Up-regulation of Expression of the Ubiquitin Carboxyl-Terminal Hydrolase L1 Gene in Human Airway Epithelium of Cigarette Smokers

Abstract

Neuroendocrine differentiation is a common feature of lung cancer and increased numbers of neuroendocrine cells and their peptides have been described in chronic smokers. To understand the effects of cigarette smoking on the gene expression profile of neuroendocrine cells, microarray analysis with TaqMan confirmation was used to assess airway epithelial samples obtained by fiberoptic bronchoscopy from 81 individuals [normal nonsmokers, normal smokers, smokers with early chronic obstructive lung disease (COPD), and smokers with established COPD]. Of 11 genes considered to be neuroendocrine cell specific, only ubiquitin carboxyl-terminal hydrolase L1 (UCHL1), a member of the ubiquitin proteasome pathway, was consistently up-regulated in smokers compared with nonsmokers. Up-regulation of UCHL1 at the protein level was observed with immunohistochemical analysis of bronchial biopsies of smokers compared with nonsmokers. UCHL1 expression was evident only in neuroendocrine cells of the airway epithelium in nonsmokers; however, UCHL1 was also expressed in ciliated epithelial cells in smokers. This observation may add further weight to recent observations that ciliated cells are capable of transdifferentiating to other airway epithelial cells. In the context that UCHL1 is involved in the degradation of unwanted, misfolded, or damaged proteins within the cell and is overexpressed in >50% of lung cancers, its overexpression in chronic smokers may represent an early event in the complex transformation from normal epithelium to overt malignancy. (Cancer Res 2006; 66(22): 10729-40)

Variability in Small Airway Epithelial Gene Expression Among Normal Smokers

“…Second, previous studies have shown that replicate determinations of the levels of gene expression in the airway epithelium of the same subject gave highly reproducible levels of expression when assessed in the same individual over time 18 . Third, there is extensive data from our group and others of TaqMan confirmation of expression levels of genes in the airway epithelium determined by microarray methods and selected genes were confirmed in this study [18][19][20][29][30][31][32][33][34] . Fourth, assessment of an independent data set of nonsmokers and smokers verified a similar pattern of increase variability in this subset of the same genes.…”

Down-regulation of the Notch Pathway in Human Airway Epithelium in Association with Smoking and Chronic Obstructive Pulmonary Disease

“…The gene expression arrays from a subset of the nonsmoker, healthy smoker, and COPD smoker groups used in this report have been used in previous reports (21,22), and the raw data from the arrays has been made available to the public (Gene Expression Omnibus [GEO] accession numbers GSE4498 and GSE5058). Neither of these studies reported on an expression of genes related to the Notch signaling pathway.…”

“…All samples were assessed in triplicate at two different cDNA concentrations to ensure that amplification efficiency for the reference gene and gene of interest was the same. All PCR reactions were run in an Applied Biosystems Sequence Detection System 7500 as previously described (21,22).…”

Overexpressed proprotein convertase 1/3 induces an epithelial-mesenchymal transition in airway epithelium

“…Interestingly, UCH-L1 expression is upregulated in PC1/3 cells (online supplementary figure S1c and table S2). As previously stated, UCH-L1 is a neuroendocrine cell-specific protein used as a marker in assessing lung cancer [25].…”

“…Surprisingly, PC1/3 is also expressed in goblet and ciliated cells in the nasal polyp epithelium. CAROLAN et al [25] have shown that ubiquitin carboxyl-terminal hydrolase (UCH)-L1, a marker of neuroendocrine cells, is expressed only in neuroendocrine cells of the airway epithelium in nonsmokers, while in smokers UCH-L1 is also upregulated in ciliated epithelial cells. In line with these studies, we suggest that both goblet cells and ciliated cells can transdifferentiate to other epithelial cells.…”