Proliferation genes repressed by TGF-β are downstream of Slug/Snail2 in normal bronchial epithelial progenitors and are deregulated in COPD

Abstract

Slug/Snail2 belongs to the Epithelial-Mesenchymal Transition (EMT)-inducing transcription factors involved in development and diseases. Slug is expressed in adult stem/progenitor cells of several epithelia, making it unique among these transcription factors. To investigate Slug role in human bronchial epithelium progenitors, we studied primary bronchial basal/progenitor cells in an air-liquid interface culture system that allows regenerating a bronchial epithelium. To identify Slug downstream genes we knocked down Slug in basal/progenitor cells from normal subjects and subjects with COPD, a respiratory disease presenting anomalies in the bronchial epithelium and high levels of TGF-{beta} in the lungs. We show that normal and COPD bronchial basal/progenitors, even when treated with TGF-{beta}, express both epithelial and mesenchymal markers, and that the epithelial marker E-cadherin is not a target of Slug and, moreover, positively correlates with Slug. We reveal that Slug downstream genes responding to both differentiation and TGF-{beta} are different in normal and COPD progenitors, with in particular a set of proliferation-related genes that are among the genes repressed downstream of Slug in normal but not COPD. In COPD progenitors at the onset of differentiation in presence of TGF-{beta}, we show that there is positive correlations between the effect of differentiation and TGF-{beta} on proliferation-related genes and on Slug protein, and that their expression levels are higher than in normal cells. As well, the expression of Smad3 and {beta}-Catenin, two molecules from TGF-{beta} signaling pathways, are higher in COPD progenitors, and our results indicate that proliferation-related genes and Slug protein are increased by different TGF-{beta}-induced mechanisms. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/674127v2_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@524a15org.highwire.dtl.DTLVardef@7dd1e5org.highwire.dtl.DTLVardef@5f3798org.highwire.dtl.DTLVardef@13ae179_HPS_FORMAT_FIGEXP M_FIG C_FIG