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Current smoking-specific gene expression signature in bronchial epithelium is enhanced in squamous cell lung cancer

ABSTRACT: Cigarette smoking is the main risk factor for the development of squamous cell lung carcinoma (SCC). However, the smoking-related molecular changes in SCC have not been studied. We wanted to identify genes in both histologically normal bronchial epithelium and SCC samples that are differentially expressed between current and ex-smokers. In addition, to analyze the levels of the smoking-related genes identified in normal bronchial epithelium with the levels in SCC. Gene expression profiles were generated using Agilent whole human genome microarrays in 28 laser microdissected normal bronchus epithelial samples and in 35 laser microdissected SCC samples of current and ex-smokers. Levels of 246 genes, mainly related to oxidative stress response, were significantly different between normal bronchial epithelium of current and ex-smokers. No significant differences were associated with the smoking status in SCC samples. Analysis of the 246 smoking specific genes in SSC from current and ex-smokers also revealed no differences. As a next step, we compared the levels of the smoking-specific gene signature between normal bronchial epithelium from ex- and current smokers to all 34 SCC samples. Twenty-two percent of the upregulated genes are further upregulated in SCC as compared to current smokers. Expression of the downregulated genes was even further downregulated for 79% of the genes in SCC as compared to bronchus epithelium of current smokers. The downregulated genes included several tumour suppressor genes. This study shows that genes upregulated in normal bronchial epithelium of current smokers are expressed at similar levels in SCC samples, while levels of downregulated genes were significantly further reduced in SCC. This indicates that these downregulated genes play a role in SCC oncogenesis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE12428 | GEO | 2008/10/01

SECONDARY ACCESSION(S): PRJNA113741

REPOSITORIES: GEO

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Project description:Cystatin A (gene: CSTA), is up-regulated in non-small-cell lung cancer (NSCLC) and dysplastic vs normal human bronchial epithelium. In the context that chronic obstructive pulmonary disease (COPD), a small airway epithelium (SAE) disorder, is independently associated with NSCLC (especially squamous cell carcinoma, SCC), but only occurs in a subset of smokers, we hypothesized that genetic variation, smoking and COPD modulate CSTA gene expression levels in SAE, with further up-regulation in SCC. Gene expression was assessed by microarray in SAE of 178 individuals [healthy nonsmokers (n=60), healthy smokers (n=82), and COPD smokers (n=36)], with corresponding large airway epithelium (LAE) data in a subset (n=52). Blood DNA was genotyped by SNP microarray. Twelve SNPs upstream of the CSTA gene were all significantly associated with CSTA SAE gene expression (p<0.04 to 5 x 10-4). CSTA gene expression levels in SAE were higher in COPD smokers (28.4 Â± 2.0) than healthy smokers (19.9 Â± 1.4, p<10-3), who in turn had higher levels than nonsmokers (16.1 Â± 1.1, p<0.04). CSTA LAE gene expression was also smoking-responsive (p<10-3). Using comparable publicly available NSCLC expression data, CSTA was up-regulated in SCC vs LAE (p<10-2) and down-regulated in adenocarcinoma vs SAE (p<10-7). All phenotypes were associated with significantly different proportional gene expression of CSTA to cathepsins. The data demonstrate that regulation of CSTA expression in human airway epithelium is influenced by genetic variability, smoking, and COPD, and is further up-regulated in SCC, all of which should be taken into account when considering the role of CSTA in NSCLC pathogenesis. CSTA gene expression was assessed in the small airway epithelium obtained by bronchoscopy from 178 individuals, including healthy nonsmokers (n= 60) and healthy smokers (n= 118) and the large airway epithelium from healthy nonsmokers (n=21) and healthy smokers(n=31). *** Processed data not provided for all gene expression records. *** Blood DNA from the majority of these individuals was genotyped and an association analysis of gene expression with genotypes of all 48 SNPs within 100 kb of CSTA was performed in PLINK, and tested for significance following 103 permutations within ancestral clusters. Supplementary file (linked below) reports genotypes of all 48 SNPs within 100 kb of the CSTA gene for the 112 genotyping Samples.

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Current smoking-specific gene expression signature in bronchial epithelium is enhanced in squamous cell lung cancer

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