Scatter factor and angiogenesis

Effects of platelet-rich plasma on the pancreatic islet survival and function, islet transplantation outcome and pancreatic pdx1 and insulin gene expression in streptozotocin-induced diabetic rats

Platelet-rich plasma (PRP) is a therapeutic option in different fields based on its growth factors. We investigated influence of PRP on islet survival, function, transplantation outcomes, and pancreatic genes expression in diabetic rats. In vitro: pancreatic isolated islets were incubated with/without PRP then viability, insulin secretion, and content were assessed. In vivo: Series 1 were designed to determine whether islet treatment with PRP improves transplantation outcome in diabetic rats by evaluating plasma glucose and insulin concentrations and oxidative parameters. Series 2, effects of PRP subcutaneous injection were evaluated on pancreatic genes expression and glucose tolerance test in diabetic rats. PRP enhanced viability and secretary function of islet. Reduced glucose and malondialdehyde levels as well as increased insulin levels, superoxide dismutase activity, and expressions of pdx1 and insulin were observed in diabetic rats. PRP treatment has positive effects on islet viability, function, transplantation outcome, and pancreatic genes expression in diabetic rats.

Mesenchymal stem cells regulate the Th17/Treg cell balance partly through hepatocyte growth factor in vitro

Introduction

Mesenchymal stem cells (MSCs) exert immunomodulatory functions by inducing the development and differentiation of naive T cells into T cells with an anti-inflammatory regulatory T cell (Treg) phenotype. Our previous study showed that hepatocyte growth factor (HGF) secreted by MSCs had immunomodulatory effects in the context of lipopolysaccharide (LPS) stimulation. We hypothesized that HGF is a key factor in the MSC-mediated regulation of the T helper 17 (Th17) cell/regulatory T (Treg) cell balance.

Methods

We investigated the effects of MSCs on the differentiation of CD4+ T cells and the functions of Th17/Treg cells in response to LPS stimulation by performing in vitro coculture experiments. MSCs were added to the upper chambers of cell culture inserts, and CD4+ T cells were plated in the lower chambers, followed by treatment with LPS or an anti-HGF antibody. Th17 (CD4+CD3+RORrt+) and Treg (CD4+CD25+Foxp3+) cell frequencies were analysed by flow cytometry, and the expression of Th17 cell- and Treg cell-related cytokines in the CD4+ T cells or culture medium was measured by quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Neutrophil functions were determined by flow cytometry after a coculture with Th17/Treg cells.

Results

The percentage of CD4+CD25+Foxp3+ cells was significantly increased in the CD4+ T cell population, while the percentage of CD4+CD3+RORrt+ cells was significantly decreased after MSC coculture. However, the MSC-induced effect was significantly inhibited by the anti-HGF antibody (p < 0.05). Furthermore, MSCs significantly inhibited the CD4+ T cell expression of IL-17 and IL-6 but increased the expression of IL-10 (p < 0.05 or p < 0.01); these effects were inhibited by the anti-HGF antibody (p < 0.05). In addition, CD4+ T cells cocultured with MSCs significantly inhibited neutrophil phagocytic and oxidative burst activities (p < 0.05 or p < 0.01); however, these MSC-induced effects were inhibited by the anti-HGF antibody (p < 0.05).

Conclusion

These data suggested that MSCs induced the conversion of fully differentiated Th17 cells into functional Treg cells and thereby modulated the Th17/Treg cell balance in the CD4+ T cell population, which was partly attributed to HGF secreted by the MSCs.

Interaction between mesenchymal stem cells and endothelial cells restores endothelial permeability via paracrine hepatocyte growth factor in vitro

Introduction

Mesenchymal stem cells (MSCs) have potent stabilising effects on vascular endothelium injury, inhibiting endothelial permeability in lung injury via paracrine hepatocyte growth factor (HGF). Recently, it has been indicated that MSCs secrete more factors by MSC-endothelial cell (MSC-EC) interactions. We hypothesised that MSC-EC interactions restore endothelial permeability induced by lipopolysaccharide (LPS) via paracrine HGF.

Methods

We investigated the endothelial permeability induced by LPS under two co-culture conditions. Human pulmonary microvascular endothelial cells (HPMECs) were added into the upper chambers of cell-culture inserts, while two different co-culture conditions were used in the lower side of the transwells, as follows: (1) MSC-EC interaction group: MSCs and HPMECs contact co-culture; (2) MSC group: MSCs only. The endothelial paracellular and transcellular permeabilities in the upper side of transwells were detected. Then the concentration of HGF was measured in the culture medium by using an enzyme-linked immunosorbent assay kit, followed by neutralisation of HGF with anti-HGF antibody in the co-culture medium. In addition, adherens junction and cytoskeleton protein expressions were measured by Western blot and immunofluorescence. HPMEC proliferation was analysed by bromodeoxyuridine incorporation assay.

Results

The paracellular permeability significantly increased after LPS stimulation in a dose-dependent and time-dependent manner. Meanwhile, MSC-EC interaction more significantly decreased endothelial paracellular and transcellular permeability induced by LPS. Moreover, HGF levels in the MSC-EC interaction group were much higher than those of the MSC group. However, neutralising HGF with anti-HGF antibody inhibited the role of MSC-EC interaction in improving endothelial permeability. Compared with the MSC group, MSC-EC interaction increased vascular endothelial (VE)-cadherin and occludin protein expression, reduced caveolin-1 protein expression in HPMECs, and restored remodelling of F-actin and junctional localisation of VE-cadherin. Furthermore, the proliferation ratio in the MSC-EC interaction group was higher than that of the MSC group. However, the effects of MSCs were significantly blocked by anti-HGF antibody.

Conclusions

These data suggested that MSC-EC interaction decreased endothelial permeability induced by LPS, which was attributed mainly to HGF secreted by MSCs. The main mechanisms by which HGF restored the integrity of endothelial monolayers were remodelling of endothelial intercellular junctions, decreasing caveolin-1 protein expression, and inducing proliferation in HPMECs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0025-1) contains supplementary material, which is available to authorized users.

Asef mediates HGF protective effects against LPS-induced lung injury and endothelial barrier dysfunction

Increased vascular endothelial permeability and inflammation are major pathological mechanisms of pulmonary edema and its life-threatening complication, the acute respiratory distress syndrome (ARDS). We have previously described potent protective effects of hepatocyte growth factor (HGF) against thrombin-induced hyperpermeability and identified the Rac pathway as a key mechanism of HGF-mediated endothelial barrier protection. However, anti-inflammatory effects of HGF are less understood. This study examined effects of HGF on the pulmonary endothelial cell (EC) inflammatory activation and barrier dysfunction caused by the gram-negative bacterial pathogen lipopolysaccharide (LPS). We tested involvement of the novel Rac-specific guanine nucleotide exchange factor Asef in the HGF anti-inflammatory effects. HGF protected the pulmonary EC monolayer against LPS-induced hyperpermeability, disruption of monolayer integrity, activation of NF-kB signaling, expression of adhesion molecules intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, and production of IL-8. These effects were critically dependent on Asef. Small-interfering RNA-induced downregulation of Asef attenuated HGF protective effects against LPS-induced EC barrier failure. Protective effects of HGF against LPS-induced lung inflammation and vascular leak were also diminished in Asef knockout mice. Taken together, these results demonstrate potent anti-inflammatory effects by HGF and delineate a key role of Asef in the mediation of the HGF barrier protective and anti-inflammatory effects. Modulation of Asef activity may have important implications in therapeutic strategies aimed at the treatment of sepsis and acute lung injury/ARDS-induced gram-negative bacterial pathogens.

Hepatocyte growth factor-induced Asef-IQGAP1 complex controls cytoskeletal remodeling and endothelial barrier

Hepatocyte growth factor (HGF) attenuates agonist-induced endothelial cell (EC) permeability and increases pulmonary endothelial barrier function via Rac-dependent enhancement of the peripheral actin cytoskeleton. However, the precise mechanisms of HGF effects on the peripheral cytoskeleton are not well understood. This study evaluated a role for Rac/Cdc42-specific guanine nucleotide exchange factor Asef and the multifunctional Rac effector, IQGAP1, in the mechanism of HGF-induced EC barrier enhancement. HGF induced Asef and IQGAP1 co-localization at the cell cortical area and stimulated formation of an Asef-IQGAP1 functional protein complex. siRNA-induced knockdown of Asef or IQGAP1 attenuated HGF-induced EC barrier enhancement. Asef knockdown attenuated HGF-induced Rac activation and Rac association with IQGAP1, and it abolished both IQGAP1 accumulation at the cell cortical layer and IQGAP1 interaction with actin cytoskeletal regulators cortactin and Arp3. Asef activation state was essential for Asef interaction with IQGAP1 and protein complex accumulation at the cell periphery. In addition to the previously reported role of the IQGAP1 RasGAP-related domain in the Rac-dependent IQGAP1 activation and interaction with its targets, we show that the IQGAP1 C-terminal domain is essential for HGF-induced IQGAP1/Asef interaction and Asef-Rac-dependent activation leading to IQGAP1 interaction with Arp3 and cortactin as a positive feedback mechanism of IQGAP1 activation. These results demonstrate a novel feedback mechanism of HGF-induced endothelial barrier enhancement via Asef/IQGAP1 interactions, which regulate the level of HGF-induced Rac activation and promote cortical cytoskeletal remodeling via IQGAP1-Arp3/cortactin interactions.

Microtubule dynamics control HGF-induced lung endothelial barrier enhancement

Microtubules (MT) play a vital role in many cellular functions, but their role in peripheral actin cytoskeletal dynamics which is essential for control of endothelial barrier and monolayer integrity is less understood. We have previously described the enhancement of lung endothelial cell (EC) barrier by hepatocyte growth factor (HGF) which was associated with Rac1-mediated remodeling of actin cytoskeleton. This study investigated involvement of MT-dependent mechanisms in the HGF-induced enhancement of EC barrier. HGF-induced Rac1 activation was accompanied by phosphorylation of stathmin, a regulator of MT dynamics. HGF also stimulated MT peripheral growth monitored by time lapse imaging and tracking analysis of EB-1-decorated MT growing tips, and increased the pool of acetylated tubulin. These effects were abolished by EC pretreatment with HGF receptor inhibitor, downregulation of Rac1 pathway, or by expression of a stathmin-S63A phosphorylation deficient mutant. Expression of stathmin-S63A abolished the HGF protective effects against thrombin-induced activation of RhoA cascade, permeability increase, and EC barrier dysfunction. These results demonstrate a novel MT-dependent mechanism of HGF-induced EC barrier regulation via Rac1/PAK1/stathmin-dependent control of MT dynamics.

IQGAP1 regulates endothelial barrier function via EB1-cortactin cross talk

Cross talk between the actin cytoskeleton and microtubules (MT) has been implicated in the amplification of agonist-induced Rho signaling, leading to increased vascular endothelial permeability. This study tested the involvement of actin-MT cross talk in the mechanisms of barrier enhancement induced by hepatocyte growth factor (HGF) and evaluated the role of the adaptor protein IQGAP1 in integrating the MT- and actin-dependent pathways of barrier enhancement. IQGAP1 knockdown by small interfering RNA attenuated the HGF-induced increase in endothelial barrier properties and abolished HGF-activated cortical actin dynamics. IQGAP1 reduction abolished HGF-induced peripheral accumulation of Rac cytoskeletal effector cortactin and cortical actin remodeling. In addition, HGF stimulated peripheral MT growth in an IQGAP1-dependent fashion. HGF also induced Rac1-dependent IQGAP1 association with the MT fraction and the formation of a protein complex containing end-binding protein 1 (EB1), IQGAP1, and cortactin. Decreasing endogenous IQGAP1 abolished HGF-induced EB1-cortactin colocalization at the cell periphery. In turn, expression of IQGAP1ΔC (IQGAP1 lacking the C-terminal domain) attenuated the cortactin association with EB1 and suppressed HGF-induced endothelial cell peripheral actin cytoskeleton enhancement. These results demonstrate for the first time the MT-actin cross talk mechanism of HGF-induced endothelial barrier enhancement and suggest that IQGAP1 functions as a hub linking HGF-induced signaling to MT and actin remodeling via EB1-IQGAP1-cortactin interactions.

Antiplatelet-derived growth factor (PDGF) activity in the saliva of ixodid ticks is linked with their long mouthparts

The saliva of blood-feeding arthropods modulates their vertebrate hosts' haemostatic, inflammatory and immune responses to facilitate blood feeding. In a previous study, we showed that salivary gland products from ixodid tick species also manipulate the wound-healing response by targeting at least four different mammalian growth factors: transforming growth factor β1, hepatocyte growth factor, fibroblast growth factor 2 and platelet-derived growth factor (PDGF). In addition, species that showed PDGF-binding activity also inhibited cell proliferation in vitro and induced changes in cell morphology accompanied by disruption of the actin cytoskeleton. Here, we show a correlation between the length of the tick hypostome, the sclerotized feeding tube of the mouthparts inserted into the host's skin and anti-PDGF activity. This apparent link between hypostome length, and hence the potential depth of skin damage, and PDGF-binding activity was not apparent for the other growth factors or for other cytokines important in wound healing (keratinocyte growth factor, interleukin 6 and stromal cell-derived factor 1). However, PDGF-binding activity was no longer correlated with anti-cell activities, indicating that an additional as yet unidentified activity in tick saliva may affect cellular changes in wound repair.

Dual delivery of vascular endothelial growth factor and hepatocyte growth factor coacervate displays strong angiogenic effects

Controlled delivery of multiple growth factors (GFs) holds great potential for the clinical treatment of ischemic diseases and might be more therapeutically effective to reestablish vasculature than the provision of a single GF. Vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) are two potent angiogenic factors. However, due to rapid degradation and dilution in the body, their clinical potential will rely on an effective mode of delivery. A coacervate, composed of heparin and a biodegradable polycation, which protects GFs from proteolysis and potentiates their bioactivities, is developed. Here, the coacervate incorporates VEGF and HGF and sustains their release for at least three weeks. Their strong angiogenic effects on endothelial cell proliferation and tube formation in vitro are confirmed. Furthermore, it is demonstrated that coacervate-based delivery of these factors has stronger effects than free application of both factors and to coacervate delivery of each GF separately.

Barrier enhancing signals in pulmonary edema

Increased endothelial permeability and reduction of alveolar liquid clearance capacity are two leading pathogenic mechanisms of pulmonary edema, which is a major complication of acute lung injury, severe pneumonia, and acute respiratory distress syndrome, the pathologies characterized by unacceptably high rates of morbidity and mortality. Besides the success in protective ventilation strategies, no efficient pharmacological approaches exist to treat this devastating condition. Understanding of fundamental mechanisms involved in regulation of endothelial permeability is essential for development of barrier protective therapeutic strategies. Ongoing studies characterized specific barrier protective mechanisms and identified intracellular targets directly involved in regulation of endothelial permeability. Growing evidence suggests that, although each protective agonist triggers a unique pattern of signaling pathways, selected common mechanisms contributing to endothelial barrier protection may be shared by different barrier protective agents. Therefore, understanding of basic barrier protective mechanisms in pulmonary endothelium is essential for selection of optimal treatment of pulmonary edema of different etiology. This article focuses on mechanisms of lung vascular permeability, reviews major intracellular signaling cascades involved in endothelial monolayer barrier preservation and summarizes a current knowledge regarding recently identified compounds which either reduce pulmonary endothelial barrier disruption and hyperpermeability, or reverse preexisting lung vascular barrier compromise induced by pathologic insults.

Therapeutic potentials occurring during the early differentiation process of mesenchymal stem cells in a rats model with thioacetamide-induced liver fibrosis

BACKGROUNDS/AIMS

Mesenchymal stem cells (MSCs) have the capacity to differentiate into hepatocytes, The purpose of this study is to investigate the MSCs' differentiation process and therapeutic potentials by comparing isolated MSCs with HGF-treated MSCs in rat's model with thiacetamide (TAA)-induced cirrhosis.

METHODS

Male Sprague-Dawley (SD) rats, weighing 100-150 g were used in this study. To induce liver fibrosis, recipient rats were taken with 0.04% thioacetamide (TAA) in the drinking water (400 mg TAA/L) for 8 weeks. The rats underlying liver cirrhosis were divided into 3 groups according to the transplanted materials, compared to normal saline as control (I) and isolated MSCs (II) HGF-treated MSCs.

RESULTS

Severe hepatic fibrosis and hepatocyte destruction were detected in the control group. Less hepatic cirrhosis and collagen formation, more hepatocyte regeneration and glycogen storage were detected in isolated MSCs compared to HGF-treated MSCs group, Distribution of red autofluorescence is mainly localized near the sinusoids in isolated MSCs, scattered away the sinusoids in HGF-treated MSCs group. MSCs transdifferentiated into CK-19 postive Oval cells and then to albulmin-producing hepatocytes, HGF treated MSCs differentiated into hepatocyte without the intermediate oval cells phase. HGF treated MSCs became the CK18-positive, MSCs became CD 90-positive.

CONCLUSIONS

Significant hepatocyte differentiation occurred in not HGF-treated MSCs but isolated MSCs group unexpectedly. These results suggest that the beneficial effect of MSCs on in rat's model with TAA-induced cirrhosis may occur during early differentiation course of MSCs. Mature hepatocyte itself has a little effect on the accelerated differentiation and functional capacity of hepatic lineage cell-line.

MET targeted therapy for lung cancer: clinical development and future directions

MET, the receptor for hepatocyte growth factor, has been identified as a novel promising target in various human malignancies, including lung cancer. Research studies have demonstrated that MET signaling plays important physiologic roles in embryogenesis and early development, whereas its deregulation from an otherwise quiescent signaling state in mature adult tissues can lead to upregulated cell proliferation, survival, scattering, motility and migration, angiogenesis, invasion, and metastasis in tumorigenesis and tumor progression. The MET pathway can be activated through ligand (hepatocyte growth factor, HGF) or MET receptor overexpression, genomic amplification, MET mutations, and alternative splicing. A number of novel therapeutic agents that target the MET/hepatocyte growth factor pathway have been tested in early-phase clinical studies with promising results. Phase III studies of MET targeting agents have recently been initiated. This paper will review the MET signaling pathway and biology in lung cancer, and the recent clinical development and advances of MET/hepatocyte growth factor targeting agents. Emphasis will be placed on discussing various unanswered issues and key strategies needed to optimize further clinical development of MET targeting personalized lung cancer therapy.

Clinical correlations and prognostic relevance of tissue angiogenic factors in patients with gastric cancer

AIMS

To evaluate the relationship between vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) levels in gastric cancer tissue and clinicopathological features and to determine whether these factors were correlated with survival.

MATERIALS AND METHODS

We analysed tissue samples from 58 patients with gastric cancer and used 24 normal gastric mucosae as controls. Tissue levels of VEGF and HGF were measured in tissue extracts by enzyme-linked immunosorbent assay.

RESULTS

HGF and VEGF levels were significantly higher in gastric cancer tissue than in matched normal gastric mucosa. VEGF levels were significantly increased in cancer tissue from cases involving lymphatic invasion. HGF levels were significantly increased according to the disease stage. Patients with high levels of VEGF or HGF showed significantly worse survival rates than patients with low levels. Using multivariate analysis, a high level of VEGF or HGF was an independent factor predicting poor survival.

CONCLUSIONS

Intratumoral levels of HGF and VEGF are an important prognostic determinant in gastric cancer. The current findings suggest that high concentrations of HGF and VEGF may induce aggressive tumour growth and metastasis.

A phase I dose-escalation study of Tivantinib (ARQ 197) in adult patients with metastatic solid tumors

BACKGROUND

Tivantinib, an oral, non-ATP competitive, selective c-MET inhibitor, exhibited antitumor activity in preclinical models. This open-label, phase I, dose-escalation study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of tivantinib in patients with advanced or metastatic solid tumors refractory to standard therapy.

METHODS

Thirteen dose levels of tivantinib ranging from 10 to 360 mg twice a day were administered to patient cohorts in 21-day cycles (14 days on/7 days off); three active pharmaceutical ingredient forms of tivantinib (amorphous, crystalline A, and crystalline B) were also investigated. Treatment was continued until the occurrence of unacceptable toxicity, tumor progression, patient withdrawal, or death.

RESULTS

A total of 79 patients with advanced solid tumors were enrolled. A maximum tolerated dose was not determined. Tivantinib was well tolerated, with mild to moderate toxicities. Two patients discontinued the study drug due to treatment-emergent adverse events. Dose-limiting grade of 3 or more toxicities including leukopenia, neutropenia, thrombocytopenia, vomiting, and dehydration, were observed in 2 patients treated with tivantinib 360 mg twice a day. The rate of absorption of tivantinib peaked approximately 2 to 4 hours after initial dosing, followed by a linear decrease in plasma concentrations. Increases in tivantinib exposure were not dose proportional. There was significant interpatient pharmacokinetic variability; however the clinical safety of tivantinib seemed unaffected. Three patients (3.8%) achieved a partial response and 40 patients (50.6%) maintained stable disease for a median of 19.9 weeks.

CONCLUSIONS

Tivantinib 360 mg twice a day was well tolerated in patients with refractory advanced solid tumors. The results of this trial warrant further clinical investigation. Clin Cancer Res; 17(24); 7754-64. ©2011 AACR.

Phase I trial of a selective c-MET inhibitor ARQ 197 incorporating proof of mechanism pharmacodynamic studies

PURPOSE

The hepatocyte growth factor/c-MET axis is implicated in tumor cell proliferation, survival, and angiogenesis. ARQ 197 is an oral, selective, non-adenosine triphosphate competitive c-MET inhibitor. A phase I trial of ARQ 197 was conducted to assess safety, tolerability, and target inhibition, including intratumoral c-MET signaling, apoptosis, and angiogenesis.

PATIENTS AND METHODS

Patients with solid tumors amenable to pharmacokinetic and pharmacodynamic studies using serial biopsies, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and circulating endothelial cell (CEC) and circulating tumor cell (CTC) enumeration were enrolled.

RESULTS

Fifty-one patients received ARQ 197 at 100 to 400 mg twice per day. ARQ 197 was well tolerated, with the most common toxicities being grade 1 to 2 fatigue, nausea, and vomiting. Dose-limiting toxicities included grade 3 fatigue (200 mg twice per day; n = 1); grade 3 mucositis, palmar-plantar erythrodysesthesia, and hypokalemia (400 mg twice per day; n = 1); and grade 3 to 4 febrile neutropenia (400 mg twice per day, n = 2; 360 mg twice per day, n = 1). The recommended phase II dose was 360 mg twice per day. ARQ 197 systemic exposure was dose dependent and supported twice per day oral dosing. ARQ 197 decreased phosphorylated c-MET, total c-MET, and phosphorylated focal adhesion kinase and increased terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling (TUNEL) staining in tumor biopsies (n = 15). CECs decreased in 25 (58.1%) of 43 patients, but no significant changes in DCE-MRI parameters were observed after ARQ 197 treatment. Of 15 patients with detectable CTCs, eight (53.3%) had ≥ 30% decline in CTCs after treatment. Stable disease, as defined by Response Evaluation Criteria in Solid Tumors (RECIST), ≥ 4 months was observed in 14 patients, with minor regressions in gastric and Merkel cell cancers.

CONCLUSION

ARQ 197 safely inhibited intratumoral c-MET signaling. Further clinical evaluation focusing on combination approaches, including an erlotinib combination in non-small-cell lung cancer, is ongoing.

Cooperative signaling for angiogenesis and neovascularization by VEGF and HGF following islet transplantation

BACKGROUND

Delayed angiogenesis remains a significant challenge to the survival of transplanted islets. In this study, using a murine model of subcutaneous islet transplantation with matrigel basement membrane matrix, we determined the role of the proangiogenic growth factors in enhancing the islet engraftment.

METHODS

BALB/c islets were transplanted subcutaneously in growth factor reduced (GFR) or growth factor supplemented (GFS) matrigel into diabetic severe combined immunodeficient mice. GFS matrigel was prepared by supplementing GFR with proangiogenic factors, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). The functioning grafts were harvested at 15 days and vessel formation was analyzed histopathologically.

RESULTS

Our results demonstrate that suboptimal (250) islet equivalents in GFS-VEGF+HGF were able to restore normoglycemia, whereas those transplanted in GFR failed to reverse diabetes. Histopathology of the GFS-VEGF+HGF graft revealed 12±3 blood vessels per field, whereas GFR, GFS-VEGF, and GFS-HGF grafts had only 3±1, 6±2, and 4±1 blood vessels, respectively. Insulin staining demonstrated increased number of islets in matrigel supplemented with VEGF and HGF. Protein and mRNA analysis demonstrated enhanced intercellular adhesion molecule and vascular cell adhesion molecule within the islets when supplemented with both VEGF+HGF suggesting stable blood vessel formation. Transcription factors focal adhesion kinase phosphorylation and extracellular signal-regulated kinase1/2 phosphorylation were also increased (8-fold and 4.6-fold, respectively) when both the growth factors were present. There was weak expression of transcription factors when VEGF or HGF were supplemented alone.

CONCLUSION

We conclude that proangiogenic growth factors, VEGF and HGF, synergistically enhance angiogenesis after islet transplantation leading to stable engraftment.

Novel therapeutic inhibitors of the c-Met signaling pathway in cancer

A wide variety of human malignancies exhibit sustained c-Met stimulation, overexpression, or mutation, including carcinomas of the breast, liver, lung, ovary, kidney, and thyroid. Notably, activating mutations in c-Met have been positively identified in patients with a particular hereditary form of papillary renal cancer, directly implicating c-Met in human tumorigenesis. Aberrant signaling of the c-Met signaling pathway due to dysregulation of the c-Met receptor or overexpression of its ligand, hepatocyte growth factor (HGF), has been associated with an aggressive phenotype. Extensive evidence that c-Met signaling is involved in the progression and spread of several cancers and an enhanced understanding of its role in disease have generated considerable interest in c-Met and HGF as major targets in cancer drug development. This has led to the development of a variety of c-Met pathway antagonists with potential clinical applications. The three main approaches of pathway-selective anticancer drug development have included antagonism of ligand/receptor interaction, inhibition of the tyrosine kinase catalytic activity, and blockade of the receptor/effector interaction. Several c-Met antagonists are now under clinical investigation. Preliminary clinical results of several of these agents, including both monoclonal antibodies and small-molecule tyrosine kinase inhibitors, have been encouraging. Several multitargeted therapies have also been under investigation in the clinic and have demonstrated promise, particularly with regard to tyrosine kinase inhibition.

Augmented anti-tumor therapy through natural targetability of macrophages genetically engineered by NK4 plasmid DNA

The objective of this study is to genetically engineer macrophages (Mphi) for biological activation and evaluate their anti-tumor activity in a tumor-bearing mouse model. Mouse peritoneal Mphi were incubated on the surface of a culture dish which had been coated with the complex of a cationized dextran and luciferase plasmid DNA complex plus a cell adhesion protein, Pronectin for gene transfection (reverse transfection). When compared with the conventional transfection where Mphi were transfected in the medium containing the complex, the level of gene expression by the reverse method was significantly high and the time period of gene expression was prolonged. Confocal microscopic observation revealed that the plasmid DNA was localized in the cell nucleus to a higher extent by the reverse transfection method. Following the reverse transfection of Mphi by the plasmid DNA of a hepatocyte growth factor antagonist (NK4) complexed with the cationized dextran, the NK4 protein was secreted at a higher amount for a longer time period in contrast to the conventional transfection of free plasmid DNA. The NK4-transfected Mphi exhibited a stronger inhibition activity for in vitro growth of Meth-A fibrosarcoma cells. When injected intravenously into mice carrying a mass of Meth-A tumor cells, the Mphi engineered were accumulated in the tumor tissue and showed significant anti-tumor activity. It is concluded that the Mphi injected functioned as the natural carrier of tumor targeting for anti-tumor NK4 molecules, resulting in enhanced suppression of tumor growth at a high selectivity.

HGF attenuates thrombin-induced endothelial permeability by Tiam1-mediated activation of the Rac pathway and by Tiam1/Rac-dependent inhibition of the Rho pathway

Reorganization of the endothelial cell (EC) cytoskeleton and cell adhesive complexes provides a structural basis for increased vascular permeability implicated in the pathogenesis of many diseases, including asthma, sepsis, and acute respiratory distress syndrome (ARDS). We have recently described the barrier-protective effects of hepatocyte growth factor (HGF) on the human pulmonary EC. In the present study, we explored the involvement of Rac-GTPase and Rac-specific nucleotide exchange factor Tiam1 in the mechanisms of EC barrier protection by HGF. HGF protected EC monolayers from thrombin-induced hyperpermeability, disruption of intercellular junctions, and formation of stress fibers and paracellular gaps by inhibiting thrombin-induced activation of Rho GTPase, Rho association with nucleotide exchange factor p115-RhoGEF, and myosin light chain phosphorylation, which was opposed by stimulation of Rac-dependent signaling. The pharmacological Rac inhibitor or silencing RNA (siRNA) based depletion of either Rac or Tiam1 significantly attenuated HGF-induced peripheral translocation of Rac effector cortactin, cortical actin ring formation, and EC barrier enhancement. Moreover, Tiam1 knockdown using the siRNA approach, attenuated the protective effect of HGF against thrombin-induced activation of Rho signaling, monolayer disruption, and EC hyperpermeability. This study demonstrates the Tiam1/Rac-dependent mechanism of HGF-induced EC barrier protection and provides novel mechanistic insights into regulation of EC permeability via dynamic interactions between Rho- and Tiam1/Rac-mediated pathways.

Enhanced suppression of tumor growth using a combination of NK4 plasmid DNA-PEG engrafted cationized dextran complex and ultrasound irradiation

This investigation aims to determine experimentally whether or not ultrasound (US) irradiation is effective in enhancing the in vivo gene expression of NK4 plasmid DNA and suppressing tumor growth. NK4, composed of the NH2-terminal hairpin and subsequent four-kringle domains of hepatocyte growth factor (HGF), acts as an HGF-antagonist and angiogenesis inhibitor. Dextran was cationized by introducing spermine to the hydroxyl groups to allow for polyionic complexation with NK4 plasmid DNA. The cationized dextran was additionally modified with poly(ethylene glycol) (PEG) molecules giving PEG engrafted cationized dextran. Significant suppression of tumor growth was observed when PEG engrafted cationized dextran-NK4 plasmid DNA complexes were intravenously injected into mice carrying a subcutaneous Lewis lung carcinoma tumor mass with subsequent US irradiation when compared with the cationized dextran-NK4 plasmid DNA complex and naked NK4 plasmid DNA with or without US irradiation. We conclude that complexation with PEG-engrafted cationized dextran in combination with US irradiation is a promising way to target the NK4 plasmid DNA to the tumor for gene expression.

Involvement of hepatocyte growth factor in the development of bone metastasis of a mouse mammary cancer cell line, BALB/c-MC

Some cancers frequently affect the skeleton, and the bone microenvironment supports growth of certain cancer cells. After tumors metastasize to bone, they stimulate osteoclastogenesis and expand in the bone tissue. Hepatocyte growth factor (HGF), which was originally identified as a potent mitogen for hepatocytes, promotes tumor growth, invasion and metastasis. HGF is mainly produced by cells of mesenchymal origin, and osteoblasts/osteocytes and bone marrow stromal cells originate from mesenchymal cells. However, it is not clear what effect HGF has on tumor progression in bone metastasis. In the present study, we investigated the roles of HGF in bone metastasis using the mouse mammary cancer cell line BALB/c-MC. Cancer cells injected into hearts of mice metastasized to bone in their hind limbs. HGF immunoreactivity was detected in the stroma surrounding the tumor nests, and blood vessels expressing CD31 (a marker of endothelial cells) were observed in the HGF-positive area. To identify the cells producing HGF, we measured concentration of HGF in culture media. HGF concentration was elevated in osteoblast cultures (3.13+/-0.25 ng/ml), whereas HGF was undetectable (<0.4 ng/ml) in BALB/c-MC and bone marrow cell cultures. HGF concentration in osteoblast cultures increased 2.5-fold in response to 10(-6) M PGE(2). Addition of HGF to BALB/c-MC cultures caused doubling of the cell number. Moreover, Western blot analysis revealed expression of c-Met/HGF receptor by BALB/c-MC. In the Matrigel invasion chamber assay, addition of HGF to the bottom well increased the rate at which BALB/c-MC invaded the bottom well through the membrane. Furthermore, when osteoblasts were cultured in the bottom well, the number of BALB/c-MC cells that invaded the bottom well through the membrane increased 3.7-fold, compared to assays without osteoblasts. Addition of NK4, an inhibitor of HGF, completely abolished the enhancement of the invasive potential of the BALB/c-MC cells in the presence of osteoblasts. These findings suggest that HGF produced by osteoblasts induces migration of cancer cells from sinusoidal capillaries to bone marrow space and stimulates growth of cancer cells in the bone microenvironment. Thus, osteoblasts appear to promote bone metastasis of some cancers via HGF-c-Met signaling.

Role of hepatocyte growth factor activator (HGF activator) in invasive growth of human glioblastoma cells in vivo

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional growth factor that is involved in invasive growth of tumor cells via its receptor MET, a protein product of c-met proto-oncogene. HGF activator (HGFA) is a serine proteinase responsible for the activation of proform of HGF/SF (proHGF/SF). In our study, we examined the effects of engineered expression of HGFA on 2 human glioblastoma cell lines (YKG-1 and U251). Both cells expressed MET, while only YKG-1 expressed endogenous proHGF/SF. Enhanced MET phosphorylation and increased migratory activity were induced by the expression of HGFA in YKG-1 cells in vitro in the presence of thrombin, which is a known activator of proHGFA. In contrast, MET phosphorylation was consistently observed in U251 that lacked endogenous HGF/SF, suggesting ligand-independent activation of MET in this cell line. Consequently, the expression of HGFA in U251 did not enhance the MET phosphorylation and following cellular response even with the thrombin treatment. However, addition of exogenous proHGF/SF resulted in enhanced migratory activity of HGFA-expressing U251 cells in the presence of thrombin in vitro. The engineered HGFA expression resulted in significantly enhanced tumor growth with increased vascular density in vivo when YKG-1 cells were implanted in nude mouse brain. This effect was not observed in U251 lacking endogenous proHGF/SF. These results indicate the possible existence of multiple mechanisms of MET activation in glioblastomas and that the activation system of proHGF/SF is important in progression of glioblastomas that express endogenous proHGF/SF and require ligand-dependent MET activation.

Adenosine A2A receptor stimulation increases angiogenesis by down-regulating production of the antiangiogenic matrix protein thrombospondin 1

Topical adenosine A2A receptor agonists promote wound healing by, among other effects, increasing microvessel formation. Results of representational display analysis of human umbilical vein endothelial cells suggested that A2A receptor occupancy modulates expression of the antiangiogenic matrix protein thrombospondin 1 (TSP1). We therefore determined whether A2A receptor occupation stimulates angiogenesis by modulating TSP1 secretion. Human microvascular endothelial cells (HMVEC) were treated with medium alone, 2-p-[2-carboxyethyl] phenethyl-amino-5'-N-ethylcarboxamido-adenosine (CGS-21680), or 2-[2-(4-chlorophenyl)ethoxy]adenosine (MRE0094), selective A2A receptor agonists. TSP1 protein secretion was down-regulated after treatment with the A2A agonists CGS-21680 or MRE0094 in a dose-dependent manner (EC50 = 6.65 nM and 0.23 microM respectively). The selective A2A receptor antagonist 4-[2-[7-amino-2-(2-furyl)[1,2,4]triazolo-[2,3-a][1,3,5]triazin-5-ylamino]ethyl]phenol (ZM241385) but not the A1 and A2B receptor antagonists diphenylcyclopentylxanthine, enprofylline, and N-(4-acetylphenyl)-2-[4-(2,3,6,7-tetrahydro-2,6-dioxo-1,3-dipropyl-1H-purin-8-yl)phenoxy]acetamide (MRS1706) completely abrogated the A2A receptor agonist-mediated effect on TSP1. Vascular tube formation by HMVEC was increased by adenosine A2A receptor agonists in a dose-dependent fashion (EC50 = 0.1 microM for both), and this effect was reversed by the A2A antagonist. Moreover, in the presence of antibodies to TSP1 and CD36, the receptor for TSP1, the adenosine A2A receptor agonists stimulated no increase in vascular tube formation. These results indicate that the angiogenic effects of adenosine A2A receptor activation are, at least in part, caused by the suppression of TSP1 secretion.

Multiple myeloma cells catalyze hepatocyte growth factor (HGF) activation by secreting the serine protease HGF-activator

Multiple myeloma (MM) is a common hematologic neoplasm consisting of malignant plasma cells, which expand in the bone marrow. A potential key signal in the evolution of MM is hepatocyte growth factor (HGF), which acts as a potent paracrine and/or autocrine growth factor and survival factor for MM cells. Proteolytic conversion of HGF into its active form is a critical limiting step in HGF/MET signaling. Here, we show that malignant MM plasma cells convert HGF into its active form and secrete HGF-activator (HGFA), a serine protease specific for HGF activation. By using serine protease inhibitors and neutralizing antibodies, we demonstrate that HGFA produced by the MM cells is responsible for their ability to catalyze HGF activation. We, therefore, suggest that autocatalyzation of HGF conversion by MM cells is an important step in HGF/MET-induced myeloma growth and survival, which may have implications for the management of this incurable form of cancer. (Blood. 2004;104:2172-2175)

Suppression of tumor metastasis by NK4 plasmid DNA released from cationized gelatin

NK4, composed of the NH(2)-terminal hairpin and subsequent four-kringle domains of hepatocyte growth factor (HGF), acts as an HGF-antagonist and angiogenesis inhibitor. This study is an investigation to evaluate the feasibility of controlled release formulation of NK4 plasmid DNA in suppressing the tumor growth, and lung metastasis. Biodegradable cationized gelatin microspheres were prepared for the controlled release of an NK4 plasmid DNA. The cationized gelatin microspheres incorporating NK4 plasmid DNA could continuously release plasmid DNA over 28 days as a result of microspheres degradation following the subcutaneous injection. The injection of cationized gelatin microspheres incorporating NK4 plasmid DNA into the subcutaneous tissue significantly prolonged the survival time period of the mice bearing Lewis lung carcinoma tumor. Increases in the tumor volume and the number of lung metastatic nodules of NK4 plasmid DNA release group were suppressed to a significantly greater extent than that of solution-injected group (77.4 and 64.0%, respectively). The number of blood vessels and the apoptosis cells in the tumor tissue were significantly suppressed (80.4%) and increased (127.3%) against free NK4 plasmid DNA-injected group. Thus, the controlled release of NK4 plasmid DNA augmented angiogenesis suppression and apoptosis of tumor cells, which resulted in suppressed tumor growth. We conclude that this controlled release technology is promising to enhance the tumor suppression achieved by gene expression of NK4.

Expression of angiogenic factors in chronic myeloid leukaemia: role of the bcr/abl oncogene, biochemical mechanisms, and potential clinical implications

Chronic myeloid leukaemia (CML) is a stem cell disease characterized by an increased production and accumulation of clonal BCR/ABL-positive cells in haematopoietic tissues. The chronic phase of CML is inevitably followed by an accelerated phase of the disease, with consecutive blast crisis. However, depending on genetic stability, epigenetic events, and several other factors, the clinical course and survival appear to vary among patients. Recent data suggest that angiogenic cytokines such as vascular endothelial growth factor (VEGF), are up-regulated in CML, and play a role in the pathogenesis of the disease. These factors appear to be produced and released in leukaemic cells in patients with CML. In line with this notion, increased serum-levels of angiogenic growth factors are measurable in CML patients. In this study we provide an overview of angiogenic growth factors expressed in CML cells, discuss the possible pathogenetic role of these cytokines, the biochemical basis of their production in leukaemic cells, and their potential clinical implications.

c-met overexpression in supraglottic laryngeal squamous cell carcinoma and its relation to lymph node metastases

BACKGROUND

The c-met oncogene encodes the receptor for the hepatocyte growth factor/scatter factor (HGF/SF), which is known to have the effects of stimulation of cell motility, dissociation of epithelial sheets, invasion of cellular matrix, and induction of angiogenesis. Many studies in solid tumors have indicated a role for c-met and HGF/SF in the progression of the disease.

METHODS

The expression of c-met in tissue specimens was studied by immunohistochemical examination in 60 patients with supraglottic laryngeal squamous cell carcinoma. Patients were chosen such that there were 30 with lymph node metastases in the neck and 30 without metastases. TNM staging, differentiation, lymphovascular and perineural invasion, and growth pattern for tumors were also recorded, and their relation to lymph node metastases was analyzed.

RESULTS

Overexpression of c-met was observed in 90% of the cases at the primary site and in 83% of the cases with lymph node metastases in the neck. Lymphovascular invasion (P = 0.005) and the N stage (P = 0.001) were found to be related to lymph node metastases, but other variables-c-met overexpression, the T stage, perineural invasion, and growth pattern-were found to have no relation to lymph node metastases in multivariate analysis of the data with linear regression.

CONCLUSIONS

c-met overexpression is observed in both the primary site and the neck in supraglottic laryngeal squamous cell carcinoma. We believe that it may have a role in the progression of malignancy, but we were unable to find a definite relation between c-met expression and lymph node metastases.

c-Met tyrosine kinase receptor expression and function in human and canine osteosarcoma cells

To further characterize the role of hepatocyte growth factor-scatter factor (HGF-SF) and its receptor (c-Met) in osteosarcoma (OS), human OS cell lines with low (SAOS-2) and high (SAOS-LM2) metastatic potential, and cell lines derived from spontaneous canine OS were studied. All cell lines were evaluated for c-Met and HGF-SF expression and receptor activation using Northern, RT-PCR, and Western blot analyses, respectively. Functional activity of receptor-ligand interaction was measured using c-Met phosphorylation status, proliferation assays (anchorage-dependent and -independent), Matrigel invasion, modulation of urokinase plasminogen activator (uPA) expression, and cell dispersion (scattering). All cell lines exhibited steady-state mRNA expression of c-Met. The canine OS cell lines also expressed HGF-SF mRNA as determined by RT-PCR analysis. Western analysis showed c-Met protein expression and HGF-stimulated (human) or constitutive (canine) receptor autophosphorylation. Treatment with recombinant human HGF resulted in enhanced proliferation in 3 of 5 OS cell lines and enhanced colony formation in 2 of 5 OS cell lines. Matrigel invasion was significantly enhanced in 3 of the cell lines and uPA levels were significantly increased in the SAOS-2 cells following HGF treatment. Scattering was enhanced in both the SAOS-2 and SAOS-LM2 cells. These data support the involvement of c-Met and HGF-SF in the growth and progression of human and canine OS, and may offer new targets for the development of therapeutic strategies for OS.

Hepatocyte growth factor/scatter factor mediates angiogenesis through positive VEGF and negative thrombospondin 1 regulation

Hepatocyte growth factor/scatter factor (HGF/SF), acting through the Met receptor, plays an important role in most human solid tumors, and inappropriate expression of this ligand-receptor pair is often associated with poor prognosis. The molecular basis for the malignant potential of the HGF/SF-Met signal in cancer cells has mostly been attributed to its mitogenic and invasive properties. However, HGF/SF also induces angiogenesis, but the signaling mechanism has not been fully explained, nor has this activity been directly associated with HGF/SF-Met-mediated tumorigenesis. It is known that HGF/SF induces in vitro expression of vascular endothelial growth factor (VEGF), a key agonist of tumor angiogenesis; by contrast, thrombospondin 1 (TSP-1) is a negative regulator of angiogenesis. Here, we show that, in the very same tumor cells, in addition to inducing VEGF expression, HGF/SF dramatically down-regulates TSP-1 expression. We show that TSP-1 shut-off plays an important, extrinsic role in HGF/SF-mediated tumor development, because ectopic expression of TSP-1 markedly inhibits tumor formation through the suppression of angiogenesis. Interestingly, although VEGF-induced expression is sensitive to inhibitors of several pathways, including mitogen-activated protein kinase, phosphoinositide 3-kinase, and signal transducer and activator of transcription 3, TSP-1 shut-off by HGF/SF is prevented solely by inhibiting mitogen-activated protein kinase activation. These studies identify HGF/SF as a key switch for turning on angiogenesis. They suggest that TSP-1 is a useful antagonist to tumor angiogenesis and that it may have therapeutic value when used in conjunction with inhibitors of VEGF.

Expression of angiogenic factors in neurofibromas

We studied the expression of angiogenic factors (vascular endothelial growth factor, basic fibroblast growth factor, platelet-derived growth factor and hepatocyte growth factor) in cutaneous neurofibroma samples from patients with neurofibromatosis-1. Immunohistochemical staining and the reverse transcribed polymerase chain reaction (RT-PCR) method demonstrated that vascular endothelial and basic fibroblast growths factor are highly expressed in neurofibroma cells at both the protein and mRNA level. These data suggest that vascular endothelial and basic fibroblast growth factors may contribute to both the angiogenesis and hypervascularity of neurofibromas.

Impact of c-Met expression on angiogenesis in soft tissue sarcomas: correlation to microvessel-density

PURPOSE AND METHODS

The c-Met protein is significant for oncogenesis and angiogenesis within the c-Met/HGF/SF-mediator system. The aim of this study was the analysis of c-Met immunoexpression/-synthesis and microvessel density as parameters for angiogenesis and prognosis in 115 soft tissue sarcomas.

RESULTS

C-Met could be detected by immunohistochemistry in 87% of sarcomas. In all, 60.9% of cases exhibited absent or faint expression of c-Met protein, and 39.1% high expression of c-Met protein with a correlation between tumor grading and c-Met immunoexpression. Using in situ hybridization with detection of c-met-mRNA-transcripts, c-Met protein synthesis within tumor cells could be demonstrated. A statistically significant correlation between c-Met immunoexpression and tumor microvessel density was found. No prognostic value of c-Met expression and microvessel density could be detected in 56 patients with clinical follow-up ( P=0.8506 and P=0.9329 for disease-free survival).

CONCLUSIONS

The results underline a role of c-Met as an oncoprotein in soft tissue sarcomas with correlation between immunoexpression and grading. The statistically significant correlation between c-Met expression and microvessel density (as a parameter of tumor angiogenesis) suggests an angiogenic function of the c-Met/HGF/SF mediator system in malignant mesenchymal tumors.

Role of tyrosine kinase signaling in endothelial cell barrier regulation

Phosphorylation of proteins on tyrosine acts as a reversible and specific trigger mechanism, forming or disrupting regulatory connections between proteins. Tyrosine kinases and phosphatases participate in multiple cellular processes, and considerable evidence now supports a role for tyrosine phosphorylation in vascular permeability. A semipermeable barrier between the vascular compartment and the interstitium is maintained by the integrity of endothelial monolayer, controlling movement of fluids, macromolecules and leucocytes. Barrier function is regulated by the adjustment of paracellular gaps between endothelial cells (ECs) by two antagonistic forces, centripetal cytoskeletal tension and opposing cell-cell and cell-matrix adhesion forces. Both cytoskeletal filaments and adhesion sites are intimately linked in complex machinery which is regulated by multiple signaling events including protein phosphorylation and/or protein translocation to specific intracellular positions. Tyrosine kinases occupy key positions in the mechanism controlling cell responses mediated through various cell surface receptors, which use tyrosine phosphorylation to transduce extracellular signal.

Hepatocyte growth factor enhances endothelial cell barrier function and cortical cytoskeletal rearrangement: potential role of glycogen synthase kinase-3beta

The stabilization of endothelial cell (EC) barrier function within newly formed capillaries is a critical feature of angiogenesis. We examined human lung EC barrier regulation elicited by hepatocyte growth factor (HGF), a recognized angiogenic factor and EC chemoattractant. HGF rapidly and dose-dependently elevated transendothelial electrical resistance (TER) of EC monolayers (>50% increase at 100 ng/ml), with immunofluorescence microscopic evidence of both cytoplasmic actin stress fiber dissolution and strong augmentation of the cortical actin ring. HGF rapidly stimulated phosphatidylinositol 3'-kinase, ERK, p38 mitogen-activated protein kinase, and protein kinase C activities. Pharmacological inhibitor studies demonstrated each pathway to be intimately involved in HGF-induced increases in TER, cortical actin thickening, and phosphorylation of the Ser/Thr glycogen synthase kinase-3beta (GSK-3beta), a potential target for the HGF barrier-promoting response. GSK-3beta phosphorylation was strongly correlated with reductions in both HGF-induced TER and enhanced beta-catenin immunoreactivity observed at cell-cell junctions. Our data suggest a model in which HGF-mediated EC cytoskeletal rearrangement and barrier enhancement depend critically on the activation of a complex kinase cascade that converges at GSK-3beta to increase the availability of beta-catenin, thereby enhancing endothelial junctional integrity and vascular barrier function.

Formation of vascularized meniscal tissue by combining gene therapy with tissue engineering

Ingrowth of host blood vessels into engineered tissues has potential benefits for successful transplantation of engineered tissues as well as healing of surrounding host tissues. In particular, the use of a vascularized bioengineered tissue could be beneficial for treating injuries to the meniscus, a structure in the knee where the lack of a vascular supply is associated with an inadequate healing response. In this study, gene transfer using an adenovirus vector encoding the hepatocyte growth factor gene (AdHGF) was used to induce blood vessel formation in tissue-engineered meniscus. Bovine meniscal cells were treated with AdHGF, a vector encoding a marker gene E. coli beta-galactosidase (Adbetagal), or no virus. Cells were seeded onto poly-glycolic acid felt scaffolds and then transplanted into the subcutaneous pouch of athymic nude mice for 8 weeks. Expression of the marker gene and HGF was detectable for several weeks after gene transfer. Ink injection studies showed that AdHGF-treated meniscal cells formed tissue which contained fourfold more blood vessels at 2 weeks (p < 0.02) and 2.5-fold more blood vessels at 8 weeks (p < 0.001) posttransplantation than controls. This study demonstrates the feasibility of using adenovirus-mediated gene transfer to engineer a blood supply in the bioengineered meniscal tissue.

VEGF enhances intraneural angiogenesis and improves nerve regeneration after axotomy

Whilst there is an increased understanding of the cell biology of nerve regeneration, it remains unclear whether there is a direct interrelationship between vascularisation and efficacy of nerve regeneration within a nerve conduit. To establish this is important as in clinical surgery peripheral nerve conduit grafting has been widely investigated as a possible alternative to the use of nerve autografts. The aim of this study was to assess whether vascular endothelial growth factor (VEGF), a highly specific endothelial cell mitogen, can enhance vascularisation and, indirectly, axonal regeneration within a silicone nerve regeneration chamber. Chambers containing VEGF (500-700 ng/ml) in a laminin-based gel (Matrigel) were inserted into 1 cm rat sciatic nerve defects and nerve regeneration examined in relation to angiogenesis between 5 and 180 d. Longitudinal sections were stained with antibodies against endothelial cells (RECA-1), axons (neurofilament) and Schwann cells (S-100) to follow the progression of vascular and neural elements. Computerised image analysis demonstrated that the addition of VEGF significantly increased blood vessel penetration within the chamber from d 5, and by d 10 this correlated with an increase of axonal regeneration and Schwann cell migration. The pattern of increased nerve regeneration due to VEGF administration was maintained up to 180 d, when myelinated axon counts were increased by 78 % compared with plain Matrigel control. Furthermore the dose-response of blood vessel regeneration to VEGF was clearly reflected in the increase of axonal regrowth and Schwann cell proliferation, indicating the close relationship between regenerating nerves and blood vessels within the chamber. Target organ reinnervation was enhanced by VEGF at 180 d as measured through the recovery of gastrocnemius muscle weights and footpad axonal terminal density, the latter showing a significant increase over controls (P < 0.05). The results demonstrate an overall relationship between increased vascularisation and enhanced nerve regeneration within an acellular conduit, and highlight the interdependence of the 2 processes.

Hepatocyte growth factor/scatter factor in the eye

Hepatocyte growth factor, also known as scatter factor (HGF/SF) is a multipotential cytokine which can produce a range of responses in target cells and its influence in the eye in health and disease is just beginning to be appreciated. Usually HGF/SF is synthesised by mesenchymally derived cells and targets and signals epithelial cells in a paracrine manner via their c-Met surface receptor. However, there is growing evidence for the existence of autocrine loops in a number of cell systems prominent among which are ocular cells such as the corneal endothelium, the lens epithelium, the retinal pigment epithelium (RPE) and others. Marked cellular proliferation is stimulated when activated HGF/SF is exposed to hepatocytes, renal epithelium, melanocytes and vascular endothelial cells but it is often a poor mitogen for other cell types. In target cells the cytokine promotes other bioactions such as junctional breakdown, shape change, cell scattering, directional and nondirectional migration, cell survival, invasive behaviour and/or tubule formation. These activities seem to depend on HGF/SF linking with the c-Met receptor and pathways to stimulate the various types of cytokine/receptor response are being unravelled at the present time. In corneal wound healing, HGF/SF is produced by stromal keratocytes and targets the repairing epithelium. HGF/SF is a constituent of tears, aqueous humour and vitreous humour at levels above that found in plasma although it is not clear how much is activated. Aqueous HGF/SF may well influence lens epithelial, corneal endothelial and trabecular meshwork cell survival. Vitreous levels of HGF/SF are elevated in proliferative vitreoretinopathy (PVR), where a target cell is the RPE and in proliferative diabetic retinopathy (PDR) where HGF/SF has been shown to be a major angiogenesis factor. Finally HGF/SF may be involved in the metastatic spread of tumour cells from uveal melanomata and in the formation of vascular channels in these tumours.

Hepatocyte growth factor decreases sensitivity to chemotherapeutic agents and stimulates cell adhesion, invasion, and migration

Hepatocyte growth factor (HGF), also known as scatter factor (SF), plays an important role in cell:cell adhesion, cell proliferation, motility, and invasiveness of epithelial cells and tumor cells. In this study, we examined the effects of HGF on these types of biological activities and chemosensitivity in Chinese hamster ovary (CHO) cells by stable transfection of the HGF gene. HGF-transfected clones produced very high titers of HGF protein, whereas control vector-transfected clones did not produce detectable HGF protein. HGF-transfected clones showed modestly increased proliferation rates and became more resistant to cell death and apoptosis caused by two anticancer drugs, adriamycin (ADR) and camptothecin (CPT), compared to controlvector-transfected clones. Furthermore, HGF-transfected clones also exhibited increased activities of cell adhesion, migration, and invasion. The current study is the first demonstration that overexpression of the HGF gene affects chemosensitivity and cell metastasis behaviors, suggesting that HGF signaling pathway is a promising new target of therapeutic intervention of tumors.

Hepatocyte growth factor in vitreous and serum from patients with proliferative diabetic retinopathy

BACKGROUND

Hepatocyte growth factor (HGF) is an endothelium specific growth factor that has been implicated in angiogenesis, a crucial event for the development of proliferative diabetic retinopathy (PDR). The aim of the study is to determine the intravitreous concentrations of HGF in diabetic patients with PDR, and to investigate whether its serum levels could contribute to its intravitreous concentration.

METHODS

17 diabetic patients and seven non-diabetic patients in whom a vitrectomy was performed were studied. Both groups were matched by serum levels of HGF. Venous blood and vitreous samples were collected simultaneously at the time of vitreoretinal surgery. Vitreous and serum HGF were determined by ELISA.

RESULTS

Intravitreous concentrations of HGF (median and range) were higher in diabetic patients (17.04 ng/ml (9.98-80)) in comparison with non-diabetic patients (5.88 ng/ml (2.57-14.20); p=0. 003). Intravitreous HGF concentrations were strikingly higher than serum HGF concentrations both in diabetic patients (17.04 ng/ml (9. 98-80) v 0.66 ng/ml (0.26-1.26); p<0.001) and in the control group (5.88 ng/ml (2.57-14.20) v 0.68 ng/ml (0.49-0.96); p=0.003). No correlation was found between serum and vitreous levels of HGF in both groups (diabetic patients, r= -0.31; p=0.5 and control subjects r= -0.15; p=0.5).

CONCLUSION

The high vitreous levels of HGF observed in diabetic patients with PDR cannot be attributed to serum diffusion across the blood-retinal barrier. Therefore, intraocular synthesis appears to be the main contributing factor for the high vitreous HGF concentrations in diabetic patients, a cytokine that seems to be directly involved in the pathogenesis of PDR.

Glioma inhibition by HGF/NK2, an antagonist of scatter factor/hepatocyte growth factor

Strategies that antagonize growth factor signaling are attractive candidates for the biological therapy of brain tumors. HGF/NK2 is a secreted truncated splicing variant and potential antagonist of scatter factor/hepatocyte growth factor (SF/HGF), a multifunctional cytokine involved in the malignant progression of solid tumors including glioblastoma. U87 human malignant glioma cells that express an autocrine SF/HGF stimulatory loop were transfected with the human HGF/NK2 cDNA and clonal cell lines that secrete high levels of HGF/NK2 protein (U87-NK2) were isolated. The effects of HGF/NK2 gene transfer on the U87 malignant phenotype were examined. HGF/NK2 gene transfer had no effect on 2-dimensional anchorage-dependent cell growth. In contrast, U87-NK2 cell lines were approximately 20-fold less clonogenic in soft agar and approximately 4-fold less migratory than control-transfected cell lines. Intracranial tumor xenografts derived from U87-NK2 cells grew much slower than controls. U87-NK2 tumors were approximately 50-fold smaller than controls at 21 days post-implantation and HGF/NK2 gene transfer resulted in a trend toward diminished tumorigenicity. This report shows that the predominant effect of transgenic HGF/NK2 overexpression by glioma cells that are autocrine for SF/HGF stimulation is to inhibit their malignant phenotype.

Molecular pathology of soft tissue and bone tumors. A review

OBJECTIVE

To present recent concepts on the molecular pathogenesis of tumors of soft tissue and bone, and on the use of molecular genetic methods, including their significance as diagnostic markers and prognostic indicators.

DATA SOURCES AND STUDY SELECTION

Reports on tumors of bone and/or soft tissue published in the English language literature and observations made using specimens available at the Departments of Pathology at Albany Medical College and Loyola University Medical Center.

DATA EXTRACTION AND SYNTHESIS

Studies on bone and soft tissue tumors containing chromosomal or genetic evaluation were selected for further analysis. Specific chromosomal abnormalities, such as numerical aberrations or translocations with production of fusion genes, were classified according to the tumor of origin. Data were also collected on mutations in tumor suppressor genes, genes coding for growth factors or their receptors, and genes coding for tyrosine kinases. Also noted were mutations of uncertain significance, for which the pathogenic connection between tumor production and mutated gene function is still unclear.

CONCLUSIONS

In general, the mutations reported interfere with the action of peptide growth factors coordinating mesenchyme proliferation and differentiation, although membrane-bound receptors expressing the intracellular signaling modifier, tyrosine kinase activity, have also been involved. Functional types of genes most commonly affected include tumor suppressors, oncogenes, and nuclear transcription factors. Thus, the mutations involved in the pathogenesis of soft tissue and bone tumors have affected multiple genes. Moreover, aberrant fusion gene products may be formed in tumoral tissue and may then act as transcription regulators stimulating cellular proliferation. Cytogenetic studies help at the clinical level by demonstrating aneuploidy and increased ploidy, which may correlate with malignant behavior. Diagnostic tumor-specific chromosomal translocations may be detected with Southern hybridization analysis, polymerase chain reaction, reverse-transcription polymerase chain reaction, or with the fluorescence in situ hybridization technique. Notably, early metastatic disease may be detectable in blood specimens using polymerase chain reaction or reverse-transcription polymerase chain reaction techniques.

Hepatocyte growth factor prevents lipopolysaccharide-induced hepatic sinusoidal endothelial cell injury and intrasinusoidal fibrin deposition in rats

BACKGROUND

Acute endotoxemia is known to cause activation of Kupffer cells as well as serious injury in parenchymal and nonparenchymal cells in the liver. We have recently shown that a continuous recombinant hepatocyte growth factor (rHGF) supply prevents lipopolysaccharide (LPS)-induced liver injury in rats. As an attempt to elucidate the mechanism, here we investigate the cytoprotective effect of rHGF on sinusoidal endothelial cells (SECs) in LPS-induced liver injury in rats.

MATERIALS AND METHODS

In order to supply rHGF continuously to the liver, syngenic rat fibroblasts genetically modified to secret rat rHGF were implanted in the spleen. Fourteen days after cell implantation, we injected LPS intravenously and evaluated SEC damage histologically and blood chemically.

RESULTS

Phosphotungstic acid-hematoxylin staining revealed that rHGF treatment greatly attenuated intrasinusoidal LPS-induced fibrin deposition. The ultrastructural changes in SECs caused by LPS administration in control rats were barely detectable in rHGF-treated rats. Blood chemical analyses showed that rHGF potently suppressed the LPS-induced increase in serum hyaluronic acid and transaminase levels.

CONCLUSIONS

Our results indicate an important role for HGF in SEC protection in vivo and would suggest a novel therapeutic strategy for liver diseases with SEC injury.

High levels of hepatocyte growth factor/scatter factor in diffuse-type bronchioloalveolar cell carcinoma

BACKGROUND

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent mitogen for various neoplastic cells, including neoplastic bronchial epithelia.

METHODS

Immunoreactive hepatocyte growth factor/scatter factor (HGF/SF) was measured in extracts prepared from 129 nonsmall cell lung carcinoma (NSCLC) specimens, using an enzyme-linked immunosorbent assay. These specimens represented 5 cases of solitary/localized bronchioloalveolar cell carcinoma (BAC), 4 cases of diffuse/infiltrative BAC, 90 cases of non-BAC adenocarcinoma, 25 cases of squamous cell carcinoma, and 5 cases of large cell carcinoma.

RESULTS

The mean concentration of immunoreactive HGF/SF was more than 19-fold higher in tissue extracts from diffuse-type BAG (265.0 +/- 110.2 ng/100 mg protein) than in those from solitary-type BAC (13.9 +/- 15.9, P < 0.005), non-BAC adenocarcinoma (13.8 +/- 14.9, P < 0.001), squamous cell carcinoma (13.2 +/- 14.4, P < 0.001), or large cell carcinoma (11.2 +/- 6.5, P < 0.005). When immunohistochemical staining for HGF/SF was performed, intense HGF/SF staining was uniformly observed in diffuse-type BAC tumor cells, but not in solitary-type BAC.

CONCLUSIONS

Although BAC is included as a subtype of adenocarcinoma in the World Health Organization classification, diffuse-type BAC should be considered a distinct biologic entity, at least in terms of HGF/SF expression, from solitary-type BAC or non-BAC adenocarcinoma. In addition, the solitary and diffuse forms of BAC are known to be associated with different prognoses; for the latter, the prognosis is much poorer than for the former. The results of this study may at least partly explain this difference in prognosis.

Overexpression of scatter factor and its receptor (c-met) in oral squamous cell carcinoma

HYPOTHESIS

Scatter factor (SF) is a pleiotropic growth factor that recently has been shown to induce epithelial cell proliferation, random motility, and invasion via interaction with its receptor, a tyrosine kinase encoded by the c-met proto-oncogene. Studies involving a variety of solid tumors have suggested that overexpression of the SF/c-met ligand-receptor pair is associated with the acquisition of a malignant phenotype. We hypothesize that SF and c-met are overexpressed in epithelial malignancies of the head and neck including squamous cell carcinoma (SCC) of the oral cavity.

STUDY DESIGN

Immunohistochemical staining of randomly selected normal, dysplastic, and malignant oral tissues.

METHODS

Formalin-fixed, paraffin-embedded tissues were obtained from the Department of Oral Pathology at Shands Hospital (University of Florida), Gainesville, Florida. Examples of mild dysplasia, severe dysplasia, well-differentiated SCC, moderately differentiated SCC, and poorly differentiated SCC were randomly selected from the dictated reports of one of two staff oral pathologists. Histologically normal margins of each specimen served as normal controls. The tissues were immunohistochemically stained using commercially available antibodies against SF and c-met. Appropriate negative controls were run with each batch to ensure staining specificity. Evaluation of staining intensity was carried out using a computerized image analysis system. A one-way analysis of variance (ANOVA) with pairwise multiple-comparison procedures (Fisher method) was used to analyze the data.

RESULTS

Statistically significant differences (P < .0001) in the intensity of staining were noted between the malignant and normal and the malignant and dysplastic tissues for both SF and c-met. No differences were appreciated when staining of normal and dysplastic sections of the SF-stained tissue were compared.

CONCLUSIONS

The results suggest that the SF/c-met ligand-receptor pair is overexpressed in SCC of the oral cavity.