Partial purification and characterization of hepatocyte growth factor from serum of hepatectomized rats

Changes in growth factor and cytokine mRNA levels after hepatectomy in rat with CCl(4)-induced cirrhosis

Cirrhotic liver is considered to regenerate less actively than normal liver after hepatic resection. However, the mechanisms responsible for this impaired regeneration and the cross talk of implicated factors still remain unclear. In the present study, mRNA levels for cyclins, growth factors, and cytokines were quantitatively assessed by a RT-PCR method at different times after hepatectomy in order to determine the relationships between these factors and the impaired regenerative process observed in cirrhotic liver. In our model of CCl(4)-induced cirrhosis, mRNA levels for cyclins and thymidine kinase provide evidence for the impaired and delayed hepatic regeneration. Moreover, we observed a significant decrease in interleukin (IL)-6 and tumor necrosis factor-alpha mRNA and a significant increase for IL-1beta mRNA. No significant change of hepatocyte growth factor (HGF) mRNA level was detected, contrasting with the decrease both at mRNA and protein levels in the expression of the c-Met/HGF receptor. Therefore, the impaired regeneration of the cirrhotic liver is associated not only with a lowered level of signals that normally promote liver growth but also with a strong decrease in c-Met receptor despite a normal expression of its specific ligand.

Immunopathogenesis of hepatic fibrosis in chronic liver injury induced by repeatedly administered concanavalin A

Liver fibrosis is commonly observed in chronic liver disease. However, the immunological mechanisms underlying hepatic fibrosis due to chronic inflammation are not well defined, mainly because suitable experimental models have not been established. We have found that weekly i.v. administration of concanavalin A (Con A) in BALB/c mice brought about a striking alanine aminotransferase increase, resulting in piecemeal necrosis with bridging fibrosis in the parenchyma. Using this fibrosis model, we demonstrated the kinetics of cytokine mRNA expression in liver. Transforming growth factor (TGF)-beta1, TGF-alpha, basic fibroblast growth factor (bFGF) and hepatocyte growth factor mRNAs were up-regulated after each Con A administration. Furthermore, either anti-IFN-gamma, anti-tumor necrosis factor (TNF)-alpha or anti-TGF-beta mAb given together with Con A markedly inhibited the development of hepatic fibrosis. Treatment with either anti-IFN-gamma or anti-TNF-alpha mAb also completely prevented hepatic injury; in contrast, treatment with anti-TGF-beta mAb did not. The treatment with anti-TGF-beta mAb did not affect the levels of hepatic mRNAs for either IFN-gamma or TNF-alpha after Con A injection. Treatment with either anti-IFN-gamma or anti-TNF-alpha did not affect the expression levels of TGF-beta in the liver. In conclusion, the continuous presence of both severe liver damage and up-regulation of TGF-beta synthesis is necessary to induce hepatic fibrosis in this model.

Prostaglandin production in mouse mammary tumour cells confers invasive growth potential by inducing hepatocyte growth factor in stromal fibroblasts

Interactions between stromal and mammary tumour cells play a crucial role in determining the malignant behaviour of tumour cells. Although MMT mouse mammary tumour cells do not produce hepatocyte growth factor (HGF), addition of conditioned medium (CM) from MMT cells to cultures of human fibroblasts derived from skin and breast tissues stimulated the production of HGF, thereby indicating that MMT cells secrete an inducing factor for HGF. This HGF-inducing factor, purified from MMT-derived CM, proved to be prostaglandin E2 (PGE2). Consistently, treatment of MMT cells with indomethacin, an inhibitor of cyclooxygenase, abolished this HGF-inducing activity in MMT-derived CM, while treatment of MMT cells with HGF stimulated cell growth and cell motility. Likewise, HGF strongly enhanced urokinase-type plasminogen activator activity and invasion of MMT cells through Matrigel: a 15-fold stimulation in the invasion of MMT cells was seen by HGF. Finally, MMT cells in the upper compartment were co-cultivated with fibroblasts in the lower compartment of the Matrigel chamber, HGF levels in the co-culture system exceeded the level in fibroblasts alone and suppression occurred with exposure to indomethacin. Together with increase in the HGF level, the invasion of MMT cells was enhanced by co-cultivation with fibroblasts, whereas the increased invasion of MMT cells was significantly inhibited by an anti-HGF antibody and by indomethacin. These results indicate mutual interactions between MMT cells and fibroblasts: MMT-derived PGE2 plays a role in up-regulating HGF production in fibroblasts, while fibroblast-derived HGF leads to invasive growth in MMT cells. The mutual interactions mediated by HGF and prostaglandins may possibly be a mechanism regulating malignant behaviour of mammary tumour cells, through tumour-stromal interactions.

Association of the HGF/SF receptor, c-met, with the cell-surface adhesion molecule, E-cadherin, and catenins in human tumor cells

Tumour cell metastatic potential is significantly enhanced following treatment with HGF/SF, the ligand for the c-met receptor tyrosine kinase. Following c-met activation in tumour cells, phosphorylation of beta-catenin occurs, together with loss of intercellular adhesion and a gain in the motile and invasive nature of the cell. In this study we show that c-met is co-localised with beta-catenin and E-cadherin at regions of cell-cell contact in human colon cancer (HRT18 and HT115) and two breast cancer (MCF7 and MDA MB 231) cell lines. Immunoprecipitation studies demonstrated an association between c-met and members of the cadherin adhesion complex in these epithelial tumour cells, along with the membrane tyrosine protein phophatase, PTPmu. We conclude that the HGF/SF receptor, c-met, together with members of the cadherin/catenin cell-cell adhesion system and PTPmu, may form part of a protein complex in E-cadherin positive tumour cells that acts to regulate intercellular adhesion following HGF/SF stimulation.

Autocrine and paracrine motility factors and their involvement in invasiveness in a human oral carcinoma cell line

Invasive potentials of malignant cancer cells are regulated by cell motility factors. To examine the regulation of motility and invasiveness in oral squamous carcinoma, we investigated autocrine- and/or paracrine-acting cell motility factors, using a newly established human cell line (IF cells) from oral squamous cell carcinoma, which has highly invasive and metastatic characteristics. Conditioned medium derived from IF cells stimulated cell scattering and migration of GB-d1 gallbladder carcinoma cells, indicating that IF cells secreted cell motility factors. Using antibodies, IF-derived cell motility factors proved to be transforming growth factor (TGF)-alpha and TGF-beta1. Antibodies against TGF-alpha and TGF-beta1 inhibited autonomous migration of the IF cells. On the other hand, in vitro invasion of IF cells was strongly enhanced by hepatocyte growth factor (HGF) but only slightly by TGF-alpha and TGF-beta1. The conditioned medium from fibroblasts enhanced in vitro invasion of IF cells, an event abrogated by anti-HGF antibody, but not by antibodies against TGF-alpha and TGF-beta1. Importantly, IF cells secreted a factor inducing HGF production in fibroblasts and the factor was identified as interleukin-1, which means that a mutual interaction exists between tumour cells and fibroblasts, as mediated by the HGF/HGF-inducer loop. These results indicate that IF cells utilize TGF-alpha and TGF-beta1 as autocrine-acting motility factors and HGF as a paracrine-acting motility factor, and that invasiveness of IF cells is particularly stimulated by HGF derived from stromal fibroblasts. Utilization of multiple cell motility/invasion factors that act in distinct pathways may confer highly invasive and metastatic potentials in IF oral squamous carcinoma cells.

Prognostic value of serum hepatocyte growth factor in patients with acute coronary syndromes

The present study examined whether or not hepatocyte growth factor (HGF), an endothelium-specific growth factor that stimulates regeneration of the endothelium, is increased or has a prognostic significance in patients with acute coronary syndromes. HGF was measured in 106 patients with coronary artery disease (20 stable effort angina, 12 unstable angina without adverse events, 24 unstable angina with adverse events and 50 acute myocardial infarction) on admission and 21 normal volunteers. The measurements in all patients were recorded before administration of heparin, and in acute myocardial infarction patients they were recorded from days 2 to 6 after heparin discontinuation on day 1. HGF levels (ng/ml) were 0.30+/-0.06 for the controls, 0.31+/-0.08 for stable effort angina patients, 0.31+/-0.08 for unstable angina patients without adverse events, 0.40+/-0.20 for unstable angina patients with adverse events and in acute myocardial infarction patients they were 0.45+/-0.18 on day 0, 0.57+/-0.45 on day 2, 0.50+/-0.35 on day 3, 0.48+/-0.32 on day 4, 0.44+/-0.20 on day 5, and 0.38+/-0.14 on day 6. HGF plays a crucial role in the restoration of injured endothelial cells and is a predictor of adverse events in patients with acute coronary syndromes.

Scatter factor/hepatocyte growth factor (SF/HGF) content and function in human gliomas

Scatter factor/hepatocyte growth factor (SF/HGF) is a pleiotrophic cytokine that stimulates motility and invasion of several cancer cell types and induces angiogenesis. Its receptor MET is a transmembrane tyrosine kinase encoded by the C-MET proto-oncogene. To assess the potential relevance of SF/HGF in gliomas we performed functional studies in vivo and in vitro, expression analyses and correlative studies. We showed that both SF/HGF and MET are expressed in gliomas in vivo and are upregulated during transition from low grade to malignant glioma. When SF/HGF cDNA was transfected into glioma cells that expressed the MET receptor the cells formed considerably larger and more vascularized intracranial tumors in vivo than SF/HGF negative control clones. In other glioma cells, which constitutively expressed both SF/HGF and MET, we abolished SF/HGF expression by antisense ribozyme-targeting, which led to a significant decrease in tumorigenicity and tumor growth. In vitro SF/HGF strongly stimulated glioma cell motility and to a lesser degree proliferation. SF/HGF also strongly increased endothelial cell motility in vitro and extracts of tumors derived from SF/HGF-transfected glioma cells were more mitogenic for endothelial cells and more angiogenic in the rat cornea angiogenesis assay than extracts from control tumors. In a three-dimensional in vitro angiogenesis assay basic fibroblast growth factor (bFGF) was found to synergize with either SF/HGF or vascular endothelial growth factor (VEGF) in inducing endothelial capillary-like tubes, whereas neither SF/HGF nor VEGF alone or in combination were effective. Interestingly, while both VEGF and SF/HGF levels appeared to be increased in malignant gliomas compared with low grade ones, this was not the case for bFGF of which biologically relevant levels were already present in low grade gliomas. It thus seems that bFGF alone is insufficient to induce angiogenesis in gliomas but may act synergistically with either VEGF and/or SF/HGF when these become upregulated during malignant progression. In conclusion, we showed that SF/HGF may contribute to glioma progression by stimulating tumor invasiveness, proliferation and neovascularization.

Hepatocyte growth factor concentration in rat bile is affected by hepatic resection volume and external biliary drainage

BACKGROUND/AIMS

Hepatocyte growth factor (HGF) concentrations in bile have been shown to be useful in the early assessment of liver function after hepatectomy. The aim of the present study is to prove the hypothesis that the level of bile HGF is proportional to the regeneration capacity of the liver using a rat model.

METHODS

Blood and bile were sampled from rats who underwent 30 or 70% hepatectomy, with or without biliary drainage. HGF concentrations were determined using enzyme-linked immunosorbent assay.

RESULTS

Liver regeneration was significantly suppressed after hepatectomy in the rats that underwent external biliary drainage. The bile HGF concentration was positively correlated with the resected liver volume within 24 h of hepatectomy, and HGF levels were markedly increased by external biliary drainage. The postoperative changes in plasma HGF were less dramatic.

CONCLUSIONS

HGF appears to play an important role in liver regeneration. Bile HGF concentrations, unlike plasma HGF levels, are a good reflection of the hepatic biosynthesis of this growth factor. Increased concentrations of HGF in bile after external biliary drainage may reflect a compensatory response to the continuous loss of hepatocyte growth factor-rich fluid.

Hepatocyte growth factor prevents endotoxin-induced lethal hepatic failure in mice

Sepsis and endotoxemia are involved in the development of fulminant hepatic failure, the prognosis of which is extremely poor and the mortality is high, with no available effective therapy. Here, we report that hepatocyte growth factor (HGF) exerts potent antiapoptotic effects in vivo and effectively prevents endotoxin-induced fulminant hepatic failure in mice. The animals were intraperitoneally injected three times with 120 micrograms human recombinant HGF or saline 6 hours and 30 minutes before and 3 hours after an intraperitoneal injection of lipopolysaccharide (LPS) and D-galactosamine (GalN). Administration of LPS + GalN, without HGF, rapidly led to massive hepatocyte apoptosis and severe liver injury, and all mice died of hepatic failure within 8 hours. In contrast, administration of human recombinant HGF strongly suppressed extensive progress of hepatocyte apoptosis and the liver injury induced by LPS + GalN, and 75% of the HGF-treated mice survived. Moreover, HGF strongly induced Bcl-xL expression and blocked apoptotic signal transduction upstream of CPP32 (caspase-3) in the liver, thereby leading to inhibition of massive hepatocyte apoptosis. We suggest that HGF may well have the potential to prevent fulminant hepatic failure, at least through its potent antiapoptotic action.

Effects of exogenous human heparin-binding epidermal growth factor-like growth factor on DNA synthesis of hepatocytes in normal mouse liver

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been reported to stimulate DNA synthesis of the hepatocytes in culture and highly express in regenerating rat liver after partial hepatectomy. We examined mitogenic effects and activation of transcription factors caused by exogenous human HB-EGF (hHB-EGF) in mouse liver. The mean labeling index in hepatocytes of hHB-EGF-injected mice was 2.6%, a significant increase over that in saline-injected controls (under 0.01%). By exogenous hHB-EGF injection, activation of transcription factors such as nuclear factor (NF)-kappaB and activator factor (AP)-1 was observed in the liver. By Northern blot analysis, hepatocyte growth factor (HGF) gene expression in the liver was found to be induced in the hHB-EGF-injected mice. In conclusion, intravenously injected hHB-EGF showed a limited but definite effect on the DNA synthesis of hepatocytes in the mice liver. HB-EGF may serve as a hepatotrophic factor in vivo.

In vitro modulation of microglia motility by glioma cells is mediated by hepatocyte growth factor/scatter factor

OBJECTIVE

Considered as immune effector cells of the central nervous system, microglia represent a major component of the inflammatory cells found in malignant gliomas. Although their role in brain tumor biology is unclear, accumulation of microglia in malignant brain tumors may be mediated through active secretion of cytokines by glioma cells. Because hepatocyte growth factor/scatter factor (HGF/SF) has been shown to modulate glioma motility through an autocrine mechanism, and because microglia have been reported to express the HGF/SF receptor Met, we hypothesized that microglia recruitment by gliomas may also occur through the secretion of HGF/SF.

METHODS

The effect of glioma cells in augmenting BV-2 murine microglia motility was studied by using an in vitro Boyden chamber migration assay. To determine the chemokines involved in microglia migration, neutralizing monoclonal antibodies against monocyte chemotactic protein-1 and HGF/SF were tested. Immunoblotting was used to check for the expression of HGF/SF by glioma cells, and the expression of Met by BV-2 cells was examined by flow cytometry.

RESULTS

BV-2 migration was noted within 7 hours of incubation with both human (U251 MG and U373 MG) and murine (GL261) glioma cell lines. This migration corresponded to HGF/SF secretion by glioma cells and was completely inhibited by neutralizing monoclonal antibody against HGF/SF, but not monocyte chemotactic protein-1. Exposure of BV-2 cells to recombinant HGF/SF, but not monocyte chemotactic protein-1, resulted in their migration and down-regulation of Met in a dose-dependent fashion.

CONCLUSION

HGF/SF, which plays a role in glioma motility and mitogenesis, may also act as a chemokine for microglia and may be responsible for the microglia infiltration in malignant gliomas. This active recruitment of microglia may play an important role in glioma biology.

Expression of the human hepatocyte growth factor cDNA in primary cultures of rat hepatocytes

Hepatocyte growth factor (HGF) and epidermal growth factor (EGF) are primary mitogens for hepatocytes in culture. hepatocytes express the HGF-receptor MET but not HGF itself. To investigate the influence of autocrine HGF expression on the proliferative potential of hepatocytes, primary cultures were submitted to retrovirus-mediated transduction of the human hgf (huHGF) cDNA. Expression of the transduced cDNA revealed a minimum 2-fold increase in HGF-mRNA, whereas expression of the Escherichia coli beta-galactosidase gene remained even. Estimation of huHGF copy numbers showed there was a minimum 4-fold increase, suggesting an increase in the population of transduced cells. Immunoprecipitation of excreted huHGF and growth bioassays proofed that HGF was present and functional. HGF is excreted into the medium and therefore, by diffusion, available to transduced and non-transduced cells. The increase in huHGF-transduced cells suggests that the autocrine pathway as opposed to the paracrine pathway, which are both present at the same time, confers a growth advantage to these cells.

Expression of hepatocyte growth factor (HGF) and HGF receptor (c-met) proteins in liver diseases: an immunohistochemical study

BACKGROUND

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes in vivo as well as in vitro. Serum levels of HGF vary in liver diseases, reflecting liver damage and dysfunction. However there are no studies reporting expression of HGF and HGF receptor (c-met protein) simultaneously in various liver diseases.

METHODS

To clarify the clinical significance of HGF/c-met protein expression in liver diseases, liver tissues from 62 patients consisting of 7 with acute hepatitis (AH), 20 with chronic hepatitis (CH), 9 with liver cirrhosis (LC) and 26 with hepatocellular carcinoma (HCC) were immunohistochemically examined.

RESULTS

Intense staining of HGF was observed in patients from AH, CH and LC, although no immunoreactivity was seen in HCC. The expression of c-met protein was higher in patients with HCC and AH than in those with CH (p < 0.05). A correlation of immunoreactivity between HGF and c-met protein was not observed expect in patients with LC (p < 0.01). The extent of c-met expression had no correlation with differentiation of HCC, tumour size, presence of portal invasion, or serum AFP levels.

CONCLUSION

The results of the present study suggest that HGF plays an important role in human liver diseases, mostly in a manner independent of c-met protein expression.

The expression of mRNAs for hepatocyte growth factor/scatter factor, its receptor c-met, and one of its activators tissue-type plasminogen activator show a systematic relationship in the developing and adult cerebral cortex and hippocampus

The temporal and spatial expression in brain of the mRNAs for the pleiotropic cytokine hepatocyte growth factor/scatter factor (HGF/SF) and its receptor c-met were compared to those of a known HGF/SF activator, tissue-type plasminogen activator (tPA). In addition to the previously described expression in the developing and adult olfactory system [D.P. Thewke, N.W. Seeds, Expression of hepatocyte growth factor/scatter factor, its receptor, c-met, and tissue-type plasminogen activator during development of the murine olfactory system, J. Neurosci. 16 (1996) 6933-6944] two other regions of the mouse brain were found where the expression of tPA mRNA appeared to co-localized with HGF/SF and/or c-met mRNA. In the developing hippocampus, tPA mRNA was expressed coincident with HGF/SF and c-met mRNAs in the CA1 field. tPA mRNA was expressed in all areas of the adult hippocampus, while HGF/SF expression was restricted to the CA2 and CA3 fields, and c-met mRNA was seen primarily in the CA1 field. In the developing cerebral cortex, the expression of tPA mRNA was observed in the subplate and inner cortical plate between two layers of c-met expression, whereas HGF/SF mRNA was localized to the proliferative zone lining the lateral ventricle. Layer specific expression of both HGF/SF and c-met mRNA were observed in the adult cortex, where HGF/SF was expressed in layers IV and V and c-met in layers II-III, IV and V. The expression of tPA mRNA in the adult cortex was low and not layer specific, although homogenates of adult cortex did have detectable levels of tPA activity when subjected to zymography. Immunohistochemical analysis using HGF/SF and c-met antibodies on adult brain sections showed a distribution similar to the in situ hybridization results. C-met antibodies appeared to stain large neurons in the cortex and hippocampus. These results are consistent with the hypothesis that HGF/SF plays a role in the development and maintenance of both the cerebral cortex and hippocampus, and that tPA may act as a regulator of HGF/SF activity in these structures.

The multisubstrate docking site of the MET receptor is dispensable for MET-mediated RAS signaling and cell scattering

The scatter factor/hepatocyte growth factor regulates scattering and morphogenesis of epithelial cells through activation of the MET tyrosine kinase receptor. In particular, the noncatalytic C-terminal tail of MET contains two autophosphorylation tyrosine residues, which form a multisubstrate-binding site for several cytoplasmic effectors and are thought to be essential for signal transduction. We show here that a MET receptor mutated on the four C-terminal tyrosine residues, Y1311F, Y1347F, Y1354F, and Y1363F, can induce efficiently a transcriptional response and cell scattering, whereas it cannot induce cell morphogenesis. Although the mutated receptor had lost its ability to recruit and/or activate known signaling molecules, such as GRB2, SHC, GAB1, and PI3K, by using a sensitive association-kinase assay we found that the mutated receptor can still associate and phosphorylate a approximately 250-kDa protein. By further examining signal transduction mediated by the mutated MET receptor, we established that it can transmit efficient RAS signaling and that cell scattering by the mutated MET receptor could be inhibited by a pharmacological inhibitor of the MEK-ERK (MAP kinase kinase-extracellular signal-regulated kinase) pathway. We propose that signal transduction by autophosphorylation of the C-terminal tyrosine residues is not the sole mechanism by which the activated MET receptor can transmit RAS signaling and cell scattering.

Hepatocyte growth factor is a major mediator in heparin-induced angiogenesis

Heparin has a potent angiogenic effect in experimental animals and patients with ischemic diseases; however, the precise mechanism behind this angiogenesis remains to be clarified. The aim of this study was to determine whether the administration of heparin affects the levels of heparin-binding angiogenic factors in human plasma, and to identify the molecule responsible for heparin-induced angiogenesis. Plasma levels of hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) were measured before and after administration of 100 U, 3,000 U or 10,000 U of heparin in patients with coronary artery disease. Administration of 3,000 U or 10,000 U of heparin caused significant increases in plasma HGF (40- and 54-fold, respectively), in absence of obvious increases in bFGF and VEGF levels. Furthermore, compared with the serum collected before heparin administration, the serum collected after heparin administration had more prominent growth-promoting and vascular tube-inducing properties on endothelial cells, and these increased activities were completely inhibited by neutralization of HGF, whereas neutralization of bFGF and VEGF had no effect. These findings suggest that HGF plays a significant role in heparin-induced angiogenesis.

Hepatocyte growth factor gene therapy of liver cirrhosis in rats

Liver cirrhosis is the irreversible end result of fibrous scarring and hepatocellular regeneration, characterized by diffuse disorganization of the normal hepatic structure of regenerative nodules and fibrotic tissue. It is associated with prominent morbidity and mortality, and is induced by many factors, including chronic hepatitis virus infections, alcohol drinking and drug abuse. Hepatocyte growth factor (HGF), originally identified and cloned as a potent mitogen for hepatocytes, shows mitogenic, motogenic and morphogenic activities for a wide variety of cells. Moreover, HGF plays an essential part in the development and regeneration of the liver, and shows anti-apoptotic activity in hepatocytes. In a rat model of lethal liver cirrhosis produced by dimethylnitrosamine administrations, repeated transfections of the human HGF gene into skeletal muscles induced a high plasma level of human as well as enodogenous rat HGF, and tyrosine phosphorylation of the c-Met/HGF receptor. Transduction with the HGF gene also suppressed the increase of transforming growth factor-beta1 (TGF-beta1), which plays an essential part in the progression of liver cirrhosis, inhibited fibrogenesis and hepatocyte apoptosis, and produced the complete resolution of fibrosis in the cirrhotic liver, thereby improving the survival rate of rats with this severe illness. Thus, HGF gene therapy may be potentially useful for the treatment of patients with liver cirrhosis, which is otherwise fatal and untreatable by conventional therapy.

Hepatocyte growth factor leads to recovery from alcohol-induced fatty liver in rats

A fatty liver is characterized by the hyperaccumulation of lipids within hepatocytes and is often caused by excessive alcohol intake. Rats fed ethanol-containing diets for 37 days showed remarkable increase in hepatic lipids and lipid droplet accumulation in the hepatocytes, indicating the onset of alcoholic fatty liver. Administration of hepatocyte growth factor (HGF) for the last seven days of ethanol treatment markedly decreased hepatic lipids to a level lower than that seen before HGF treatment. In contrast, serum levels of lipids and lipoproteins increased with HGF administration. Primary cultured hepatocytes prepared from the fatty liver retained lipid droplets during a 48-hour culture. However, when cultured in the presence of HGF, intracellular lipid concentrations decreased and lipid secretion was enhanced. Consistent with these events, HGF stimulated the rate of protein synthesis of apolipoprotein B (apoB) and enhanced subsequent mobilization of lipids into the medium. These results indicate that HGF administration induced recovery from the fatty liver, at least in part, by enhancing apoB synthesis and the subsequent mobilization of lipids from hepatocytes with fatty change. The possibility that HGF can be therapeutic for subjects with an alcohol-related fatty liver warrants further attention.

Growth and differentiation of cultured fetal hepatocytes isolated various developmental stages

We examined the relationship between cell proliferation and differentiation of cultured rat fetal and newborn hepatocytes isolated from various developmental stages. The albumin production rate increased along with cell growth under in vitro culture and became maximal two days after the growth cessation. AFP was secreted by both fetal and newborn hepatocytes with growth ability. Furthermore, the responses to HGF addition in fetal hepatocyte cultures were observed in terms of growth stimulation and down-regulated of the Met receptor. We also studied the changes in RB and liver enriched transcription factors (C/EBPs) for investigating the mechanism underlying proliferation and differentiation of fetal hepatocytes. Western blot analysis of hepatocytes taken from various gestation stages of rat liver showed that the expression of RB and C/EBP beta increased as gestation stage proceeded. When RB antisense S-oligonucleotide was added to the culture medium, proliferation and AFP expression increased, while C/EBP alpha and albumin expressions decreased. These results indicated that the tumor suppressor gene product RB had a profound role not only in cell proliferation but also hepatocyte differentiation.

Wy-14,643, a peroxisome proliferator, inhibits compensative cell proliferation and hepatocyte growth factor mRNA expression in the rat liver

Previously, we found that a peroxisome proliferator significantly reduced hepatic and plasma hepatocyte growth factor (HGF) levels in male F-344 rats, and that the growth of preneoplastic or neoplastic cells induced by this peroxisome proliferator was markedly inhibited by HGF. Here, we examined the effects of [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio] acetic acid (Wy-14,643), a peroxisome proliferator, on cell proliferation and HGF mRNA levels in the liver of rats after stimulation of compensative cell proliferation. After 2 weeks of treatment with Wy-14,643, hepatic DNA synthesis caused by partial hepatectomy was decreased by 50% compared with untreated controls. DNA synthesis was maintained at the same reduced level for up to 10 weeks. During this period, hepatic HGF mRNA level was also much lower in Wy-14,643-treated rats than untreated controls. Therefore Wy-14,643, a peroxisome proliferator, would inhibit the growth of normal hepatocytes, and then produce an advantageous circumstance for the selective growth of neoplastic or preneoplastic cells.

Enhanced hepatocyte growth factor expression associated with prolonged rat hepatic allograft survival in recipients pretreated with donor-specific blood

BACKGROUND

Pretransplantation injection of freshly heparinized donor blood (donor-specific blood transfusion, or DST) significantly prolongs the survival of hepatic allografts from ACI(RT1a) to LEW(RT1l) rats. We investigated hepatocyte growth factor (HGF) expression in rat hepatic allografts of recipients pretreated with or without DST.

METHODS

The levels of HGF mRNA and protein in hepatic allografts were determined after transplantation. The localization of HGF+ cells was identified with a rat anti-HGF monoclonal antibody.

RESULTS

Plasma HGF concentrations in transplanted rats treated with DST were significantly and persistently increased compared to untreated rats with hepatic allografts. The number of HGF+ cells in hepatic allografts of recipients pretreated with DST on day 14 was significantly greater than that in allografts of untreated recipients on day 7. HGF+ cells were also found in the marginal zone and red pulp of recipient spleens. Northern blot analysis revealed the presence of three HGF+ cell phenotypes: HGF+ED1+, HGF+ED2+, and HGF+ED1-ED2-. Most HGF+ cells were ED1-ED2-. In situ hybridization demonstrated HGF mRNA in the mononuclear cells in the portal and sinusoidal areas as well as the marginal zone and red pulp in both DST-treated and untreated recipient spleens.

CONCLUSIONS

Enhanced HGF expression in rat hepatic allografts is associated with immunologic unresponsiveness induced by DST.

Active form of human hepatocyte growth factor is excreted into bile after hepatobiliary resection

BACKGROUND/AIMS

We have shown that hepatocyte growth factor is excreted into bile after hepatectomy in patients with biliary tract carcinoma. However, it is not certain whether hepatocyte growth factor in bile is an active molecule or degradation products.

METHODS

Bile was obtained from five patients after hepatobiliary resection. Bile hepatocyte growth factor was purified on a heparin-Sepharose column and subjected to Western blotting. It was also tested for growth-stimulating activity with rat primary cultured hepatocytes. Biles from 50 patients who underwent various types of hepatobiliary resections were examined with respect to hepatocyte growth factor by an enzyme-linked immunosorbent assay.

RESULTS

Upon Western blotting following nonreducing electrophoresis, the purified bile hepatocyte growth factor showed an 85 kDa peptide corresponding to native hepatocyte growth factor. Under reducing conditions, it showed bands of a-subunit at 69 kDa and beta-subunit at 34 kDa with corresponding monoclonal antibodies. The purified bile hepatocyte growth factor stimulated the [3H]thymidine incorporation into primary cultured hepatocytes with a specific activity comparable to recombinant human hepatocyte growth factor. It was observed that the levels of bile hepatocyte growth factor increased after the various types of hepatobiliary resections, including bile duct resection without hepatectomy.

CONCLUSIONS

The human bile obtained after hepatobiliary resection contains active hepatocyte growth factor that can stimulate hepatocyte growth. Bile hepatocyte growth factor increased not only in hepatectomy but in bile duct resection. These results suggest that the biliary tract system may play an important role in the production of bile hepatocyte growth factor.

Hepatocyte growth factor and Madin-Darby canine kidney cells: in vitro models of epithelial cell movement and morphogenesis

It is becoming increasingly apparent that epithelial cell movement and changes in morphology are central to both development and regeneration of epithelial organs and are involved with pathological processes such as transformation of epithelia to carcinoma and metastasis. Hepatocyte growth factor (HGF) is a mesenchymally derived growth factor with pleiotrophic effects on epithelia depending on culture conditions. In vivo, HGF plays a role in mesenchymal-epithelial interactions. Madin-Darby canine kidney (MDCK) cells, which share many properties with polarized epithelia in vivo, are remarkably sensitive to HGF. In vitro models of HGF-treated MDCK cells have proven to be useful for the study of epithelial cell movement and changes in morphology. When cultured on plastic at low density, MDCK cells scatter in response to HGF. MDCK cells grown as cell suspensions in collagen gels form complex branching tubular structures in response to HGF. When cultivated as a monolayer on permeant supports, MDCK cells are well polarized with established E-cadherin mediated cell-cell junctions and dedifferentiate in response to HGF. Some of the mechanisms responsible for changes in cell movement and morphology that have been characterized using these models are summarized in this review. Models of MDCK cells exposed to HGF will continue to be useful in the study of epithelial cell movement and morphogenesis in vitro and will provide important clues into the cellular mechanisms important during in vivo epithelial processes such as organ development, regeneration, and transformation to carcinoma.

The current status of primary hepatocyte culture

Recently, there have been significant advances toward the development of culture conditions that promote proliferation of primary rodent hepatocytes. There are two major methods for the multiplication of hepatocytes in vitro: one is the use of nicotinamide, the other is the use of a nutrient-rich medium. In the medium containing a high concentration of nicotinamide and a growth factor, primary hepatocytes can proliferate well. In this culture condition small mononucleate cells, which are named small hepatocytes, appear and form colonies. Small hepatocytes have a high potential to proliferate while maintaining hepatic characteristics, and can differentiate into mature ones. On the other hand, combining the nutrient-rich medium with 2% DMSO, the proliferated hepatocytes can recover the hepatic differentiated functions and maintain them for a long time. In this review I describe the culture conditions for the proliferation and differentiation of primary hepatocytes and discuss the small hepatocytes, especially their roles in liver growth.

Crystal structure of the NK1 fragment of human hepatocyte growth factor at 2.0 A resolution

BACKGROUND

Hepatocyte growth factor (HGF) is a mitogen for hepatocytes and has also been implicated as an epithelial morphogen in tumor invasion. HGF activates its specific cellular receptor, c-met, through an aggregation mechanism potentiated by heparan sulfate glycosaminoglycans. HGF consists of an N-terminal (N) domain, four kringle domains (the first of which carries receptor-binding determinants), and an inactive serine-protease-like domain. NK1, a naturally occurring fragment of HGF, acts as an antagonist of HGF in the absence of heparin.

RESULTS

The N domain of NK1 consists of a central five-stranded antiparallel beta sheet flanked by an alpha helix and a two-stranded beta ribbon. The overall N domain structure in the context of the NK1 fragment is similar to the structure of the isolated domain; two lysines and an arginine residue coordinate a bound sulfate ion. The NK1 kringle domain is homologous to kringle 4 from plasminogen, except that the lysine-binding pocket is altered by the insertion of a glycine residue. Here, a HEPES molecule is bound in the pocket. The asymmetric unit of the crystal contains a 'head-to-tail' NK1 dimer. We use this dimer to propose a model of the NK2 fragment of HGF.

CONCLUSIONS

A cluster of exposed lysine and arginine residues in or near the hairpin-loop region of the N domain might form part of the NK1 heparin-binding site. In our NK2 model, both kringle domains pack loosely against the N domain, and a long, positively charged groove lines the interface. This groove might be involved in glycosaminoglycan binding. The HGF receptor-binding determinants are clustered near the binding pocket of the first kringle domain, opposite the N domain.

Hepatocyte growth factor and the kidney: it is not just for the liver

Mesenchymal-epithelial interactions are important for many biological processes in epithelial organs such as the kidney. Hepatocyte growth factor (HGF) is a mesenchymally derived polypeptide cytokine that acts through its tyrosine kinase c-met receptor and is an important mediator of these interactions. This article reviews data showing the in vitro actions of HGF on renal epithelial cells that result in such diverse responses as mitogenesis, motogenesis, and morphogenesis. It also examines the in vivo evidence linking HGF and the c-met receptor to kidney development, regeneration following injury, and renal disease. Elucidating cellular mechanisms underlying the coordinated control of diverse HGF-induced phenotypic changes in renal epithelia in vitro should contribute to a clearer understanding of complex biological processes such as organogenesis, regeneration, and carcinogenesis in epithelial organs such as the kidney.

Coexpression of hepatocyte growth factor and c-Met proto-oncogene product in synovial sarcoma

Hepatocyte growth factor (HGF) is a heterodimeric polypeptide growth factor that has pleiotropic roles, including those of mitogen, motogen and morphogen. The HGF receptor is characterized as a c-Met proto-oncogene product (c-Met), which is a heterodimeric tyrosine kinase receptor. Hepatocyte growth factor acts as a mediator between the mesenchymal and epithelial tissues because HGF is produced by mesenchymal cells and c-Met is mainly expressed on various epithelial cells. Furthermore, the HGF/c-Met system plays an important role in embryogenesis and the regeneration of various organs. Synovial sarcoma (SS) are unique sarcoma that show epithelial differentiation, but little is known about their histogenesis. The expression of HGF and c-Met was examined by immunohistochemistry in SS specimens from 12 patients (six each of biphasic and monophasic fibrous types). Immunohistochemical coexpression of HGF and c-Met was demonstrated in the epithelial component of five biphasic SS, while only c-Met was expressed in the epithelioid nests of three monophasic fibrous SS. The spindle cell component was negative for HGF and c-Met. In SS, positivity for epithelial markers, such as cytokeratins and epithelial membrane antigen, was diffusely observed in the epithelial component and was focally observed in spindle cells, while vimentin was positive predominantly in the spindle cell component. The areas expressing HGF and c-Met corresponded to distinct epithelial structures; however, HGF and c-Met expression were not found in any other tumor cells expressing epithelial markers in the spindle cell component of SS. Considering the morphogenic effect of HGF, which has been known to be one of its most important roles, the unique immunohistochemical localization of HGF and c-Met in SS suggests that the HGF/c-Met system may be closely related to the formation of epithelial (glandular) structures in biphasic SS.

Natural hepatocyte growth factor (HGF) from human serum and a bound form of recombinant HGF with heparan sulfate are indistinguishable in their physicochemical properties

Natural hepatocyte growth factor (nHGF) purified from human serum showed a difference in molecular mass (Mr) between SDS PAGE (76-90 kDa) and gel filtration chromatography on a Sephadex G-200 column (> 200 kDa), whereas nHGF or recombinant HGF (rHGF) from cell culture medium did almost the same Mr (74-100 kDa). A bound form of rHGF with heparan sulfate (or heparin), and an aggregate form of rHGF itself showed a homogeneous band with a Mr of 76-90 kDa on SDS PAGE, but showed a Mr larger than 200 kDa on a Sephadex G-200 column. Both nHGFs, rHGF and the bound form were basic, but the aggregate form was acidic in ionic nature. No significant difference was found in affinity for heparin among these HGF preparations. The bound form treated by the procedures for purification of nHGF from human serum still showed a larger molecular form. The bound form mimicked physicochemical properties of nHGF purified from human serum. These results suggest that a possible form of nHGF in human serum may be a bound form with heparin-like molecules such as heparan sulfate, which are found in the circulation and on cell surface, and purified as the bound form.

Coexpression of HGF and c-Met/HGF receptor in human bone and soft tissue tumors

To understand the interaction between hepatocyte growth factor (HGF) and its receptor c-Met on various bone and soft tissue tumors, their expressions were investigated by western blot analysis, immunohistochemistry and enzyme immunoassay. Western blot analysis revealed that c-Met protein was expressed in 21 (38.8%) of 54 tumors, which detailed to seven (25.9%) of 27 bone tumors and 14 (51.8%) of 27 soft tissue tumors. Most malignant fibrous histiocytomas (MFH) and all neurofibromas expressed c-Met protein. The highest expression of c-Met protein was seen in a case of biphasic synovial sarcoma, where its immunoreactivity was localized only on the epithelial component and not on the sarcomatous component. By enzyme immunoassay for HGF, all but one MFH showed HGF production and the mean level of HGF was the highest among the tumors investigated. Neurofibromas and osteosarcomas had the next highest mean levels of HGF production, respectively. Coexpression of HGF and c-Met was observed in 19 (35.2%) of 54 tumors and was frequently observed in neurofibroma, followed by MFH and synovial sarcoma. Although the mode of interaction between HGF and c-Met varies among the various bone and soft tissue tumors including MFH, their signaling system may play an important role in the development and progression of bone and soft tissue tumors.

Activated rat stellate cells express c-met and respond to hepatocyte growth factor to enhance transforming growth factor beta1 expression and DNA synthesis

Hepatocyte growth factor (HGF) decreases transforming growth factor beta1 (TGFbeta1) levels in the liver and attenuates hepatic fibrosis caused by dimethylnitrosamine in rats. In the liver, HGF is presumed to act predominantly on parenchymal cells, and TGFbeta1 is produced mainly by mesenchymal cells. In hepatic fibrosis, stellate cells play a central role with undergoing activation, which also occurs when the cells are cultured on plastic. Thus, we wondered if HGF could act directly on stellate cells. c-Met was detected in rat stellate cells activated by culture for 10 days, but not in the cells cultured for 3 days. Specific binding of HGF to the activated cells was determined, and Scatchard analysis indicated an apparent Kd of 1.5 nM. c-Met mRNA was detected in freshly isolated stellate cells from rats treated with carbon tetrachloride for 8 weeks, but not in those cells from normal rats. These results indicate that stellate cells express c-met when activated in vitro and in vivo. HGF enhanced TGFbeta1 production and DNA synthesis in the activated cells.

Contribution of a vascular modulator, hepatocyte growth factor (HGF), to the pathogenesis of cardiovascular disease

HGF is a mesenchyme-derived pleiotropic factor which regulates cell growth, cell motility, and morphogenesis of various types of cells, and is thus considered a humoral mediator of epithelial-mesenchymal interactions responsible for morphogenic tissue interactions during embryonic development and organogenesis. Although HGF is originally identified as a most potent mitogen for hepatocytes, HGF is also belonged to a member of endothelium-specific growth factors. Since endothelial cells are known to secrete various anti-proliferative and vasodilating factors, an agent that promotes seeding or regeneration of endothelium may have potential therapeutic value against vascular smooth muscle cell proliferation. The mitogenic action of HGF on human endothelial cells was most potent among growth factors. Moreover, the presence of local HGF system (HGF and its specific receptor, c-met) was observed in vascular cells and cardiac myocytes in vitro as well as in vivo. Production of local HGF production in vascular cells was regulated by various cytokines including transforming growth factor (TGF)-beta and Ang II. Furthermore, HGF may be therapeutic growth factors for the treatment of restenosis after angioplasty and arteriosclerosis oblerance, etc., as gene therapy. On the other hand, serum HGF concentration was significantly correlated with blood pressure. These results suggest that HGF secretion might be elevated in response to high blood pressure as a counter-system against endothelial dysfunction, and may be considered as an index of severity of hypertension. In this review, we discussed the potential role of HGF in cardiovascular disease.

Portal branch ligation with a continuous hepatocyte growth factor supply makes extensive hepatectomy possible in cirrhotic rats

In a cirrhotic liver, the regenerative ability and specific functions are so impaired that excessive resection easily complicates postoperative liver dysfunction, which frequently leads to life-threatening multiple-organ failure. Hepatocyte growth factor (HGF), first identified as the most potent stimulator of DNA synthesis in primary hepatocytes, not only stimulates liver regeneration, but also accelerates hepatic function, improves fibrosis, and protects liver cells against injury. Therefore, we investigated the efficacy of preoperative portal branch ligation (PBL) (which can induce compensatory hypertrophy of the unaffected lobes) combined with a continuous HGF supply in the performance of extensive hepatectomy in cirrhotic rats. Cirrhosis was induced by intraperitoneal injections of dimethylnitrosamine (DMN) three times per week for 3 weeks. Five days after the last injection, when 70% hepatectomy is lethal, the rats underwent portal ligation of the left lateral and median branches (corresponding to approximately 70% of the total volume of the liver). Simultaneously, they were continuously treated with either recombinant human HGF (rhHGF) or vehicle from an intraperitoneally implanted osmotic pump. Four days after the portal ligation, the occluded lobes were resected. The HGF treatment rapidly increased both the wet weight of the unoccluded lobes and the hepatocellular DNA synthesis. The blood chemical analysis indicated that HGF significantly suppressed the posthepatectomy liver dysfunction. Most importantly, the HGF treatment markedly improved the survival rate of the rats at 48 hours after the major hepatectomy. In conclusion, PBL combined with a continuous HGF supply makes extensive hepatectomy possible in cirrhotic rats, mainly by promoting the hypertrophy of the unaffected lobes.

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.

Expression of hepatocyte growth factor and its receptor c-met in human leukemia-lymphoma cell lines

Recent studies have shown that hepatocyte growth factor (HGF) is a regulatory protein for the proliferation and differentiation of hematopoietic progenitors. The proto-oncogene c-met encodes a tyrosine kinase receptor that binds HGF. To obtain information about their possible involvement in the pathogenesis of hematopoietic tumors, we have examined the expression of HGF and c-met in a large panel of leukemia-lymphoma cell lines encompassing all major hematopoietic cell lineages. HGF and c-met mRNAs were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blotting. The panel of 92 cell lines analyzed comprised seven B-cell precursor, ten B-cell, six plasma cell, 13 T-cell, four natural killer (NK) cell, 16 myelocytic, 12 monocytic, 13 erythroid-megakaryocytic and 11 Hodgkin-anaplastic large cell lymphoma (ALCL) lines. In total 64 (70%) were RT-PCR-positive for HGF and 43 (47%) for c-met. The highest percentages of expression were found for HGF in the plasma cell (100%), NK (100%) and myeloid (75-92%) cell line categories, whereas c-met was found predominantly in plasma cell (100%) and Hodgkin-ALCL (91%) cell lines. The concomitant expression of HGF and c-met in plasma cell lines (100%) and Hodgkin-ALCL (73%) cell lines should be noted. The high HGF expression in myelocytic-monocytic cell lines (75 and 92%) contrasts with the low c-met expression (18 and 8%) in these cell lineages. In 50 cell lines, mRNA expression of these two genes was also examined at the Northern blot level: 12/50 (24%) and 4/48 (8%) were positive for HGF and c-met mRNA expression, respectively. Of note, three of the four c-met + lines belonged to the category Hodgkin-ALCL; the Hodgkin cell line SUP-HD-1 showed both HGF and c-met mRNA bands suggesting the possibility of an autocrine loop. In conclusion, we detected HGF expression in various types of leukemia-lymphoma cell lines, particularly in plasma cell and myeloid malignancies; c-met expression was found in plasma cell and Hodgkin-ALCL cell lines. Further detailed analysis of the role of this ligand-receptor pair in the pathogenesis of hematopoietic neoplasms is indicated; to this end the HGF + and c-met + cell lines described here represent exquisite model systems.

Analysis of deleted variant of hepatocyte growth factor by alanine scanning mutagenesis: identification of residues essential for its biological function and generation of mutants with enhanced mitogenic activity on rat hepatocytes

To understand the structure-function relationship of hepatocyte growth factor (HGF) in more detail, we analyzed one of the other forms of HGF, deleted variant of HGF (dHGF), by alanine scanning mutagenesis. We show here that there are at least four sites important for dHGF to stimulate DNA synthesis in cultured adult rat hepatocytes, and that the residues of HGF essential for exerting its biological activity are not identical to those of dHGF. In addition, two mutants showed a decrease (approximately three-fold) in EC50 compared with wild-type dHGF in an assay of mitogenic activity on rat hepatocytes.

Retinal pigment epithelial cells secrete and respond to hepatocyte growth factor

Hepatocyte growth factor (HGF) is normally expressed by mesenchymal cells while its receptor, c-Met, is expressed in epithelial cells. Since HGF is critically involved in epithelial-mesenchyme interactions and the retinal pigment epithelium (RPE) is present at the interface between the retina and choroid, this study was initiated to determine whether the RPE expresses or responds to HGF in vitro. Cultured adult and fetal human RPE expressed mRNA for HGF and c-Met by RT-PCR. ELISA assay demonstrated the secretion of HGF into RPE culture supernatants. Tyrosine phosphorylation of c-Met was constitutively found in 72 hour RPE cultures and could be rapidly induced in serum-starved cells by concentrated RPE supernatants. HGF was mitogenic for cultured RPE (100 ng/ml.) and stimulated their chemotaxis (maximal response at 50 ng/ml). RPE are one of only a very limited number of epithelia that express both HGF and its receptor, suggesting the possibility of an autocrine action for this growth factor.

Hepatocyte growth factor stimulates fetal gastric epithelial cell growth in vitro

BACKGROUND

The growth and development of the fetal gastrointestinal tract is likely mediated, in part, by peptide growth factors. We compared the mitogenic effects of graded doses of hepatocyte growth factor (HGF) to epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and insulin-like growth factor-1 (IGF-1) on fetal rabbit gastric epithelial cells.

MATERIALS AND METHODS

Fetal rabbit gastric epithelial cells were purified by mechanical dissociation and selected culture and grown in short-term (24 h) and long-term (12 days) culture. Stimulation of fetal gastric epithelial cell growth in response to individual peptide growth factors was measured by [3H]thymidine incorporation and cell counting.

RESULTS

In short-term culture, HGF stimulated [3H]thymidine incorporation in a dose-dependent manner from a threshold at 10 pM to a maximum at 100 pM. For EGF and TGF-alpha, maximal stimulation occurred at 100 pM. For HGF, maximal [3H]thymidine incorporation was 3.6 +/- 0.7 times basal. For EGF and TGF-alpha, maximal [3H]thymidine incorporation was 4.3 +/- 0.4, and 3.6 +/- 0.4 times basal, respectively. For IGF-1, maximal [3H]thymidine incorporation was only 70% of the maximal effect observed for the other growth factors tested. Rabbit amniotic fluid increased [3H]thymidine uptake in a dose-dependent manner. In long-term culture, purification to greater than 90% epithelial cells was attained after 12 days treatment. For HGF, EGF, TGF-alpha, and 20% rabbit amniotic fluid, significant increases in cell number above control (P < 0.05) were observed at 1 nM concentrations. None of these individual factors, however, increased cell growth as significantly as that of 10% fetal bovine serum.

CONCLUSIONS

Our results suggest that: (1) HGF stimulates [3H]thymidine uptake and cell proliferation in fetal rabbit gastric epithelial cells in vitro, and (2) HGF's mitogenic effect on fetal rabbit gastric epithelial cell growth is comparable to that observed for EGF and TGF-alpha, but superior to the effect observed for IGF-1.

Hepatocyte growth factor promotes liver regeneration with prompt improvement of hyperbilirubinemia in hepatectomized cholestatic rats

BACKGROUND

In hepatectomy for patients with liver cirrhosis or cholestasis, prolonged postoperative hyperbilirubinemia is a troublesome complication and, if uncontrolled, often leads to life-threatening hepatic failure. Hepatocyte growth factor (HGF), first identified as the most potent mitogen for primary hepatocytes, has been shown to have multiple biological properties on liver, including mitogenic, antifibrotic, and cytoprotective activities. This study investigated the beneficial effects of a perioperative HGF supply to jaundiced liver after hepatectomy in rats.

MATERIALS AND METHODS

As a model of jaundiced liver, we used an alpha-naphtylisocyocyanate (ANIT)-induced intrahepatic cholestasis model. Forty-eight hours after intraperitoneal injection of ANIT (75 mg/kg), when the total serum bilirubin level was moderately increased, a 70 % hepatectomy was performed. Human recombinant HGF (250 microgram/kg) (n = 15) or vehicle alone (n = 15) was intermittently administered to the rats 12 h before surgery and every 12 h after that until sacrifice.

RESULTS

Perioperative HGF treatment effectively accelerated hepatocellular DNA synthesis of cholestatic liver followed by increase in the regenerated liver weight. Moreover, HGF supply promptly improved hyperbilirubinemia within 24 h after surgery. Histological examination revealed that HGF administration attenuated periportal inflammation and formation of bile duct obstructions. Postoperative serum concentrations of tumor necrosis factor-alpha, a representative inflammatory cytokine, were not altered by HGF treatment.

CONCLUSIONS

Perioperative HGF supply not only promotes liver regeneration but also ameliorates hyperbilirubinemia in hepatectomized cholestatic rats. This mode of HGF treatment may be clinically useful for hepatectomy in patients with cholestasis.

Evaluation of hepatocyte growth factor activator inhibitor expression in normal and malignant colonic mucosa

Gene expression of hepatocyte growth factor activator inhibitor (HAI), a recently identified Kunitz-type serine proteinase inhibitor, was analyzed in a series of human colorectal carcinoma cell lines and in human colorectal tissues. All of the 14 cell lines derived from adenocarcinoma of the colorectum expressed HAI in vitro, whereas a colon carcinoma cell line of neuroendocrine origin did not. In vivo, HAI was consistently expressed in the normal colorectal mucosa. Although the expression of HAI mRNA was conserved in adenocarcinoma tissues of the colorectum, the levels of expression were decreased in the adenocarcinoma tissues compared to the normal counterparts. There was a tendency towards an inverse correlation, albeit not well defined, between the amounts of HAI mRNA and the tumor progression. Immunohistochemical study indicated that HAI protein is present predominantly on the surface of epithelial cells of the colon and the immunoreactivity was decreased in the adenocarcinoma cells.

Plasma heparin-binding EGF-like growth factor levels in patients after partial hepatectomy as determined with an enzyme-linked immunosorbent assay

We recently showed that heparin-binding EGF-like growth factor (HB-EGF) has hepatotrophic effects. In this study, we developed an ELISA system with high specificity and sensitivity for human plasma HB-EGF. In 14 patients who underwent partial hepatectomy, plasma HB-EGF levels were measured serially after surgery. In patients who underwent gross hepatectomy (lobectomy and segmentectomy), plasma HB-EGF levels increased, reaching maximal levels approximately 5 to 7 days after surgery. In patients who underwent minor hepatectomy (subsegmentectomy), plasma HB-EGF levels did not increase. Maximal plasma HB-EGF levels were significantly higher in patients who had a percent increased volume of the remaining liver (%ILV) above 20% than those who had a %ILV below 20% (32.4 +/- 19.6 pg/ml vs 7.4 +/- 2.7, P < 0.05). The plasma HB-EGF values did not correlate with WBC counts, C-reactive protein, or alanine aminotransferase. Plasma HB-EGF may be a marker for liver regeneration after hepatectomy in humans.

Potential role of a novel vascular modulator, hepatocyte growth factor (HGF), in cardiovascular disease: characterization and regulation of local HGF system

Since endothelial cells (EC) are known to secrete various anti-proliferative and vasodilating factors, an agent that promotes seeding or regeneration of EC may have potential therapeutic value against vascular smooth muscle cell (VSMC) proliferation. To seek an endothelium specific growth factor, we have focused on hepatocyte growth factor (HGF). HGF is belonged to a member of endothelium specific growth factors, whose mitogenic action on EC was most potent among growth factors. Moreover, the presence of local HGF system (HGF and its specific receptor, c-met) was observed in EC and VSMC of rat and human in vitro as well as in vivo. Production of local HGF production in vascular cells was regulated by various cytokines including transforming growth factor (TGF)-beta and angiotensin II (Ang II). Furthermore, HGF may be a therapeutic growth factor for the treatment of restenosis after angioplasty and arteriosclerosis obliterance, etc., as gene therapy. From these characteristics of HGF, we hypothesized that HGF might contribute to the protection or repair of vascular endothelial cells. Indeed, serum HGF concentration was significantly correlated with blood pressure, suggesting that HGF secretion might be elevated in response to high blood pressure as a counter-system against endothelial dysfunction. In this review, we discussed that HGF is a member of the endothelium specific growth factors whose serum concentration is significantly associated with blood pressure.

Intestinal fibroblasts regulate intestinal epithelial cell proliferation via hepatocyte growth factor

Although the presence of subepithelial intestinal fibroblasts has been well recognized, the effects of fibroblasts on intestinal epithelial cell (IEC) growth are incompletely understood. In vitro studies were undertaken to evaluate the effects of fibroblasts on the proliferation of model IEC lines. IECs (Caco-2, T84, and IEC-6) were grown alone or in the presence of human intestinal (CCD-18), lung (CCD-37), or skin explant-derived fibroblasts. Cocultures were carried out directly on irradiated fibroblasts or by Transwell coculture technique with fibroblasts and epithelial cells separated by a porous filter. Cell proliferation was assessed by [3H]thymidine incorporation and cell counts. Hepatocyte growth factor (HGF) and c-met transcript expression in IECs and fibroblasts was examined by RT-PCR and Northern blotting; protein expression was evaluated by immunoblotting. Intestinal as well as lung and skin fibroblasts substantially stimulated proliferation of Caco-2, T84, and IEC-6 cells in both direct and Transwell cocultures. In addition, fibroblast-conditioned medium stimulated IEC proliferation, suggesting a paracrine mechanism. Anti-human HGF-neutralizing antibodies blocked the growth-promoting effects in both fibroblasts and fibroblast-conditioned medium. Recombinant human HGF dose dependently promoted IEC proliferation. HGF mRNA and protein expression was restricted to fibroblasts. High levels of c-met expression were found in Caco-2 and T84 cells; in contrast, expression in fibroblasts was weak. In summary, fibroblasts stimulate IEC proliferation through a paracrine mechanism mediated predominantly by HGF.

Regulation of invasive potential of human prostate cancer cell lines by hepatocyte growth factor

BACKGROUND

The growth and progression of prostate cancer depends on the stromal-epithelial interaction which is under paracrine control. Hepatocyte growth factor (HGF), produced by mesenchymal cells, is a multifunctional growth factor stimulating the movement and growth of epithelial cells including cancer cells. We therefore assessed the relationship between the invasive potential of prostate cancer and HGF in vitro.

METHODS

Three human prostate cancer cell lines were used including PC-3 and DU145 (androgen-independent), and LNCaP (androgen-dependent). We studied the expression of the HGF receptor c-met proto-oncogene (c-met) by Western blot analysis, and also determined the effects of HGF on cell scattering, and the mechanisms of invasion and proliferation, by microscopic observation, the matrigel invasion chamber assay, and the MTT assay.

RESULTS

c-met was detected in PC-3 and DU145 cells, but not in the LNCaP cells. There was increased cell motility in the scatter assay and an increased cell invasive potential in the matrigel invasion chamber assay by stimulation with HGF only with DU145 cells.

CONCLUSION

HGF plays an important role in the invasion and metastasis of the DU145 cell line through a paracrine mechanism mediated by the c-metreceptor. In the PC-3 cell line, the lack of downstream signal transduction after the c-met receptor is suggested.

Vascular endothelial growth factor expression in non-small-cell lung cancer: prognostic significance in squamous cell carcinoma

BACKGROUND

Recently, some studies have focused on the tumor angiogenesis and its prognostic value. We studied the expression of vascular endothelial growth factor, microvessel counts, and serum concentrations of vascular endothelial growth factor to investigate their association with clinicopathologic factors and prognosis in non-small-cell lung cancer.

METHODS

The expression of vascular endothelial growth factor was determined by an immunohistochemical analysis from 91 paraffin specimens of completely resected non-small-cell lung cancers using anti-growth factor polyclonal antibody. Microvessel staining was performed by immunohistochemical analysis with anti-factor VIII-related antigen polyclonal antibody. Measurement of the serum concentrations of vascular endothelial growth factor used the sandwich enzyme-linked immunosorbent assay technique.

RESULTS

Expression of vascular endothelial growth factor was detected in 48 of the 91 tumors. The positive ratio was significantly higher in patients with adenocarcinoma than in those with squamous cell carcinoma. The microvessel counts were significantly higher in the patients with nodal metastasis than in those without nodal metastasis. The serum concentrations of vascular endothelial growth factor were also significantly higher in the patients with T3-4 disease than in those with T1-2 disease. The microvessel counts were closely associated with expression of vascular endothelial growth factor. The prognosis of patients with a positive growth factor ratio was significantly worse than that of the patients with a negative ratio (p = 0.002), especially in squamous cell carcinoma. According to a multivariate analysis, only nodal status and expression of vascular endothelial growth factor were found to be independent prognostic factors.

CONCLUSIONS

The expression of vascular endothelial growth factor was one of the most important prognostic factors in completely resected non-small-cell lung cancer, especially in squamous cell carcinoma.

Serum concentration of hepatocyte growth factor in patients with metastatic breast cancer

The serum concentration of hepatocyte growth factor (HGF) was examined in 34 patients with metastatic breast cancer. Although no significant difference was observed between HGF concentration and the site of metastasis, serum HGF levels were slightly higher in patients with liver metastasis and in patients with multiple metastatic sites than in patients with other lesions. Significantly higher levels of serum HGF were observed in patients with progressive metastasis of breast cancer compared with those with stable metastasis. The patients with high HGF levels exhibited a significantly shorter survival rate than those with low HGF levels. Circulating HGF levels may be a useful indicator for the progression of metastatic lesions and the prognosis of patients with metastatic breast cancer.

Hepatocyte growth factor/scatter factor stimulates chemotaxis and growth of malignant mesothelioma cells through c-met receptor

Hepatocyte growth factor (HGF) and its receptor c-met are present in several human tissues but their expression in mesothelial cells has not been examined. In this study, we have investigated the expression of HGF and c-met in normal human mesothelial cells and 11 human malignant mesothelioma cell lines. Using RT-PCR and Western blotting we found that HGF is produced by 3/11 mesothelioma cell lines whereas c-met is expressed in 11/11 mesothelioma cell lines. In addition, c-met expression was also found in 6/6 cell samples obtained from pleural fluids of patients with mesothelioma. In contrast, neither normal cultured mesothelial cells nor mesothelial cells obtained directly from patients without mesothelioma expressed HGF nor c-met. We have also analysed the biological function of HGF and c-met in mesothelioma cell lines. Recombinant human (rh) HGF stimulated both directional (chemotactic) and random (chemokinetic) motility in all mesothelioma cell lines tested. Furthermore, mesothelioma serum free conditioned medium containing HGF stimulated mesothelioma cell migration. This effect could be blocked in the presence of neutralizing anti-HGF monoclonal antibodies (MAbs) in the assay. Addition of HGF to mesothelioma cells cultured on collagen type IV was associated with induction of bipolar shape and protrusion of prominent pseudopodia. We have also found that rhHGF was mitogenic for mesothelioma cells. Our findings suggest that expression of HGF/c-met is involved not only in mesothelioma progression but also in its growth and migration and that c-met expression found in mesothelioma cells taken directly from patients may be of diagnostic importance.

HGF: its organotrophic role and therapeutic potential

Hepatocyte growth factor (HGF), originally implicated as a long-sought after hepatotrophic factor, supports epithelial branching duct formation in the developing lung as, a mesenchymal-derived morphogen. HGF elicits a potent organotrophic function for regeneration of organs including the liver, kidney and lung, through epithelial-stromal interactions. It prevents the onset or progress of hepatic fibrosis/cirrhosis, as well as the accompanying severe hepatic failure, and may become an effective drug for the treatment of fatty liver. HGF prevents the onset of acute and chronic renal failure, acts as pulmotrophic factor which enhances lung regeneration, and suppresses the onset of lung fibrosis. HGF may also be effective for treatment of vascular diseases, gastric ulcers, diabetes mellitus and neuronal diseases. Our results provide a new therapeutic strategy for treating such diseases.

Hepatocyte growth factor (HGF) acts as a mesenchyme-derived morphogenic factor during fetal lung development

Mesenchymal-epithelial tissue interactions are important for development of various organs, and in many cases, soluble signaling molecules may be involved in this interaction. Hepatocyte growth factor (HGF) is a mesenchyme-derived factor which has mitogenic, motogenic and morphogenic activities on various types of epithelial cells and is considered to be a possible mediator of epithelial-mesenchymal interaction during organogenesis and organ regeneration. In this study, we examined the role of HGF during lung development. In situ hybridization analysis showed HGF and the c-met/HGF receptor gene to be respectively expressed in mesenchyme and epithelium in the developing lung. In organ cultures, exogenously added HGF apparently stimulated branching morphogenesis of the fetal lung. In contrast, HGF translation arrest or neutralization assays resulted in clear inhibition of epithelial branching. These results suggest that HGF is a putative candidate for a mesenchyme-derived morphogen regulating lung organogenesis. We also found that HGF is involved in epithelial branching, in collaboration with fibroblast growth factor (FGF) family molecule(s). In mesenchyme-free culture, HGF alone did not induce epithelial morphogenesis, however, addition of both HGF and acidic FGF (aFGF) or keratinocyte growth factor (KGF), ligands for the KGF receptor, induced epithelial branching more extensively than that was observed in explants treated with aFGF or KGF alone. In addition, the simultaneous inhibition of HGF- and FGF-mediated signaling using neutralizing antibody and antisense oligo-DNA resulted in drastic impairment of epithelial growth and branching. Possible interactions between HGF and FGFs or other growth factors in lung development is given consideration.

Abrogation of Fas-induced fulminant hepatic failure in mice by hepatocyte growth factor

Excessive activity of the Fas system in the liver is an essential event and contributor to fulminant hepatic failure, whose prognosis is extremely poor with high mortality due to lack of effective therapy. Administration of agonistic anti-Fas antibody to mice rapidly led to massive liver apoptosis and fulminant hepatic failure. In contrast, administration of human recombinant hepatocyte growth factor (HGF) abrogated Fas-induced massive liver apoptosis and the lethal hepatic failure. Addition of anti-Fas antibody to hepatocytes in primary culture induced cell death, but Fas-mediated cell death was potently suppressed by HGF. HGF strongly induced Bcl-xL expression and subsequently blocked Fas-mediated signaling pathway upstream of CPP32 in the liver. These results implicate a potential therapeutic usage of HGF for treatment of fulminant hepatic failure.