Leucine-rich α-2-glycoprotein promotes TGFβ1-mediated growth suppression in the Lewis lung carcinoma cell lines

Leucine-Rich Alpha-2-Glycoprotein 1 Promotes Metastatic Colorectal Cancer Growth Through Human Epidermal Growth Factor Receptor 3 Signaling

BACKGROUND & AIMS

Therapy failure in patients with metastatic colorectal cancer (mCRC, ∼80% occur in the liver) remains an overarching challenge. Preclinical studies demonstrated that human epidermal growth factor receptor 3 (HER3) promotes colorectal cancer (CRC) cell survival, but therapies blocking the neuregulin-induced canonical HER3 signaling have made little impact in the clinic. Recent studies suggest that the liver microenvironment promotes CRC growth by activating HER3 in a neuregulin-independent fashion, thus elucidation of these mechanisms may reveal new strategies for treating patients with mCRC.

METHODS

Patient-derived primary liver endothelial cells (ECs) were used to interrogate EC-CRC crosstalk. We conducted proteomic analysis to identify EC-secreted factor(s) that triggers noncanonical HER3 activation in CRC and determined the subsequent effects on mCRC using diverse murine mCRC models. In vitro studies with genetic and pharmacological interventions were used to map the noncanonical HER3 pathway.

RESULTS

We demonstrated that EC-secreted leucine-rich alpha-2-glycoprotein 1 (LRG1) directly binds and activates HER3 and promotes CRC growth distinct from neuregulin, the canonical HER3 ligand. Blocking host-derived LRG1 by gene knockout or a neutralizing antibody impaired mCRC outgrowth in the liver and prolonged mouse survival. We identified protein synthesis activated by the PI3K-PDK1-RSK-eIF4B axis as the biologically relevant signaling cascade downstream of the LRG1-HER3 interaction, which was not blocked by conventional HER3-specific antibodies that failed in prior clinical trials.

CONCLUSIONS

LRG1 is a novel HER3 ligand and mediates liver-mCRC crosstalk. The LRG1-HER3 signaling axis is distinct from canonical HER3 signaling and represents a new therapeutic opportunity to treat patients with mCRC, and potentially other types of liver metastases.

LRG1 promotes the apoptosis of pulmonary microvascular endothelial cells through KLK10 in chronic obstructive pulmonary disease

INTRODUCTION

Cigarette smoking is one of the most important causes of COPD and could induce the apoptosis of pulmonary microvascular endothelial cells (PMVECs). The conditional knockout of LRG1 from endothelial cells reduced emphysema in mice. However, the mechanism of the deletion of LRG1 from endothelial cells rescued by cigarette smoke (CS) induced emphysema remains unclear. This research aimed to demonstrate whether LRG1 promotes the apoptosis of PMVECs through KLK10 in COPD.

METHODS

Nineteen patients were divided into three groups: control non-COPD (n=7), smoker non-COPD (n=7), and COPD (n=5). The emphysema mouse model defined as the CS exposure group was induced by CS exposure plus cigarette smoke extract (CSE) intraperitoneal injection for 28 days. Primary PMVECs were isolated from the mouse by magnetic bead sorting method via CD31-Dynabeads. Apoptosis was detected by western blot and flow cytometry.

RESULTS

LRG1 was increased in lung tissue of COPD patients and CS exposure mice, and CSE-induced PMVECs apoptosis model. KLK10 was over-expressed in lung tissue of COPD patients and CS exposure mice, and CSE-induced PMVECs apoptosis model. LRG1 promoted apoptosis in PMVECs. LRG1 knockdown reversed CSE-induced apoptosis in PMVECs. The mRNA and protein expression of KLK10 were increased after over-expressed LRG1 in PMVECs isolated from mice. Similarly, both the mRNA and protein levels of KLK10 were decreased after LRG1 knockdown in PMVECs. The result of co-immunoprecipitation revealed a protein-protein interaction between LRG1 and KLK10 in PMVECs. KLK10 promoted apoptosis via the down-regulation of Bcl-2/Bax in PMVECs. KLK10 knockdown could reverse CSE-induced apoptosis in PMVECs.

CONCLUSIONS

LRG1 promotes apoptosis via up-regulation of KLK10 in PMVECs isolated from mice. KLK10 promotes apoptosis via the down-regulation of Bcl-2/Bax in PMVECs. There was a direct protein-protein interaction between LRG1 and KLK10 in PMVECs. Our novel findings provide insights into the understanding of LRG1/KLK10 function as a potential molecule in COPD.

LRG1 Promotes ECM Integrity by Activating the TGF-β Signaling Pathway in Fibroblasts

Leucine-rich alpha-2-glycoprotein 1 (LRG1) mediates skin repair and fibrosis by stimulating the transforming growth factor-beta (TGF-β) signaling pathway. In the present study, we investigated the effect of LRG1 on extracellular matrix (ECM) integrity in fibroblasts, as well as on skin aging. The treatment of dermal fibroblasts with purified recombinant human LRG1 increased type I collagen secretion and decreased matrix metalloproteinase-1 secretion. Additionally, LRG1 promoted SMAD2/SMAD3 phosphorylation in a pattern similar to that of TGF-β1 treatment. An inhibitor of TGF-β receptor 1 abolished LRG1-induced SMAD2 phosphorylation. RNA sequencing identified "extracellular region", "extracellular space", and "extracellular matrix" as the main Gene Ontology terms in the differentially expressed genes of fibroblasts treated with or without LRG1. LRG1 increased TGF-β1 mRNA levels, suggesting that LRG1 partially transactivates the expression of TGF-β1. Furthermore, an increased expression of type I collagen was also observed in fibroblasts grown in three-dimensional cultures on a collagen gel mimicking the dermis. LRG1 mRNA and protein levels were significantly reduced in elderly human skin tissues with weakened ECM integrity compared to in young human skin tissues. Taken together, our results suggest that LRG1 could retard skin aging by activating the TGF-β signaling pathway, increasing ECM deposition while decreasing its degradation.

LRG-1 promotes fat graft survival through the RAB31-mediated inhibition of hypoxia-induced apoptosis

Autologous adipose tissue is an ideal soft tissue filling material, and its biocompatibility is better than that of artificial tissue substitutes, foreign bodies and heterogeneous materials. Although autologous fat transplantation has many advantages, the low retention rate of adipose tissue limits its clinical application. Here, we identified a secretory glycoprotein, leucine‐rich‐alpha‐2‐glycoprotein 1 (LRG‐1), that could promote fat graft survival through RAB31‐mediated inhibition of hypoxia‐induced apoptosis. We showed that LRG‐1 injection significantly increased the maintenance of fat volume and weight compared with the control. In addition, higher fat integrity, more viable adipocytes and fewer apoptotic cells were observed in the LRG‐1‐treated groups. Furthermore, we discovered that LRG‐1 could reduce the ADSC apoptosis induced by hypoxic conditions. The mechanism underlying the LRG‐1‐mediated suppression of the ADSC apoptosis induced by hypoxia was mediated by the upregulation of RAB31 expression. Using LRG‐1 for fat grafts may prove to be clinically successful for increasing the retention rate of transplanted fat.

Mass spectrometry, data re-analysis, and homology modelling predict posttranslational modifications of leucine-rich alpha-2-glycoprotein as a marker of myelodysplastic syndrome

BACKGROUND

Leucine-rich alpha-2-glycoprotein (LRG) has been repeatedly proposed as a potential plasma biomarker for myelodysplastic syndrome (MDS).

OBJECTIVE

The goal of our work was to establish the total LRG plasma level and LRG posttranslational modifications (PTMs) as a suitable MDS biomarker.

METHODS

The total plasma LRG concentration was determined with ELISA, whilst the LRG-specific PTMs and their locations, were established using mass spectrometry and public mass spectrometry data re-analysis. Homology modelling and sequence analysis were used to establish the potential impact of PTMs on LRG functions via their impact on the LRG structure.

RESULTS

While the results showed that the total LRG plasma concentration is not a suitable MDS marker, alterations within two LRG sites correlated with MDS diagnosis (p= 0.0011). Sequence analysis and the homology model suggest the influence of PTMs within the two LRG sites on the function of this protein.

CONCLUSIONS

We report the presence of LRG proteoforms that correlate with diagnosis in the plasma of MDS patients. The combination of mass spectrometry, re-analysis of publicly available data, and homology modelling, represents an approach that can be used for any protein to predict clinically relevant protein sites for biomarker research despite the character of the PTMs being unknown.

LRG1: an emerging player in disease pathogenesis

The secreted glycoprotein leucine-rich α-2 glycoprotein 1 (LRG1) was first described as a key player in pathogenic ocular neovascularization almost a decade ago. Since then, an increasing number of publications have reported the involvement of LRG1 in multiple human conditions including cancer, diabetes, cardiovascular disease, neurological disease, and inflammatory disorders. The purpose of this review is to provide, for the first time, a comprehensive overview of the LRG1 literature considering its role in health and disease. Although LRG1 is constitutively expressed by hepatocytes and neutrophils, Lrg1-/- mice show no overt phenotypic abnormality suggesting that LRG1 is essentially redundant in development and homeostasis. However, emerging data are challenging this view by suggesting a novel role for LRG1 in innate immunity and preservation of tissue integrity. While our understanding of beneficial LRG1 functions in physiology remains limited, a consistent body of evidence shows that, in response to various inflammatory stimuli, LRG1 expression is induced and directly contributes to disease pathogenesis. Its potential role as a biomarker for the diagnosis, prognosis and monitoring of multiple conditions is widely discussed while dissecting the mechanisms underlying LRG1 pathogenic functions. Emphasis is given to the role that LRG1 plays as a vasculopathic factor where it disrupts the cellular interactions normally required for the formation and maintenance of mature vessels, thereby indirectly contributing to the establishment of a highly hypoxic and immunosuppressive microenvironment. In addition, LRG1 has also been reported to affect other cell types (including epithelial, immune, mesenchymal and cancer cells) mostly by modulating the TGFβ signalling pathway in a context-dependent manner. Crucially, animal studies have shown that LRG1 inhibition, through gene deletion or a function-blocking antibody, is sufficient to attenuate disease progression. In view of this, and taking into consideration its role as an upstream modifier of TGFβ signalling, LRG1 is suggested as a potentially important therapeutic target. While further investigations are needed to fill gaps in our current understanding of LRG1 function, the studies reviewed here confirm LRG1 as a pleiotropic and pathogenic signalling molecule providing a strong rationale for its use in the clinic as a biomarker and therapeutic target.

LRG1 destabilizes tumor vessels and restricts immunotherapeutic potency

BACKGROUND

A poorly functioning tumor vasculature is pro-oncogenic and may impede the delivery of therapeutics. Normalizing the vasculature, therefore, may be beneficial. We previously reported that the secreted glycoprotein leucine-rich α-2-glycoprotein 1 (LRG1) contributes to pathogenic neovascularization. Here, we investigate whether LRG1 in tumors is vasculopathic and whether its inhibition has therapeutic utility.

METHODS

Tumor growth and vascular structure were analyzed in subcutaneous and genetically engineered mouse models in wild-type and Lrg1 knockout mice. The effects of LRG1 antibody blockade as monotherapy, or in combination with co-therapies, on vascular function, tumor growth, and infiltrated lymphocytes were investigated.

FINDINGS

In mouse models of cancer, Lrg1 expression was induced in tumor endothelial cells, consistent with an increase in protein expression in human cancers. The expression of LRG1 affected tumor progression as Lrg1 gene deletion, or treatment with a LRG1 function-blocking antibody, inhibited tumor growth and improved survival. Inhibition of LRG1 increased endothelial cell pericyte coverage and improved vascular function, resulting in enhanced efficacy of cisplatin chemotherapy, adoptive T cell therapy, and immune checkpoint inhibition (anti-PD1) therapy. With immunotherapy, LRG1 inhibition led to a significant shift in the tumor microenvironment from being predominantly immune silent to immune active.

CONCLUSIONS

LRG1 drives vascular abnormalization, and its inhibition represents a novel and effective means of improving the efficacy of cancer therapeutics.

FUNDING

Wellcome Trust (206413/B/17/Z), UKRI/MRC (G1000466, MR/N006410/1, MC/PC/14118, and MR/L008742/1), BHF (PG/16/50/32182), Health and Care Research Wales (CA05), CRUK (C42412/A24416 and A17196), ERC (ColonCan 311301 and AngioMature 787181), and DFG (CRC1366).

Detection of leucine-rich alpha-2-glycoprotein 1-containing immunocomplexes in the plasma of lung cancer patients with epitope-specific mAbs

BACKGROUND

Lung cancer is the leading cause of cancer-related deaths worldwide. With the expectation of improved survival, tremendous efforts and resources have been invested in the discovery of specific biomarkers for early detection of the disease. Several investigators have reported the presence of cancer-associated autoantibodies in the plasma or serum of lung cancer patients. Previously, we used a monoclonal-antibody proteomics technology platform for the discovery of novel lung cancer-associated proteins.

OBJECTIVE

The identification of specific protein epitopes associated with various cancers is a promising method in biomarker discovery. Here, in a preliminary study, we aimed to detect autoantibody-leucine-rich alpha-2-glycoprotein 1 (LRG1) immunocomplexes using epitope-specific monoclonal antibodies (mAbs).

METHODS

We performed sandwich ELISA assays using the LRG1 epitope-specific capture mAbs, Bsi0352 and Bsi0392, and an IgG-specific polyclonal antibody coupled to a reporter system as the detection reagent. We tested the plasma of lung-cancer patients and apparently healthy controls.

RESULTS

Depending on the epitope specificity of the capture monoclonal mAb, we were either unable to distinguish the control from LC-groups or showed a higher level of LRG1 and IgG autoantibody containing immunocomplexes in the plasma of non-small cell lung cancer and small cell lung cancer subgroups of lung cancer patients than in the plasma of control subjects.

CONCLUSIONS

Our findings underline the importance of protein epitope-specific antibody targeted approaches in biomarker research, as this may increase the accuracy of previously described tests, which will need further validation in large clinical cohorts.

Paradoxical Roles of Leucine-Rich α2-Glycoprotein-1 in Cell Death and Survival Modulated by Transforming Growth Factor-Beta 1 and Cytochrome c

Leucine-rich α₂-glycoprotein-1 (LRG1) has been shown to impact both apoptosis and cell survival, pleiotropic effects similar to one of its known ligands, transforming growth factor-beta 1 (TGF-β1). Recent studies have given insight into the TGF-β1 signaling pathways involved in LRG1-mediated death versus survival signaling, i.e., canonical or non-canonical. Interaction of LRG1 with another ligand, extracellular cytochrome c (Cyt c), promotes cell survival, at least for lymphocytes. LRG1 has been shown to bind Cyt c with high affinity, higher than it binds TGF-β1, making it sensitive to small changes in the level of extracellular Cyt c within a microenvironment that may arise from cell death. Evidence is presented here that LRG1 can bind TGF-β1 and Cyt c simultaneously, raising the possibility that the ternary complex may present a signaling module with the net effect of signaling, cell death versus survival, determined by the relative extent to which the LRG1 binding sites are occupied by these two ligands. A possible role for LRG1 should be considered in studies where extracellular effects of TGF-β1 and Cyt c have been observed in media supplemented with LRG1-containing serum.

Serum biomarker discovery related to pathogenesis in acute coronary syndrome by proteomic approach

Acute coronary syndrome (ACS) results from inadequate supply of blood flow from the coronary arteries to the heart or ischemia. ACS has an extremely high morbidity and mortality. The levels of biomarkers currently used for detection of ACS also increase in response to myocardial necrosis and other diseases and are not elevated immediately after symptoms appear, thus limiting their diagnostic capacity. Therefore, we aimed to discover new ACS diagnostic biomarkers with high sensitivity and specificity that are specifically related to ACS pathogenesis. Sera from 50 patients with ACS and healthy controls (discovery cohort) each were analyzed using mass spectrometry (MS) to identify differentially expressed proteins, and protein candidates were evaluated as ACS biomarkers in 120 people in each group (validation cohort). α-1-acid glycoprotein 1 (AGP1), complement C5 (C5), leucine-rich α-2-glycoprotein (LRG), and vitronectin (VN) were identified as biomarkers whose levels increase and gelsolin (GSN) as a biomarker whose levels decrease in patients with ACS. We concluded that these biomarkers are associated with the pathogenesis of ACS and can predict the onset of ACS prior to the appearance of necrotic biomarkers.

The Skin-Liver Axis Modulates the Psoriasiform Phenotype and Involves Leucine-Rich α-2 Glycoprotein

Leucine-rich α-2 glycoprotein (LRG), one of the acute phase proteins mainly produced by the liver, similar to C-reactive protein, has been recognized as an inflammatory biomarker for rheumatoid arthritis and inflammatory bowel diseases. We recently demonstrated that LRG was also increased in the sera of psoriasis patients and correlated well with disease activity with a sensitivity and specificity much higher than C-reactive protein; however, whether LRG mechanistically contributed to the pathogenesis of psoriasis remained unclear. In this study, we explored the role of LRG in psoriasiform inflammation using LRG-knockout (KO) mice in an imiquimod (IMQ)-mediated model. Following topical treatment with IMQ, serum levels of LRG and its expression in the liver were abruptly elevated. Similarly, an acute surge of proinflammatory cytokines was observed in the liver, including IL-1β, TNF-α, and IL-6, although LRG-KO mice showed delayed responses. LRG-KO mice showed less skin inflammation in the IMQ model than wild-type mice. K5.Stat3C mice developed psoriasis-like lesions following tape stripping, which also abruptly induced LRG expression in the liver. A deficiency of Lrg mitigated tape stripping-induced lesions, similar to the IMQ model. These results indicate that LRG modulates both feed-forward and feedback loops of cytokines in the skin-liver axis involved with psoriasiform inflammation.

The involvement of leucine-rich α-2 glycoprotein in the progression of skin and lung fibrosis in bleomycin-induced systemic sclerosis model

OBJECTIVE

Systemc sclerosis (SSc) is an autoimmune disorder characterized by fibrosis of the skin and internal organs. Recently, it has been shown that leucine-rich α-2 glycoprotein (LRG) functions as a modulator of transforming growth factor-β (TGF-β) signaling in fibrosis. We aimed to characterize the effect of LRG in SSc model and SSc patients.

METHODS

Histological analysis was performed on LRG knockout (KO) and wild type (WT) mouse in the skin and the lung after bleomycin administration. Serum LRG levels were measured during the injection period. Gene expression analysis of the skin and lung tissue from LRG KO and WT mice was performed. In addition, serum LRG levels were determined in SSc patients and healthy controls.

RESULTS

LRG KO mice display an inhibition of fibrosis in the skin in association with a decrease of dermal thickness, collagen deposition, and phospho-Smad3 expression after bleomycin. Serum LRG concentration significantly increased in WT mice after bleomycin. There was also a suppression of inflammation and fibrosis in the LRG KO mouse lung indicated by a reduction of lung weight, collagen content, and phospho-Smad3 expression after bleomycin. Gene expressions of TGF-β and Smad2/3 were significantly reduced in LRG KO mice. Serum LRG levels in SSc patients were significantly higher than those in controls.

CONCLUSION

LRG promotes fibrotic processes in SSc model through TGF-β-Smad3 signaling, and LRG can be a biomarker for SSc in humans and also a potential therapeutic target for SSc.

Intracellular leucine-rich alpha-2-glycoprotein-1 competes with Apaf-1 for binding cytochrome c in protecting MCF-7 breast cancer cells from apoptosis

Leucine-rich alpha-2-glycoprotein-1 (LRG1) has been shown to compete with apoptosis activating factor-1 (Apaf-1) for binding cytochrome c (Cyt c) and could play a role in inhibition of apoptosis. Employing MCF-7 breast cancer cells, we report that intracellular LRG1 does protect against apoptosis. Thus, cells transfected with the lrg1 gene and expressing higher levels of LRG1 were more resistant to hydrogen peroxide-induced apoptosis than parental cells, while cells in which LRG mRNA was knocked down by short hairpin (sh) RNA-induced degradation were more sensitive. The amount of Cyt c co-immunoprecipitated with Apaf-1 from the cytosol of apoptotic cells was inversely related to the level of LRG1 expression. In lrg1-transfected cells partially-glycosylated LRG1 was found in the cytosol and there was an increase in cytosolic Cyt c in live lrg1-transfected cells relative to parental cells. However, apoptosis was not spontaneously induced because Cyt c was bound to LRG1 and not to Apaf-1. Cyt c was the only detectable protein co-immunoprecipitated with LRG1. Following hydrogen peroxide treatment degradation of LRG1 allowed for induction of apoptosis. We propose that intracellular LRG1 raises the threshold of cytoplasmic Cyt c required to induce apoptosis and, thus, prevents onset of the intrinsic pathway in cells where Cyt c release from mitochondria does not result from committed apoptotic signaling. This mechanism of survival afforded by LRG1 is likely to be distinct from its extracellular survival function that has been reported by several research groups.

Correlation of increased serum leucine-rich α2-glycoprotein levels with disease prognosis, progression, and activity of interstitial pneumonia in patients with dermatomyositis: A retrospective study

OBJECTIVE

To investigate whether leucine-rich α2-glycoprotein (LRG) can be a biomarker for the disease activity, progression, and prognosis of interstitial pneumonia (IP) in patients with dermatomyositis (DM).

METHODS

Correlations between the clinical findings and serum LRG levels were investigated in 46 patients with DM-IP (33 with acute/subacute IP [A/SIP] and 13 patients with chronic IP [CIP], including 10 fatal cases of IP).

RESULTS

The median serum LRG level of 18.4 (14.6-25.2) μg/mL in DM-IP patients was higher than that in healthy control subjects. The median levels of serum LRG at baseline and at 2 and 4 weeks after the initiation of treatment in the patients who died were significantly higher than those in the surviving patients (P = 0.026, 0.029, and 0.008, respectively). The median level of serum LRG in the DM-A/SIP patients was significantly higher than that in the DM-CIP patients (P = 0.0004), and that in the anti-MDA5-Ab-positive group was slightly higher than that in the anti-ARS-Ab-positive group. The serum LRG levels correlated significantly with the serum levels of LDH, C-reactive protein, ferritin, AaDO2, %DLco, and total ground-glass opacity score. The survival rate after 24 weeks in patients with an initial LRG level ≥ 17.6 μg/mL (survival rate: 40%) was significantly lower than that in patients with an initial LRG level < 17.6 μg/mL (100%) (P = 0.0009).

CONCLUSION

The serum LRG level may be a promising marker of disease activity, progression, and prognosis in patients with DM-IP.

LRG1 Suppresses Migration and Invasion of Esophageal Squamous Cell Carcinoma by Modulating Epithelial to Mesenchymal Transition

Background: Esophageal squamous cell carcinoma (ESCC) is a common cancer with poor prognosis. The molecular pathogenesis underlying ESCC remains to be explored. Leucine-rich ɑ-2-glycoprotein 1 (LRG1) has been implicated in the pathogenesis of various cancer types, however its role in ESCC is unknown.

Materials and Methods: Data from the public database was analyzed to address the expression of LRG1 in ESCC. Gain-of-function studies were performed in select ESCC cell lines by over-expression or addition of recombinant LRG1, while loss-of-function studies achieved by small interfering RNA mediated knockdown. Wound healing and transwell assays were conducted to investigate ESCC cell migration and invasion upon manipulating LRG1 levels. Western blot and Immunofluorescence staining were used to examine the changes in epithelial to mesenchymal transition (EMT) and TGFβ signaling pathway.

Results: LRG1 mRNA levels were found to be significantly down-regulated in patients with ESCC as well as in several ESCC cell lines. Silencing of LRG1 promoted, while overexpression of LRG1 inhibited ESCC cell migration and invasion. In line with this, Silencing of LRG1 enhanced, while overexpression of LRG1 reduced TGFβ signaling and EMT of ESCC cells.

Conclusion/Significance: LRG1 suppresses ESCC cell migration and invasion via negative modulation of TGFβ signaling and EMT. Down-regulation of LRG1 in ESCC patients may favor tumor metastasis and disease progression.

Evaluation of a biomarker for the diagnosis of pancreas cancer using an animal model

Many approaches have been taken to identify new biomarkers of pancreatic ductal carcinoma (PDC). Since animal models can be sampled under controlled conditions, better standardization is possible compared with heterogeneous human studies. Transgenic rats with conditional activation of oncogenic RAS in pancreatic tissue develop PDC that closely resembles the biological and histopathological features of human PDC. Using this model, we evaluated the usefulness of leucine-rich α2-glycoprotein-1 (LRG-1) as a serum marker. In this study, we found that LRG-1 was overexpressed in rat PDC compared with normal pancreas tissue of the control rats. Serum levels of LRG-1 were also significantly higher in rats bearing PDC than in controls. Importantly, chronic pancreatitis in male Wistar Bonn/Kobori rats, which is a widely accepted as a model of chronic pancreatitis, did not cause serum levels of LRG-1 to become elevated. These results strongly support serum LRG-1 as a candidate biomarker for noninvasive diagnosis of PDC. Our models of pancreas cancer provide a useful strategy for evaluation of candidate markers applicable to human cancer.

LRG1 Promotes Apoptosis and Autophagy through the TGFβ-smad1/5 Signaling Pathway to Exacerbate Ischemia/Reperfusion Injury

Leucine-rich α2-glycoprotein1 (LRG1), a pleiotropic protein, plays a pathogenic role in multiple human diseases. However, its pathophysiological function in ischemia/reperfusion injury remains unclear. In this study, we discussed the function and mechanism of LRG1 in acute ischemic stroke from both basic and clinical research points of view. Mice underwent transient middle cerebral artery occlusion (tMCAO) surgery 2 weeks after LRG1 was overexpressed by the delivery of adeno-associated virus (AAV). For wild-type mice, both the protein and the transcript of LRG1 in the brain tissue were elevated after tMCAO. Meanwhile, the serum levels of LRG1 were decreased after tMCAO. The neuronal injury was shown aggravated in the AAV-LRG1 group (AAV-LRG1 mice with tMCAO) through infarction volume, neurological score, HE, and Nissl staining. Meanwhile, LRG1 significantly enhanced apoptosis and autophagy during tMCAO, as detected by caspase3, Bax, Bcl-2, LC3II/LC3I, Beclin1, p62, and a TUNEL assay. Furthermore, by overexpression of LRG1, the protein of ALK1 was upregulated and the TGFβ-smad1/5 signaling pathway was activated upon tMCAO. We also showed that patients with acute cerebral infarction had lower serum levels of LRG1 compared to healthy controls. In addition, LRG1 levels were associated with infarction volume, stroke severity, and prognosis in patients with supratentorial infarction. Taken together, the data from this study revealed that LRG1 promoted apoptosis and autophagy through the TGFβ-smad1/5 signaling pathway by up-regulating ALK1, which exacerbates ischemia/reperfusion injury.

Epithelial-mesenchymal transition via transforming growth factor beta in pancreatic cancer is potentiated by the inflammatory glycoprotein leucine-rich alpha-2 glycoprotein

We previously showed that an inflammation‐related, molecule leucine‐rich alpha‐2 glycoprotein (LRG) enhances the transforming growth factor (TGF)‐β1‐induced phosphorylation of Smad proteins and is elevated in patients with pancreatic ductal adenocarcinoma (PDAC). As TGF‐β/Smad signaling is considered to play a key role in epithelial‐mesenchymal transition (EMT), we attempted to clarify the mechanism underlying LRG‐related EMT in relation to metastasis in PDAC. We cultured LRG‐overexpressing PDAC cells (Panc1/LRG) and evaluated the morphology, EMT‐related molecules and TGF‐β/Smad signaling pathway in these cells. We also assessed the LRG levels in plasma and resected specimens from patients with PDAC. Inflammatory cytokines induced LRG production in PDAC cells. A spindle‐like shape was visualized more frequently than other shapes in Panc1/LRG with TGF‐β1 exposure. The expression of E‐cadherin in Panc1/LRG was decreased with TGF‐β1 exposure. Invasion increased with TGF‐β1 stimulation of Panc1/LRG. The phosphorylation of smad2 in Panc1/LRG was increased in comparison with parental Panc1 under TGF‐β1 stimulation. In the plasma LRG‐high group, the recurrence rate tended to be higher and the recurrence‐free survival (RFS) tended to be worse in comparison with the plasma LRG‐low group. LRG enhanced EMT induced by TGF‐β signaling, thus indicating that LRG has a significant effect on the metastasis of PDAC.

Yangfei Kongliu Formula, a compound Chinese herbal medicine, combined with cisplatin, inhibits growth of lung cancer cells through transforming growth factor-β1 signaling pathway

OBJECTIVE

To investigate the tumor inhibition effect of Yangfei Kongliu Formula (YKF), a compound Chinese herbal medicine, combined with cisplatin (DDP) and its action mechanisms.

METHODS

C57BL/6 mice with Lewis lung carcinoma were divided into six groups: control group (C), DDP group (2 mg/kg, DDP), low-dose YKF group (2.43 g/kg, L), high-dose YKF group (24.3 g/kg, H), low-dose YKF combined with DDP group (L + DDP) and high-dose YKF combined with DDP group (H + DDP). Transforming growth factor-β1 (TGF-β1), mothers against decapentaplegic homolog 3 (Smad3) and Smad7 levels were measured with quantitative real-time polymerase chain reaction (qPCR), Western blotting and immunohistochemistry. An enzyme-linked immunosorbent assay was used to analyze the expressions of interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α).

RESULTS

YKF combined with DDP significantly inhibited the growth and metastasis of tumors relative to the control group, and YKF groups (P < 0.05). There was no significant difference between high-dose YKF group and low-dose YKF group (P > 0.05). We also found that the expression levels of TGF-β1 and Smad3 were both significantly decreased by YKF relative to the control group (P < 0.05). Furthermore, after treatment with YKF combined with DDP, the expression levels of TGF-β1 and Smad3 were decreased but the expression level of Smad7 was increased relative to the DDP group (P < 0.05). Compared to the DDP group, the combination of YKF and DDP enhanced the effect of tumor inhibition (P < 0.05), showing obvious synergy between YKF and DDP. Treatment with DDP or YKF decreased serum levels of IL-2 and TNF-α relative to the control group (P < 0.05). Furthermore, the expression levels of IL-2 and TNF-α were significantly decreased when treated with YKF in combination with DDP. Co-treatment with YKF and DDP significantly inhibited tumor growth, decreased the expressions of TGF-β1, Smad3, IL-2 and TNF-α and increased the expression of Smad7; these differences were significant relative to both YKF groups and the control group (P < 0.05).

CONCLUSION

YKF can inhibit tumor growth synergistically with DDP, mainly through the TGF-β1 signaling pathway.

LRG is a novel inflammatory marker clinically useful for the evaluation of disease activity in rheumatoid arthritis and inflammatory bowel disease

By proteomic screening of sera obtained from patients with rheumatoid arthritis (RA), we previously identified leucine rich α2 glycoprotein (LRG) as a possible marker for inflammation. Unlike C-reactive protein (CRP), a biomarker widely used to evaluate inflammation, LRG is induced not only by IL-6 but also by other proinflammatory cytokines. In addition, LRG is upregulated not only in liver but also in local inflammatory sites. Therefore, serum LRG is a novel inflammatory marker applicable to evaluate inflammation in many diseases including ulcerative colitis in which serum CRP often fails to reflect disease activity and RA to which IL-6-blocking biologic agents such as tocilizumab are given as a first line therapy. Interestingly, evidence indicates that LRG is functionally involved in pathogenesis of inflammation, by promoting cellular proliferation, differentiation and angiogenesis via modulating TGF-β signaling.

Leucine-rich α-2 glycoprotein promotes lung fibrosis by modulating TGF-β signaling in fibroblasts

TGF‐β has an important role in fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). Detailed analysis of TGF‐β signaling in pulmonary fibrosis at the molecular level is needed to identify novel therapeutic targets. Recently, leucine‐rich alpha‐2 glycoprotein (LRG) was reported to function as a modulator of TGF‐β signaling in angiogenesis and tumor progression. However, the involvement of LRG in fibrotic disorders, including IPF, has not yet been investigated. In this study, we investigated the role of LRG in fibrosis by analyzing LRG knockout (KO) mice with bleomycin‐induced lung fibrosis, an animal model of pulmonary fibrosis. The amount of LRG in the lungs of wild‐type (WT) mice was increased by bleomycin administration prior to fibrosis development. In LRG KO mice, lung fibrosis was significantly suppressed, as indicated by attenuated Masson's trichrome staining and lower collagen content than those in WT mice. Moreover, in the lungs of LRG KO mice, phosphorylation of Smad2 was reduced and expression of α‐SMA was decreased relative to those in WT mice. In vitro experiments indicated that LRG enhanced the TGF‐β‐induced phosphorylation of Smad2 and the expression of Serpine1 and Acta2, the downstream of Smad2, in fibroblasts. Although endoglin, an accessory TGF‐β receptor, is essential for LRG to promote TGF‐β signaling in endothelial cells during angiogenesis, we found that endoglin did not contribute to the ability of LRG to enhance Smad2 phosphorylation in fibroblasts. Taken together, our data suggest that LRG promotes lung fibrosis by modulating TGF‐β‐induced Smad2 phosphorylation and activating profibrotic responses in fibroblasts.

Leucine-rich α2-glycoprotein overexpression in the brain contributes to memory impairment

We previously reported increase in leucine-rich α2-glycoprotein (LRG) concentration in cerebrospinal fluid is associated with cognitive decline in humans. To investigate relationship between LRG expression in the brain and memory impairment, we analyzed transgenic mice overexpressing LRG in the brain (LRG-Tg) focusing on hippocampus. Immunostaining and Western blotting revealed age-related increase in LRG expression in hippocampal neurons in 8-, 24-, and 48-week-old controls and LRG-Tg. Y-maze and Morris water maze tests indicated retained spatial memory in 8- and 24-week-old LRG-Tg, while deteriorated in 48-week-old LRG-Tg compared with age-matched controls. Field excitatory postsynaptic potentials declined with age in LRG-Tg compared with controls at 8, 24, and 48 weeks. Paired-pulse ratio decreased with age in LRG-Tg, while increased in controls. As a result, long-term potentiation was retained in 8- and 24-week-old LRG-Tg, whereas diminished in 48-week-old LRG-Tg compared with age-matched controls. Electron microscopy observations revealed fewer synaptic vesicles and junctions in LRG-Tg compared with age-matched controls, which became significant with age. Hippocampal LRG overexpression contributes to synaptic dysfunction, which leads to memory impairment with advance of age.

Leucine-rich alpha 2 glycoprotein promotes Th17 differentiation and collagen-induced arthritis in mice through enhancement of TGF-β-Smad2 signaling in naïve helper T cells

Background

Leucine-rich alpha 2 glycoprotein (LRG) has been identified as a serum protein elevated in patients with active rheumatoid arthritis (RA). Although the function of LRG is ill-defined, LRG binds with transforming growth factor (TGF)-β and enhances Smad2 phosphorylation. Considering that the imbalance between T helper 17 (Th17) cells and regulatory T cells (Treg) plays important roles in the pathogenesis of RA, LRG may affect arthritic pathology by enhancing the TGF-β-Smad2 pathway that is pivotal for both Treg and Th17 differentiation. The purpose of this study was to explore the contribution of LRG to the pathogenesis of arthritis, with a focus on the role of LRG in T cell differentiation.

Methods

The differentiation of CD4 T cells and the development of collagen-induced arthritis (CIA) were examined in wild-type mice and LRG knockout (KO) mice. To examine the influence of LRG on T cell differentiation, naïve CD4 T cells were isolated from LRG KO mice and cultured under Treg- or Th17-polarization condition in the absence or presence of recombinant LRG.

Results

In the CIA model, LRG deficiency led to ameliorated arthritis and reduced Th17 differentiation with no influence on Treg differentiation. By addition of recombinant LRG, the expression of IL-6 receptor (IL-6R) was enhanced through TGF-β-Smad2 signaling. In LRG KO mice, the IL-6R expression and IL-6-STAT3 signaling was attenuated in naïve CD4 T cells, compared to wild-type mice.

Conclusions

Our findings suggest that LRG upregulates IL-6R expression in naïve CD4 T cells by the enhancement of TGF-β-smad2 pathway and promote Th17 differentiation and arthritis development.

LRG1 promotes angiogenesis through upregulating the TGF‑β1 pathway in ischemic rat brain

Stroke is a life-threatening disease that results in significant disability in the human population. Despite the advances in current stroke therapies, a host of patients do not benefit from the conventional treatments. Thus, more effective therapies are required. It has been previously reported that leucine-rich-α2-glycoprotein 1 (LRG1) is crucial during the formation of new blood vessels in retinal diseases. However, the function of LRG1 in the brain during the neovessel growth process following ischemic stroke has not been fully elucidated and the mechanism underlying its effect on angiogenesis remains unclear. The purpose of the current study was to demonstrate whether LRG1 may promote angiogenesis through the transforming growth factor (TGF)-β1 signaling pathway in ischemic rat brain following middle cerebral artery occlusion (MCAO). In the present study, the spatial and temporal expression of LRG1, TGF-β1, vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) were detected in ischemic rat brain following MCAO using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot analysis and immunohistochemistry. CD34 immunohistochemistry staining was used as an indicator of microvessel density (MVD). The RT-qPCR and western blotting results revealed that the levels of LRG1 and TGF-β1 mRNA and protein expression were significantly increased as early as 6 and 12 h after MCAO (P<0.05), respectively, peaked at 3 days and persisted at significantly higher level until 14 days, in comparison with the control group. Additionally, VEGF and Ang-2 were also increased following MCAO. Furthermore, the immunohistochemistry results suggested that the MVD was increased following MCAO. In addition, the results also revealed that the percentage of LRG1-positive cells was positively correlated with the percentage of TGF-β1-positive cells, and the percentage of LRG1-positive and TGF-β1-positive cells had a positively correlation with the MVD. Taken together, the present study indicated that LRG1 may promote angiogenesis through upregulating the TGF-β1 signaling pathway in ischemic rat brain following MCAO. This may provide a potential therapeutic target for the treatment of ischemic stroke.

Sputum Leucine-Rich Alpha-2 Glycoprotein as a Marker of Airway Inflammation in Asthma

Background

Asthma is a chronic inflammatory disease of airways, but an ideal biomarker that accurately reflects ongoing airway inflammation has not yet been established. The aim of this study was to examine the potential of sputum leucine-rich alpha-2 glycoprotein (LRG) as a new biomarker for airway inflammation in asthma.

Methods

We obtained induced sputum samples from patients with asthma (N = 64) and healthy volunteers (N = 22) and measured LRG concentration by sandwich enzyme-linked immunosorbent assay (ELISA). Ovalbumin (OVA)-induced asthma model mice were used to investigate the mechanism of LRG production during airway inflammation. The LRG concentrations in the bronchoalveolar lavage fluid (BALF) obtained from mice were determined by ELISA and mouse lung sections were stained with anti-LRG antibody and periodic acid-Schiff (PAS) reagent.

Results

Sputum LRG concentrations were significantly higher in patients with asthma than in healthy volunteers (p = 0.00686). Consistent with patients’ data, BALF LRG levels in asthma model mice were significantly higher than in control mice (p = 0.00013). Immunohistochemistry of lung sections from asthma model mice revealed that LRG was intensely expressed in a subpopulation of bronchial epithelial cells, which corresponded with PAS-positive mucus producing cells.

Conclusion

These findings suggest that sputum LRG is a promising biomarker of local inflammation in asthma.

Overexpression of glypican-1 implicates poor prognosis and their chemoresistance in oesophageal squamous cell carcinoma

Background:

Despite the recent improvements in multimodal therapies for oesophageal squamous cell carcinoma (ESCC), the prognosis remains poor. The identification of suitable biomarkers for predicting the prognosis and chemo-sensitivity is required to develop targeted treatments and improve treatment results.

Methods:

Proteins highly expressed in ESCC cell lines compared with normal oesophageal cell lines were screened by isobaric tag for relative and absolute quantitation (iTRAQ). We identified glypican-1 (GPC1) as a novel molecule. The clinicopathological characteristics of GPC1 were evaluated by immunohistochemistry using ESCC specimens, and clinical parameters were assessed. The correlation between GPC1 expression levels and chemo-sensitivity were analysed in vitro.

Results:

In the immunohistochemical assessment of 175 ESCC patients, 98.8% expressed GPC1. These patients demonstrated significantly poorer prognosis compared with patients with low-GPC1 expression by survival assay (P<0.001). Higher chemoresistance was observed in the GPC1 high-expression group. GPC1 expression levels positively correlated with chemo-sensitivity against cis-Diammineplatinum (II) dichloride (CDDP), and are potentially associated with anti-apoptotic function based on alterations in the MAPK downstream signalling pathway and Bcl-2 family member proteins.

Conclusions:

GPC1 is an independent prognostic factor in ESCC and is a critical molecule for altering the threshold of chemoresistance to CDDP.

Myeloid cell-derived LRG attenuates adverse cardiac remodelling after myocardial infarction

AIMS

Leucine-rich α2-glycoprotein (LRG) is considered as a biomarker of the clinical activities of chronic inflammatory diseases, including heart failure. However, its pathophysiological roles in cardiac remodelling after myocardial infarction (MI) remain to be clarified. In this study, we have addressed functional roles of LRG in cardiac remodelling after MI.

METHODS AND RESULTS

MI was generated by ligating the left coronary artery in mice. Real-time reverse transcription (RT)-PCR and immunoblot analyses revealed that the expressions of LRG transcript and protein were up-regulated in post-infarct myocardium. LRG protein was produced by heart-infiltrating myeloid cells, such as macrophages and neutrophils. To elucidate functional roles of LRG in cardiac remodelling, we generated MI in wild-type (WT) and LRG-deficient (LRG(-/-)) mice and found that LRG gene ablation aggravated myocardial fibrosis with cardiac dysfunction after MI. Immunohistochemical analyses with anti-CD31 antibody revealed that capillary density decreased at border zone in LRG(-/-) mice compared with WT mice. Consistently, the expression of apelin receptor was reduced in LRG(-/-) mice, implying that the impaired angiogenic activity is associated with adverse cardiac remodelling in LRG(-/-) mice. Moreover, LRG gene ablation suppressed the activation of smad1/5/8, a pro-angiogenic signalling pathway. Finally, the transplantation of WT bone marrow cells into LRG(-/-) mice attenuated cardiac fibrosis with functional improvement after MI, accompanied by restoration of capillary density compared with the bone marrow transplantation from LRG(-/-) mice.

CONCLUSION

LRG, produced by heart-infiltrating myeloid cells, suppresses adverse cardiac remodelling after MI as a novel cardioprotective factor. LRG signalling could be a therapeutic target against cardiovascular diseases.