Expression of transforming growth factor-alpha and epidermal growth factor receptor is increased following bleomycin-induced lung injury in rats

Type 2 innate lymphoid cell-derived amphiregulin regulates type II alveolar epithelial cell transdifferentiation in a mouse model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a common complication in preterm infants characterized by alveolar growth arrest. Interleukin (IL)-33 and type 2 innate lymphoid cell (ILC2) affect type II alveolar epithelial cell (AECII) differentiation in BPD mice and may cause increased lung epithelial-mesenchymal transition (EMT). Amphiregulin (AREG) can be produced by ILC2 and is associated with tissue repair. However, the action mechanism of AREG produced by ILC2 to alveolar development in BPD is unclear. In this study, we aimed to demonstrate the role and mechanism of AREG in influencing AECII transdifferentiation in the lung tissue of BPD mice. The effects of ILC2-derived AREG on AECII transdifferentiation were verified in vivo and in vitro, and the role of IL-33 on ILC2-derived AREG in AECII transdifferentiation in BPD mice and a preliminary investigation of the role of AREG's receptor-epidermal growth factor receptor (EGFR) on AECII transdifferentiation. The results showed that neonatal mice developed severe lung injury after hyperoxia, and IL-33 induced AREG production via ILC2 affected normal AECII differentiation and promoted EMT. In addition, the blockade of EGFR was found to alleviate the impaired AECII differentiation under hyperoxia in an in vitro study. In summary, our study demonstrates that AREG secreted by ILC2 affects AECII transdifferentiation in BPD mice, which provides a new idea for the clinical treatment of BPD.

Downregulation of amphiregulin improves cardiac hypertrophy via attenuating oxidative stress and apoptosis

Amphiregulin (AREG) is a ligand of epidermal growth factor receptor and participates in the fibrosis of multiple organs. However, whether AREG can regulate hypertrophic cardiomyopathy is not well known. This research aims to explore the effect of AREG on cardiac hypertrophy, and whether the oxidative stress and apoptosis was involved in the influence of AREG on cardiac hypertrophy. Angiotensin (Ang) II induced cardiac hypertrophy in mice and neonatal rat cardiomyocytes (NRCMs) or HL-1 cells in vitro. AREG expressions raised in the heart of mice. After AREG downregulation, the increases of Ang II induced cardiac weight and cardiomyocytes area were inhibited. Down-regulation of AREG could inhibit Ang II induced the increases of atrial natriuretic peptide, brain natriuretic peptide, beta-myosin heavy chain in the heart of mice, and NRCMs and HL-1 cells. The enhancement of oxidative stress in mice heart with Ang II treatment was alleviated by AREG knockdown. The raises of Ang II induced Bax and cleaved caspase3 in mice heart were inhibited by AREG downregulation. AREG downregulation reduced myocardial hypertrophy via inhibition of oxidative and apoptosis. AREG may be a target for future cardiac hypertrophy treatment.

Evaluation and Characterization of Post-Stroke Lung Damage in a Murine Model of Cerebral Ischemia

After stroke and other brain injuries, there is a high incidence of respiratory complications such as pneumonia or acute lung injury. The molecular mechanisms that drive the brain-lung interaction post-stroke have not yet been elucidated. We performed transient middle cerebral artery occlusion (MCAO) and sham surgery on C57BL/6J mice and collected bronchoalveolar lavage fluid (BALF), serum, brain, and lung homogenate samples 24 h after surgery. A 92 proteins-panel developed by Olink Proteomics® was used to analyze the content in BALF and lung homogenates. MCAO animals had higher protein concentration levels in BALF than sham-controls, but these levels did not correlate with the infarct volume. No alteration in alveolar-capillary barrier permeability was observed. A total of 12 and 14 proteins were differentially expressed between the groups (FDR < 0.1) in BALF and lung tissue homogenates, respectively. Of those, HGF, TGF-α, and CCL2 were identified as the most relevant to this study. Their protein expression patterns were verified by ELISA. This study confirmed that post-stroke lung damage was not associated with increased lung permeability or cerebral ischemia severity. Furthermore, the dysregulation of HGF, TGF-α, and CCL2 in BALF and lung tissue after ischemia could play an important role in the molecular mechanisms underlying stroke-induced lung damage.

EGFR Signaling in Lung Fibrosis

In this review article, we will first provide a brief overview of the ErbB receptor-ligand system and its importance in developmental and physiological processes. We will then review the literature regarding the role of ErbB receptors and their ligands in the maladaptive remodeling of lung tissue, with special emphasis on idiopathic pulmonary fibrosis (IPF). Here we will focus on the pathways and cellular processes contributing to epithelial-mesenchymal miscommunication seen in this pathology. We will also provide an overview of the in vivo studies addressing the efficacy of different ErbB signaling inhibitors in experimental models of lung injury and highlight how such studies may contribute to our understanding of ErbB biology in the lung. Finally, we will discuss what we learned from clinical applications of the ErbB1 signaling inhibitors in cancer in order to advance clinical trials in IPF.

Multiomic study of skin, peripheral blood, and serum: is serum proteome a reflection of disease process at the end-organ level in systemic sclerosis?

BACKGROUND

Serum proteins can be readily assessed during routine clinical care. However, it is unclear to what extent serum proteins reflect the molecular dysregulations of peripheral blood cells (PBCs) or affected end-organs in systemic sclerosis (SSc). We conducted a multiomic comparative analysis of SSc serum profile, PBC, and skin gene expression in concurrently collected samples.

METHODS

Global gene expression profiling was carried out in skin and PBC samples obtained from 49 SSc patients enrolled in the GENISOS observational cohort and 25 unaffected controls. Levels of 911 proteins were determined by Olink Proximity Extension Assay in concurrently collected serum samples.

RESULTS

Both SSc PBC and skin transcriptomes showed a prominent type I interferon signature. The examination of SSc serum profile revealed an upregulation of proteins involved in pro-fibrotic homing and extravasation, as well as extracellular matrix components/modulators. Notably, several soluble receptor proteins such as EGFR, ERBB2, ERBB3, VEGFR2, TGFBR3, and PDGF-Rα were downregulated. Thirty-nine proteins correlated with severity of SSc skin disease. The differential expression of serum protein in SSc vs. control comparison significantly correlated with the differential expression of corresponding transcripts in skin but not in PBCs. Moreover, the differentially expressed serum proteins were significantly more connected to the Well-Associated-Proteins in the skin than PBC gene expression dataset. The assessment of the concordance of between-sample similarities revealed that the molecular profile of serum proteins and skin gene expression data were significantly concordant in patients with SSc but not in healthy controls.

CONCLUSIONS

SSc serum protein profile shows an upregulation of profibrotic cytokines and a downregulation of soluble EGF and other key receptors. Our multilevel comparative analysis indicates that the serum protein profile in SSc correlates more closely with molecular dysregulations of skin than PBCs and might serve as a reflection of disease severity at the end-organ level.

Repurposing Anticancer Drugs for the Treatment of Idiopathic Pulmonary Fibrosis and Antifibrotic Drugs for the Treatment of Cancer: State of the Art

Idiopathic pulmonary fibrosis (IPF) is an aggressive pulmonary disease which shares several molecular, pathophysiological and clinical aspects with lung cancer, including high mortality rates. The antifibrotic drugs Nintedanib and Pirfenidone have recently been introduced in clinical practice for the treatment of IPF. Nintedanib is also used for the treatment of several malignancies, including non-small cell lung cancer (NSCLC) in combination with Docetaxel, while Pirfenidone showed some anti-neoplastic effects in preclinical studies. On the other hand, novel targeted agents and immunotherapies have been introduced in the last decade for the treatment of NSCLC, and some of them showed anti-fibrotic properties in recent studies. These evidences, based on the common pathophysiological backgrounds of IPF and lung cancer, make possible the mutual or combined use of anti-fibrotic and anti-neoplastic drugs to treat these highly lethal diseases. The aim of the present review is to depict the current scientific landscape regarding the repurposing of anti-neoplastic drugs in IPF and anti-fibrotic drugs in lung cancer, and to identify future research perspectives on the topic.

Growth Hormone-Releasing Hormone in Lung Physiology and Pulmonary Disease

Growth hormone-releasing hormone (GHRH) is secreted primarily from the hypothalamus, but other tissues, including the lungs, produce it locally. GHRH stimulates the release and secretion of growth hormone (GH) by the pituitary and regulates the production of GH and hepatic insulin-like growth factor-1 (IGF-1). Pituitary-type GHRH-receptors (GHRH-R) are expressed in human lungs, indicating that GHRH or GH could participate in lung development, growth, and repair. GHRH-R antagonists (i.e., synthetic peptides), which we have tested in various models, exert growth-inhibitory effects in lung cancer cells in vitro and in vivo in addition to having anti-inflammatory, anti-oxidative, and pro-apoptotic effects. One antagonist of the GHRH-R used in recent studies reviewed here, MIA-602, lessens both inflammation and fibrosis in a mouse model of bleomycin lung injury. GHRH and its peptide agonists regulate the proliferation of fibroblasts through the modulation of extracellular signal-regulated kinase (ERK) and Akt pathways. In addition to downregulating GH and IGF-1, GHRH-R antagonist MIA-602 inhibits signaling pathways relevant to inflammation, including p21-activated kinase 1-signal transducer and activator of transcription 3/nuclear factor-kappa B (PAK1-STAT3/NF-κB and ERK). MIA-602 induces fibroblast apoptosis in a dose-dependent manner, which is an effect that is likely important in antifibrotic actions. Taken together, the novel data reviewed here show that GHRH is an important peptide that participates in lung homeostasis, inflammation, wound healing, and cancer; and GHRH-R antagonists may have therapeutic potential in lung diseases.

The Importance of Tyrosine Phosphorylation Control of Cellular Signaling Pathways in Respiratory Disease: pY and pY Not

Reversible phosphorylation of proteins on tyrosine residues is an essential signaling mechanism by which diverse cellular processes are closely regulated. The tight temporal and spatial control of the tyrosine phosphorylation status of proteins by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) is critical to cellular homeostasis as well as to adaptations to the external environment. Via regulation of cellular signaling cascades involving other protein kinases and phosphatases, receptors, adaptor proteins, and transcription factors, PTKs and PTPs closely control diverse cellular processes such as proliferation, differentiation, migration, inflammation, and maintenance of cellular barrier function. Given these key regulatory roles, it is not surprising that dysfunction of PTKs and PTPs is important in the pathogenesis of human disease, including many pulmonary diseases. The roles of various PTKs and PTPs in acute lung injury and repair, pulmonary fibrosis, pulmonary vascular disease, and inflammatory airway disease are discussed in this review. It is important to note that although there is overlap among many of these proteins in various disease states, the mechanisms by which they influence the pathogenesis of these conditions differ, suggesting wide-ranging roles for these enzymes and their potential as therapeutic targets.

Molecular Mechanisms of Pulmonary Fibrogenesis and Its Progression to Lung Cancer: A Review

Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause, occurring primarily in older adults, and limited to the lungs. Despite the increasing research interest in the pathogenesis of IPF, unfavorable survival rates remain associated with this condition. Recently, novel therapeutic agents have been shown to control the progression of IPF. However, these drugs do not improve lung function and have not been tested prospectively in patients with IPF and coexisting lung cancer, which is a common comorbidity of IPF. Optimal management of patients with IPF and lung cancer requires understanding of pathogenic mechanisms and molecular pathways that are common to both diseases. This review article reflects the current state of knowledge regarding the pathogenesis of pulmonary fibrosis and summarizes the pathways that are common to IPF and lung cancer by focusing on the molecular mechanisms.

Anticancer therapy and lung injury: molecular mechanisms

INTRODUCTION

Chemotherapy and radiation therapy are two mainstream strategies applied in the treatment of cancer that is not operable. Patients with hematological or solid tumor malignancies substantially benefit from chemotherapeutic drugs and/or ionizing radiation delivered to the site of malignancy. However, considerable adverse effects, including lung inflammation and fibrosis, are associated with the use of these treatment modalities. Areas covered: As we move toward the era of precision health, we are compelled to understand the molecular basis of chemoradiation-induced pathological lung remodeling and to develop effective treatment strategies that mitigate the development of chronic lung disease (i.e. fibrosis) in cancer patients. The review discusses chemotherapeutic agents that are reported to induce or associate with acute and/or chronic lung injury. Expert commentary: There is a need to molecularly understand how chemotherapeutic drugs induce or associate with respiratory toxicities and whether such characteristics are inherently related to their antitumor effect or are collateral. Once such mechanisms have been identified and/or fully characterized, they may be able to guide disease-management decisions including effective intervention strategies for the adverse effects. In the meantime, radiation oncologists should be judicious on the dose of radiation delivered to the lungs, the volume of lung irradiated, and concurrent use of chemotherapeutic drugs.

Amphiregulin enhances cardiac fibrosis and aggravates cardiac dysfunction in mice with experimental myocardial infarction partly through activating EGFR-dependent pathway

Cardiac fibrosis (CF), a main process of ventricular remodeling after myocardial infarction (MI), plays a crucial role in the pathogenesis of heart failure (HF) post-MI. It is known that amphiregulin (AR) is involved in fibrosis of several organs. However, the expression of AR and its role post-MI are yet to be determined. This study aimed to investigate the impact of AR on CF post-MI and related mechanisms. Significantly upregulated AR expression was evidenced in the infarct border zone of MI mice in vivo and the AR secretion was enhanced in macrophages, but not in cardiac fibroblasts. In vitro, treatment with AR increased cardiac fibroblast migration, proliferation and collagen synthesis, and upregulated the expression of epidermal growth factor receptor (EGFR) and the downstream genes such as Akt, ERK1/2 and Samd2/3 on cardiac fibroblasts. All these effects could be abrogated by pretreatment with a specific EGFR inhibitor. To verify the functions of AR in MI hearts, lentivirus-AR-shRNA and negative control vectors were delivered into the infarct border zone. After 28 days, knock-down of AR increased the survival rate and improved cardiac function, while decreasing the extent of myocardial fibrosis of MI mice. Moreover, EGFR and the downstream genes were significantly downregulated in lentivirus-AR-shRNA treated MI mice. Our results thus indicate that AR plays an important role in promoting CF after MI partly though activating the EGFR pathway. Targeting AR might be a novel therapeutic option for attenuating CF and improve cardiac function after MI.

Expression and Function of the Epidermal Growth Factor Receptor in Physiology and Disease

The epidermal growth factor receptor (EGFR) is the prototypical member of a family of membrane-associated intrinsic tyrosine kinase receptors, the ErbB family. EGFR is activated by multiple ligands, including EGF, transforming growth factor (TGF)-α, HB-EGF, betacellulin, amphiregulin, epiregulin, and epigen. EGFR is expressed in multiple organs and plays important roles in proliferation, survival, and differentiation in both development and normal physiology, as well as in pathophysiological conditions. In addition, EGFR transactivation underlies some important biologic consequences in response to many G protein-coupled receptor (GPCR) agonists. Aberrant EGFR activation is a significant factor in development and progression of multiple cancers, which has led to development of mechanism-based therapies with specific receptor antibodies and tyrosine kinase inhibitors. This review highlights the current knowledge about mechanisms and roles of EGFR in physiology and disease.

Immunohistochemical localization of epidermal growth factor system in the lung of the Japanese quail (Coturnix coturnix japonica) during the post-hatching period

The purpose of this study is to determine the possible changes in the localization of the four Epidermal Growth Factor Receptors and three ligands in quail lungs from the first day of hatching until the 125th after hatching using immunohistochemical methods. Immunohistochemical results demonstrated that four EGFRs and their ligands are chiefly located in the cytoplasm of cells. Additionally, ErbB4, AREG, and NRG1 are localized to the nucleus and nucleolus, but EGF is present in the nucleolus. ErbB2 was also found in the cell membrane. In the epithelium of secondary bronchi, the goblet cells only exhibited ErbB1 and ErbB2, whereas the basal and ciliated cells exhibited EGFRs and ligands immunoreactivity. The atrial granular cells displayed moderate levels of ErbB1-ErbB3 and EGF and strong levels of ErbB4, AREG, and NRG1 immunoreactivity. While the squamous atrial cells and squamous respiratory cells of air capillaries and endothelial cells of blood capillaries exhibited moderate to strong ErbB2, ErbB4, AREG, and NRG1 immunoreactivity, they had negative or weak ErbB1, ErbB3, and EGF immunoreactivity. The expression levels of ErbB2-ErbB4, EGF, AREG, and NRG1 were also detected in fibroblasts. Although ErbB2 was highly expressed in the bronchial and vascular smooth muscle cells, weak expression of ErbB1, ErbB3, AREG and EGF and moderate expression of ErbB4 and NRG1 were observed. Macrophages were only negative for ErbB1. In conclusion, these data indicate that the EGFR-system is functionally active at hatching, which supports the hypothesis that the members of EGFR-system play several cell-specific roles in quail lung growth after hatching.

The role of tyrosine kinases in the pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with a median survival time from diagnosis of 2-3 years. Although the pathogenic pathways have not been fully elucidated, IPF is believed to be caused by persistent epithelial injury in genetically susceptible individuals. Tyrosine kinases are involved in a range of signalling pathways that are essential for cellular homeostasis. However, there is substantial evidence from in vitro studies and animal models that receptor tyrosine kinases, such as the platelet-derived growth factor receptor, vascular endothelial growth factor receptor and fibroblast growth factor receptor, and non-receptor tyrosine kinases, such as the Src family, play critical roles in the pathogenesis of pulmonary fibrosis. For example, the expression and release of tyrosine kinases are altered in patients with IPF, while specific tyrosine kinases stimulate the proliferation of lung fibroblasts in vitro. Agents that inhibit tyrosine kinases have shown anti-fibrotic and anti-inflammatory effects in animal models of pulmonary fibrosis. Recently, the tyrosine kinase inhibitor nintedanib has shown positive results in two phase III trials in patients with IPF. Here, we summarise the evidence for involvement of specific tyrosine kinases in the pathogenesis of IPF and the development of tyrosine kinase inhibitors as treatments for IPF.

Pulmonary epithelial barrier function: some new players and mechanisms

The pulmonary epithelium serves as a barrier to prevent access of the inspired luminal contents to the subepithelium. In addition, the epithelium dictates the initial responses of the lung to both infectious and noninfectious stimuli. One mechanism by which the epithelium does this is by coordinating transport of diffusible molecules across the epithelial barrier, both through the cell and between cells. In this review, we will discuss a few emerging paradigms of permeability changes through altered ion transport and paracellular regulation by which the epithelium gates its response to potentially detrimental luminal stimuli. This review is a summary of talks presented during a symposium in Experimental Biology geared toward novel and less recognized methods of epithelial barrier regulation. First, we will discuss mechanisms of dynamic regulation of cell-cell contacts in the context of repetitive exposure to inhaled infectious and noninfectious insults. In the second section, we will briefly discuss mechanisms of transcellular ion homeostasis specifically focused on the role of claudins and paracellular ion-channel regulation in chronic barrier dysfunction. In the next section, we will address transcellular ion transport and highlight the role of Trek-1 in epithelial responses to lung injury. In the final section, we will outline the role of epithelial growth receptor in barrier regulation in baseline, acute lung injury, and airway disease. We will then end with a summary of mechanisms of epithelial control as well as discuss emerging paradigms of the epithelium role in shifting between a structural element that maintains tight cell-cell adhesion to a cell that initiates and participates in immune responses.

Transforming growth factor alpha is a critical mediator of radiation lung injury

Radiation fibrosis of the lung is a late toxicity of thoracic irradiation. Epidermal growth factor (EGF) signaling has previously been implicated in radiation lung injury. We hypothesized that TGF-α, an EGF receptor ligand, plays a key role in radiation-induced fibrosis in lung. Mice deficient in transforming growth factor (TGF-α(-/-)) and control C57Bl/6J (C57-WT) mice were exposed to thoracic irradiation in 5 daily fractions of 6 Gy. Cohorts of mice were followed for survival (n ≥ 5 per group) and tissue collection (n = 3 per strain and time point). Collagen accumulation in irradiated lungs was assessed by Masson's trichrome staining and analysis of hydroxyproline content. Cytokine levels in lung tissue were assessed with ELISA. The effects of TGF-α on pneumocyte and fibroblast proliferation and collagen production were analyzed in vitro. Lysyl oxidase (LOX) expression and activity were measured in vitro and in vivo. Irradiated C57-WT mice had a median survival of 24.4 weeks compared to 48.2 weeks for irradiated TGF-α(-/-) mice (P = 0.001). At 20 weeks after irradiation, hydroxyproline content was markedly increased in C57-WT mice exposed to radiation compared to TGF-α(-/-) mice exposed to radiation or unirradiated C57-WT mice (63.0, 30.5 and 37.6 μg/lung, respectively, P = 0.01). C57-WT mice exposed to radiation had dense foci of subpleural fibrosis at 20 weeks after exposure, whereas the lungs of irradiated TGF-α (-/-) mice were largely devoid of fibrotic foci. Lung tissue concentrations of IL-1β, IL-4, TNF-α, TGF-β and EGF at multiple time points after irradiation were similar in C57-WT and TGF-α(-/-) mice. TGF-α in lung tissue of C57-WT mice rose rapidly after irradiation and remained elevated through 20 weeks. TGF-α(-/-) mice had lower basal LOX expression than C57-WT mice. Both LOX expression and LOX activity were increased after irradiation in all mice but to a lesser degree in TGF-α(-/-) mice. Treatment of NIH-3T3 fibroblasts with TGF-α resulted in increases in proliferation, collagen production and LOX activity. These studies identify TGF-α as a critical mediator of radiation-induced lung injury and a novel therapeutic target in this setting. Further, these data implicate TGF-α as a mediator of collagen maturation through a TGF-β independent activation of lysyl oxidase.

Risk of interstitial lung disease associated with EGFR-TKIs in advanced non-small-cell lung cancer: a meta-analysis of 24 phase III clinical trials

PURPOSE

To assess the risk of interstitial lung disease (ILD) with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) gefitinib, erlotinib, and afatinib.

METHOD

PubMed databases were searched for relevant articles. Statistical analyses were conducted to calculate the summary incidence, odds ratio (OR), and 95% confidence intervals (CIs) by using either random-effects or fixed-effect models.

RESULTS

The incidence of all-grade and high-grade (≧ grade 3) ILD associated with EGFR-TKIs was 1.6% (95% CI, 1.0-2.4%) and 0.9% (95% CI, 0.6%-1.4%), with a mortality of 13.0% (95% CI, 7.6-21.6%). Patients treated with EGFR-TKIs had a significantly increased risk of developing all-grade (OR, 1.74; 95% CI, 1.25-2.43; P = 0.001) and high-grade (OR, 4.38; 95% CI, 2.18-8.79; P<0.001) ILD. No significant difference in the risk of ILD was found in sub-group analysis according to EGFR-TKIs, percentage of EGFR mutation, study location, EGFR-TKIs-based regimens, and controlled therapy.

CONCLUSIONS

Treatment with EGFR-TKIs is associated with a significantly increased risk of developing ILD.

Inhibition of the αvβ6 integrin leads to limited alteration of TGF-α-induced pulmonary fibrosis

A number of growth factors and signaling pathways regulate matrix deposition and fibroblast proliferation in the lung. The epidermal growth factor receptor (EGFR) family of receptors and the transforming growth factor-β (TGF-β) family are active in diverse biological processes and are central mediators in the initiation and maintenance of fibrosis in many diseases. Transforming growth factor-α (TGF-α) is a ligand for the EGFR, and doxycycline (Dox)-inducible transgenic mice conditionally expressing TGF-α specifically in the lung epithelium develop progressive fibrosis accompanied with cachexia, changes in lung mechanics, and marked pleural thickening. Although recent studies demonstrate that EGFR activation modulates the fibroproliferative effects involved in the pathogenesis of TGF-β induced pulmonary fibrosis, in converse, the direct role of EGFR induction of the TGF-β pathway in the lung is unknown. The αvβ6 integrin is an important in vivo activator of TGF-β activation in the lung. Immunohistochemical analysis of αvβ6 protein expression and bronchoalveolar analysis of TGF-β pathway signaling indicates activation of the αvβ6/TGF-β pathway only at later time points after lung fibrosis was already established in the TGF-α model. To determine the contribution of the αvβ6/TGF-β pathway on the progression of established fibrotic disease, TGF-α transgenic mice were administered Dox for 4 wk, which leads to extensive fibrosis; these mice were then treated with a function-blocking anti-αvβ6 antibody with continued administration of Dox for an additional 4 wk. Compared with TGF-α transgenic mice treated with control antibody, αvβ6 inhibition significantly attenuated pleural thickening and altered the decline in lung mechanics. To test the effects of genetic loss of the β6 integrin, TGF-α transgenic mice were mated with β6-null mice and the degree of fibrosis was compared in adult mice following 8 wk of Dox administration. Genetic ablation of the β6 integrin attenuated histological and physiological changes in the lungs of TGF-α transgenic mice although a significant degree of fibrosis still developed. In summary, inhibition of the β6 integrin led to a modest, albeit significant, effect on pleural thickening and lung function decline observed with TGF-α-induced pulmonary fibrosis. These data support activation of the αvβ6/TGF-β pathway as a secondary effect contributing to TGF-α-induced pleural fibrosis and suggest a complex contribution of multiple mediators to the maintenance of progressive fibrosis in the lung.

Understanding the origin, activation and regulation of matrix-producing myofibroblasts for treatment of fibrotic disease

Fibrosis and scar formation results from chronic progressive injury in virtually every tissue and affects a growing number of people around the world. Myofibroblasts drive fibrosis, and recent work has demonstrated that mesenchymal cells, including pericytes and perivascular fibroblasts, are their main progenitors. Understanding the cellular mechanisms of pericyte/fibroblast-to-myofibroblast transition, myofibroblast proliferation and the key signalling pathways that regulate these processes is essential to develop novel targeted therapeutics for the growing patient population suffering from solid organ fibrosis. In this review, we summarize the current knowledge about different progenitor cells of myofibroblasts, discuss major pathways that regulate their transdifferentiation and discuss the current status of novel targeted anti-fibrotic therapeutics in development.

A cytokine axis regulates elastin formation and degradation

Underlying the dynamic regulation of tropoelastin expression and elastin formation in development and disease are transcriptional and post-transcriptional mechanisms that have been the focus of much research. Of particular importance is the cytokine-governed elastin regulatory axis in which the pro-elastogenic activities of transforming growth factor β-1 (TGFβ1) and insulin-like growth factor-I (IGF-I) are opposed by anti-elastogenic activities of basic fibroblast growth factor (bFGF/FGF-2), heparin-binding epidermal growth factor-like growth factor (HB-EGF), EGF, PDGF-BB, TGFα, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β and noncanonical TGFβ1 signaling. A key mechanistic feature of the regulatory axis is that cytokines influence elastin formation through effects on the cell cycle involving control of cyclin-cyclin dependent kinase complexes and activation of the Ras/MEK/ERK signaling pathway. In this article we provide an overview of the major cytokines/growth factors that modulate elastogenesis and describe the underlying molecular mechanisms for their action on elastin production.

Amphiregulin, an epidermal growth factor receptor ligand, plays an essential role in the pathogenesis of transforming growth factor-β-induced pulmonary fibrosis

Dysregulated amphiregulin (AR) expression and EGR receptor (EGFR) activation have been described in animal models of pulmonary fibrosis and in patients with idiopathic pulmonary fibrosis. However, the exact role of AR in the pathogenesis of pulmonary fibrosis has not been clearly defined. Here, we show that a potent profibrogenic cytokine TGF-β1 significantly induced the expression of AR in lung fibroblasts in vitro and in murine lungs in vivo. AR stimulated NIH3T3 fibroblast cell proliferation in a dose-dependent manner. Silencing of AR expression by siRNA or chemical inhibition of EGFR signaling, utilizing AG1478 and gefitinib, significantly reduced the ability of TGF-β1 to stimulate fibroblast proliferation and expression of α-smooth muscle actin, collagen, and other extracellular matrix-associated genes. TGF-β1-stimulated activation of Akt, ERK, and Smad signaling was also significantly inhibited by these interventions. Consistent with these in vitro findings, AR expression was impressively increased in the lungs of TGF-β1 transgenic mice, and either siRNA silencing of AR or chemical inhibition of EGFR signaling significantly reduced TGF-β1-stimulated collagen accumulation in the lung. These studies showed a novel regulatory role for AR in the pathogenesis of TGF-β1-induced pulmonary fibrosis. In addition, these studies suggest that AR, or AR-activated EGFR signaling, is a potential therapeutic target for idiopathic pulmonary fibrosis associated with TGF-β1 activation.

Successful treatment of gefitinib-induced acute interstitial pneumonitis with corticosteroid and non-invasive BIPAP-ventilation

This is the case of a 63 year-old male who was diagnosed adenocarcinoma in the left upper lung with ipsilateral malignant pleural effusion. At diagnosis it had already spread to left pulmonary HLN (hilar lymph node) and left supraclavicular lymph node and mediastinal lymph nodes. The patient received combined chemotherapy with bevacizumab and GP (gemcitabine and carboplatin) for 6 courses. Disease progression on chest CT scan was recognized, daily treatment with oral gefitinib (250 mg/day) was commenced. One week later, he was admitted under the impression of gefitinib-related interstitial pneumonitis, gefitinib was discontinued immediately and methylprednisolone with BIPAP assisted ventilation were used. The patient was followed up for 2 months after the start of treatment with corticosteroids and BIPAP assisted ventilation and remained well.

Molecular mechanisms of lung-specific toxicity induced by epidermal growth factor receptor tyrosine kinase inhibitors

Lung-specific toxicity induced by epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) for the treatment of non-small cell lung cancer (NSCLC) has emerged as a critical side-effect. Although the clinical features of the pulmonary side-effects of TKIs have been characterized, the details of the molecular mechanisms in the development of this lung-specific toxicity remain to be elucidated. EGFR-dependent epithelial regeneration and restoration plays an important role in the recovery process from lung injury. The lung comprises a unique environment where epithelial cells are exposed to internal agents in the systemic circulation and to airborne particles through the mouth and nose. This unique environment may also be associated with the development of lung-specific toxicity induced by EGFR-TKIs. Therefore, the aim of this review was to provide further insight into the molecular mechanisms of lung-specific toxicity in the context of treatment with EGFR-TKIs.

Tyrosine kinase signaling in fibrotic disorders: Translation of basic research to human disease

Tyrosine kinases regulate a broad variety of physiological cell processes, including metabolism, growth, differentiation and apoptosis. Abnormal tyrosine kinase activity disturbs the physiological cell homeostasis and can lead to cancer, vascular disease, and fibrosis. In regard to fibrosis, different tyrosine kinases have been identified as determinants of disease progression and potential targets for anti-fibrotic therapies. This includes both receptor tyrosine kinases (e.g., PDGF receptor, VEGF receptor, EGF receptor, and JAK kinases) as well as non-receptor tyrosine kinases (e.g., c-Abl, c-Kit, and Src kinases). Given their central role in the pathogenesis of fibrosis, researchers of our field study the anti-fibrotic effects of monoclonal antibodies or small-molecule inhibitors to block the aberrant tyrosine kinase activity and treat fibrosis in preclinical models of various fibrotic diseases (e.g., idiopathic pulmonary fibrosis, renal fibrosis, liver fibrosis, and dermal fibrosis). The results of these studies were promising and prompted clinical trials with different compounds in fibrotic diseases. So far, results from studies with intedanib in idiopathic pulmonary fibrosis and imatinib in idiopathic pulmonary fibrosis and systemic sclerosis have been reported. Although none of these studies reported a positive primary outcome, promising trends in anti-fibrotic efficacy awaken our hopes for a new class of effective anti-fibrotic targeted therapies. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Construction of a computable cell proliferation network focused on non-diseased lung cells

BACKGROUND

Critical to advancing the systems-level evaluation of complex biological processes is the development of comprehensive networks and computational methods to apply to the analysis of systems biology data (transcriptomics, proteomics/phosphoproteomics, metabolomics, etc.). Ideally, these networks will be specifically designed to capture the normal, non-diseased biology of the tissue or cell types under investigation, and can be used with experimentally generated systems biology data to assess the biological impact of perturbations like xenobiotics and other cellular stresses. Lung cell proliferation is a key biological process to capture in such a network model, given the pivotal role that proliferation plays in lung diseases including cancer, chronic obstructive pulmonary disease (COPD), and fibrosis. Unfortunately, no such network has been available prior to this work.

RESULTS

To further a systems-level assessment of the biological impact of perturbations on non-diseased mammalian lung cells, we constructed a lung-focused network for cell proliferation. The network encompasses diverse biological areas that lead to the regulation of normal lung cell proliferation (Cell Cycle, Growth Factors, Cell Interaction, Intra- and Extracellular Signaling, and Epigenetics), and contains a total of 848 nodes (biological entities) and 1597 edges (relationships between biological entities). The network was verified using four published gene expression profiling data sets associated with measured cell proliferation endpoints in lung and lung-related cell types. Predicted changes in the activity of core machinery involved in cell cycle regulation (RB1, CDKN1A, and MYC/MYCN) are statistically supported across multiple data sets, underscoring the general applicability of this approach for a network-wide biological impact assessment using systems biology data.

CONCLUSIONS

To the best of our knowledge, this lung-focused Cell Proliferation Network provides the most comprehensive connectivity map in existence of the molecular mechanisms regulating cell proliferation in the lung. The network is based on fully referenced causal relationships obtained from extensive evaluation of the literature. The computable structure of the network enables its application to the qualitative and quantitative evaluation of cell proliferation using systems biology data sets. The network is available for public use.

Effects of erlotinib on lung injury induced by intratracheal administration of bleomycin (BLM) in rats

Interstitial lung disease has been reported in cancer patients treated with epidermal growth factor receptor tyrosine kinase inhibitors, erlotinib and gefitinib. Preclinical safety studies with erlotinib did not show any evidence for an induction of injury on intact lungs in rats and dogs. In the present study, we investigated the effects of erlotinib on lung injury induced by intratracheal administration of bleomycin (BLM) in rats. In Experiment 1, we examined the effects of short-term (7- and 21-day) administration of erlotinib (10 mg/kg/day, p.o.; subtoxic dose) on the BLM (0.1 or 0.6 mg/rat)-induced lung injury of slight and moderate severity. In Experiment 2, we examined the effects of long term (up to 63-day) administration of higher-dose (up to 20 mg/kg/day; toxic dose; accompanied with decreased body weight gain and severe skin lesions) erlotinib on the BLM-induced lung injury. In rats receiving erlotinib alone, no lung lesions were noted. In rats receiving BLM alone, diffuse alveolar damage (DAD) and, subsequently, pulmonary fibrosis of slight or moderate severity was observed. The administration of erlotinib to BLM-treated rats showed no exacerbation of lung injuries in indices such as macroscopic findings, lung weights, histopathological scores (lung lesion density and lung fibrosis score), and pulmonary hydroxyproline (HyP) level. These results suggest that erlotinib does not have any exacerbating effects on lung injuries induced by BLM in rats.

Epithelial Repair and Regeneration

Contact with the environment positions the respiratory epithelium at risk for acute and chronic injury from infectious pathogens, noxious agents, and inflammatory processes. Thus, to protect gas transfer within the lung the epithelium is programmed for routine maintenance and repair. Programs for repair are directed by epithelial, mesenchymal, and inflammatory signals that collectively constitute highly regulated networks. Principal components of the repair network are developmental morphogens, integrin and growth factor signaling molecules, and transcription factors. The epithelium responds to these signals with a remarkable plasticity and is bulwarked by a population of lung progenitor cells to ensure maintenance and repair for fluid balance and host defense functions.

Standing the test of time in Europe? Gefitinib in the treatment of non-small-cell lung cancer

Lung cancer is the most common cancer worldwide, with 1.3 million new cases diagnosed every year. Non-small-cell lung carcinoma (NSCLC) has previously had a very poor prognosis with few effective therapies; however, research has identified that it is associated with a high rate of expression of epidermal growth factor receptor (EGFR) tyrosine kinase. This has led to discoveries in drug manipulation of this receptor, to provide effective new therapies against NSCLC. Gefitinib is a small molecule kinase inhibitor which inhibits the cytoplasmic domain of the EGFR; the evidence behind its use and future role is presented in this review.

Amphiregulin attenuates bleomycin-induced pneumopathy in mice

Amphiregulin, an EGF receptor (EGFR) ligand, is essential for epithelial development in various organs. A recent report suggested that amphiregulin acts as a protective factor in a liver injury model. Little is known about the roles of amphiregulin in lung injury and pulmonary fibrosis. The purpose of the present study was to investigate the role of amphiregulin in an experimental model of bleomycin-induced pneumopathy in mice. C57BL/6 mice were administered a bleomycin hydrochloride solution intratracheally. Recombinant human amphiregulin was injected intraperitoneally at 6, 8, 10, and 12 days after the bleomycin instillation. The grades of inflammation and fibrosis were assessed histologically and biochemically, and the numbers of apoptotic cells were counted after TdT-mediated dUTP nick end labeling (TUNEL) staining in the lung tissues. We also examined downstream survival signals of EGFR, namely phosphorylated Akt and phosphorylated Erk, in lung tissues by Western blotting analysis and immunohistochemistry. Expression of intrinsic amphiregulin was increased in murine lung tissues after bleomycin instillation. Administration of recombinant amphiregulin improved the survival rate and suppressed the degrees of inflammation and fibrosis and the number of TUNEL-positive cells in lung tissues. Amphiregulin treatment enhanced the activation of Akt and Erk in lung epithelial cells. Amphiregulin may play a protective role in bleomycin-induced pneumopathy in mice, probably through the activation of survival signals. Administration of amphiregulin may be a novel therapeutic strategy against lung injury and fibrosis.

Suppression of surfactant protein A by an epidermal growth factor receptor tyrosine kinase inhibitor exacerbates lung inflammation

Interstitial lung disease (ILD) is reported as a serious adverse event in lung cancer patients treated with gefitinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). However, the mechanisms of ILD associated with gefitinib remain unknown. To address the molecular mechanisms of ILD-associated gefitinib, we determined the effect of gefitinib treatment on surfactant protein expression in vitro and in vivo. Gefitinib treatment suppressed surfactant protein (SP)-A expression in H441 human lung adenocarcinoma cells expressing SP-A, -B, -C and -D by inhibiting epidermal growth factor signal. Next, gefitinib (200 mg/kg) was given p.o. to the mice daily for 1 week. Daily administration of gefitinib gradually reduced SP-A level in the bronchoalveolar lavage fluid. When lipopolysaccharide (LPS) was instilled intratracheally to the mice pretreated with gefitinib for 1 week, lung inflammation by LPS was exacerbated and prolonged. This exacerbation of lung inflammation was rescued by intranasal administration of SP-A. These results demonstrated that pretreatment with gefitinib exacerbated LPS-induced lung inflammation by reducing SP-A expression in the lung. This study suggests that epidermal growth factor receptor tyrosine kinase inhibitor may reduce SP-A expression in the lungs of lung cancer patients and thus patients treated with epidermal growth factor receptor tyrosine kinase inhibitor may be susceptible to pathogens.

EGF receptor tyrosine kinase inhibitors diminish transforming growth factor-α-induced pulmonary fibrosis

Transforming growth factor-α (TGF-α) is a ligand for the EGF receptor (EGFR). EGFR activation is associated with fibroproliferative processes in human lung disease and animal models of pulmonary fibrosis. We determined the effects of EGFR tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva) on the development and progression of TGF-α-induced pulmonary fibrosis. Using a doxycycline-regulatable transgenic mouse model of lung-specific TGF-α expression, we determined effects of treatment with gefitinib and erlotinib on changes in lung histology, total lung collagen, pulmonary mechanics, pulmonary hypertension, and expression of genes associated with synthesis of ECM and vascular remodeling. Induction in the lung of TGF-α caused progressive pulmonary fibrosis over an 8-wk period. Daily administration of gefitinib or erlotinib prevented development of fibrosis, reduced accumulation of total lung collagen, prevented weight loss, and prevented changes in pulmonary mechanics. Treatment of mice with gefitinib 4 wk after the induction of TGF-α prevented further increases in and partially reversed total collagen levels and changes in pulmonary mechanics and pulmonary hypertension. Increases in expression of genes associated with synthesis of ECM as well as decreases of genes associated with vascular remodeling were also prevented or partially reversed. Administration of gefitinib or erlotinib did not cause interstitial fibrosis or increases in lavage cell counts. Administration of small molecule EGFR tyrosine kinase inhibitors prevented further increases in and partially reversed pulmonary fibrosis induced directly by EGFR activation without inducing inflammatory cell influx or additional lung injury.

Bleomycin-induced pulmonary fibrosis is attenuated by a monoclonal antibody targeting HER2

The importance of HER2/HER3 signaling in decreasing the effects of lung injury was recently demonstrated. Transgenic mice unable to signal through HER2/HER3 had significantly less bleomycin-induced pulmonary fibrosis and showed a survival benefit. Based on these data, we hypothesized that pharmacological blockade of HER2/HER3 in vivo in wild-type mice would have the same beneficial effects. We tested this hypothesis in a bleomycin lung injury model using 2C4, a monoclonal antibody directed against HER2 that blocks HER2/HER3 signaling. The administration of 2C4 before injury decreased the effects of bleomycin at days 15 and 21 after injury. HER2/HER3 blockade resulted in less collagen deposition (362.8 +/- 37.9 compared with 610.5 +/- 27.1 microg/mg; P = 0.03) and less lung morphological changes (injury score of 1.99 +/- 1.55 vs. 3.90 +/- 0.76; P < 0.04). In addition, HER2/HER3 blockade resulted in a significant survival advantage with 50% vs. 25% survival at 30 days (P = 0.04). These results confirm that HER2 signaling can be pharmacologically targeted to reduce lung fibrosis and remodeling after injury.

Gefitinib-induced pneumonitis in non-small cell lung cancer: radiological and clinical findings in five patients

PURPOSE

The objective of this study was to describe the radiological and clinical features of gefitinib-induced pneumonitis in non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Five patients who suffered dyspnea after gefitinib treatment were selected. Chest radiographs and computed tomography (CT) findings, along with clinical course, were evaluated.

RESULTS

Patients complained of subacute dyspnea and hypoxia. Three patients improved after discontinuation of gefitinib, while remaining two showed no response. Unilateral or bilateral ground glass opacity was observed on chest radiographs and CT.

CONCLUSION

Radiological findings of gefitinib-induced pneumonitis were nonspecific, but radiologists should be aware of this adverse reaction, which can appear during the treatment in NSCLC patients.

Signal peptide of eosinophil cationic protein upregulates transforming growth factor-alpha expression in human cells

Eosinophil cationic protein (ECP) is a major component of eosinophil granule protein that is used as a clinical bio-marker for asthma and allergic inflammatory diseases. Previously, it has been reported that the signal peptide of human ECP (ECPsp) inhibits the cell growth of Escherichia coli (E. coli) and Pichia pastoris (P. pastoris), but not mammalian A431 cells. The inhibitory effect is due to the lack of human signal peptide peptidase (hSPP), a protease located on the endoplasmic reticulum (ER) membrane, in the lower organisms. In this study, we show that the epidermal growth factor receptor (EGFR) is upregulated by the exogenous ECPsp-eGFP as a result of the increased expression of the transforming growth factor-alpha (TGF-alpha) at both transcriptional and translational levels in A431 and HL-60 clone 15 cell lines. Furthermore, the N-terminus of ECPsp fragment generated by the cleavage of hSPP (ECPspM1-G17) gives rise to over threefold increase of TGF-alpha protein expression, whereas another ECPsp fragment (ECPspL18-A27) and the hSPP-resistant ECPsp (ECPspG17L) do not show similar effect. Our results indicate that the ECPspM1-G17 plays a crucial role in the upregulation of TGF-alpha, suggesting that the ECPsp not only directs the secretion of mature ECP, but also involves in the autocrine system.

Genomic profile of matrix and vasculature remodeling in TGF-alpha induced pulmonary fibrosis

Expression of transforming growth factor alpha (TGF-alpha) in the respiratory epithelium of transgenic mice caused pulmonary fibrosis, cachexia, pulmonary hypertension, and altered lung function. To identify genes and molecular pathways mediating lung remodeling, mRNA microarray analysis was performed at multiple times after TGF-alpha expression and revealed changes consistent with a role for TGF-alpha in the regulation of extracellular matrix and vasculogenesis. Transcripts for extracellular matrix proteins were augmented along with transcripts for genes previously identified to have roles in pulmonary fibrosis, including tenascin C, osteopontin, and serine (or cysteine) peptidase inhibitor, clade F, member 1. Transcripts regulating vascular processes including endothelin receptor type B, endothelial-specific receptor tyrosine kinase, and caveolin, caveolae protein 1 were decreased. When TGF-alpha expression was no longer induced, lung remodeling partially reversed and lung function and pulmonary hypertension normalized. Transcripts increased during resolution included midkine, matrix metalloproteinase 2, and hemolytic complement. Hierarchical clustering revealed that genes regulated by TGF-alpha were similar to those altered in the lungs of patients with idiopathic pulmonary fibrosis. These studies support a role for epithelial cell-derived TGF-alpha in the regulation of processes that alter the airway and vascular architecture and function.

Predictive factors for interstitial lung disease, antitumor response, and survival in non-small-cell lung cancer patients treated with gefitinib

PURPOSE

Interstitial lung disease (ILD) is a serious adverse effect of gefitinib, but its prevalence and risk factors remain largely unknown. We examined the prevalence of and risk factors for gefitinib-induced ILD associated with practical use of the drug in Japanese with non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Clinical information was retrospectively assembled for NSCLC patients who started gefitinib treatment at affiliated institutions of the West Japan Thoracic Oncology Group between August 31 and December 31, 2002. Medical records of patients who developed pulmonary infiltrates were reviewed by a central committee of extramural experts for identification of patients with gefitinib-induced ILD. Multivariate logistic or Cox regression analysis was performed to identify independent predictive factors for ILD, antitumor response, and survival.

RESULTS

Seventy cases of and 31 deaths from gefitinib-induced ILD were identified among 1,976 consecutively treated patients at 84 institutions, corresponding to a prevalence of 3.5% and mortality of 1.6%. Gefitinib-induced ILD was significantly associated with male sex, a history of smoking, and coincidence of interstitial pneumonia (odds ratios = 3.10, 4.79, and 2.89, respectively). Predictive factors for response were female sex, no history of smoking, adenocarcinoma histology, metastatic disease, and good performance status (PS), whereas predictive factors for survival were female sex, no history of smoking, adenocarcinoma histology, nonmetastatic disease, good PS, and previous chest surgery.

CONCLUSION

ILD is a serious adverse effect of gefitinib in the clinical setting that cannot be ignored. However, patient selection based on sex and smoking history can minimize ILD risk and maximize the clinical benefit of gefitinib.

Gefitinib prevents bleomycin-induced lung fibrosis in mice

RATIONALE

Transforming growth factor-alpha and epidermal growth factor (EGF), the ligands for EGF receptor (EGFR), stimulate fibroblast proliferation and play an important role in the pathogenesis of pulmonary fibrosis. Therefore, inhibition of the EGFR signal by an EGFR tyrosine kinase inhibitor (EGFR-TKI) may prevent pulmonary fibrosis. However, there is a possibility that blocking the EGFR signal may inhibit epithelial cell repair, thereby exaggerating lung fibrosis.

OBJECTIVE

To investigate the effect of EGFR-TK inhibition on lung fibrosis.

METHODS

We looked at the effects of the EGFR-TKIs gefitinib (20, 90, 200 mg/kg) and AG1478 (12 mg/kg) on a bleomycin-induced lung fibrosis model in mice.

MEASUREMENTS AND MAIN RESULTS

Gefitinib prevented lung fibrosis at all three doses. Furthermore, in those mice that did not receive bleomycin treatment, gefitinib at 200 mg/kg did not induce lung fibrosis. Immunohistochemistry revealed that phosphorylation of EGFR in lung mesenchymal cells induced by bleomycin was inhibited by gefitinib. AG1478 also attenuated the lung fibrosis. In vitro studies further demonstrated that the addition of gefitinib or AG1478 suppressed the EGFR ligand-induced proliferation of lung fibroblasts.

CONCLUSIONS

These findings suggest that, in the preclinical setting, EGFR-TKIs may have a protective effect on lung fibrosis induced by bleomycin. Because these molecular targeted drugs may have differing effects depending on species and individuals, a cautious interpretation is warranted.

Regulation of mucin expression: mechanistic aspects and implications for cancer and inflammatory diseases

Mucins are large multifunctional glycoproteins whose primary functions are to protect and lubricate the surfaces of epithelial tissues lining ducts and lumens within the human body. Several lines of evidence also support the involvement of mucins in more complex biological processes such as epithelial cell renewal and differentiation, cell signaling, and cell adhesion. Recent studies have uncovered the role of select mucins in the pathogenesis of cancer, underscoring the importance of a detailed knowledge about mucin biology. Under normal physiological conditions, the production of mucins is optimally maintained by a host of elaborate and coordinated regulatory mechanisms, thereby affording a well-defined pattern of tissue-, time-, and developmental state-specific distribution. However, mucin homeostasis may be disrupted by the action of environmental and/or intrinsic factors that affect cellular integrity. This results in an altered cell behavior that often culminates into a variety of pathological conditions. Deregulated mucin production has indeed been associated with numerous types of cancers and inflammatory disorders. It is, therefore, crucial to comprehend the underlying basis of molecular mechanisms controlling mucin production in order to design and implement adequate therapeutic strategies for combating these diseases. Herein, we discuss some physiologically relevant regulatory aspects of mucin production, with a particular emphasis on aberrations that pertain to pathological situations. Our views of the achievements, the conceptual and technical limitations, as well as the future challenges associated with studies of mucin regulation are exposed.

Susceptibility of signal transducer and activator of transcription-1-deficient mice to pulmonary fibrogenesis

The signal transducer and activator of transcription (Stat)-1 mediates growth arrest and apoptosis. We postulated that lung fibrosis characterized by excessive proliferation of lung fibroblasts would be enhanced in Stat1-deficient (Stat1-/-) mice. Two weeks after bleomycin aspiration (3 U/kg), Stat1-/- mice exhibited a more severe fibroproliferative response and significantly elevated total lung collagen compared to wild-type mice. Growth factors [epidermal growth factor (EGF) or platelet-derived growth factor (PDGF)] enhanced [3H]thymidine uptake in lung fibroblasts isolated from Stat1-/- mice compared to wild-type mice. Interferon (IFN)-gamma, which signals growth arrest via Stat1, inhibited EGF- or PDGF-stimulated mitogenesis in wild-type fibroblasts but enhanced [3H]thymidine uptake in Stat1-/- fibroblasts. Moreover, IFN-gamma treatment in the absence of growth factors induced a concentration-dependent increase in [3H]thymidine uptake in Stat1-/- but not wild-type fibroblasts. Mitogen-activated protein kinase (ERK-1/2) phosphorylation in response to PDGF or EGF did not differ among Stat1-/- and wild-type fibroblasts. However, Stat3 phosphorylation induced by PDGF, EGF, or IFN-gamma increased twofold in Stat1-/- fibroblasts compared to wild-type fibroblasts. Our findings indicate that Stat1-/- mice are more susceptible to bleomycin-induced lung fibrosis than wild-type mice due to 1) enhanced fibroblast proliferation in response to growth factors (EGF and PDGF), 2) stimulation of fibroblast growth by a Stat1-independent IFN-gamma signaling pathway, and 3) increased activation of Stat3.

Gefitinib-induced lung injury successfully treated with high-dose corticosteroids

A 55-year-old man was treated with gefitinib for disseminated pleural lesions, 1 year after resection of the left lower lobe for non-small cell lung cancer. After 6 weeks of continuous daily treatment with oral gefitinib, he developed dyspnoea on exertion and a non-productive cough. CXR and CT revealed focal areas of ground-glass opacity (GGO) in the right upper lobe. Despite gefitinib being discontinued, high-resolution CT revealed extension of GGO and restructuring of lung parenchyma, suggesting acute interstitial pneumonia. Transbronchial biopsy revealed acute-phase diffuse alveolar damage. After administration of methylprednisolone pulse therapy (1 g/day intravenously) for three consecutive days, the areas of GGO shrank on high-resolution CT and symptoms resolved. Diffuse alveolar damage caused by gefitinib can be successfully treated in the early phase with high-dose corticosteroids. Patients receiving gefitinib should be carefully examined for symptoms and undergo CT if their condition deteriorates.

Is neutrophil elastase the missing link between emphysema and fibrosis? Evidence from two mouse models

BACKGROUND

The separation of emphysema from fibrosis is not as clear-cut as it was thought in early studies. These two pathologies may be present at the same time in human lungs and in mice either instilled with elastolytic enzymes or bleomycin or exposed to cigarette-smoke. According to a current view, emphysema originates from a protease/antiprotease imbalance, and a role for antiproteases has also been suggested in the modulation of the fibrotic process. In this study we investigate in experimental animal models of emphysema and fibrosis whether neutrophil elastase may constitute a pathogenic link between these two pathologies.

METHODS

This study was done in two animal models in which emphysema and fibrosis were induced either by bleomycin (BLM) or by chronic exposure to cigarette-smoke. In order to assess the protease-dependence of the BLM-induced lesion, a group mice was treated with 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride, a serine proteinase inhibitor active toward neutrophil elastase. Lungs from each experimental group were used for the immunohistochemical assessment of transforming growth factor-beta (TGF-beta) and transforming growth factor-alpha (TGF-alpha) and for determination of the mean linear intercept as well as the percent volume densities of fibrosis and of emphysematous changes. Additionally, the lungs were also assessed for desmosine content and for the determination of elastase levels in the pulmonary interstitium by means of immunoelectron microscopy.

RESULTS

We demonstrate that in BLM-treated mice (i) the development of elastolytic emphysema precedes that of fibrosis; (ii) significant amount of elastase in alveolar interstitium is associated with an increased expression of TGF-beta and TGF-alpha; and finally, (iii) emphysematous and fibrotic lesions can be significantly attenuated by using a protease inhibitor active against neutrophil elastase. Also, in a strain of mice that develop both emphysema and fibrosis after chronic cigarette-smoke exposure, the presence of elastase in alveolar structures is associated with a positive immunohistochemical reaction for reaction for both TGF-beta and TGF-alpha.

CONCLUSION

The results of the present study strongly suggest that neutrophil elastase may represent a common pathogenic link between emphysema and fibrosis. Proteases and in particular neutrophil elastase could act as regulatory factors in the generation of soluble cytokines with mitogenic activity for mesenchymal cells resulting either in emphysema or in fibrosis or both.

Cytokine-induced endothelial arginase expression is dependent on epidermal growth factor receptor

L-arginine is metabolized to nitric oxide (NO) by NO synthase (NOS), or to urea and L-ornithine by arginase. L-ornithine contributes to vascular remodeling in pulmonary hypertension via metabolism to polyamines and proline. Previously we found that cytokines upregulate both NOS and arginase in pulmonary arterial endothelial cells. We hypothesized that cytokine-induced arginase I and II expression depend on epidermal growth factor (EGF) receptor (EGFR) activity. Bovine pulmonary arterial endothelial cells were treated with lipopolysaccharide and tumor necrosis factor-alpha (L/T). L/T treatment resulted in a substantial increase in urea production, and this increase in urea production was potently inhibited by both genistein and AG1478, inhibitors of EGFR. Levels of arginase I protein and arginase II mRNA were increased in response to L/T treatment, and genistein prevented the L/T-induced elevations in both arginase I protein and arginase II mRNA levels. L/T treatment increased production of nitrites and inducible NOS mRNA accumulation, and genistein and AG1478 had little effect on these changes. EGF (50 ng/ml) treatment resulted in enhanced urea production. Finally, a 170-kD protein was phosphorylated upon treatment with either EGF or L/T. Our results indicate that arginase induction by L/T depends in part on EGFR activity. We speculate that EGFR inhibitors may attenuate vascular remodeling without affecting NO release, and thus may represent novel therapeutic modalities for pulmonary hypertensive disorders.

Chronic exposure to EGF affects trafficking and function of ENaC channel in cystic fibrosis cells

Using the whole-cell patch-clamp technique, we identified an amiloride (AMI)-sensitive Na(+) current in cystic fibrosis cells, JME/CF15, growing in standard medium. The reversal potential of this current depended on Na(+) concentrations and the cation selectivity was much higher for Na(+) than for K(+), indicating that the current is through ENaC channels. In contrast, cells from EGF-containing medium lacked AMI-sensitive Na(+) currents. In permeabilized cells growing in EGF-containing medium, alphaENaC was mainly detected in a perinuclear region, while in cells from standard medium it was distributed over the cell body. Western-blot analysis showed that in standard medium cells expressed fast-migrating EndoH-insensitive and slow-migrating EndoH-sensitive alphaENaC fractions, while in cells growing in the presence of EGF, alphaENaC was only detected as the fast-migrating EndoH-insensitive fraction. Long-term incubation of cells with EGF resulted in an increased basal Ca(2+) level, [Ca(2+)](i). A similar increase of [Ca(2+)](i) was also observed in the presence of 2muM thapsigargin, resulting in inhibition of ENaC function. Thus, in JME/CF15 cells inhibition of the ENaC function by chronic incubation with EGF is a Ca(2+)-mediated process that affects trafficking and surface expression of ENaC channels.

Interstitial lung disease in lung cancer: separating disease progression from treatment effects

Lung cancer often develops in individuals with pre-existing pulmonary and cardiac pathology. Many of these individuals with pre-existing pathology are also at risk of occupational lung disease. New and worsening symptoms can be secondary to pre-existing pathology, progressive cancer or treatment. Pulmonary toxicity, including interstitial lung disease, following radiotherapy and conventional cytotoxic chemotherapy (e.g. cyclophosphamide, bleomycin), has been recognised for many years. Pulmonary toxicity also occurs with the newer classes of cytotoxic agents, including the deoxycytidine analogue gemcitabine. A small percentage (0.88%) of patients treated with the epidermal growth factor receptor tyrosine kinase inhibitor gefitinib have developed interstitial lung disease. This complication has been reported at a higher frequency in Japanese patients than in US patients (1.9% vs 0.34%, respectively) and in those with pre-existing pulmonary fibrosis. This review discusses the difficulties in both recognition and treatment of gefitinib-associated interstitial lung disease. Symptoms are vague, such as dyspnoea, cough and fever and can be difficult to differentiate from progressive disease, co-existing morbidity and new pulmonary pathology. Diagnosis is, therefore, by rigorous investigation to exclude all other differential diagnoses. Treatment, at present, is supportive and includes discontinuation of gefitinib, oxygen supplementation, high-dose corticosteroids and antibacterials.