Identity of a tumor cytotoxic factor from human fibroblasts and hepatocyte growth factor

Mesocaval shunt inhibits primary and metastatic hepatoma growth and enhances apoptosis

BACKGROUND

Previous reports indicate that hepatocyte growth factor and other hepatic trophic factors reach the liver presumably by portal venous inflow and stimulate experimental hepatic tumor growth, invasion, and metastasis. This study tests this hypothesis by evaluating whether a mesocaval shunt (MCS) alters hepatic tumor growth, the mitotic rate, apoptosis, and incidence and growth of lung metastasis in rats with implanted hepatoma.

METHODS

Morris hepatoma (1 x 10(5)) cells were implanted intrahepatically in 19 ACI rats. One week after implantation, 10 rats underwent MCS operation and nine controls a sham operation. Rats were killed 21 days after the operation to assess tumor volume, tumor cell mitosis, apoptosis, area of tumor necrosis, pulmonary metastases and percentage of lung tumor area.

RESULTS

Mesocaval shunt induced a significant increase in the rate of tumor apoptosis (25 +/- 5 v 14 +/- 6, P < .01) and the percentage of area of tumor necrosis (29% +/- 17% v 13% +/- 8%, P < .05), a decreased tumor volume (839 +/- 1,195 v 2,909 +/- 2,572, P < .05), a reduction in tumor mitosis (70 +/- 28 v 93 +/- 11, P < .05) and decreased percentage area of pulmonary metastatic tumor (9.8 +/- 6.8 v 18.8 +/- 14, P < .05).

CONCLUSION

These observations show that growth of intrahepatic tumor is influenced by portal venous inflow and suggest that MCS or other methods of regulating portal vein flow may be useful as adjunctive therapy in the treatment of advanced hepatoma.

Tissue-specific chromatin structure at the hepatocyte growth factor/scatter factor gene promoter

Hepatocyte growth factor/scatter factor (HGF/SF) is a recently characterised molecule with many remarkable functions. Its involvement in important processes such as cell proliferation, cell migration, morphogenesis and organ development implies that its activity should be tightly regulated. To understand the molecular mechanisms controlling HGF/SF transcription, we have analysed DNaseI hypersensitive sites (DHS) along rat and human HGF/SF genes in various tissues and cell types. We identified five DHS along the rat gene, two in the 5'-flanking region and three in the first intron. These sites are only found in rat tissues and rat cell lines, which express HGF/SF. The strongest hypersensitive site map to a region that corresponds to the promoter by start site analysis. A single tissue-specific DHS is present in human cell lines that express HGF/SF and corresponds to the promoter region. Our results suggest that chromatin accessibility plays a major role in the regulation of HGF/SF transcription regulation.

Identification of heparin-binding stretches of a naturally occurring deleted variant of hepatocyte growth factor (dHGF)

A deleted variant of hepatocyte growth factor (dHGF) is a naturally occurring major variant of HGF, which lacks five consecutive amino acid residues in the first kringle domain. While both HGF and dHGF bind to heparin, the residues involved in the binding to heparin have not been identified in either protein. To identify the residues involved in the binding, we made a series of dHGF mutants in which basic residues in the N-terminal and the first kringle domains were replaced with alanine residue. The analysis of heparin-binding ability revealed that three stretches, 42RCTRNK in the hairpin loop structure, and 2RKRR and 27KIKTKK in the N-terminal basic region, are involved in the binding. Alanine substitution of each basic residue except 3K and 27K in the stretches reduced the heparin-binding ability of dHGF, and the decrease was additive. Conversely, lysine substitution of 37D, 38Q or 64Q in the N-terminal domain increased heparin-binding ability. These results suggest that stretches distant from each other in the primary structure come into close proximity when the polypeptide folds into protein, and form a heparin-binding site with clusters of basic residues.

Hepatocyte growth factor stimulates DNA synthesis in rat preneoplastic hepatocytes but not in liver carcinoma cells

BACKGROUND & AIMS

It is not well clarified whether hepatocyte growth factor (HGF) stimulates the growth of preneoplastic hepatocytes and liver carcinoma cells in vivo. The effect of HGF on in vivo DNA synthesis in these cells and also its effect on tyrosine phosphorylation of the HGF receptor protein (c-Met) in liver carcinoma were examined.

METHODS

Lesions were induced in rats using 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB). The rats were given intravenous recombinant human HGF or vehicle, and DNA synthesis was assessed by the 5-bromo-2'-deoxyuridine labeling index. Tyrosine phosphorylation of c-Met by HGF was analyzed by Western blot.

RESULTS

The labeling indices were significantly higher in the HGF group than in the vehicle control group in altered foci and hyperplastic nodules (preneoplastic hepatic lesions). No significant differences in the labeling indices were observed between the two groups with carcinoma. Tyrosine phosphorylation of c-Met in carcinoma cells was unaffected by HGF administration.

CONCLUSIONS

HGF promotes the growth of preneoplastic hepatocytes but does not affect the growth of liver carcinoma cells in 3'-Me-DAB-treated rats.

Preventive effects of the deleted form of hepatocyte growth factor against various liver injuries

The effects of a naturally occurring deleted form of hepatocyte growth factor (HGF) on hepatic disorder were studied in various models of hepatic failure. The pretreatment of rats and mice with the deleted form of HGF prevented the liver injuries and coagulopathy induced by endotoxin, dimethylnitrosamine and acetaminophen and reduced the mortality due to hepatic dysfunction induced by these hepatotoxins. The concurrent administration of the deleted form of HGF also prevented the liver injury and hepatic fibrosis in mice treated with alpha-naphthylisothiocyanate and in rats treated with dimethylnitrosamine. Moreover, the deleted form of HGF normalized the results of the bromosulphalein-clearance test and ameliorated jaundice in rats with periportal cholangiolitic hepatopathy induced by alpha-naphthylisothiocyanate. The deleted form of HGF also reversed the coagulopathy in rats with hepatic disorder induced by dimethylnitrosamine or by 70% resection of cirrhotic liver (induced by carbon tetrachloride). In Long Evans cinnamon rats receiving vehicle, 20 out of 21 animals died within 4 days after the onset of jaundice. After infusion of the deleted form of HGF for 4 days, 7 out of 20 Long-Evans cinnamon rats survived. These results indicate that the deleted form of HGF could have therapeutic potency in patients with severe hepatic failure.

Hepatocyte growth factor (HGF/SF) in Alzheimer's disease

Hepatocyte growth factor (HGF/SF), is a heparin-binding polypeptide which stimulates DNA synthesis in a variety of cell types and also promotes cell migration and morphogenesis. HGF/SF mRNA has been found in a variety of tissues, including brain. In a previous study, we showed that basic fibroblast growth factor (bFGF), another heparin-binding protein is increased in Alzheimer's disease (AD), and appears to be associated with the heparan-sulfate proteoglycans bound to B/A4 amyloid (Biochem. Biophys. Res. Commun. 171 (1990) 690-696). In the present study, we examined the distribution of HGF/SF in 4% paraformaldehyde fixed samples of prefrontal cortex from control and Alzheimer patients, in order to assess the possibility that HGF/SF may be found in association with the pathologic changes which occur in Alzheimer's disease. A specific polyclonal antibody directed against HGF/SF revealed widespread HGF/SF-like immunoreactivity in both the cerebral cortex and white matter. Confocal microscopy confirmed that HGF/SF could be found in both GFAP positive astrocytes and LN3 positive microglia cells, as well as rare scattered cortical neurons. In the AD cases studied, the immunoreactivity was increased within both the astrocytes and microglial cells surrounding individual senile plaques. No staining was seen within the neurofibrillary tangles. Western blot analysis confirmed the normal molecular form of HGF/SF in Alzheimer's disease. Quantitative ELISA assay demonstrated a significant increase in HGF/SF in AD relative to age matched controls. These studies confirm the presence of HGF/SF immunoreactivity within neurons, astrocytes and microglial cells. They also indicate that HGF/SF may be increased within senile plaques as a function of the gliosis and microglial proliferation which occurs in association with these structures in Alzheimer's disease.

Deleted form of hepatocyte growth factor (dHGF) increases the number of platelets in rats with liver cirrhosis

The effect of the deleted form of hepatocyte growth factor (dHGF) on thrombopoiesis was studied in rats. When normal rats were injected with dHGF (0.5 mg/kg i.v. twice a day), the number of platelets increased to about 1.5-fold the initial level. In addition, the treatment with dHGF (0.5 mg/kg i.v. twice daily) significantly increased the number of platelets in rats with liver cirrhosis induced by carbon tetrachloride and phenobarbital. When dHGF was given to rats at a dose of 0.05 or 0.5 mg/kg from the beginning of the induction of dimethylnitrosamine liver cirrhosis to day 28, dHGF dose-dependently ameliorated thrombocytopenia and completely prevented it at a dose of 0.5 mg/kg. These results indicate that dHGF may be applicable to the treatment of thrombocytopenia associated with liver cirrhosis.

Control of invasive growth by hepatocyte growth factor (HGF) and related scatter factors

Hepatocyte growth factor (HGF) is the prototype of a family of structurally related soluble molecules, named scatter factors (SFs). These control a complex genetic programme leading to cell-dissociation, migration in the extracellular matrix, growth, acquisition of polarity and tubule formation. This programme is pivotal during the embryonic development of epithelial and some mesodermal-derived tissues. In the adult HGF sustains cell survival and regeneration. A structurally related molecule, originally identified as macrophage stimulating protein (MSP), triggers the same complex genetic programme in epithelial and neural cells. The receptors for HGF and MSP are the tyrosine kinases encoded by the homologous genes MET and RON. As a distinctive feature, these receptors act via a two-phosphotyrosine docking site, capable of concomitant activation of multiple intracellular transducers and signalling pathways. In a number of malignant tumours, MET and RON constitutively sustain the genetic programme of scattering, leading to invasive growth and metastatic phenotype. Four MET-related receptors have been recently identified (the SEX protein family). These molecules are predominantly expressed during development and are likely to mediate repelling cues between cells of different type.

Interaction of c-myc with transforming growth factor alpha and hepatocyte growth factor in hepatocarcinogenesis

Double transgenic mice bearing fusion genes consisting of mouse albumin enhancer/promoter-mouse c-myc cDNA and mouse metallothionein 1 promoter-human TGF-alpha cDNA were generated to investigate the interaction of these genes in hepatic oncogenesis and to provide a general paradigm for characterizing the interaction of nuclear oncogenes and growth factors in tumorigenesis. Coexpression of c-myc and TGF-alpha as transgenes in the mouse liver resulted in a tremendous acceleration of neoplastic development in this organ as compared to expression of either of these transgenes alone. The two distinct cellular reactions that occurred in the liver of the double transgenic mice prior to the appearance of liver tumors were dysplastic and apoptotic changes in the existing hepatocytes followed by emergence of multiple focal lesions composed of both hyperplastic and dysplastic cell populations. These observations suggest that the interaction of c-myc and TGF-alpha, during development of hepatic neoplasia contributes to the selection and expansion of the preneoplastic cell populations which consequently increases the probability of malignant conversion. These studies have now been extended to examine the interaction of hepatocyte growth factor (HGF) with c-myc during hepatocarcinogenesis in the transgenic mouse model. While sustained overexpression of c-myc in the liver leads to cancer, coexpression of HGF and c-myc in the liver delayed the appearance of preneoplastic lesions and prevented malignant conversion. Similarly, tumor promotion by phenobarbital was completely inhibited in the c-myc/HGF double transgenic mice whereas phenobarbital was an effective tumor promoter in the c-myc single transgenic mice. The results indicate that HGF may function as a tumor suppressor during early stages of liver carcinogenesis, and suggest the possibility of therapeutic application for this cytokine. Furthermore, we show for the first time that interaction of c-myc with HGF or TGF-alpha results in profoundly different outcomes of the neoplastic process in the liver.

Isolation of a novel cytokine from human fibroblasts that specifically inhibits osteoclastogenesis

A factor which inhibits osteoclast-like cell formation was found in the conditioned medium of human embryonic lung fibroblasts, IMR-90. The factor, termed osteoclastogenesis inhibitory factor, OCIF, was purified to homogeneity. OCIF is a heparin-binding basic glycoprotein and has been isolated as a monomer with an apparent molecular weight (Mr) of 60,000 and a homodimer with a Mr of 120,000. The N-terminus of OCIF is blocked and the determination of internal amino acid sequences revealed that OCIF has no homology to known proteins. OCIF inhibited in a dose-dependent manner osteoclastogenesis elicited through three distinct signaling pathways stimulated by 1 alpha,25-dihydroxy vitamin D3, parathyroid hormone, and interleukin-11, respectively, in a dose range of 1 to 40 ng/ml (IC50 = 4 to 6 ng/ml). OCIF neither inhibits bone resorption by mature osteoclasts nor exerts any other biological activities. These data strongly suggest that OCIF is a novel cytokine which specifically inhibits osteoclastogenesis.

Hepatocyte Growth Factor Is Constitutively Produced by Human Bone Marrow Stromal Cells and Indirectly Promotes Hematopoiesis

Bone marrow (BM) stromal cells are required for normal hematopoiesis. A number of soluble factors secreted by these cells that mediate hematopoiesis have been characterized. However, the mechanism of hematopoiesis cannot be explained solely by these known factors, and the existence of other, still unknown stromal factors has been postulated. We showed that hepatocyte growth factor (HGF ) is one such cytokine produced by human BM stromal cells. BM stromal cells were shown to constitutively produce HGF and also to express the c-MET/HGF receptor. The production of HGF was enhanced by addition of heparin and phorbol ester. Dexamethasone and tumor growth factor-β (TGF-β) inhibited the production of HGF. Interleukin-1α (IL-1α) tumor necrosis factor-α (TNF-α), and N6,2′-o-dibutyryl-adenosine-3′:5′-cyclic monophosphate (dbc-AMP) showed no obvious influence on HGF production. Western blot analysis of HGF derived from BM stromal cells showed two bands at 85 and 28 kD corresponding to native and variant HGF, respectively. Addition of recombinant HGF significantly promoted the formation of burst-forming unit-erythroid (BFU-E) and colony-forming unit-granulocyte erythroid macrophage (CFU-GEM) by BM mononuclear cells in the presence of erythropoietin and granulocyte-macrophage colony-stimulating factor (GM-CSF ), but the formation of CFU-GM was not modified. However, HGF had no effects on colony formation by purified CD34+ cells. Within BM mononuclear cells, c-MET was expressed on a proportion of cells (CD34−, CD33+, CD13+, CD14+, and CD15+), but was not found on CD34+ cells. We conclude that HGF is constitutively produced by BM stromal cells and that it enhances hematopoiesis. In addition, expression of c-MET on the stromal cells suggests the presence of an autocrine mechanism, operating through HGF, among stromal cells.

Hepatocyte Growth Factor Is Constitutively Produced by Human Bone Marrow Stromal Cells and Indirectly Promotes Hematopoiesis

Bone marrow (BM) stromal cells are required for normal hematopoiesis. A number of soluble factors secreted by these cells that mediate hematopoiesis have been characterized. However, the mechanism of hematopoiesis cannot be explained solely by these known factors, and the existence of other, still unknown stromal factors has been postulated. We showed that hepatocyte growth factor (HGF ) is one such cytokine produced by human BM stromal cells. BM stromal cells were shown to constitutively produce HGF and also to express the c-MET/HGF receptor. The production of HGF was enhanced by addition of heparin and phorbol ester. Dexamethasone and tumor growth factor-β (TGF-β) inhibited the production of HGF. Interleukin-1α (IL-1α) tumor necrosis factor-α (TNF-α), and N6,2′-o-dibutyryl-adenosine-3′:5′-cyclic monophosphate (dbc-AMP) showed no obvious influence on HGF production. Western blot analysis of HGF derived from BM stromal cells showed two bands at 85 and 28 kD corresponding to native and variant HGF, respectively. Addition of recombinant HGF significantly promoted the formation of burst-forming unit-erythroid (BFU-E) and colony-forming unit-granulocyte erythroid macrophage (CFU-GEM) by BM mononuclear cells in the presence of erythropoietin and granulocyte-macrophage colony-stimulating factor (GM-CSF ), but the formation of CFU-GM was not modified. However, HGF had no effects on colony formation by purified CD34+ cells. Within BM mononuclear cells, c-MET was expressed on a proportion of cells (CD34−, CD33+, CD13+, CD14+, and CD15+), but was not found on CD34+ cells. We conclude that HGF is constitutively produced by BM stromal cells and that it enhances hematopoiesis. In addition, expression of c-MET on the stromal cells suggests the presence of an autocrine mechanism, operating through HGF, among stromal cells.

Wild-type but not mutant p53 activates the hepatocyte growth factor/scatter factor promoter

p53 transactivates the expression of a variety of genes by binding to specific DNA sequences within the promoter. We have investigated the ability of wild-type p53 and a non-DNA binding p53 mutant to activate the hepatocyte growth factor/scatter factor (HGF/SF) promoter using chloramphenicol acetyltransferase reporter constructs. We also used deletion sequences of the HGF/SF promoter to identify which regions, if any, were responsible for p53 binding. Our results show that wild-type but not mutant p53 activates the HGF/SF promoter when using -3000 and -755 bp upstream of the HGF/SF gene. This activation is lost when promoter sequences covering -365 and -239 bp are used. Analysis of the DNA sequence between -365 and -755 bp shows one putative p53 half-site with 80% homology to the consensus sequence and another half-site 3 bases downstream of this with 100% homology to the consensus sequence. In contrast to previously identified p53 binding DNA sequences, the downstream half-site is inverted. We propose that the HGF/SF promoter can be activated by wild-type p53 in vivo and that this could be as a result of a novel form of sequence-specific DNA binding.

Immunodetection of c-met-oncogene's protein product in renal cell neoplasia

The proto-oncogene c-met encodes a transmembrane tyrosine kinase receptor for hepatocyte growth factor and is expressed in normal kidney tissue. This receptor may be involved in the carcinogenesis of various organs. The aim of this study was to investigate the relationship between c-met immunohistochemical expression and pathological tumor variables in human renal cell carcinomas (RCCs) and adenomas (RAs). Formalin fixed, paraffin embedded tissues from 35 RCCs, 16 RAs and 17 normal kidneys were immunostained (Strept. ABC/HRP) with a polyclonal antibody against c-met protein (Santa Cruz, Clone C-12). The statistical analysis was performed using the linear trend in proportions and Fisher's exact test. C-met protein was detected in the cytoplasm and the plasma membranes of neoplastic cells in 19/35 RCCs (54%), 10/16 adenomas (63%) (p = 0.41) and in 17/17 controls in the epithelial cells of distal renal tubules and collecting ducts. C-met protein expression was not related with gender (p = 0.45), age (p = 0.18), tumor size (p = 0.99), cell type (p = 0.26), grade (p = 0.86) and stage (p = 0.33). Moreover, c-met immunopositive tumor cell percentage and intensity were increased in stage [RCCs, but these results were not statistically significant. Apart from glandular differentiation, c-met protein expression was not related to other histopathological features (i.e. to the type of cells or to any selective overexpression in tumor cells). C-met product may be involved in the malignant transformation of tubular epithelial cells as an early event in RCC carcinogenesis. C-met expression does not seem to have any prognostic significance for RCCs, as it was not associated with any pathological prognosticator.

Inhibition of neoplastic development in the liver by hepatocyte growth factor in a transgenic mouse model

Overexpression of the c-myc oncogene is associated with a variety of both human and experimental tumors, and cooperation of other oncogenes and growth factors with the myc family are critical in the evolution of the malignant phenotype. The interaction of hepatocyte growth factor (HGF) with c-myc during hepatocarcinogenesis in a transgenic mouse model has been analyzed. While sustained overexpression of c-myc in the liver leads to cancer, coexpression of HGF and c-myc in the liver delayed the appearance of preneoplastic lesions and prevented malignant conversion. Furthermore, tumor promotion by phenobarbital was completely inhibited in the c-myc/HGF double transgenic mice, whereas phenobarbital was an effective tumor promoter in the c-myc single transgenic mice. The results indicate that HGF may function as a tumor suppressor during early stages of liver carcinogenesis, and suggest the possibility of therapeutic application for this cytokine.

Amelioration of disordered hepatic protein synthesis by the deleted form of hepatocyte growth factor in models of liver failure in rats

Because the liver plays an important role in protein synthesis and cholesterol metabolism and reductions in these functions are observed in almost all hepatic disorders, the effects of the deleted form of hepatocyte growth factor (dHGF) on disordered hepatic protein synthesis were studied in various liver-injured rat models using Wistar male rats. In the 70% hepatectomized rats, plasma clotting time was prolonged and the serum level of total protein and the liver protein content were decreased. The treatment of the animals with dHGF (100-500 micrograms kg-1, i.v., twice daily) ameliorated these parameters at 48 or 72 h. The administration of carbon tetrachloride or D-galactosamine to hepatectomized rats induced a marked prolongation of plasma clotting time and hypoproteinaemia. In the animals treated with dHGF (500 micrograms kg-1, i.v., twice daily) these parameters were rapidly reversed compared with those of control groups. In a hepatocellular necrosis model induced by dimethylnitrosamine, the plasma clotting time was extremely prolonged, and liver protein content, serum total protein, albumin, HDL-cholesterol (as an index of lipoprotein) and plasma lecithin-cholesterol acyltransferase activity severely reduced. In this severely injured model, dHGF (5-500 micrograms kg-1, i.v., twice daily for 28 days) dose-dependently prevented the loss of liver protein content and improved the disordered plasma coagulability and serum protein levels. These results suggest that dHGF is useful for ameliorating the disorders in hepatic functions such as protein synthesis.

Heparin induces dimerization and confers proliferative activity onto the hepatocyte growth factor antagonists NK1 and NK2

Hepatocyte growth factor (HGF) is a potent epithelial mitogen whose actions are mediated through its receptor, the proto-oncogene c-Met. Two truncated variants of HGF known as NK1 and NK2 have been reported to be competitive inhibitors of HGF binding to c-Met, and to function as HGF antagonists (Lokker, N.A., and P.J. Godowski. 1993. J. Biol. Chem. 268: 17145-17150; Chan, A.M., J.S. Rubin, D.P. Bottaro, D.W. Hirschfield, M. Chedid, and S.A. Aaronson. 1991. Science (Wash. DC). 254:1382-1387). We show here, however, that NK1 acts as a partial agonist in mink lung cells. Interestingly, NK1, which is an HGF antagonist in hepatocytes in normal conditions, was converted to a partial agonist by adding heparin to the culture medium. The interaction of NK1 and heparin was further studied in BaF3 cells, which express little or no cell surface heparan sulfate proteoglycans. In BaF3 cells transfected with a plasmid encoding human c-Met, heparin and NK1 synergized to stimulate DNA synthesis and cell proliferation. There was no effect of heparin on the IL-3 sensitivity of BaF3-hMet cells, and no effect of NK1 plus heparin in control BaF3 cells, indicating that the response was specific and mediated through c-Met. The naturally occurring HGF splice variant NK2 also stimulated DNA synthesis in mink lung cells and exerted a heparin-dependent effect on BaF3-hMet cells, but not on BaF3-neo cells. The activating effect of heparin was mimicked by a variety of sulfated glycosaminoglycans. Mechanistic studies revealed that heparin increased the binding of NK1 to BaF3-hMet cells, stabilized NK1, and induced dimerization of NK1. Based on these studies, we propose that the normal agonist activity of NK1 and NK2 in mink lung cells is due to an activating interaction with an endogenous glycosaminoglycan. Consistent with that model, a large portion of the NK1 binding to mink lung cells could be blocked by heparin. Moreover, a preparation of glycosaminoglycans from the surface of mink lung cells induced dimerization of NK1. These data show that the activity of NK1 and NK2 can be modulated by heparin and other related glycosaminoglycans to induce proliferation in cells expressing c-Met.

Hepatocyte growth factor/scatter factor is present in most pleural effusion fluids from cancer patients

Pleural effusion samples were obtained from 55 patients with malignant disease, including patients with primary lung cancers and those with a variety of other tumours metastatic to the pleura. The effusions were assayed for the presence of hepatocyte growth factor/scatter factor (HGF/SF), by both ELISA and bioassay. The presence of malignant cells in the effusions was also assessed. Detectable amounts of the factor, as judged by both criteria, were found in over 90% of all the effusions, including those from patients with a wide variety of carcinomas and also lymphomas. A wide range of HGF/SF levels were found for all tumour classes, some effusions containing high levels above 4 ng ml-1. It is concluded that tumours within the pleura and adjacent lung tissue are usually exposed to biologically significant levels of HGF/SF.

Basic fibroblast growth factor stimulates hepatocyte growth factor/scatter factor secretion by human mesenchymal cells

Basic fibroblast growth factor (bFGF) together with other pleiotropic factors plays an important role in many complex physiological processes such as embryonic development, angiogenesis, and wound repair. Among these factors, hepatocyte growth factor/scatter factor (HGF/SF) which is secreted by cells of mesodermal origin exerts its mito- and motogenic activities on cells of epithelial and endothelial origin. Knowledge of the regulatory mechanisms of HGF/SF may contribute to the understanding of its role in physio-pathological processes. We observed that the secretion of HGF/SF by MRC-5 cells and by other fibroblast-derived cell cultures in conditioned media was enhanced by exposure to bFGF. HGF/SF was measured by the scatter assay, a bioassay for cell motility, and was further characterized by Western blot analysis with anti-HGF/SF antibodies. Exposure of MRC-5 cultures to 10 ng/ml of bFGF resulted already 6 h posttreatment in a threefold higher amount of scatter factor secreted into the medium as compared to untreated cultures. HGF/SF secretion was sustained after bFGF treatment for the following 72 h when increased amounts of HGF/SF were detected both in conditioned media as well as associated to the extracellular matrix. The secretion of HGF/SF in cell supernatants increased dose dependently upon treatment with bFGF starting from basal levels of 6 U/ml and reaching 27 U/ml at 30 ng/ml bFGF, plateauing thereafter. Upregulation of HGF/SF by IL-1, already described by others, was confirmed in this study. Based on our findings an articulated interaction can be speculated for bFGF, HGF/SF, and IL-1, e.g., in tissue regeneration during inflammatory processes or in wound healing.

Hepatocyte growth factor levels in bone marrow plasma of patients with leukaemia and its gene expression in leukaemic blast cells

Hepatocyte growth factor (HGF) has been known as a multiple function factor, which also stimulates early haematopoiesis. In this study, we found that HGF was expressed at both the RNA and protein levels in acute myeloid leukaemia (AML) and chronic myeloid leukaemia (CML). In patients with AML (n = 20) and CML (n = 5), bone marrow plasma HGF concentrations were 20.44 +/- 6.26 (mean +/- s.e.) ng ml-1 and 7.17 +/- 0.53 ng ml-1 respectively. These were significantly higher (P < 0.01) than the value for normal subjects (n = 26): mean 0.92 +/- 0.09 ng ml-1. Constitutive HGF production was observed in freshly prepared leukaemic blast cells from three patients with high HGF levels of bone marrow plasma. Expression of HGF mRNA was correlated with bone marrow plasma HGF levels. After complete remission was obtained in six patients, bone marrow plasma HGF levels were significantly decreased. In contrast, the HGF mRNA was less abundantly expressed in acute lymphoid leukaemia (ALL). In patients with ALL (n = 5), bone marrow plasma HGF concentration (0.69 +/- 0.14 ng ml-1) remained low within the value for normal subjects. These results suggest that some populations of myeloid lineage cells have the ability to produce HGF.

Characterization of heparan sulfate oligosaccharides that bind to hepatocyte growth factor

Proteoglycans from rat liver had the ability to bind hepatocyte growth factor (HGF). Digestion of the proteoglycans with heparitinase resulted in the complete loss of the activity, while the digestion with chondroitinase ABC had no effect. Heparan sulfate (HS)-conjugated gel also bound HGF, and the binding was competitively inhibited by heparin and bovine liver HS, but not by Engelbreth-Holm-Swarm sarcoma HS, pig aorta HS, or other glycosaminoglycans, suggesting the specific structural domain in HS for the binding of HGF. Among limited digests with heparitinase I of bovine liver HS, octasaccharide is the minimal size to bind HGF. Comparison of the disaccharide unit compositions revealed a marked difference in IdoA(2SO4)-GlcNSO3(6SO4) unit between the bound and unbound octasaccharides. The contents of this disaccharide unit were calculated to be 2 mol/mol for the bound octasaccharide but 1 mol/mol for the unbound one. Considering both the substrate specificity and properties of heparitinase I, the above results suggest that the bound octasaccharide should contain two units of IdoA(2SO4)-GlcNSO3(6SO4) contiguously or alternately in the vicinity of the reducing end. The bound decasaccharide was more than 20 times as active as the unbound one with regard to the ability to release HGF bound to rat liver HS proteoglycan. The ability was comparable to the one-fourth of that of heparin.

Hepatocyte growth factor--pleiotropic cytokine produced by human leukemia cells

Hepatocyte growth factor (HGF) was identified, purified and molecularly cloned as a potent mitogen for mature rat hepatocytes in primary culture. It is one of the largest cytokines and is composed of disulfide-linked subunits of approximately 60 (heavy chain) and 35 kilodaltons (light chain). Recent observations revealed that HGF is mitogenic to various epithelial cells other than hepatocytes and to endothelial cells, and that it also acts as a motogen, morphogen and tumor-suppressor as well as a mitogen. These various biological activities of HGF are presumably transduced through the same receptor, c-Met, which is a member of the tyrosine kinase receptor family. Although it shows multiple biological activities on cells in culture, HGF is most likely the physiological hepatotrophic factor which triggers liver regeneration. It may also function as a renotrophic and pulmotrophic factor after tissue injury. HGF production in the liver, kidney and lung increases after injury to these organs. An elevated HGF level may act as an inducer of compensatory DNA synthesis. The regulation of HGF production is, therefore, important for the control of organ regeneration. HGF is produced mainly by mesenchymal cells such as fibroblasts and vascular smooth muscle cells. Various types of human leukemia cells also secrete HGF both in vitro and in vivo. Some biological activities of HGF on hematopoietic cells, including co-mitogenic activity on myeloid leukemia cell lines, were recently demonstrated. HGF gene expression and the protein production in leukemia and fibroblast cells are modulated by various cytokines and hormones. Those modulators may indirectly affect organ regeneration and other biological processes by controlling HGF production.

Induction of invasive growth in a gallbladder cancer cell line by hepatocyte growth factor in vitro

To study the mechanism of invasion and metastasis of gallbladder cancer cells, we established a cancer cell line, GB-d1, from a metastatic lymphnode of poorly differentiated adenocarcinoma of the gallbladder. GB-d1 cells proliferate well in a dish culture and form small cystic cell clusters in a collagen gel containing 10% fetal bovine serum. A conditioned medium of human embryonic lung fibroblasts (HEL) stimulated the proliferation of GB-d1 cells and induced cell scattering in the dish culture. In the gel culture, the conditioned medium induced a transformation of the spherical clusters to arborizating colonies with tubular projections that mimicked an invasion of cancer cells into the surrounding tissue. Similar results were obtained when 10 ng/ml of human recombinant hepatocyte growth factor (h-rHGF) was added to the culture medium. The proliferative and morphological changes induced by the conditioned medium were inhibited by antiserum against h-HGF. HEL and human gallbladder stromal fibroblast-like cells produced substantial levels of HGF in the culture media, while GB-d1 did not produce any detectable level of HGF. These results suggest that HGF promotes the invasive growth of gallbladder cancer cells in vitro, and it was also suggested that stromal fibroblasts may play an important role in the invasive progression of gallbladder cancer in a paracrine fashion.

The biology of hepatocyte growth factor/scatter factor

Hepatocyte growth factor, a potent mitogen for epithelial and other cell types, and scatter factor, a stimulant of epithelial cell motility are identical. In addition to these mitogenic and motogenic functions, the factor has been shown to be an epithelial morphogen and also has antiproliferative effects in some cancer cell lines. The membrane receptor for hepatocyte growth factor/scatter factor has been identified as the c-met proto-oncogene product.

Epiregulin. A novel epidermal growth factor with mitogenic activity for rat primary hepatocytes

Epiregulin, a novel epidermal growth factor (EGF)-related growth regulating peptide, was purified from conditioned medium of the mouse fibroblast-derived tumor cell line NIH3T3/clone T7. It was a 46-amino-acid single chain polypeptide, and its amino acid sequence exhibited 24-50% amino acid sequence identity with sequences of other EGF-related growth factors. Epiregulin exhibited bifunctional regulatory properties: it inhibited the growth of several epithelial tumor cells and stimulated the growth of fibroblasts and various other types of cells. Epiregulin bound to the EGF receptors of epidermoid carcinoma A431 cells much more weakly than did EGF, but was nevertheless much more potent than EGF as a mitogen for rat primary hepatocytes and Balb/c 3T3 A31 fibroblasts. These findings suggest that epiregulin plays important roles in regulating the growth of epithelial cells and fibroblasts by binding to receptors for EGF-related ligands.

Characterization of the scatter factor/hepatocyte growth factor gene promoter. Positive and negative regulatory elements direct gene expression to mesenchymal cells

Scatter factor/hepatocyte growth factor (SF/HGF) and its receptor c-Met represent a paracrine signaling system involved in mesenchymal-epithelial interactions during development and during tumor progression. We have examined the promoters of the mouse and human SF/HGF genes by deletion mapping followed by CAT assays as well as by gel retardation and footprinting analysis. The promoter sequences are highly conserved (89.5% identity) up to position -453 from the major transcription start site but diverged considerably further upstream. Both promoters are active in mesenchymal but not epithelial cells thus reflecting the expression pattern of the SF/HGF gene in cells in vitro and in vivo. We have here identified two regulatory sequences in the SF/HGF promoter: a negative element at positions -239 to -258 and a positive element near the major transcription start site; specific deletions destroyed the activities of these elements. We were not able to localize elements on the SF/HGF promoter region that mediate the previously described effects of transforming growth factor beta, 12-O-tetradecanoylphorbol-13-acetate, and coculture of epithelial cells on SF/HGF gene expression. This study represents a first step toward understanding the intricately regulated and cell type-specific expression of the paracrine acting SF/HGF.

Factors controlling growth, motility, and morphogenesis of normal and malignant epithelial cells

Factors that control epithelial growth, motility, and morphogenesis play important roles in malignancy and in normal development. Here we discuss the molecular nature and the function of two types of molecules that control the development and maintenance of epithelia: Components that regulate epithelial cell adhesion; and soluble factors and their receptors that regulate growth, motility, differentiation, and morphogenesis. In development, the establishment of epithelial cell characteristics and organization is crucially dependent on cell adhesion and the formation of functional adherens junctions. The integrity of adherens junctions is frequently disturbed late in tumor progression, and the resulting loss of epithelial characteristics correlates with the metastatic potential of carcinoma cells. Various soluble factors that induce epithelial growth, motility, or differentiation in cell culture, function via tyrosine kinase receptors. We concentrate here on receptors that are expressed exclusively or predominantly on epithelia, and on ligands that are derived from the mesenchyme. In development, these receptors and their ligands function in mesenchymal-epithelial interactions, which are known to govern growth, morphogenesis, and differentiation of epithelia. During tumor development, mutations or overexpression of the receptors are frequently observed; these alterations contribute to the development and progression of carcinomas.

Induction of hepatocyte growth factor in human skin fibroblasts by epidermal growth factor, platelet-derived growth factor and fibroblast growth factor

Hepatocyte growth factor (HGF) is a potent mitogen for rat and human hepatocytes in primary culture and appears to be the physiological hepatotrophic factor that triggers or modulates liver regeneration. Regulation of HGF gene expression and the protein production in human skin fibroblasts was examined. Addition of epidermal growth factor (EGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), acidic fibroblast growth factor (aFGF) and transforming growth factor-alpha (TGF-alpha) to confluent cultures of the cells markedly stimulated HGF secretion from the cells. The stimulating effect of EGF, PDGF and bFGF was further investigated. The effect of all three growth factors was maximal at 3-30 ng/ml and was accompanied by an increase in HGF mRNA levels. The mRNA levels were not elevated at 5 h but were at 10 h or more after addition of EGF. The levels of HGF mRNA in fibroblasts treated with the optimal doses of EGF, PDGF, bFGF, aFGF and TGF-alpha for 24 h were 6, 4, 5, 4 and 5 times that of control cultures incubated in medium only, respectively. The growth factor-induced HGF mRNA expression and HGF secretion was inhibited by addition of TGF-beta 1 or dexamethasone. Pretreatment with a high dose of phorbol 12-myristate 13-acetate (PMA), which causes down-regulation in protein kinase C (PKC) activity and PMA-induced HGF secretion, did not reduce the effects of the growth factors on HGF mRNA expression and HGF secretion, but rather enhanced them.(ABSTRACT TRUNCATED AT 250 WORDS)

Autocrine stimulation of motility in SBC-5 human lung carcinoma cells by a two-kringle variant of HGF

Hepatocyte growth factor (HGF), a ligand for the c-met protooncogene product, is a pleiotropic cytokine which elicits mitogenic, motogenic and morphogenic activities. Among various human lung carcinoma cells, we found that SBC-5 small cell lung carcinoma cells simultaneously expressed the c-Met/HGF receptor and a smaller variant-type of HGF composed of N-terminal two-kringle domains, without expressing authentic heterodimeric HGF. The addition of anti-HGF antibodies to cultures of SBC-5 cells specifically inhibited spreading and motility of the cells without affecting growth, and the conditioned medium of SBC-5 cells also induced scattering of other lineage lung carcinoma. Thus, simultaneous expression of the unique smaller variant HGF and its receptor, c-Met, in SBC-5 cells suggests the involvement of a smaller variant HGF in the development or progression of the lung carcinoma cells, through an autocrine mechanism.

Expression of hepatocyte growth factor mRNA, and c-met mRNA (hepatocyte growth factor receptor) in human liver tumours

We have quantified mRNA for the hepatocyte growth factor and its putative receptor the c-met proto-oncogene protein product, in a series of human primary and secondary liver tumours and adjacent non-neoplastic liver. In all hepatocellular cancers, hepatocyte growth factor 6 kb mRNA expression was less (mean 23.93% +/- 6.33% S.E.M. n = 7) in the tumours than in the adjacent normal liver. Both relative over- and under-expression of c-met transcripts were found in tumour tissue compared to non-neoplastic liver. Thus hepatocellular cancer tissue does not over-express mRNA for hepatocyte growth factor, though this growth factor might play a role in hyperproliferative states leading to liver cancer.

Significant amount of hepatocyte growth factor detected in blood and bone marrow plasma of leukaemia patients

Hepatocyte growth factor (HGF) has been known as a versatile functional molecule, and as being involved in the colony formation of haemopoietic progenitor cells. Clinically, an elevated HGF level in the blood has been associated with liver diseases such as fulminant hepatic failure and acute hepatitis. We have found a high level of HGF in blood and bone marrow plasma from patients with various types of leukaemia and lymphoma. In particular, 21/31 acute myeloblastic leukaemia (AML) patients showed a significant level of HGF (> 0.40 ng/ml) in their blood or bone marrow plasma. The mean value of HGF in the plasma of AML patients was 2.03 ng/ml, which was higher than that in the serum of patients with acute hepatitis. This demonstrates, for the first time, evidence of frequent association of increased levels of HGF in non-lymphocytic leukaemias, though its significance in the disease remains unknown.

Production of hepatocyte growth factor by human haematopoietic cell lines

Hepatocyte growth factor (HGF) is a multi-functional molecule characterized as a mitogen, a motogen, a morphogen and a tumour suppressor. Little is known about cell types which produce HGF, so we analysed HGF production from cultured cell lines of haematopoietic cell lineage. A total of 138 human leukemia and virus-transformed cell lines were studied and the levels of HGF were measured by ELISA. A significant amount of HGF was detected in a variety of cell lines, including one T, four B, five non-T non-B, eight myeloid one erythroid and two EBV-transformed B cell lines. The amount of HGF spontaneously produced by three of the myeloid cell lines, KCL-22 (33.48 ng/ml), KG-1A (26.21 ng/ml), and KG-1 (18.81 ng/ml), is comparable to the amount produced by human embryonic lung fibroblast cells, known as high HGF-producers. Biological assays together with Western blot analyses verified that the immunoreactive HGF detected in the culture supernatant of haematopoietic cell lines had the same properties as authentic HGF. Moreover, HGF mRNA was detected in high HGF producers by Northern blot analysis. Our findings that lymphoid and myeloid cells function as a source of HGF may provide significant evidence for the involvement of haematopoietic cells in HGF-related morphogenesis and cell growth.

A scatter factor-like factor is produced by a metastatic variant of a rat bladder carcinoma cell line

The rat bladder carcinoma epithelial NBT-II cell line undergoes, in vitro, a morphological transition to a fibroblast-like state in the presence of different growth factors. We have selected, in vivo, a metastatic clone, designated M-NBT-II, which has a mesenchymal phenotype and secretes into the culture medium a factor able to dissociate epithelial clusters of NBT-II or MDCK cells. This factor was designated scatter factor-like (SFL) by analogy to the HGF/SF, which has the same dissociating effect in these two cell lines. Here, we show that SFL factor and HGF/SF are different factors: (i) no HGF/SF transcripts could be detected using either specific rat HGF/SF cDNA probes or PCR; (ii) blocking antibodies against rat HGF/SF do not inhibit the SFL activity; and (iii) crude culture medium or partially purified SFL factor-containing fractions do not induce MDCK tubulogenesis, a biological assay that is specific for HGF/SF activity in vitro. We report the partial purification of the SFL factor, based on ion exchange and reverse-phase chromatography. The results indicate that the M-NBT-II metastatic variant secretes a dissociating factor sharing some common biological properties with the HGF/SF, which suggests that the SFL factor is a member of the HGF/SF family and may be involved in tumor progression.

Hepatocyte growth factor in transgenic mice: effects on hepatocyte growth, liver regeneration and gene expression

Attention has recently been focused on hepatocyte growth factor as a major candidate factor in liver regeneration because it is the most potent known mitogen for hepatocytes in vitro. However, hepatocyte growth factor also displays diverse activities in vitro as scatter factor, as an epithelial morphogen, as a pluripotent mitogen and as a growth inhibitor. Consequently, we developed transgenic mice that expressed hepatocyte growth factor under the control of albumin regulatory sequences to examine its in vivo role in hepatocyte growth. Hepatocytes of these mice expressed increased levels of hepatocyte growth factor as an autocrine growth factor. Hepatocyte growth factor was a potent stimulus for liver repair; the livers of hepatocyte growth factor-transgenic mice recovered completely in half the time needed for their normal siblings after partial hepatectomy. This transgenic model also enabled us to study the chronic effects of hepatocyte growth factor expression. During several months of observation, the labeling index of hepatocytes in albumin-hepatocyte growth factor mice was doubled, and liver DNA content was increased compared with that in wild-type mice. To identify intermediate signaling pathways for hepatocyte growth factor that might regulate this increased growth response, we examined transgenic mice for changes in expression of genes that are known to be regulated during liver regeneration. We found that levels of c-myc and c-jun mRNA were increased in the hepatocyte growth factor-transgenic mice. In additional experiments the increased c-myc expression was the consequence of increased transcription rates as seen in nuclear run-on and myc-CAT reporter gene experiments. We conclude that hepatocyte growth factor increases growth and repair processes when expressed for long periods in the liver and that c-myc and c-jun may be important intermediaries in the hepatocyte growth response caused by hepatocyte growth factor.

Immunohistochemistry with antibodies to hepatocyte growth factor and its receptor protein (c-MET) in human brain tissues

Hepatocyte growth factor (HGF) is a potent mitogen for mature hepatocytes, and also has multifunctional effects on some other cells in various organs. The human c-Met proto-oncogene product has recently been identified as its high-affinity receptor. We examined HGF-like and c-Met protein-like immunoreactivities in the brains of neurologically normal, lacunar stroke and Alzheimer disease (AD) cases. The HGF antibody stained only round cells in the capillaries and astrocytes in the white matter. Positive staining with the antibody to c-Met protein was seen in microglia, predominantly in the white matter. The possibility of interactions between astrocytes and microglia through HGF and its receptor is suggested.

Partial purification and characterization of 'injurin-like' factor which stimulates production of hepatocyte growth factor

We have previously reported the evidence for presence of a humoral factor 'injurin', which induces expression of the hepatocyte growth factor (HGF) gene in MRC-5 human embryonic lung fibroblasts. We have now purified a factor from porcine liver which stimulates HGF production but differs from injurin. When injurin activity was measured as a stimulatory effect on HGF production by MRC-5 cells, this activity was found in various acid extracts from porcine tissues, including liver, kidney, brain, and lung, and acid extracts from the liver was used for purification. When the acid extract was applied to Q-Sepharose anion-exchange chromatography, 50-60% of the total injurin activity was absorbed to the column and the remaining activity was detected in the flow through fractions. Injurin activity was eluted from the Q-Sepharose column by NaCl concentration gradient with four peaks at 0.5-0.6 M, 0.7-0.8 M, 0.9-1.2 M. 1.5-2.0 M NaCl, thereby suggesting that the factor exists in heterogenous or various forms in tissues. The major active fractions were combined and applied to Mono-Q FPLC anion-exchange chromatography. Injurin activity eluted with a single peak at 0.9-1.5 M NaCl and this activity was 4286 fold purified from the starting extract. Addition of this fraction to MRC-5 cells increased the amount of HGF pulse-labeled with [35S]methionine to a 3-4-fold higher level than that seen in control cells, whereas it had no significant effect on HGF mRNA levels. Therefore, this factor seems to stimulate HGF synthesis affecting translational processes and is distinct from the previously characterized injurin which stimulates HGF gene expression. Chemical treatments and SDS-polyacrylamide gel electrophoresis of this injurin-like factor indicated that injurin-like factor is a acid- and heat-stable non-proteinous factor with an apparent M(r) of 8-15 kDa. Since the injurin activity of the factor was decreased by heparinase treatment, the factor may be a polysulfated glycosaminoglycan related to heparin or to heparan sulfate. These results suggest that HGF production may be regulated by this non-proteinous injurin-like factor and that this factor may also play an important role in the regeneration of organs, through translationally enhancing HGF production.

Hepatocyte growth factor elevates the activity levels of glycolipid sulfotransferases in renal cell carcinoma cells

Accumulation of sulfoglycolipids associated with markedly elevated activity levels of glycolipid sulfotransferases has previously been demonstrated in the human renal cell carcinoma cell line, SMKT-R3. To elucidate the regulatory mechanisms of sulfoglycolipid synthesis in SMKT-R3 cells, the effects of various growth factors on the metabolic enzymes of sulfoglycolipids were investigated. Hepatocyte growth factor (HGF) significantly increased the activity levels of the sulfotransferases in a dose-dependent manner, but did not change that of arylsulfatase A, which hydrolyzes sulfoglycolipids. Scatchard analysis of 125I-HGF binding to SMKT-R3 cells indicated that the cells expressed high-affinity receptors for HGF with a Kd of 36 pM and 750 sites/cell. Furthermore, metabolic labeling with [35S]sulfate revealed that the addition of HGF to the culture medium of the cells resulted in an increment of sulfoglycolipid synthesis. Therefore, these observations suggest that HGF can function as a regulatory factor in sulfoglycolipid synthesis through the modulation of the sulfotransferase activity levels in renal cell carcinoma cells. In addition, HGF stimulated the proliferation and motility of SMKT-R3 cells, suggesting that HGF has multiple biological activities in renal cell carcinoma cells.

Stimulation of prostaglandin production by hepatocyte growth factor in human gastric carcinoma cells

Hepatocyte growth factor (HGF), a protein with pleiotropic biological activity affecting cell growth and motility, was found to markedly activate prostaglandin production in human gastric carcinoma TMK-1 cells. HPLC analysis revealed that HGF stimulated the production of prostaglandin E2 (PGE2), which is the major prostaglandin produced in these cells. HGF maximally stimulated PGE2 production at a concentration of 10 ng/ml, and it was a more potent stimulator of PGE2 production than epidermal growth factor (EGF), which is known to stimulate prostaglandin production in various cell lines. The simultaneous addition of HGF and EGF caused no further stimulation of the PGE2 production observed in HGF-treated cells. We showed also that HGF increased the arachidonate release from TMK-1 cells, which release was completely suppressed by the addition of phospholipase A2 (PLA2) inhibitors. Further studies in vitro showed that HGF enhanced cellular activities of cytosolic PLA2 and cyclooxygenase 1.5-fold each. These results indicate that HGF stimulates prostaglandin production through increases in both cytosolic PLA2 and cyclooxygenase activities.

Hepatocyte growth factor/scatter factor, liver regeneration and cancer metastasis

Hepatocyte growth factor (HGF) is the most potent stimulator of hepatocyte growth and DNA synthesis identified; it is now known to be the same molecule as scatter factor, which increases the motility of a variety of cell types. HGF is becoming recognized as one of the most important factors in the regulation of liver regeneration after surgical resection or chemical damage. HGF is produced by several tissues, including neoplasms; it can therefore provide a stimulus for increased motility of malignant cells by both a paracrine and autocrine mechanism. The receptor for HGF has been identified as the product of the oncogene c-met, raising the possibility that this gene plays a key role in facilitating cellular invasion. HGF may therefore be important not only for liver cell growth but also in metastasis. This article summarizes the current position of research on HGF, and presents both clinical and scientific evidence that strongly implicates this factor in liver regeneration and cancer invasion and metastasis.

Hepatocyte growth factor-like protein is identical to macrophage stimulating protein

Although the hepatocyte growth factor-like protein (HLP) shares a 50% homology with the hepatocyte growth factor, the biological function of HLP has remained unknown. Addition of conditioned medium of COS-7 cells transfected with the expression plasmid for HLP cDNA to cultures of resident peritoneal macrophages induced specific activation of macrophages, and the factor which stimulates macrophages was purified from the conditioned medium. The purified protein showed M(r) of 85 kDa on SDS-PAGE, and this M(r) is in agreement with that of macrophage-stimulating protein (MSP) previously purified from human serum, as well as with the predicted M(r) of HLP. Amino acid composition of the purified protein coincided with the compositions of human HLP and MSP. Together with the finding that the partial amino acid sequences of MSP are highly homologous to that of HLP, we conclude that the biological function of HLP is to activate macrophages and that HLP and MSP are identical molecules.

Scatter factor/hepatocyte growth factor and its receptor, the c-met tyrosine kinase, can mediate a signal exchange between mesenchyme and epithelia during mouse development

Scatter factor/hepatocyte growth factor (SF/HGF) has potent motogenic, mitogenic, and morphogenetic activities on epithelial cells in vitro. The cell surface receptor for this factor was recently identified: it is the product of the c-met protooncogene, a receptor-type tyrosine kinase. We report here the novel and distinct expression patterns of SF/HGF and its receptor during mouse development, which was determined by a combination of in situ hybridization and RNase protection experiments. Predominantly, we detect transcripts of c-met in epithelial cells of various developing organs, whereas the ligand is expressed in distinct mesenchymal cells in close vicinity. In addition, transient SF/HGF and c-met expression is found at certain sites of muscle formation; transient expression of the c-met gene is also detected in developing motoneurons. SF/HGF and the c-met receptor might thus play multiple developmental roles, most notably, mediate a signal given by mesenchyme and received by epithelial. Mesenchymal signals are known to govern differentiation and morphogenesis of many epithelia, but the molecular nature of the signals has remained poorly understood. Therefore, the known biological activities of SF/HGF in vitro and the embryonal expression pattern reported here indicate that this mesenchymal factor can transmit morphogenetic signals in epithelial development and suggest a molecular mechanism for mesenchymal epithelial interactions.

Proteolytic processing of the hepatocyte growth factor/scatter factor receptor by furin

The hepatocyte growth factor/scatter factor (HGF/SF) receptor consists of an alpha- and a beta-subunit, which are derived from a single-chain precursor by endoproteolytic processing. The precursor is not proteolytically processed in LoVo colon carcinoma cells. The uncleaved receptor immunopurified from the cells was cleaved in vitro by furin. Furthermore, the HGF/SF receptor was proteolytically processed in LoVo cells transfected with furin cDNA. These results indicate that furin is a processing endoprotease for the HGF/SF receptor. Tyrosine autophosphorylation of the uncleaved receptor was induced by HGF/SF, and the growth of the cells expressing the uncleaved receptor was stimulated by HGF/SF, indicating that the proteolytic processing of the receptor is not essential for the signal transduction of HGF/SF.

The Met receptor tyrosine kinase transduces motility, proliferation, and morphogenic signals of scatter factor/hepatocyte growth factor in epithelial cells

Depending on the target cells and culture conditions, scatter factor/hepatocyte growth factor (SF/HGF) mediates several distinct activities, i.e., cell motility, proliferation, invasiveness, tubular morphogenesis, angiogenesis, or cytotoxicity. A small isoform of SF/HGF encoded by a natural splice variant, which consists of the NH2-terminal hairpin structure and the first two kringle domains but not the protease homology region, induces cell motility but not mitogenesis. Two types of SF/HGF receptors have recently been discovered in epithelial cells, the high affinity c-Met receptor tyrosine kinase, and low affinity/high capacity binding sites, which are probably located on heparan sulfate proteoglycans. In the present study, we have addressed the question whether the various biological activities of SF/HGF are transduced into cells by a single type of receptor. We have here examined MDCK epithelial cells transfected with a hybrid cDNA encoding the ligand binding domain of the nerve growth factor (NGF) receptor and the membrane-spanning and tyrosine kinase domains of the Met receptor. We demonstrate that all biological effects of SF/HGF upon epithelial cells such as the induction of cell motility, proliferation, invasiveness, and tubular morphogenesis can now be triggered by the addition of NGF. Thus, it is likely that all known biological signals of SF/HGF are transduced through the receptor tyrosine kinase encoded by the c-Met protooncogene.