Dissociation of heparan sulfate and receptor binding domains of hepatocyte growth factor reveals that heparan sulfate-c-met interaction facilitates signaling

Betaglycan sustains HGF/Met signaling in lung cancer and endothelial cells promoting cell migration and tumor growth

Persistent HGF/Met signaling drives tumor growth and dissemination. Proteoglycans within the tumor microenvironment might control HGF availability and signaling by affecting its accessibility to Met (HGF receptor), likely defining whether acute or sustained HGF/Met signaling cues take place. Given that betaglycan (BG, also known as type III TGFβ receptor or TGFBR3), a multi-faceted proteoglycan TGFβ co-receptor, can be found within the tumor microenvironment, we addressed its hypothetical role in oncogenic HGF signaling. We found that HGF/Met promotes lung cancer and endothelial cells migration via PI3K and mTOR. This effect was enhanced by recombinant soluble betaglycan (solBG) via a mechanism attributable to its glycosaminoglycan chains, as a mutant without them did not modulate HGF effects. Moreover, soluble betaglycan extended the effect of HGF-induced phosphorylation of Met, Akt, and Erk, and membrane recruitment of the RhoGEF P-Rex1. Data-mining analysis of lung cancer patient datasets revealed a significant correlation between high MET receptor, HGF, and PREX1 expression and reduced patient survival. Soluble betaglycan showed biochemical interaction with HGF and, together, they increased tumor growth in immunocompetent mice. In conclusion, the oncogenic properties of the HGF/Met pathway are enhanced and sustained by GAG-containing soluble betaglycan.

Unlocking c-MET: A comprehensive journey into targeted therapies for breast cancer

Breast cancer is the most common malignancy among women, posing a formidable health challenge worldwide. In this complex landscape, the c-MET (cellular-mesenchymal epithelial transition factor) receptor tyrosine kinase (RTK), also recognized as the hepatocyte growth factor (HGF) receptor (HGFR), emerges as a prominent protagonist, displaying overexpression in nearly 50% of breast cancer cases. Activation of c-MET by its ligand, HGF, secreted by neighboring mesenchymal cells, contributes to a cascade of tumorigenic processes, including cell proliferation, metastasis, angiogenesis, and immunosuppression. While c-MET inhibitors such as crizotinib, capmatinib, tepotinib and cabozantinib have garnered FDA approval for non-small cell lung cancer (NSCLC), their potential within breast cancer therapy is still undetermined. This comprehensive review embarks on a journey through structural biology, multifaceted functions, and intricate signaling pathways orchestrated by c-MET across cancer types. Furthermore, we highlight the pivotal role of c-MET-targeted therapies in breast cancer, offering a clinical perspective on this promising avenue of intervention. In this pursuit, we strive to unravel the potential of c-MET as a beacon of hope in the fight against breast cancer, unveiling new horizons for therapeutic innovation.

Extracellular matrix-derived materials for tissue engineering and regenerative medicine: A journey from isolation to characterization and application

Biomaterial choice is an essential step during the development tissue engineering and regenerative medicine (TERM) applications. The selected biomaterial must present properties allowing the physiological-like recapitulation of several processes that lead to the reestablishment of homeostatic tissue or organ function. Biomaterials derived from the extracellular matrix (ECM) present many such properties and their use in the field has been steadily increasing. Considering this growing importance, it becomes imperative to provide a comprehensive overview of ECM biomaterials, encompassing their sourcing, processing, and integration into TERM applications. This review compiles the main strategies used to isolate and process ECM-derived biomaterials as well as different techniques used for its characterization, namely biochemical and chemical, physical, morphological, and biological. Lastly, some of their applications in the TERM field are explored and discussed.

A novel agonist for the HGF receptor MET promotes differentiation of human pluripotent stem cells into hepatocyte-like cells

Hepatocyte growth factor (HGF) is the natural ligand of the MET receptor tyrosine kinase. This ligand-receptor couple is essential for the maturation process of hepatocytes. Previously, the rational design of a synthetic protein based on the assembly of two K1 domains from HGF led to the production of a potent and stable MET receptor agonist. In this study, we compared the effects of K1K1 with HGF during the differentiation of hepatocyte progenitors derived from human induced pluripotent stem cells (hiPSCs). In vitro, K1K1, in the range of 20 to 200 nM, successfully substituted for HGF and efficiently activated ERK downstream signaling. Analysis of the levels of hepatocyte markers showed typical liver mRNA and protein expression (HNF4α, albumin, alpha-fetoprotein, CYP3A4) and phenotypes. Although full maturation was not achieved, the results suggest that K1K1 is an attractive candidate MET agonist suitable for replacing complex and expensive HGF treatments to induce hepatic differentiation of hiPSCs.

A glycan-based approach to cell characterization and isolation: Hematopoiesis as a paradigm

Cell surfaces display a wide array of molecules that confer identity. While flow cytometry and cluster of differentiation (CD) markers have revolutionized cell characterization and purification, functionally heterogeneous cellular subtypes remain unresolvable by the CD marker system alone. Using hematopoietic lineages as a paradigm, we leverage the extraordinary molecular diversity of heparan sulfate (HS) glycans to establish cellular "glycotypes" by utilizing a panel of anti-HS single-chain variable fragment antibodies (scFvs). Prospective sorting with anti-HS scFvs identifies functionally distinct glycotypes within heterogeneous pools of mouse and human hematopoietic progenitor cells and enables further stratification of immunophenotypically pure megakaryocyte-erythrocyte progenitors. This stratification correlates with expression of a heptad of HS-related genes that is reflective of the HS epitope recognized by specific anti-HS scFvs. While we show that HS glycotyping provides an orthogonal set of tools for resolution of hematopoietic lineages, we anticipate broad utility of this approach in defining and isolating novel, viable cell types across diverse tissues and species.

Cryo-electron Microscopic Analysis of Single-Pass Transmembrane Receptors

Single-pass transmembrane receptors (SPTMRs) represent a diverse group of integral membrane proteins that are involved in many essential cellular processes, including signal transduction, cell adhesion, and transmembrane transport of materials. Dysregulation of the SPTMRs is linked with many human diseases. Despite extensive efforts in past decades, the mechanisms of action of the SPTMRs remain incompletely understood. One major hurdle is the lack of structures of the full-length SPTMRs in different functional states. Such structural information is difficult to obtain by traditional structural biology methods such as X-ray crystallography and nuclear magnetic resonance (NMR). The recent rapid development of single-particle cryo-electron microscopy (cryo-EM) has led to an exponential surge in the number of high-resolution structures of integral membrane proteins, including SPTMRs. Cryo-EM structures of SPTMRs solved in the past few years have tremendously improved our understanding of how SPTMRs function. In this review, we will highlight these progresses in the structural studies of SPTMRs by single-particle cryo-EM, analyze important structural details of each protein involved, and discuss their implications on the underlying mechanisms. Finally, we also briefly discuss remaining challenges and exciting opportunities in the field.

Paradoxical effects of osteoprotegerin on vascular function: inhibiting inflammation while promoting oxidative stress?

Osteoprotegerin (OPG), also known as osteoclastogenesis inhibitory factor or tumor necrosis factor receptor superfamily member 11B, is well known as a modulator of bone remodeling. The contribution of OPG to cardiovascular disease (CVD) has been suggested, but its molecular mechanism is complex and remains unclear. In the present study, Alves-Lopes et al. (Clin. Sci. (Lond.) (2021) 135(20): https://doi.org/10.1042/CS20210643) reported the critical role of syndecan-1 (SDC-1, also known as CD138), a surface protein part of the endothelial glycocalyx, in OPG-induced vascular dysfunction. The authors found that in endothelial cells (ECs), through SDC-1, OPG increased eNOS Thr495 phosphorylation, thereby inhibiting eNOS activity. Furthermore, the OPG-SDC-1 interaction increased reactive oxygen species (ROS) production through NOX1/4 activation. Both the reduced eNOS activity and induced ROS production inhibited NO production and impaired EC function. In vascular smooth muscle cells (VSMCs), the OPG-SDC-1 interaction increased ROS production through NOX1/4 activation, subsequently increased MLC phosphorylation-mediated Rho kinase-MYPT1 regulation, leading to increased vascular contraction. Ultilizing wire myography and mechanistic studies, the authors nicely provide the evidence that SDC-1 plays a crucial role in OPG-induced vascular dysfunction. As we mentioned above, the molecular mechanism and roles of OPG in cardiovascular system are complex and somewhat confusing. In this commentary, we briefly summarize the OPG-mediated signaling pathways in cardiovascular system.

Engineering, Characterization, and Biological Evaluation of an Antibody Targeting the HGF Receptor

The Hepatocyte growth factor (HGF) and its receptor (MET) promote several physiological activities such as tissue regeneration and protection from cell injury of epithelial, endothelial, neuronal and muscle cells. The therapeutic potential of MET activation has been scrutinized in the treatment of acute tissue injury, chronic inflammation, such as renal fibrosis and multiple sclerosis (MS), cardiovascular and neurodegenerative diseases. On the other hand, the HGF-MET signaling pathway may be caught by cancer cells and turned to work for invasion, metastasis, and drug resistance in the tumor microenvironment. Here, we engineered a recombinant antibody (RDO24) and two derived fragments, binding the extracellular domain (ECD) of the MET protein. The antibody binds with high affinity (8 nM) to MET ECD and does not cross-react with the closely related receptors RON nor with Semaphorin 4D. Deletion mapping studies and computational modeling show that RDO24 binds to the structure bent on the Plexin-Semaphorin-Integrin (PSI) domain, implicating the PSI domain in its binding to MET. The intact RDO24 antibody and the bivalent Fab2, but not the monovalent Fab induce MET auto-phosphorylation, mimicking the mechanism of action of HGF that activates the receptor by dimerization. Accordingly, the bivalent recombinant molecules induce HGF biological responses, such as cell migration and wound healing, behaving as MET agonists of therapeutic interest in regenerative medicine. In vivo administration of RDO24 in the murine model of MS, represented by experimental autoimmune encephalomyelitis (EAE), delays the EAE onset, mitigates the early clinical symptoms, and reduces inflammatory infiltrates. Altogether, these results suggest that engineered RDO24 antibody may be beneficial in multiple sclerosis and possibly other types of inflammatory disorders.

A single injection of CM1021, a long half-life hepatocyte growth factor mimetic, increases liver mass in mice

Despite years of positive animal data, hepatocyte growth factor (HGF) has never been developed into a useful pharmaceutical, primarily due to its poor pharmacological properties. CM1021 is a fusion protein containing the K1 loop of HGF and the human IgG1 Fc region. The experiments described here demonstrate that CM1021 has the biological properties of HGF and the pharmacological properties of a monoclonal antibody. CM1021 stimulates scattering and branching morphogenesis in MDCK cells and stimulates liver growth in vivo. Unlike HGF, it is available via intraperitoneal injection and has an estimated half-life similar to an antibody.

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Fusion of the K1 loop of HGF to the Fc region of IgG creates CM1021, a long half-life HGF mimetic.

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CM1021 has the biological properties of HGF without the pharmacological liabilities.

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CM1021 stimulates hepatocyte division in vivo.

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CM1021 can realize the potential of HGF in regenerative medicine.

Structural basis of the activation of c-MET receptor

The c-MET receptor is a receptor tyrosine kinase (RTK) that plays essential roles in normal cell development and motility. Aberrant activation of c-MET can lead to both tumors growth and metastatic progression of cancer cells. C-MET can be activated by either hepatocyte growth factor (HGF), or its natural isoform NK1. Here, we report the cryo-EM structures of c-MET/HGF and c-MET/NK1 complexes in the active state. The c-MET/HGF complex structure reveals that, by utilizing two distinct interfaces, one HGF molecule is sufficient to induce a specific dimerization mode of c-MET for receptor activation. The binding of heparin as well as a second HGF to the 2:1 c-MET:HGF complex further stabilize this active conformation. Distinct to HGF, NK1 forms a stable dimer, and bridges two c-METs in a symmetrical manner for activation. Collectively, our studies provide structural insights into the activation mechanisms of c-MET, and reveal how two isoforms of the same ligand use dramatically different mechanisms to activate the receptor.

Activation of c-MET receptor tyrosine kinase involves hepatocyte growth factor (HGF) and glycosaminoglycans, but the molecular mechanism is still under debate. Here, the authors present cryoEM structures of c-MET bound to two HGF splice variants and heparin, revealing the structural basis for c-MET activation.

What Are the Potential Roles of Nuclear Perlecan and Other Heparan Sulphate Proteoglycans in the Normal and Malignant Phenotype

The recent discovery of nuclear and perinuclear perlecan in annulus fibrosus and nucleus pulposus cells and its known matrix stabilizing properties in tissues introduces the possibility that perlecan may also have intracellular stabilizing or regulatory roles through interactions with nuclear envelope or cytoskeletal proteins or roles in nucleosomal-chromatin organization that may regulate transcriptional factors and modulate gene expression. The nucleus is a mechano-sensor organelle, and sophisticated dynamic mechanoresponsive cytoskeletal and nuclear envelope components support and protect the nucleus, allowing it to perceive and respond to mechano-stimulation. This review speculates on the potential roles of perlecan in the nucleus based on what is already known about nuclear heparan sulphate proteoglycans. Perlecan is frequently found in the nuclei of tumour cells; however, its specific role in these diseased tissues is largely unknown. The aim of this review is to highlight probable roles for this intriguing interactive regulatory proteoglycan in the nucleus of normal and malignant cell types.

Activation of the MET receptor attenuates doxorubicin-induced cardiotoxicity in vivo and in vitro

Background and Purpose

Doxorubicin anti‐cancer therapy is associated with cardiotoxicity, resulting from DNA damage response (DDR). Hepatocyte growth factor (HGF) protects cardiomyocytes from injury, but its effective use is compromised by low biodistribution. In this study, we have investigated whether the activation of the HGF receptor—encoded by the Met gene—by an agonist monoclonal antibody (mAb) could protect against doxorubicin‐induced cardiotoxicity.

Experimental Approach

The mAb (5 mg·kg⁻¹) was injected in vivo into C57BL/6J mice, before doxorubicin (three doses of 7 mg·kg⁻¹). Cardiac functions were evaluated through MRI after treatment termination. Heart histological staining and mRNA levels of genes associated with heart failure (Acta1 and Nppa), inflammation (IL‐6), and fibrosis (Ctgf, Col1a2, Timp1, and Mmp9) were assessed. MAb (100 nM) was administered in vitro to H9c2 cardiomyoblasts before addition of doxorubicin (25 μM). DDR and apoptosis markers were evaluated by quantitative western blotting, flow cytometry, and immunofluorescence. Stattic was used for pharmacological inactivation of STAT3.

Key Results

In vivo, administration of the mAb alleviated doxorubicin‐induced cardiac dysfunction and fibrosis. In vitro, mAb mimicked the response to HGF by (a) inhibiting histone H2AX phosphorylation at S139, (b) quenching the expression of the DNA repair enzyme PARP1, and (c) reducing the proteolytic activation of caspase 3. The MET‐driven cardioprotection involved, at least in vitro, the phosphorylation of STAT3.

Conclusion and Implications

The MET agonist mAb provides a new tool for cardioprotection against anthracycline cardiotoxicity.

HSulf‑1 and palbociclib exert synergistic antitumor effects on RB‑positive triple‑negative breast cancer

Human sulfatase-1 (HSulf-1) is emerging as a novel prognostic biomarker in breast cancer. Previous studies demonstrated HSulf-1 to function as a negative regulator of cyclin D1 in breast cancer. Accumulating preclinical evidence is supporting the efficacy of cyclin-dependent kinase (CDK) 4/6 inhibitors against the luminal androgen receptor sub-type of triple-negative breast cancer (TNBC). It was therefore hypothesized that HSulf-1 may cooperate with CDK4/6 inhibitors to control cell cycle progression in breast cancer cells. HSulf-1 expression was found to be downregulated in TNBC tissues and cell lines compared with that in healthy tissues and non-breast cancer cell lines, respectively. High levels of HSulf-1 expression was also found to be associated with increased progression-free survival and overall survival in patients with TNBC. Functionally, it was demonstrated that HSulf-1 served as tumor suppressor in TNBC by inducing cell cycle arrest and apoptosis whilst inhibiting proliferation, epithelial-mesenchymal transition, migration and invasion. Subsequent overexpression of HSulf-1 coupled with treatment with the CDK4/6 inhibitor palbociclib exhibited a synergistic antitumor effect on retinoblastoma (RB)-positive TNBC. Further studies revealed the mechanism underlying this cooperative antiproliferative effect involved to be due to the prohibitive effects of HSulf-1 on the palbociclib-induced accumulation of cyclin D1 through AKT/STAT3 and ERK1/2/STAT3 signaling. Taken together, findings from the present study not only suggest that HSulf-1 may be a potential therapeutic target for TNBC, but also indicate that combinatorial treatment could be an alternative therapeutic option for RB-positive TNBC, which may open novel perspectives.

Heparan sulfate proteoglycan - A common receptor for diverse cytokines

Heparan sulfate proteoglycans (HSPG) are macromolecular glyco-conjugates expressed ubiquitously on the cell surface and in the extracellular matrix where they interact with a wide range of ligands to regulate many aspects of cellular function. The capacity of the side glycosaminoglycan chain heparan sulfate (HS) being able to interact with diverse protein ligands relies on its complex structure that is generated by a controlled biosynthesis process, involving the actions of glycosyl-transferases, sulfotransferases and the glucuronyl C5-epimerase. It is believed that activities of the modification enzymes control the HS structures that are designed to serve the biological functions in a given cell or biological status. In this review, we briefly discuss recent understandings on the roles of HSPG in cytokine stimulated cellular signaling, focusing on FGF, TGF-β, Wnt, Hh, HGF and VEGF.

Improving the protective effects of aFGF for peripheral nerve injury repair using sulfated chitooligosaccharides

Injury to the peripheral nerves can result in temporary or life-long neuronal dysfunction and subsequent economic or social disability. Acidic fibroblast growth factor (aFGF) promotes the growth and survival of neurons and is a possible treatment for peripheral nerve injury. Yet, the actual therapeutic utility of aFGF is limited by its short half-life and instability in vivo. In the present study, we prepared sulfated chitooligosaccharides (SCOS), which have heparin-like properties, to improve the bioactivity of aFGF. We investigated the protective effects of SCOS with or without aFGF on RSC96 cells exposed to Na₂S₂O₄ hypoxia/reoxygenation injury. Cell viability was measured by MTT assay and cytotoxicity induced by Na₂S₂O₄ was assessed by lactate dehydrogenase (LDH) release into the culture medium. Pretreatment with aFGF and SCOS dramatically decreased LDH release after injury compared to pretreatment with aFGF or SCOS alone. We subsequently prepared an aFGF/SCOS thermo-sensitive hydrogel with poloxamer and examined its effects in vivo. Paw withdrawal thresholds and thermal withdrawal latencies were measured in rats with sciatic nerve injury. Local injection of the aFGF/SCOS hydrogels (aFGF: 40, 80 µg/kg) increased the efficiency of sciatic nerve repair compared to aFGF (80 µg/kg) hydrogel alone. Especially aFGF/SCOS thermo-sensitive hydrogel decreased paw withdrawal thresholds from 117.75 ± 8.38 (g, 4 d) to 65.74 ± 3.39 (g, 10 d), but aFGF alone group were 140.58 ± 27.54 (g, 4 d) to 89.12 ± 5.60 (g, 10 d) (aFGF dose was 80 µg/kg, P < 0.05, n = 8). The thermal withdrawal latencies decreased from 11.61 ± 2.26 (s, 4 d) to 2.37 ±0.67 (s, 10 d). However, aFGF alone group were from 17.69 ± 1.47 (s, 4 d) to 4.65 ± 1.73 (s, 10 d) (P < 0.05, n = 8). Furthermore, the aFGF/SCOS hydrogels also exhibited good biocompatibility in mice. In summary, SCOS improved the protective effects of aFGF in RSC96 cells injured with Na₂S₂O₄ and increased the efficiency of nerve repair and recovery of function in rats with sciatic nerve injury. These findings pave an avenue for the development of novel prophylactic and therapeutic strategies for peripheral nerve injury.

Lectin ZG16p inhibits proliferation of human colorectal cancer cells via its carbohydrate-binding sites

Zymogen granule protein 16 (ZG16p) is a soluble lectin that binds to both mannose and heparin/heparan sulfate. It is highly expressed in the human digestive tract and is secreted into the mucus. In this study, we investigated the effect of ZG16p on the proliferation of human colorectal cancer cells. Overexpression of ZG16p in Caco-2 cells decreased cell growth. Recombinant ZG16p markedly inhibited proliferation of Caco-2, LS174T, HCT116 and HCT15 cells. Caco-2 cell growth was not inhibited by two mutated ZG16p proteins, D151A and M5 (K36A, R37A, R53A, R55A and R79A) lacking mannose- and heparin-binding activities, respectively. Immunofluorescent cell staining revealed that ZG16p-D151A maintained its binding to the Caco-2 cell surface, whereas ZG16p-M5 failed to bind to the cells. These results suggest that ZG16p interacts with the cell surface via basic amino acids substituted in ZG16p-M5 and inhibits Caco-2 cell proliferation via Asp151. In addition, growth of patient-derived colorectal tumor organoids in a 3D intestinal stem cell system was suppressed by ZG16p but not by ZG16p-M5. Taken together, our findings indicate that ZG16p inhibits the growth of colorectal cancer cells via its carbohydrate-binding sites in vitro and ex vivo. In this study, a novel pathway in cancer cell growth regulation through cell surface carbohydrate chains is suggested.

Targeting Heparan Sulfate Proteoglycans as a Novel Therapeutic Strategy for Mucopolysaccharidoses

Mucopolysaccharidoses (MPSs) are inherited metabolic diseases caused by the deficiency of lysosomal enzymes needed to catabolize glycosaminoglycans (GAGs). Four therapeutic options are currently considered: enzyme replacement therapy, substrate reduction therapy, gene therapy, and hematopoietic stem cell transplantation. However, while some of them exhibit limited clinical efficacy and require high costs, others are still in development. Therefore, alternative treatments for MPSs need to be explored. Here we describe an innovative therapeutic approach based on the use of a recombinant protein that is able to bind the excess of extracellular accumulated heparan sulfate (HS). We demonstrate that this protein is able to reduce lysosomal defects in primary fibroblasts from MPS I and MPS IIIB patients. We also show that, by masking the excess of extracellular accumulated HS in MPS fibroblasts, fibroblast growth factor (FGF) signal transduction can be positively modulated. We, therefore, suggest the use of a competitive binding molecule for HS in MPSs as an alternative strategy to prevent the detrimental extracellular substrate storage.

Temperature-sensitive heparin-modified poloxamer hydrogel with affinity to KGF facilitate the morphologic and functional recovery of the injured rat uterus

Endometrial injury usually results in intrauterine adhesion (IUA), which is an important cause of infertility and recurrent miscarriage in reproductive women. There is still lack of an effective therapeutic strategy to prevent occurrence of IUA. Keratinocyte growth factor (KGF) is a potent repair factor for epithelial tissues. Here, a temperature-sensitive heparin-modified poloxamer (HP) hydrogel with affinity to KGF (KGF-HP) was used as a support matrix to prevent IUA and deliver KGF. The rheology of KGF-HP hydrogel was carefully characterized. The cold KGF-HP solution was rapidly transited to hydrogel with suitable storage modulus (G') and loss modulus (G″) for the applications of uterus cavity at temperature of 33 °C. In vitro release demonstrated that KGF was released from HP hydrogels in sustained release manner for a long time. In vivo bioluminescence imaging showed that KGF-HP hydrogel was able to prolong the retention of the encapsulated KGF in injured uterus of rat model. Moreover, the morphology and function of the injured uterus were significantly recovered after administration of KGF-HP hydrogel, which were evaluated by two-dimensional ultrasound imaging and receptive fertility. Not only proliferation of endometrial glandular epithelial cells and luminal epithelial cells but also angiogenesis of injured uterus were observed by Ki67 and CD31 staining after 7 d of treatment with KGF-HP hydrogel. Finally, a close relatively relationship between autophagy and proliferation of endometrial epithelial cells (EEC) and angiogenesis was firstly confirmed by detecting expression of LC3-II and P62 after KGF treatment. Overall, KGF-HP may be used as a promising candidate for IUA treatment.

A Thermosensitive Heparin-Poloxamer Hydrogel Bridges aFGF to Treat Spinal Cord Injury

Acidic fibroblast growth factor (aFGF) exerts a protective effect on spinal cord injury (SCI) but is limited by the lack of physicochemical stability and the ability to cross the blood spinal cord barrier (BSCB). As promising biomaterials, hydrogels contain substantial amounts of water and a three-dimensional porous structure and are commonly used to load and deliver growth factors. Heparin can not only enhance growth factor loading onto hydrogels but also can stabilize the structure and control the release behavior. Herein, a novel aFGF-loaded thermosensitive heparin-poloxamer (aFGF-HP) hydrogel was developed and applied to provide protection and regeneration after SCI. To assess the effects of the aFGF-HP hydrogel, BSCB restoration, neuron and axonal rehabilitation, glial scar inhibition, inflammatory response suppression, and motor recovery were studied both in vivo and in vitro. The aFGF-HP hydrogels exhibited sustained release of aFGF and protected the bioactivity of aFGF in vitro. Compared to groups intravenously administered either drug-free HP hydrogel or aFGF alone, the aFGF-HP hydrogel group revealed prominent and attenuated disruption of the BSCB, reduced neuronal apoptosis, reactive astrogliosis, and increased neuron and axonal rehabilitation both in vivo and in vitro. This work provides an effective approach to enhance recovery after SCI and provide a successful strategy for SCI protection.

The regulatory role of heparin on c-Met signaling in hepatocellular carcinoma cells

The role of heparin as an anticoagulant is well defined; however, its role in tumorigenesis and tumor progression is not clear yet. Some studies have shown that anticoagulant treatment in cancer patients improve overall survival, however, recent clinical trials have not shown a survival benefit in cancer patients receiving heparin treatment. In our previous studies we have shown the inhibitory effects of heparin on Hepatocyte Growth Factor (HGF)-induced invasion and migration in hepatocellular carcinoma (HCC) cells. In this study, we showed the differential effects of heparin on the behaviors of HCC cells based on the presence or absence of HGF. In the absence of HGF, heparin activated HGF/c-Met signaling and promoted motility and invasion in HCC cells. Heparin treatment led to c-Met receptor dimerization and activated c-Met signaling in an HGF independent manner. Heparin-induced c-Met activation increased migration and invasion through ERK1/2, early growth response factor 1 (EGR1) and Matrix Metalloproteinases (MMP) axis. Interestingly, heparin modestly decreased the proliferation of HCC cells by inhibiting activatory phosphorylation of Akt. The inhibition of c-Met signaling reversed heparin-induced increase in motility and invasion and, proliferation inhibition. Our study provides a new perspective into the role of heparin on c-Met signaling in HCC.

Incomplete target neutralization by the anti-cancer antibody rilotumumab

The antibody rilotumumab, which has been tested in multiple Phase 2 and Phase 3 trials, has been reported to neutralize hepatocyte growth factor (HGF), the ligand for the oncogene MET. However, we report that rilotumumab does not prevent HGF from directly binding to MET on conventional and primary patient-derived human gliomasphere lines, a trait driven by the HGF α-chain, which remains free to engage cell-surface glycosaminoglycans and the receptor MET. This binding induces MET phosphorylation, initiates robust AKT and ERK signaling and potentiates biological effects such as cell scattering. This partial antagonism was highly exacerbated in the presence of activated epidermal growth factor receptor, which is common in several cancers. Hence, we confirm that rilotumumab is only a partial antagonist of HGF activity, a finding that has considerable implications for the therapeutic use of rilotumumab.

MDA-MB-231 breast cancer cell viability, motility and matrix adhesion are regulated by a complex interplay of heparan sulfate, chondroitin-/dermatan sulfate and hyaluronan biosynthesis

Proteoglycans and glycosaminoglycans modulate numerous cellular processes relevant to tumour progression, including cell proliferation, cell-matrix interactions, cell motility and invasive growth. Among the glycosaminoglycans with a well-documented role in tumour progression are heparan sulphate, chondroitin/dermatan sulphate and hyaluronic acid/hyaluronan. While the mode of biosynthesis differs for sulphated glycosaminoglycans, which are synthesised in the ER and Golgi compartments, and hyaluronan, which is synthesized at the plasma membrane, these polysaccharides partially compete for common substrates. In this study, we employed a siRNA knockdown approach for heparan sulphate (EXT1) and heparan/chondroitin/dermatan sulphate-biosynthetic enzymes (β4GalT7) in the aggressive human breast cancer cell line MDA-MB-231 to study the impact on cell behaviour and hyaluronan biosynthesis. Knockdown of β4GalT7 expression resulted in a decrease in cell viability, motility and adhesion to fibronectin, while these parameters were unchanged in EXT1-silenced cells. Importantly, these changes were associated with a decreased expression of syndecan-1, decreased signalling response to HGF and an increase in the synthesis of hyaluronan, due to an upregulation of the hyaluronan synthases HAS2 and HAS3. Interestingly, EXT1-depleted cells showed a downregulation of the UDP-sugar transporter SLC35D1, whereas SLC35D2 was downregulated in β4GalT7-depleted cells, indicating an intricate regulatory network that connects all glycosaminoglycans synthesis. The results of our in vitro study suggest that a modulation of breast cancer cell behaviour via interference with heparan sulphate biosynthesis may result in a compensatory upregulation of hyaluronan biosynthesis. These findings have important implications for the development of glycosaminoglycan-targeted therapeutic approaches for malignant diseases.

Adenovirus-mediated transfer of hepatocyte growth factor gene to human dental pulp stem cells under good manufacturing practice improves their potential for periodontal regeneration in swine

Introduction

Periodontitis is one of the most widespread infectious diseases in humans. We previously promoted significant periodontal tissue regeneration in swine models with the transplantation of autologous periodontal ligament stem cells (PDLSCs) and PDLSC sheet. We also promoted periodontal tissue regeneration in a rat model with a local injection of allogeneic bone marrow mesenchymal stem cells. The purpose of the present study is to investigate the roles of the hepatocyte growth factor (HGF) and human dental pulp stem cells (DPSCs) in periodontal tissue regeneration in swine.

Method

In the present study, we transferred an adenovirus that carried HGF gene into human DPSCs (HGF-hDPSCs) under good manufacturing practice (GMP) conditions. These cells were then transplanted into a swine model for periodontal regeneration. Twenty miniature pigs were used to generate periodontitis with bone defect of 5 mm in width, 7 mm in length, and 3 mm in depth. After 12 weeks, clinical, radiological, quantitative and histological assessment of regenerated periodontal tissues was performed to compare periodontal regeneration in swine treated with cell implantation.

Results

Our study showed that injecting HGF-hDPSCs into this large animal model could significantly improve periodontal bone regeneration and soft tissue healing. A hDPSC or HGF-hDPSC sheet showed superior periodontal tissue regeneration compared to the injection of dissociated cells. However, the sheets required surgical placement; thus, they were suitable for surgically-managed periodontitis treatments. The adenovirus-mediated transfer of the HGF gene markedly decreased hDPSC apoptosis in a hypoxic environment or in serum-free medium, and it increased blood vessel regeneration.

Conclusion

This study indicated that HGF-hDPSCs produced under GMP conditions significantly improved periodontal bone regeneration in swine; thus, this method represents a potential clinical application for periodontal regeneration.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0244-5) contains supplementary material, which is available to authorized users.

Expression array analysis of the hepatocyte growth factor invasive program

Signaling by human hepatocyte growth factor (hHGF) via its cell surface receptor (MET) drives mitogenesis, motogenesis and morphogenesis in a wide spectrum of target cell types and embryologic, developmental and homeostatic contexts. Oncogenic pathway activation also contributes to tumorigenesis and cancer progression, including tumor angiogenesis and metastasis, in several prevalent malignancies. The HGF gene encodes full-length hHGF and two truncated isoforms known as NK1 and NK2. NK1 induces all three HGF activities at modestly reduced potency, whereas NK2 stimulates only motogenesis and enhances HGF-driven tumor metastasis in transgenic mice. Prior studies have shown that mouse HGF (mHGF) also binds with high affinity to human MET. Here we show that, like NK2, mHGF stimulates cell motility, invasion and spontaneous metastasis of PC3M human prostate adenocarcinoma cells in mice through human MET. To identify target genes and signaling pathways associated with motogenic and metastatic HGF signaling, i.e., the HGF invasive program, gene expression profiling was performed using PC3M cells treated with hHGF, NK2 or mHGF. Results obtained using Ingenuity Pathway Analysis software showed significant overlap with networks and pathways involved in cell movement and metastasis. Interrogating The Cancer Genome Atlas project also identified a subset of 23 gene expression changes in PC3M with a strong tendency for co-occurrence in prostate cancer patients that were associated with significantly decreased disease-free survival.

High circulating hepatocyte growth factor levels associate with epithelial to mesenchymal transition and poor outcome in small cell lung cancer patients

We have previously shown that Met activation through the hepatocyte growth factor (HGF) increases tumorogenesis, induces epithelial-to-mesenchymal transition (EMT) and chemoresistance in SCLC. We sought to evaluate circulating HGF levels in SCLC patients and assess correlation with outcome and EMT features in the tumor. Serum samples from patients with SCLC were prospectively obtained at diagnosis, response evaluation and progression. HGF serum (sHGF) was quantified by ELISA. EMT markers and p-Met/Met were assayed by immunohistochemistry in tumor samples. Clinical data were prospectively recorder. One-hundred twelve patients were included. High baseline levels of sHGF were associated with shorter overall survival (p=0.006) and remained independently associated with survival in the multivariate analysis (p=0.016). For stage IV patients, an increase of sHGF levels at response evaluation (p=0.042) and at progression (p=0.003) were associated with poor outcome. sHGF levels were associated (p<0.05) with a mesenchymal phenotype in the tumor. In conclusion, high sHGF at diagnosis and increases during the course of the disease predict for poor outcome in SCLC patients and associate with EMT in the tumor. These data provide novel evidence on a role of sHGF in the adverse clinical behavior of SCLC and supports testing Met inhibitors in patients with high sHGF.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Semi-synthesis of a HGF/SF kringle one (K1) domain scaffold generates a potent in vivo MET receptor agonist

The development of MET receptor agonists is an important goal in regenerative medicine, but is limited by the complexity and incomplete understanding of its interaction with HGF/SF (Hepatocyte Growth Factor/Scatter Factor). NK1 is a natural occurring agonist comprising the N-terminal (N) and the first kringle (K1) domains of HGF/SF. In the presence of heparin, NK1 can self-associate into a "head to tail" dimer which is considered as the minimal structural module able to trigger MET dimerization and activation whereas isolated K1 and N domains showed a weak or a complete lack of agonistic activity respectively. Starting from these structural and biological observations, we investigated whether it was possible to recapitulate the biological properties of NK1 using a new molecular architecture of isolated N or K1 domains. Therefore, we engineered multivalent N or K1 scaffolds by combining synthetic and homogeneous site-specifically biotinylated N and K1 domains (NB and K1B) and streptavidin (S). NB alone or in complex failed to activate MET signaling and to trigger cellular phenotypes. Importantly and to the contrary of K1B alone, the semi-synthetic K1B/S complex mimicked NK1 MET agonist activity in cell scattering, morphogenesis and survival phenotypic assays. Impressively, K1B/S complex stimulated in vivo angiogenesis and, when injected in mice, protected the liver against fulminant hepatitis in a MET dependent manner whereas NK1 and HGF were substantially less potent. These data reveal that without N domain, proper multimerization of K1 domain is a promising strategy for the rational design of powerful MET agonists.

Physiological Signaling and Structure of the HGF Receptor MET

The "hepatocyte growth factor" also known as "scatter factor", is a multifunctional cytokine with the peculiar ability of simultaneously triggering epithelial cell proliferation, movement and survival. The combination of those proprieties results in the induction of an epithelial to mesenchymal transition in target cells, fundamental for embryogenesis but also exploited by tumor cells during metastatization. The hepatocyte growth factor receptor, MET, is a proto-oncogene and a prototypical transmembrane tyrosine kinase receptor. Inhere we discuss the MET molecular structure and the hepatocyte growth factor driven physiological signaling which coordinates epithelial proliferation, motility and morphogenesis.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

High-level expression and characterization of bioactive human truncated variant of hepatocyte growth factor in Escherichia coli

Hepatocyte growth factor (HGF) is an effective anti-fibrotic factor because of its bioactivity in inhibiting fibrosis-related proteins in the development of hepatic fibrosis. However, high-level production of bioactive mature form HGF is difficult because of its complex structure. Here, we report a non-fusion protein expression system to obtain truncated variant of N-terminal hairpin and first kringle domains of HGF (tvNK1) in Escherichia coli to determine its anti-fibrotic effects on hepatic stellate cells (HSCs). Under the selected conditions of cultivation and isopropyl-β-D-1-thiogalactopyranoside induction, the expression level of tvNK1 accounted for approximately 65 % of the total cellular protein and 50 % of fusion protein in the supernatant of whole cell lysates. The recombinant protein could be purified in one step with Ni(2+)-affinity chromatograph. Finally, about 65 mg recombinant tvNK1 was obtained from 1 l fermentation culture with no <95 % purity. In vitro, the final purified tvNK1 was shown to inhibit the proliferation of HSCs and decrease the mRNA and protein expression levels of fibrosis-related COL1A1 and α-smooth muscle actin genes.

Glypican-1 regulates myoblast response to HGF via Met in a lipid raft-dependent mechanism: effect on migration of skeletal muscle precursor cells

BACKGROUND

Via the hepatocyte growth factor receptor (Met), hepatocyte growth factor (HGF) exerts key roles involving skeletal muscle development and regeneration. Heparan sulfate proteoglycans (HSPGs) are critical modulators of HGF activity, but the role of specific HSPGs in HGF regulation is poorly understood. Glypican-1 is the only HSPG expressed in myoblasts that localize in lipid raft membrane domains, controlling cell responses to extracellular stimuli. We determined if glypican-1 in these domains is necessary to stabilize the HGF-Met signaling complex and myoblast response to HGF.

METHODS

C2C12 myoblasts and a derived clone (C6) with low glypican-1 expression were used as an experimental model. The activation of Met, ERK1/2 and AKT in response to HGF was evaluated. The distribution of Met and its activated form in lipid raft domains, as well as its dependence on glypican-1, were characterized by sucrose density gradient fractionation in both cell types. Rescue experiments reexpressing glypican-1 or a chimeric glypican-1 fused to the transmembrane and cytoplasmic domains of mouse syndecan-1 or myoblast pretreatment with MβCD were conducted. In vitro and in vivo myoblast migration assays in response to HGF were also performed.

RESULTS

Glypican-1 localization in membrane raft domains was required for a maximum cell response to HGF. It stabilized Met and HGF in lipid raft domains, forming a signaling complex where the active phospho-Met receptor was concentrated. Glypican-1 also stabilized CD44 in a HGF-dependent manner. In addition, glypican-1 was required for in vitro and in vivo HGF-dependent myoblast migration.

CONCLUSIONS

Glypican-1 is a regulator of HGF-dependent signaling via Met in lipid raft domains.

Heparan sulfate in angiogenesis: a target for therapy

Heparan sulfate (HS), a long linear polysaccharide of alternating disaccharide residues, interacts with a wide variety of proteins, including many angiogenic factors. The involvement of HS in signaling of pro-angiogenic factors (e.g. vascular endothelial growth factor and fibroblast growth factor 2), as well as interaction with anti-angiogenic factors (e.g. endostatin), warrants its role as an important modifier of (tumor) angiogenesis. This review summarizes our current understanding of the role of HS in angiogenic growth factor signaling, and discusses therapeutic strategies to target HS and modulate angiogenesis.

Roles of EXTL2, a member of the EXT family of tumour suppressors, in liver injury and regeneration processes

The gene products of two members of the EXT (exostosin) gene family, EXT1 and EXT2, function together as a polymerase in the biosynthesis of heparan sulfate. EXTL2 (EXT-like 2), one of the three EXTL genes in the human genome that are homologous to EXT1 and EXT2, encodes an N-acetylhexosaminyltransferase. We have demonstrated that EXTL2 terminates chain elongation of GAGs (glycosaminoglycans), and thereby regulates GAG biosynthesis. The abnormal GAG biosynthesis caused by loss of EXTL2 had no effect on normal development or normal adult homoeostasis. Therefore we examined the role of EXTL2 in CCl4 (carbon tetrachloride)-induced liver failure, a model of liver disease. On the fifth day after CCl4 administration, the liver/body weight ratio was significantly smaller for EXTL2-knockout mice than for wild-type mice. Consistent with this observation, hepatocyte proliferation following CCl4 treatment was lower in EXTL2-knockout mice than in wild-type mice. EXTL2-knockout mice experienced less HGF (hepatocyte growth factor)-mediated signalling than wild-type mice specifically because GAG synthesis was altered in these mutant mice. In addition, GAG synthesis in hepatic stellate cells was up-regulated during liver repair in EXTL2-knockout mice. Taken together, the results of the present study indicated that EXTL2-mediated regulation of GAG synthesis was important to the tissue regeneration processes that follow liver injury.

MET: a critical player in tumorigenesis and therapeutic target

Since its discovery more than 25 years ago, numerous studies have established that the MET receptor is unique among tyrosine kinases. Signaling through MET is necessary for normal development and for the progression of a wide range of human cancers. MET activation has been shown to drive numerous signaling pathways; however, it is not clear how MET signaling mediates diverse cellular responses such as motility, invasion, growth, and angiogenesis. Great strides have been made in understanding the pleotropic aspects of MET signaling using three-dimensional molecular structures, cell culture systems, human tumors, and animal models. These combined approaches have driven the development of MET-targeted therapeutics that have shown promising results in the clinic. Here we examine the unique features of MET and hepatocyte growth factor/scatter factor (HGF/SF) structure and signaling, mutational activation, genetic mouse models of MET and HGF/SF, and MET-targeted therapeutics.

SULF1 inhibits proliferation and invasion of esophageal squamous cell carcinoma cells by decreasing heparin-binding growth factor signaling

BACKGROUND

Heparin-binding growth factor signaling is involved in the pathogenesis and development of human cancers. It can be regulated by sulfation of cell-surface heparan sulfate proteoglycans (HSPG). SULF1 is a heparin-degrading endosulfatase which can modulate the sulfation of HSPGs.

AIM

The purpose of this study was to elucidate the role of SULF1 in modulating proliferation and invasion of esophageal squamous cell carcinoma (ESCC) by decreasing heparin-binding growth factor signaling.

METHODS

We restored SULF1 expression in the ESCC cell line KYSE150, and examined the effects of SULF1 expression on the proliferation and invasion of KYSE150 cells. In addition, we investigated the expression of SULF1 in human ESCC tissues and analyzed the correlation of SULF1 expression with clinicopathologic characteristics of ESCC.

RESULTS

Our study shows that re-expression of SULF1 in ESCC cell line results in the downregulation of hepatocyte growth factor-mediated activation of MAPK pathways with a resultant decrease in cell invasiveness. Cell proliferation was also inhibited in SULF1-transfected KYSE150 cells. Immunohistochemical assays reveal that SULF1 is expressed in nearly half of the human ESCC tissues but not in normal esophageal epithelial cells. SULF1 expression in human ESCC tissues is negatively correlated with tumor size and tumor invasion.

CONCLUSION

This study identified that SULF1 inhibits proliferation and invasion of ESCC by decreasing heparin-binding growth factor signaling and suggested that SULF1 plays an inhibiting role in the pathogenesis of ESCC.

High concentration but low activity of hepatocyte growth factor in periodontitis

BACKGROUND

High levels of hepatocyte growth factor (HGF), a healing factor with regenerative and cytoprotective effects, are associated with inflammatory diseases, including periodontitis. HGF biologic activity requires binding to its receptors, the proto-oncogene c-Met and heparan sulfate proteoglycan (HSPG). This study investigates HGF expression and its relationship to subgingival microbiota in medically healthy individuals with and without periodontitis.

METHODS

Saliva, gingival crevicular fluid (GCF), and blood samples from 30 patients with severe periodontitis and 30 healthy controls were analyzed for HGF concentration using enzyme-linked immunosorbent assay and binding affinity for HSPG and c-Met using surface plasmon resonance. The regenerative effects of saliva from three patients and controls were analyzed in an in vitro model of cell injury. Subgingival plaques were analyzed for the presence of 18 bacterial species.

RESULTS

Patients with periodontitis showed higher HGF concentrations in saliva, GCF, and serum (P <0.001); however, the binding affinities for HSPG and c-Met were reduced in GCF and saliva (P <0.002). In contrast to the controls, saliva from patients showed no significant regenerative effect over time on gingival epithelial cells. Compared with controls, patients had a higher prevalence of periodontally related bacteria.

CONCLUSIONS

Higher circulatory HGF levels indicate a systemic effect of periodontitis. However, the HGF biologic activity at local inflammation sites was reduced, and this effect was associated with the amount of periodontal bacteria. Loss of function of healing factors may be an important mechanism in degenerative processes in periodontally susceptible individuals.

Novel antagonists of heparin binding growth factors

Structural and functional studies of ligand-RTK interactions over the last decade highlight the importance of multiple binding events and associated conformational changes in RTK ectodomains that are required for kinase activation. These events vary in strength, and even weak interactions appear to provide necessary increments of increased stability to a signal transduction process whose complexity we are only beginning to appreciate.

Targeted disruption of heparan sulfate interaction with hepatocyte and vascular endothelial growth factors blocks normal and oncogenic signaling

Hepatocyte growth factor (HGF) and vascular endothelial cell growth factor (VEGF) regulate normal development and homeostasis and drive disease progression in many forms of cancer. Both proteins signal by binding to receptor tyrosine kinases and heparan sulfate (HS) proteoglycans on target cell surfaces. Basic residues comprising the primary HS binding sites on HGF and VEGF provide similar surface charge distributions without underlying structural similarity. Combining three acidic amino acid substitutions in these sites in the HGF isoform NK1 or the VEGF isoform VEGF165 transformed each into potent, selective competitive antagonists of their respective normal and oncogenic signaling pathways. Our findings illustrate the importance of HS in growth factor driven cancer progression and reveal an efficient strategy for therapeutic antagonist development.

Heparin inhibits Hepatocyte Growth Factor induced motility and invasion of hepatocellular carcinoma cells through early growth response protein 1

The Hepatocyte Growth Factor (HGF)/c-Met signaling pathway regulates hepatocyte proliferation, and pathway aberrations are implicated in the invasive and metastatic behaviors of hepatocellular carcinoma (HCC). In addition to c-Met, heparin acts as a co-receptor to modulate pathway activity. Recently, anti-metastatic and anti-cancer effects of heparin have been reported. However, the role of heparin in the regulation of HGF signaling remains controversial and the effects of heparin on HGF-induced biological responses during hepatocarcinogenesis is not yet defined. In this study we determined the effects of heparin on HGF-induced activities of HCC cells and the underlying molecular mechanisms. Here, we report for the first time that heparin inhibits HGF-induced adhesion, motility and invasion of HCC cells. In addition, heparin reduced HGF-induced activation of c-Met and MAPK in a dose-dependent manner, as well as decreased transcriptional activation and expression of Early growth response factor 1 (Egr1). HGF-induced MMP-2 and MMP-9 activation, and MT1-MMP expression, also were inhibited by heparin. Stable knockdown of Egr1 caused a significant decrease in HGF-induced invasion, as well as the activation and expression of MMPs. Parallel to these findings, the overexpression of Egr1 increased the invasiveness of HCC cells. Our results suggest that Egr1 activates HGF-induced cell invasion through the regulation of MMPs in HCC cells and heparin inhibits HGF-induced cellular invasion via the downregulation of Egr1. Therefore, heparin treatment might be a therapeutic approach to inhibit invasion and metastasis of HCC, especially for patients with active HGF/c-Met signaling.

Protein engineered variants of hepatocyte growth factor/scatter factor promote proliferation of primary human hepatocytes and in rodent liver

BACKGROUND & AIMS

Hepatocyte growth factor/scatter factor (HGF/SF) stimulates hepatocyte DNA synthesis and protects against apoptosis; in vivo it promotes liver regeneration and reduces fibrosis. However, its therapeutic value is limited by its complex domain structure, high cost of production, instability, and poor tissue penetration due to sequestration by heparin sulfate proteoglycans (HSPGs).

METHODS

Using protein engineering techniques, we created a full-length form of HGF/SF (called HP21) and a form of the small, naturally occurring HGF/SF fragment, NK1 (called 1K1), which have reduced affinity for HSPG. We characterized the stability and proliferative and anti-apoptotic effects of these variants in primary human hepatocytes and in rodents.

RESULTS

Analytical ultracentrifugation showed that 1K1 and NK1 were more stable than the native, full-length protein. All 4 forms of HGF/SF induced similar levels of DNA synthesis in human hepatocytes; 1K1 and NK1 required heparin, an HSPG analogue, for full agonistic activity. All the proteins reduced levels of Fas ligand-mediated apoptosis, reducing the activity of caspase-3/7 and cleavage of poly(adenosine diphosphate-ribose) polymerase. 1K1 was more active than NK1 in rodents; in healthy mice, 1K1 significantly increased hepatocyte DNA synthesis, and in mice receiving carbon tetrachloride, it reduced fibrosis. In rats, after 70% partial hepatectomy, daily administration of 1K1 for 5 days significantly increased liver mass and the bromodeoxyuridine labeling index compared with mice given NK1.

CONCLUSIONS

1K1, an engineered form of the small, naturally occurring HGF/SF fragment NK1, has reduced affinity for HSPG and exerts proliferative and antiapoptotic effects in cultured hepatocytes. In rodents, 1K1 has antifibrotic effects and promotes liver regeneration. The protein has better stability and is easier to produce than HGF/SF and might be developed as a therapeutic for acute and chronic liver disease.

Hepatocyte growth factor in patients with coronary artery disease and its relation to periodontal condition

Hepatocyte growth factor (HGF) is an angiogenic, cardioprotective factor important for tissue and vascular repair. High levels of HGF are associated with chronic inflammatory diseases, such as coronary artery disease (CAD) and periodontitis, and are suggested as a marker of the ongoing atherosclerotic event in patients with CAD. Periodontal disease is more prevalent among patients with CAD than among healthy people. Recent studies indicate a reduced biological activity of HGF in different chronic inflammatory conditions. Biologically active HGF has high affinity to heparan sulfate proteoglycan (HSPG) on cell-membrane and extracellular matrix. The aim of the study was to investigate the serum concentration and the biological activity of HGF with ELISA and surface plasmon resonance (SPR), respectively, before and at various time points after percutaneous coronary intervention (PCI) in patients with CAD, and to examine the relationship with periodontal condition. The periodontal status of the CAD patients was examined, and the presence of P. gingivalis in periodontal pockets was analyzed with PCR. The HGF concentration was significantly higher, at all time-points, in patients with CAD compared to the age-matched controls (P< 0.001), but was independent of periodontal status. The HGF concentration and the affinity to HSPG adversely fluctuated over time, and the biological activity increased one month after intervention in patients without periodontitis. We conclude that elevated concentration of HGF but with reduced biological activity might indicate a chronic inflammatory profile in patients with CAD and periodontitis.

Paradoxical action of growth factors: antiproliferative and proapoptotic signaling by HGF/c-MET

Hepatocyte growth factor (HGF)/mesenchymal-epithelial transition factor (c-MET) signaling is usually associated with the promotion of cellular growth and often with progression of tumors. Nevertheless, under certain conditions HGF can also act as an antiproliferative and proapoptotic factor and can sensitize various cancer cells, treated with anticancer drugs, to apoptosis. Not only HGF but also its various truncated forms as well as intracellular fragments of its membrane receptor, c-MET, may act as antiproliferative and proapoptotic factors toward various cells. This review focuses on different mechanisms responsible for such paradoxical action of the known typical growth factor. It also points toward the possibilities of usage of this information in anticancer therapy.

Intracellular signaling cascades triggered by the NK1 fragment of hepatocyte growth factor in human prostate epithelial cell line PNT1A

Hepatocyte Growth Factor (HGF)/c-MET signaling has an emerging role in promoting cell proliferation, survival, migration, wound repair and branching in a variety of cell types. HGF plays a crucial role as a mediator of stromal-epithelial interactions in the normal prostate but the precise biological function of HGF/c-Met interaction in the normal prostate and in prostate cancer is not clear. HGF has two naturally occurring splice variants and NK1, the smallest of these HGF variants, consists of the HGF amino terminus through the first kringle domain. We evaluated the intracellular signaling cascades and the morphological changes triggered by NK1 in human prostate epithelial cell line PNT1A which shows molecular and biochemical properties close to the normal prostate epithelium. We demonstrated that these cells express a functional c-MET, and cell exposure to NK1 induces the phosphorylation of tyrosines 1313/1349/1356 residues of c-MET which provide docking sites for signaling molecules. We observed an increased phosphorylation of ERK1/2, Akt, c-Src, p125FAK, SMAD2/3, and STAT3, down-regulation of the expression of epithelial cell-cell adhesion marker E-cadherin, and enhanced expression levels of mesenchymal markers vimentin, fibronectin, vinculin, α-actinin, and α-smooth muscle actin. This results in cell proliferation, in the appearance of a mesenchymal phenotype, in morphological changes resembling cell scattering and in wound healing. Our findings highlight the function of NK1 in non-tumorigenic human prostatic epithelial cells and provide a picture of the signaling pathways triggered by NK1 in a unique cell line.

Targeting the HGF/Met signalling pathway in cancer

Under normal conditions, hepatocyte growth factor (HGF)-induced Met tyrosine kinase (TK) activation is tightly regulated by paracrine ligand delivery, ligand activation at the target cell surface, and ligand activated receptor internalisation and degradation. Despite these controls, HGF/Met signalling contributes to oncogenesis and tumour progression in several cancers and promotes aggressive cellular invasiveness that is strongly linked to tumour metastasis. The prevalence of HGF/Met pathway activation in human malignancies has driven rapid growth in cancer drug development programmes. Pathway inhibitors can be divided broadly into biologicals and low molecular weight synthetic TK inhibitors; of these, the latter now outnumber all other inhibitor types. We review here the basic properties of HGF/Met pathway antagonists now in preclinical and clinical development as well as the latest clinical trial results. The main challenges facing the effective use of HGF/Met-targeted antagonists for cancer treatment include optimal patient selection, diagnostic and pharmacodynamic biomarker development, and the identification and testing of optimal therapy combinations. The wealth of basic information, analytical reagents and model systems available concerning HGF/Met oncogenic signalling will continue to be invaluable in meeting these challenges and moving expeditiously toward more effective disease control.

Heparan sulfate proteoglycans: structure, protein interactions and cell signaling

Heparan sulfate proteoglycans are ubiquitously found at the cell surface and extracellular matrix in all the animal species. This review will focus on the structural characteristics of the heparan sulfate proteoglycans related to protein interactions leading to cell signaling. The heparan sulfate chains due to their vast structural diversity are able to bind and interact with a wide variety of proteins, such as growth factors, chemokines, morphogens, extracellular matrix components, enzymes, among others. There is a specificity directing the interactions of heparan sulfates and target proteins, regarding both the fine structure of the polysaccharide chain as well precise protein motifs. Heparan sulfates play a role in cellular signaling either as receptor or co-receptor for different ligands, and the activation of downstream pathways is related to phosphorylation of different cytosolic proteins either directly or involving cytoskeleton interactions leading to gene regulation. The role of the heparan sulfate proteoglycans in cellular signaling and endocytic uptake pathways is also discussed.

Noncoding mutations of HGF are associated with nonsyndromic hearing loss, DFNB39

A gene causing autosomal-recessive, nonsyndromic hearing loss, DFNB39, was previously mapped to an 18 Mb interval on chromosome 7q11.22-q21.12. We mapped an additional 40 consanguineous families segregating nonsyndromic hearing loss to the DFNB39 locus and refined the obligate interval to 1.2 Mb. The coding regions of all genes in this interval were sequenced, and no missense, nonsense, or frameshift mutations were found. We sequenced the noncoding sequences of genes, as well as noncoding genes, and found three mutations clustered in intron 4 and exon 5 in the hepatocyte growth factor gene (HGF). Two intron 4 deletions occur in a highly conserved sequence that is part of the 3' untranslated region of a previously undescribed short isoform of HGF. The third mutation is a silent substitution, and we demonstrate that it affects splicing in vitro. HGF is involved in a wide variety of signaling pathways in many different tissues, yet these putative regulatory mutations cause a surprisingly specific phenotype, which is nonsydromic hearing loss. Two mouse models of Hgf dysregulation, one in which an Hgf transgene is ubiquitously overexpressed and the other a conditional knockout that deletes Hgf from a limited number of tissues, including the cochlea, result in deafness. Overexpression of HGF is associated with progressive degeneration of outer hair cells in the cochlea, whereas cochlear deletion of Hgf is associated with more general dysplasia.