinetics upon smoking. We have further found that genes with different biological functions revert to baseline with different dynamics following smoking-cessation. These data suggest that the smoking-induced field of injury can be measured non-invasively in nasal epithelium and leveraged to understand the kinetics of the reversible impact of smoking. These minimally invasive tools can be applied in population studies to assess the physiological impact of alternate tobacco products and other inhaled environmental exposures.
Citation Format: Kahkeshan Hijazi, Bozena Malyszko, Xiaohui Zhang, Gang Liu, Yuriy Alekseyev, Yves-Martine Dumas, Louise Hertsgaard, Joni Jenson, Cindy Rohde, Dorothy K Hatsukami, Stephen S. Hecht, Daniel R Brooks, George O’Connor, Marc Lenburg, Katrina Steiling, Avrum Spira. Nasal epithelial gene expression profiles reflect dynamic biological response to smoking cessation. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B07.