Squamous Metaplasia Is Increased in the Bronchial Epithelium of Smokers with Chronic Obstructive Pulmonary Disease

PLOS ONE, Dec 2019

Aims To quantify the extent of squamous metaplasia in bronchial biopsies and relate it to the presence of chronic obstructive pulmonary disease (COPD), a smoking-related pathology. Methods Bronchial biopsies (n = 15 in each group) from smokers with COPD GOLD stage1 and GOLD stage2, smokers without COPD and healthy non-smokers were stained immunohistochemically with a panel of antibodies that facilitated the identification of pseudostratified epithelium and distinction of squamous metaplasia and squamous epithelium from tangentially cut epithelium. The percentage length of each of these epithelial phenotypes was measured as a percent of total epithelial length using computerised image analysis. Sections were also stained for carcinoembryonic antigen and p53, early markers of carcinogenesis, and Ki67, and the percentage epithelial expression measured. Results The extent of squamous metaplasia was significantly increased in both COPD1 and COPD2 compared to healthy smokers and healthy non-smokers. The amount of fully differentiated squamous epithelium was also increased in COPD1 and COPD2 compared to healthy non-smokers, as was the expression of carcinoembryonic antigen. These features correlated with one other. Conclusion In subjects with COPD there is a loss of pseudostratified epithelium accompanied by an increase in squamous metaplasia with transition into a fully squamous epithelium and expression of early markers of carcinogenesis.

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Squamous Metaplasia Is Increased in the Bronchial Epithelium of Smokers with Chronic Obstructive Pulmonary Disease

May Squamous Metaplasia Is Increased in the Bronchial Epithelium of Smokers with Chronic Obstructive Pulmonary Disease Helen M. Rigden 0 1 Ahmad Alias 0 1 Thomas Havelock 0 1 Rory O'Donnell 0 1 Ratko Djukanovic 0 1 Donna E. Davies 0 1 Susan J. Wilson 0 1 0 Academic Unit of Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton , Southampton , United Kingdom , 2 NIHR Southampton Respiratory Biomedical Research Unit, University Hospital Southampton , Tremona Road, Southampton , United Kingdom 1 Editor: Srikumar Chellappan, H. Lee Moffitt Cancer Center & Research Institute , UNITED STATES Data Availability Statement; All relevant data are within the paper - OPEN ACCESS Competing Interests: The authors have declared that no competing interests exist. Aims Methods To quantify the extent of squamous metaplasia in bronchial biopsies and relate it to the presence of chronic obstructive pulmonary disease (COPD), a smoking-related pathology. Bronchial biopsies (n = 15 in each group) from smokers with COPD GOLD stage1 and GOLD stage2, smokers without COPD and healthy non-smokers were stained immunohistochemically with a panel of antibodies that facilitated the identification of pseudostratified epithelium and distinction of squamous metaplasia and squamous epithelium from tangentially cut epithelium. The percentage length of each of these epithelial phenotypes was measured as a percent of total epithelial length using computerised image analysis. Sections were also stained for carcinoembryonic antigen and p53, early markers of carcinogenesis, and Ki67, and the percentage epithelial expression measured. Results The extent of squamous metaplasia was significantly increased in both COPD1 and COPD2 compared to healthy smokers and healthy non-smokers. The amount of fully differentiated squamous epithelium was also increased in COPD1 and COPD2 compared to healthy non-smokers, as was the expression of carcinoembryonic antigen. These features correlated with one other. Conclusion In subjects with COPD there is a loss of pseudostratified epithelium accompanied by an increase in squamous metaplasia with transition into a fully squamous epithelium and expression of early markers of carcinogenesis. Introduction Squamous metaplasia (SQM) is a pre-neoplastic change of the bronchial epithelium observed in the lungs in response to toxic injury induced by cigarette smoke [ 1–4 ]. It is part of a multistage process [ 5–7 ] which may eventually lead to full neoplastic transformation, i.e. bronchial carcinoma. Not all SQM lesions progress to a neoplasia, particularly if low grade and some may regress to a normal epithelium [ 8–10 ], especially after smoking cessation [11]. Initially, during SQM quiescent basal cells within the pseudostratified epithelium re-enter the cell cycle and become hyperproliferative. During the next stage of the process, the epithelium begins to express markers of a squamous phenotype rather than those of the normal pseudostratified epithelium. These include squamous epithelial cytokeratins (CK) [ 5,6,12–14 ] and the cell adhesion molecule SQM1 [ 15 ]. Finally, when fully differentiated, having a squamous cell morphology, cells will express involucrin, a marker of terminal differentiation [ 16 ]. A history of cigarette smoking is associated with 90% of lung cancers with 15% of lifetime smokers developing lung cancer [ 17–20 ]. Chronic obstructive pulmonary disease (COPD) is also associated with smoking and is an independent risk factor for developing lung cancer, the risk being increased by up to 4.5 fold [ 21–26 ]. Between 50 and 70% of subjects with lung cancer also have COPD [ 18,27 ]. The cause of this increased susceptibility in subjects with COPD is unknown. Several possibilities have been suggested, including common molecular pathways [ 28,29 ], impaired ability to clear carcinogens due to obstructive airways [ 30 ] and ongoing chronic inflammation within the airways [ 27,31 ]. SQM is observed in the bronchial epithelium of smokers [ 11 ], but to date there have been, to our knowledge, no studies to quantify it and relate it to the coexistence and severity of COPD. We have previously identified a panel of antibodies, CK7, CK13 and involucrin, that are suitable for identification and distinction of SQM and squamous epithelium in endobronchial biopsies, from tangentially cut epithelium [ 32 ], which is difficult based on morphology alone in small biopsies. CK7 is seen in luminal cells of the pseudostratified epithelium and its expression is lost during SQM and absent in squamous epithelium. CK13 expression is restricted to the basal cells of pseudostratified epithelium but is observed throughout the epithelium with SQM or a squamous phenotype. Involucrin is restricted to cells with a fully differentiated squamous morphology. This staining pattern is summarised in Fig 1 in the results. The aim of the current study was to quantitate (...truncated)


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Helen M. Rigden, Ahmad Alias, Thomas Havelock, Rory O'Donnell, Ratko Djukanovic, Donna E. Davies, Susan J. Wilson. Squamous Metaplasia Is Increased in the Bronchial Epithelium of Smokers with Chronic Obstructive Pulmonary Disease, PLOS ONE, 2016, Volume 11, Issue 5, DOI: 10.1371/journal.pone.0156009