Cigarette smoke extract stimulates epithelial-mesenchymal transition through Src activation

Roflumilast N-oxide inhibits bronchial epithelial to mesenchymal transition induced by cigarette smoke in smokers with COPD

BACKGROUND

Epithelial to mesenchymal transition (EMT) is under discussion as a potential mechanism of small airway remodelling in COPD. In bronchial epithelium of COPD and smokers markers of EMT were described. In vitro, EMT may be reproduced by exposing well-differentiated human bronchial epithelial cells (WD-HBEC) to cigarette smoke extract (CSE). EMT may be mitigated by an increase in cellular cAMP.

OBJECTIVE

This study explored the effects of roflumilast N-oxide, a PDE4 inhibitor on CSE-induced EMT in WD-HBEC and in primary bronchial epithelial cells from smokers and COPD in vitro.

METHODS

WD-HBEC from normal donors were stimulated with CSE (2.5%) for 72 h in presence of roflumilast N-oxide (2 nM or 1 μM) or vehicle. mRNA and protein of EMT markers αSMA, vimentin, collagen-1, E-cadherin, ZO-1, KRT5 as well as NOX4 were quantified by real-time quantitative PCR or protein array, respectively. Phosphorylated and total ERK1/2 and Smad3 were assessed by protein array. cAMP and TGFβ1 were measured by ELISA. Reactive oxygen species (ROS) were determined by DCF fluorescence, after 30 min CSE (2.5%). Apoptosis was measured with Annexin V/PI labelling. In some experiments, EMT markers were determined in monolayers of bronchial epithelial cells from smokers, COPD versus controls.

RESULTS

Roflumilast N-oxide protected from CSE-induced EMT in WD-HBEC. The PDE4 inhibitor reversed both the increase in mesenchymal and the loss in epithelial EMT markers. Roflumilast N-oxide restored the loss in cellular cAMP following CSE, reduced ROS, NOX4 expression, the increase in TGFβ1 release, phospho ERK1/2 and Smad3. The PDE4 inhibitor partly protected from the increment in apoptosis with CSE. Finally the PDE4 inhibitor decreased mesenchymal yet increased epithelial phenotype markers in HBEC of COPD and smokers.

CONCLUSIONS

Roflumilast N-oxide may mitigate epithelial-mesenchymal transition in bronchial epithelial cells in vitro.

Cigarette smoke induces epithelial to mesenchymal transition and increases the metastatic ability of breast cancer cells

Background

Recent epidemiological studies demonstrate that both active and involuntary exposure to tobacco smoke increase the risk of breast cancer. Little is known, however, about the molecular mechanisms by which continuous, long term exposure to tobacco smoke contributes to breast carcinogenesis because most previous studies have focused on short term treatment models. In this work we have set out to investigate the progressive transforming effects of tobacco smoke on non-tumorigenic mammary epithelial cells and breast cancer cells using in vitro and in vivo models of chronic cigarette smoke exposure.

Results

We show that both non-tumorigenic (MCF 10A, MCF-12A) and tumorigenic (MCF7) breast epithelial cells exposed to cigarette smoke acquire mesenchymal properties such as fibroblastoid morphology, increased anchorage-independent growth, and increased motility and invasiveness. Moreover, transplantation experiments in mice demonstrate that treatment with cigarette smoke extract renders MCF 10A cells more capable to survive and colonize the mammary ducts and MCF7 cells more prone to metastasize from a subcutaneous injection site, independent of cigarette smoke effects on the host and stromal environment. The extent of transformation and the resulting phenotype thus appear to be associated with the differentiation state of the cells at the time of exposure. Analysis by flow cytometry showed that treatment with CSE leads to the emergence of a CD44^hi/CD24^low population in MCF 10A cells and of CD44⁺ and CD49f ⁺ MCF7 cells, indicating that cigarette smoke causes the emergence of cell populations bearing markers of self-renewing stem-like cells. The phenotypical alterations induced by cigarette smoke are accompanied by numerous changes in gene expression that are associated with epithelial to mesenchymal transition and tumorigenesis.

Conclusions

Our results indicate that exposure to cigarette smoke leads to a more aggressive and transformed phenotype in human mammary epithelial cells and that the differentiation state of the cell at the time of exposure may be an important determinant in the phenotype of the final transformed state.

Activation of uPAR is required for cigarette smoke extract-induced epithelial-mesenchymal transition in lung epithelial cells

Cigarette smoke is a major risk factor for lung cancer, which may contribute to lung cancer invasion and metastasis. However, the mechanism remains unclear. Epithelial-mesenchymal transition (EMT) is a critical phenotypic alteration of cells that triggers invasion and metastasis. The urokinase-type plasminogen activator receptor (uPAR) is originally thought to assist the directional invasion of migrating cells, and increasing evidences show that overexpression of uPAR in cancer cells promotes EMT. Therefore, we intend to study the role of uPAR in cigarette smoke extract (CSE)-induced EMT in lung epithelial cells. In this study, we showed that lung epithelial cells cultured after CSE treatment demonstrated changes consistent with EMT. E-cadherin was decreased, while vimentin, N-cadherin, and α-SMA expression was increased in both A549 and BEAS-2B cells. Cells acquired a mesenchymal-like morphology and increased cell motility and invasion. In addition, CSE-induced EMT was accompanied by increased expression of uPAR and activation of AKT downstream of uPAR. CSE-induced EMT and activation of AKT were blocked by uPAR gene silencing. Antagonizing PI3K also inhibits development of CSE-induced EMT. We conclude that CSE can induce EMT, and the activity of uPAR-dependent signal pathway in EMT is recapitulated in lung epithelial cells in vitro.

EMT and interstitial lung disease: a mysterious relationship

PURPOSE OF REVIEW

Pathogenesis of interstitial lung diseases (ILD) has largely been investigated in the context of the most frequent ILD, idiopathic pulmonary fibrosis (IPF). We review studies of epithelial-to-mesenchymal transition (EMT) and discuss its potential contribution to collagen-producing (myo)fibroblasts in IPF.

RECENT FINDINGS

Endoplasmic reticulum (ER) stress leading to epithelial apoptosis has been reported as a potential etiologic factor in fibrosis. Recent studies further suggest EMT as a link between ER stress and fibrosis. Combinatorial interactions among Smad3, β-catenin and other transcriptional co-activators at the α-smooth muscle actin (α-SMA) promoter provide direct evidence for crosstalk between transforming growth factor-β (TGFβ) and β-catenin pathways during EMT. Lineage tracing yielded conflicting results, with two recent studies supporting and one opposing a role for EMT in lung fibrosis.

SUMMARY

Advances have been made in elucidating causes and mechanisms of EMT, potentially leading to new treatment options, although contributions of EMT to lung fibrosis in vivo remain controversial. In addition to EMT providing a direct source of (myo)fibroblasts, expression of mesenchymal markers may reflect epithelial injury, in which case inhibition of EMT might be deleterious. EMT-derived cells may also contribute to aberrant epithelial-mesenchymal crosstalk that promotes fibrogenesis.

Resveratrol inhibits TGF-β1-induced epithelial-to-mesenchymal transition and suppresses lung cancer invasion and metastasis

Epithelial-to-mesenchymal transition (EMT) is a cellular process during which epithelial polarized cells become motile mesenchymal-appearing cells, which in turn promotes carcinoma invasion and metastasis. Resveratrol (trans-3,4',5-trihydroxystilbene) is a natural polyphenolic compound found in grapes, red wine and several other plants. Numerous reports in the literature indicate that resveratrol can suppress cancer invasion and metastasis. However, the underlying mechanisms of inhibiting metastasis by resveratrol are complex, not fully elucidated and the subject of intense scientific debate. Despite evidence indicating that EMT can be a target for resveratrol, little is known about the effect of resveratrol on lung cancer cells. Our previous studies demonstrated that TGF-β1 induces EMT to promote lung adenocarcinoma invasion and metastasis. To understand the repressive role of resveratrol in lung cancer invasion and metastasis, we sought to investigate the potential use of resveratrol as an inhibitor of TGF-β1-induced EMT development in A549 lung cancer cells in vitro. Here we show that when A549 cells are treated with TGF-β1 and resveratrol, the latter inhibits the initiation of TGF-β1-induced EMT. Our results show that 20 μM resveratrol increases expression of the epithelial phenotype marker E-cadherin and represses the expression of the mesenchymal phenotype markers, Fibronectin and Vimentin during the initiation of TGF-β1-induced EMT. Resveratrol also inhibits expression of EMT-inducing transcription factors Snail1 and Slug, although the expression of the Twist1 transcription factor remained unchanged. Resveratrol inhibits the TGF-β1-induced increase in cell adhesion, migration and invasion of A549 lung cancer cells. Taken together, our findings provide new evidence that resveratrol suppresses lung cancer invasion and metastasis in vitro through inhibiting TGF-β1-induced EMT.

Proteasome inhibition augments cigarette smoke-induced GM-CSF expression in trophoblast cells via the epidermal growth factor receptor

Maternal cigarette smoking has adverse effects on pregnancy outcomes. The granulocyte-macrophage colony-stimulating factor (GM-CSF) is an essential cytokine for a normal pregnancy. We investigated the impact of cigarette smoke extract (CSE) on GM-CSF expression in human cytotrophoblast cells and suggested a cellular mechanism underlying the CSE-induced GM-CSF expression. An immortalized normal human trophoblast cell line (B6Tert-1) was treated with CSE. The viability and proliferation of the CSE-treated B6Tert-1 cells were evaluated, and the expression of GM-CSF in these cells was quantified at the mRNA and the protein levels by means of reverse-transcription and quantitative polymerase chain reaction (RT-qPCR); and enzyme-linked immunosorbent assay (ELISA), respectively. Human trophoblast cells treated with CSE had an increased expression of GM-CSF at both the mRNA and the protein levels. The CSE-induced GM-CSF expression was synergistically enhanced by the addition of the proteasome inhibitor MG-132, but inhibited by AG-1478, an inhibitor of the epidermal growth factor receptor (EGFR) kinase. Furthermore, CSE treatment increased the phosphorylation of the extracellular-signal regulated kinases (ERK1/2) in the trophoblast cells. The expression of other growth factors such as heparin-binding epidermal growth factor-like growth factor (HB-EGF) and vascular endothelial growth factor (VEGF) was also evaluated. Our data suggested that cigarette smoking and proteasome inhibition synergistically up-regulate GM-CSF cytokine expression by activating the EGFR signaling pathway.