Hepatocyte growth factor has potent anti-proliferative activity in various tumor cell lines

Hepatocyte growth factor stimulates the growth and activates mitogen-activated protein kinase in human hepatoma cells

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and various epithelial cells. Unexpectedly, it has been reported to inhibit the growth of hepatoma cells in vitro. To clarify this phenomenon, we examined the effects of recombinant baculovirus-expressed HGF on the growth of 6 human hepatoma cell lines. The growth of Hep3B and HepG2 cells was markedly stimulated to 1.8- and 1.7-fold, respectively, PLC/PRF/5 to 1.4-fold, and SK-Hep-1 to 1.2-fold in a dose-dependent manner under HGF concentrations below 20 ng/ml. Neither HuH-7 nor HCC36 were affected. None of these cells were inhibited. All these cells expressed c-Met, the membrane receptor for HGF, and their c-Met would be activated to be phosphorylated upon addition of HGF. They also contained the ERK2 subgroup of mitogen-activated protein kinases (MAPKs). When HGF was added, their ERK2 would also be phosphorylated. The extent of ERK2 phosphorylation was partially correlated to their growth response to HGF. In conclusion, HGF could stimulate the growth of certain human hepatoma cells, probably through activation of c-Met and MAPKs.

Expression of c-Met in developing rat hippocampus: evidence for HGF as a neurotrophic factor for calbindin D-expressing neurons

Hepatocyte growth factor-scatter factor (HGF) is expressed in different parts of the nervous system, and has been shown to exhibit neurotrophic activity. Here we show that c-Met, the receptor for HGF, is expressed in developing rat hippocampus, with the highest levels during the first postnatal weeks. To study the function of HGF, hippocampal neurons were prepared from embryonic rats and treated with different HGF concentrations. In these cultures, HGF increased the number of neurons expressing the 28-kDa calcium-binding protein (calbindin D) in a dose-dependent manner. The effect of HGF was larger than that observed with either brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3), and cotreatment of the cultures with HGF and the neurotrophins was additive with respect to calbindin D neurons. Besides affecting the number of neurons, HGF significantly increased the degree of sprouting of calbindin D-positive neurons, suggesting an influence on neuronal maturation. BDNF and NT-3 stimulated neurite outgrowth of calbindin D neurons to a much smaller degree. In contrast to calbindin D neurons, HGF did not significantly increase the number of neurons immunoreactive with the neurotransmitter gamma-aminobutyric acid (GABA) in the hippocampal cultures. Immunohistochemical studies showed that c-Met-, calbindin D- and HGF-immunoreactive cells are all present in the dentate gyrus and partly colocalize within neurons. These results show that HGF acts on calbindin D-containing hippocampal neurons and increases their neurite outgrowth, suggesting that HGF plays an important role for the maturation and function of these neurons in the hippocampus.

Hepatocyte growth factor and vitamin D cooperatively inhibit androgen-unresponsive prostate cancer cell lines

Expression of MET, the receptor for hepatocyte growth factor (HGF), has been associated with androgen-insensitive prostate cancer. In this study we evaluated MET activation by HGF and HGF action in prostate cancer cell lines. HGF causes phosphorylation (activation) of the MET receptor in three androgen-unresponsive cell lines (DU 145, PC-3, and ALVA-31) together with morphological change. Although HGF is known to stimulate the growth of normal epithelial cells, including those from prostate, we found that HGF inhibited ALVA-31 and DU 145 (hormone-refractory) cell lines. Moreover, HGF and vitamin D additively inhibited growth in each androgen-unresponsive cell line, with the greatest growth inhibition in ALVA-31 cells. Further studies in ALVA-31 cells revealed distinct cooperative actions of HGF and vitamin D. In contrast to the accumulation of cells in G1 seen during vitamin D inhibition of androgen-responsive cells (LNCaP), growth inhibition of the androgen-unresponsive ALVA-31 cell line with the HGF and vitamin D combination decreased, rather than increased, the fraction of cells in G1, with a corresponding increase in the later cell cycle phases. This cell cycle redistribution suggests that in androgen-unresponsive prostate cancer cells, HGF and vitamin D act together to slow cell cycle progression via control at sites beyond the G1/S checkpoint, the major regulatory locus of growth control in androgen-sensitive prostate cells.

Close association between high serum ALT and more rapid recurrence of hepatocellular carcinoma in hepatectomized patients with HCV-associated liver cirrhosis and hepatocellular carcinoma

We investigated whether or not a high serum alanine aminotransferase (ALT) level is associated with a more rapid recurrence of hepatocellular carcinoma (HCC) in hepatectomized patients with hepatitis C virus (HCV)-associated liver cirrhosis (LC) (HCV-LC) and HCC. Thirty-three hepatectomized patients with HCV-LC and HCC of a single nodule who had no histologic evidence of portal or hepatic vein invasion and who had been followed up for more than 3 years were included in the study. They were subdivided into two groups according to their serum ALT levels, ALT being a well-known marker of inflammatory necrosis in the liver. Seventeen patients whose serum ALT levels showed several peaks or plateaus above 80 international units (IU) were designated as the high ALT group, and 16 patients whose serum ALT levels showed a sustained low level below 80 IU until the first recurrence were designated as the low ALT group, and the interval between hepatectomy and the first recurrence was observed. In the high ALT group, HCC recurred within 3 years in 70.6% of the patients. In contrast, it recurred in only 18.8% of the low ALT group within the same period (p < 0.05). There was a significant difference (p = 0.0201) between the two groups in the cumulative nonrecurrence rate. The mean interval in recurrent patients between hepatectomy and the first recurrence in the high ALT group (23.6 +/- 2.8 months; mean +/- SE) was significantly (p < 0.02) shorter than that in the low ALT group (49.3 +/- 9.7 months). The expected interval between hepatectomy and recurrence was as short as 2.8 +/- 0.5 years (mean +/- SE) in the high ALT group, compared with 5.8 +/- 0.7 years in the low ALT group (p < 0.05). These results showed that the recurrence of HCC was accelerated in the high ALT group, suggesting that suppression of the rise in ALT level after hepatectomy by treatment with anti-inflammatory drugs may prolong the interval until recurrence by about 2 years in hepatectomized patients with HCC and HCV-LC.

Hepatocyte growth factor promotes migration of human hepatocellular carcinoma via phosphatidylinositol 3-kinase

Hepatocyte growth factor (HGF) is known to be a potent mitogen and motogen for epithelial cells. Hepatocellular carcinoma (HCC) often metastasizes, and the c-Met/HGF receptor is highly expressed by HCC cells. The aim of this study was to investigate the signaling pathways associated with the motogenic effect of HGF on HCC cells via c-Met. HCC cell lines (Hep3B, HepG2, PLC, and Huh-7) and HCC cells harvested from patients were used for the Boyden chamber assay of chemotactic activity as well as for immunoprecipitation and immunoblotting studies. HGF stimulated the motility of Hep3B, HepG2, and Huh-7 cells in a dose-dependent manner in association with tyrosine phosphorylation of c-Met and activation of phosphatidylinositol 3-kinase (PI3-K). A tyrosine kinase inhibitor (genistein) and a PI3-K inhibitor (wortmannin) prevented the migration of HCC cells. However, migration was not prevented by calphostin C, an inhibitor of protein kinase C (PKC), which is a downstream target of phospholipase Cgamma (PLCgamma). HGF also stimulated the migration of HCC cells obtained from three patients, while wortmannin prevented the migration of these cells. These results indicate that HGF stimulates the migration of HCC cells through the tyrosine phosphorylation of c-Met via activation of PI3-K.

40- to 100-kD protein(s) of Helicobacter pylori stimulate DNA synthesis in epithelial cell lines without affecting apoptosis

BACKGROUND

Previous in vitro studies have demonstrated that water extracts and sonicates of Helicobacter pylori increase DNA synthesis in a small intestinal epithelial cell line. The aim of this study was to identify mitogenic factor(s) in a water extract of a H. pylori strain and to examine their effects on DNA synthesis and apoptosis in vitro.

METHODS

IEC-6 and FHs 74 cells were incubated for 24 h with different dilutions of a water extract of H. pylori (cytotoxic strain 88-23) or with 6 protein fractions obtained by gel filtration. Cells were labeled with tritiated thymidine and processed for autoradiography. DNA synthesis was evaluated by the labeling index (LI%). The proportion of IEC-6 cells undergoing apoptosis and/or necrosis was evaluated by flow cytometry using fluorescein isothiocyanate (FITC)-labeled annexin-V and propidium iodide. In vitro caspase activity was also determined as an alternative method for detection of apoptosis.

RESULTS

The water extract of H. pylori 88-23 markedly increased DNA synthesis in both epithelial cell lines (p < 0.01). A marked stimulation of DNA synthesis was also observed in IEC-6 cells incubated with fraction II- containing proteins of a molecular weight ranging between 40 and 100 kD (p < 0.01). A lesser stimulation of DNA synthesis was observed in cells incubated with higher concentrations of the other protein fractions (p < 0.01). Neither the water extract of H. pylori 88-23 nor the protein fraction II (40-100 kD) induced apoptosis in IEC-6 cells.

CONCLUSION

A water extract of H. pylori 88-23 and a protein fraction containing proteins with molecular weights of 40-100 kD stimulate DNA synthesis in a rat and human small intestinal cell line. Apoptosis was unaffected by the water extract and by protein fraction II, which indicate that the H. pylori-derived mitogen(s) have the capacity to directly enhance epithelial cell proliferation in vitro.

Hepatocyte growth factor signal coupling to various transcription factors depends on triggering of Met receptor and protein kinase transducers in human hepatoma cells HepG2

Hepatocyte growth factor (HGF) regulates a wide variety of biological activities by binding to the tyrosine kinase receptor Met. In HGF-treated hepatocarcinoma cells, we observed a biphasic activation of AP-1 and AP-2 transcription factors. For NF-kappaB complex the p50-p50 homodimer was activated before the p50-p65 heterodimer, and c-Myc/Max DNA-binding activity increased thereafter. Since these transcription factors are responders to mitogenic stimulation through protein kinase transducers, we tested the effects of inhibitors of these enzymes on the DNA binding after HGF treatment. Inhibition of protein kinase C (PKC) with H7 strikingly activated NF-kappaB above the values observed after HGF alone. Under this inhibitory condition, Met tyrosine phosphorylation was elevated as though the phosphorylation-dependent activity of the receptor was partially blocked by activation of PKC due to HGF. NF-kappaB DNA binding seems to be related to Met triggering by HGF since it was largely prevented by genistein treatment, which blocks receptor activity. Phosphatidylinositol 3-kinase seems to be involved in AP-1 binding activity stimulated by HGF. It is noteworthy that Met is responsive to HGF stimulating postreceptor signaling, which converges on the activation of transcription factors acting coordinately to regulate target gene expression.

Hepatocyte growth factor in renal failure: promise and reality

Can science discover some secrets of Greek mythology? In the case of Prometheus, we can now suppose that his amazing hepatic regeneration was caused by a peptide growth factor called hepatocyte growth factor (HGF). Increasing evidence indicates that HGF acts as a multifunctional cytokine on different cell types. This review addresses the molecular mechanisms that are responsible for the pleiotropic effects of HGF. HGF binds with high affinity to its specific tyrosine kinase receptor c-met, thereby stimulating not only cell proliferation and differentiation, but also cell migration and tumorigenesis. The three fundamental principles of medicine-prevention, diagnosis, and therapy-may be benefited by the rational use of HGF. In renal tubular cells, HGF induces mitogenic and morphogenetic responses. In animal models of toxic or ischemic acute renal failure, HGF acts in a renotropic and nephroprotective manner. HGF expression is rapidly up-regulated in the remnant kidney of nephrectomized rats, inducing compensatory growth. In a mouse model of chronic renal disease, HGF inhibits the progression of tubulointerstitial fibrosis and kidney dysfunction. Increased HGF mRNA transcripts were detected in mesenchymal and tubular epithelial cells of rejecting kidney. In transplanted patients, elevated HGF levels may indicate renal rejection. When HGF is considered as a therapeutic agent in human medicine, for example, to stimulate kidney regeneration after acute injury, strategies need to be developed to stimulate cell regeneration and differentiation without an induction of tumorigenesis.

Peroxisome proliferators induce apoptosis and decrease DNA synthesis in hepatoma cell lines

We examined the effects of various peroxisome proliferators (PPs) such as the hypolipidaemic agents clofibric acid (CLO), bezafibrate (BEZA), ciprofibrate (CIPRO) and nafenopin (NAFE) and the plasticizer di-(2-ethylhexyl)phthalate (DEHP) on peroxisomal enzyme activities, apoptosis and DNA synthesis in rat FaO and human HepG2 hepatoma cell lines. Both growing and confluent cultures were treated with PPs (250 microM) for 48 or 72 h. In accordance with our previous observations in PP-treated primary hepatocyte cultures of rat and human origin, the various PPs increased peroxisomal enzyme activities in rat FaO cells but not in human HepG2 cells. PPs strongly induced apoptosis in FaO cells. They did not affect TGFbeta-induced apoptosis, with the exception of DEHP and NAFE, respectively blocking and increasing induced apoptosis in confluent cultures. Moreover, PPs produced a minor, but significant, decrease in DNA synthesis in FaO cells. PPs also decreased DNA synthesis in growing HepG2 cells, and CLO, CIPRO and NAFE induced apoptosis in confluent HepG2 cultures. This is in opposition with the effects of PPs on primary hepatocyte cultures, i.e. inhibition of both spontaneous and TGFbeta-induced apoptosis and increases in DNA synthesis in rat hepatocytes, and unchanged mitosis-apoptosis balance in human hepatocytes.

HGF induces FAK activation and integrin-mediated adhesion in MTLn3 breast carcinoma cells

Expression of hepatocyte growth factor (HGF) and its tyrosine kinase receptor, c-Met, is positively correlated with breast carcinoma progression. We found that in invasive and metastatic MTLn3 breast carcinoma cells, HGF stimulated both initial adhesion to and motility on the extracellular matrix (ECM) ligands laminin 1, type I collagen, and fibronectin. Next, analysis with function-perturbing antibodies showed that adhesion to the different ECM proteins was mediated through specific beta1 integrins. In MTLn3 cells, HGF induced rapid tyrosine phosphorylation and activation of both c-Met and focal adhesion kinase (FAK). Cell anchorage and adhesion to the ECM substrates was required for HGF-induced FAK activation, since HGF failed to trigger tyrosine phosphorylation of FAK in suspended cells. Our results provide evidence that the 2 signaling pathways, integrin/ECM and c-Met/HGF, cooperate synergistically to induce FAK activation in an adhesion-dependent manner, leading to enhanced cell adhesion and motility. Moreover, we found that a FRNK (the FAK-related non-kinase)-like molecule is expressed in MTLn3 cells. Since FRNK acts as a competitive inhibitor of FAK function, our results suggest that a FRNK-like protein could facilitate disassembly of focal adhesions and likely be responsible for the HGF-induced scattering and motility of MTLn3 cells.

Phosphorylation/Dephosphorylation steps are crucial for the induction of CYP2B1 and CYP2B2 gene expression by phenobarbital

The effects of several protein kinase activators and protein phosphatase inhibitors on the phenobarbital (PB)-induced gene expression of CYP2B1 and CYP2B2 (CYP2B1/2B2) in adult rat hepatocytes were investigated. Insulin, epidermal growth factor, interleukin 6, cAMP, phorbol 12-myristate 13-acetate, tumor necrosis factor alpha, vanadate, and okadaic acid were found to suppress the induction of CYP2B1/2B2 at mRNA and protein levels in hepatocytes. cAMP and vanadate completely suppressed the induction of CYP2B1/2B2 gene expression in both rat hepatocytes and liver. The addition of genistein to vanadate-treated hepatocytes partially recovered the induction of CYP2B1/2B1 gene expression by PB. These results of the present study demonstrate that phosphorylation/dephosphorylation steps are crucial for the induction of CYP2B1/2B2 gene expression by PB.

Characterization of a functional relationship between hepatocyte growth factor and mouse bone marrow-derived mast cells

During the early stage (at 4 weeks) of interleukin-3 (IL-3)-induced development, mouse bone marrow-derived mast cells (BMMC) express alpha 4, alpha 5 and alpha 6 integrins, whereas with further maturation beyond 10 weeks, only alpha 5 integrin remains stably expressed. Hepatocyte growth factor (HGF) modulates the growth and movement of diverse cell types upon binding to its receptor, encoded by the proto-oncogene c-met. We report here the expression of c-met by BMMC throughout the course of their development. In addition, HGF stimulated migration of early week-4 BMMC, but not of the later stage week-10 BMMC, on fibronectin and laminin substrates. The developmental stage-dependent effect of HGF on BMMC was due to specific stimulation of the migratory function of alpha 4 and alpha 6, but not alpha 5 integrins. In addition, HGF had no effect on BMMC growth, either alone or in combination with IL-3. While HGF is stimulatory of the migratory function of BMMC, our results show that BMMC in turn can modulate HGF function. Thus, upon activation via the IgE receptors, BMMC released proteases that abolished HGF activities. Analyses of the degradation products by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot using antisera prepared against recombinant HGF and the kringle 3 domain of HGF revealed specific degradation of HGF alpha but not beta/beta' subunits. Therefore, our results suggest that: 1) the motogenic effect of HGF on BMMC varies according to the stage of their development, 2) HGF stimulation of BMMC migration is due to selective activation of alpha 4 and alpha 6, but not alpha 5 integrin function, and 3) there exists a two-way relationship between BMMC and HGF such that HGF stimulates the beta 1 integrin-mediated migratory function of BMMC, which can, in turn, modulate HGF function by release of serine proteases.

Hepatocyte growth factor supply accelerates compensatory hypertrophy caused by portal branch ligation in normal and jaundiced rats

BACKGROUND

Hepatocyte growth factor (HGF), first identified as the most potent mitogen for hepatocytes, significantly stimulates liver regeneration after hepatectomy. In this report, we examined whether HGF is also useful in accelerating compensatory hypertrophy caused by portal branch ligation in normal and jaundiced rats.

MATERIALS AND METHODS

Normal and reversible obstructive jaundiced rats underwent portal ligation of the left lateral and median branches, which supply approximately 70% of the total volume of the liver. Simultaneously, the animals were continuously treated with either recombinant human HGF (rhHGF) or vehicle alone via an intraperitoneally implanted osmotic pump. Two and four days after portal ligation, the degree of compensatory hypertrophy in unoccluded lobes was examined by measuring the wet weight ratios of the unoccluded lobes to the whole liver and the 5-bromo-2'-deoxyuridine labeling index of hepatocytes in each group.

RESULTS

The HGF treatment significantly increased the wet weight ratios and the DNA synthesis in nonoccluded lobes 2 and 4 days after portal ligation in both normal and jaundiced rats. Moreover, rhHGF supply promptly decreased serum total bilirubin level in jaundiced rats.

CONCLUSIONS

Continuous rhHGF administration not only accelerates compensatory hypertrophy in normal and jaundiced rats but also ameliorates hyperbilirubinemia in jaundiced rats.

Involvement of oxidative stress in tumor cytotoxic activity of hepatocyte growth factor/scatter factor

In this study, we show that N-acetylcysteine (NAC), a precursor of glutathione and an intracellular free radical scavenger, almost completely prevented hepatocyte growth factor (HGF)-suppressed growth of Sarcoma 180 and Meth A cells, and HGF-induced apoptosis, assessed by DNA fragmentation, and increase in caspase-3 activity, in Sarcoma 180 cells. The reduced form of glutathione also prevented HGF-suppressed growth of the cells as effective as NAC. Ascorbic acid partially prevented the effect of HGF, but other antioxidants such as superoxide dismutase, catalase, and vitamin E, and the free radical spin traps N-t-butyl-alpha-phenylnitrone and 3,3,5, 5-tetramethyl-1-pyrroline-1-oxide did not have protective effects. HGF caused morphological changes of the cells, many cells showing condensation and rounding, and enhanced the generation of intracellular reactive oxygen species (ROS) as judged by flow cytometric analysis using 2',7'-dichlorofluorescein diacetate. NAC completely prevented both HGF-induced morphological changes and the enhancement of ROS generation in the cells. However, NAC did not prevent the HGF-induced scattering of Madin-Darby canine kidney cells. To our knowledge, this is the first report that HGF stimulates the production of ROS, and our results suggest the involvement of oxidative stress in the mechanism by which HGF induces growth suppression of tumor cells.

HP33: hepatocellular carcinoma-enriched 33-kDa protein with similarity to mitochondrial N-acyltransferase but localized in a microtubule-dependent manner at the centrosome

Using a new subtraction method and chemically induced rat hepatocellular carcinomas, we identified a hepatocellular carcinogenesis and hepatocyte proliferation-related gene designated hp33 that encoded a 33-kDa protein. The predicted protein was similar to the bovine aralkyl N-acyltransferase and arylacetyl N-acyltransferase. HP33 was restrictively expressed in the liver and kidney, and its gene expression was stimulated in the regenerating liver as well as in hepatocellular carcinoma. Interestingly, it was demonstrated in various hepatic cells that HP33 was localized in regions surrounding the centrosome, where mitochondria were not concentrated. Moreover, its centrosomal localization was evident in the interphase but not in the mitotic phase of the cell cycle. The centrosomal localization of HP33 was dependent on microtubules, and ectopically expressed HP33 was seen at centrosomes even in fibroblasts, which do not exhibit a typical staining pattern of HP33. The centrosomal localization of HP33 became invisible by nocodazole treatment, whereas the mitochondrial staining pattern was not affected by it. In vitro cosedimentation experiments using purified microtubules indicated that HP33 bound to MTs directly and that its MT-binding ability was dependent on the C-terminal basic domain of the protein. These results suggest that, different from early predictions based on its primary structure, HP33 has a growth- and carcinogenesis-related function that may be independent of mitochondrial function.

Hepatocyte growth factor (HGF) induces invasion of endometrial carcinoma cell lines in vitro

OBJECTIVES

The overall goal of this study was to investigate the role of the hepatocyte growth factor (HGF)/Met pathway in the pathophysiology of invasive endometrial carcinoma. Our objectives were (1) to examine expression of HGF and Met in surgical endometrial carcinoma specimens and endometrial carcinoma cell lines, and (2) to determine if HGF would stimulate invasion of endometrial carcinoma cell lines in vitro.

METHODS

Using RT-PCR and Western immunoblotting, endometrial carcinoma specimens and the endometrial carcinoma cell lines KLE, HEC-1A, HEC-1B, and RL-95 were examined for expression of HGF and Met. A Boyden chamber invasion assay using collagen type I coated 8-microm porous membranes was then used to determine if HGF would stimulate cell invasion. Last, we assessed the capacity of endometrial stromal cells, isolated from normal human endometrium, to produce HGF as determined by an enzyme-linked immunosorbent assay and to stimulate invasion of the KLE cell line.

RESULTS

All of the endometrial carcinoma tissue samples were found to express Met mRNA, and two of four samples expressed HGF mRNA. However, the endometrial carcinoma cell lines expressed only Met and not HGF mRNA. Both the endometrial carcinoma tissue specimens and the endometrial carcinoma cell lines expressed the 140-kDa Met protein. HGF induced the invasion of the KLE and HEC-1A cells through the collagen-coated membranes in a dose-dependent fashion. The optimal concentration of HGF was between 10 and 100 ng/ml. HGF (10 ng/ml) stimulated KLE invasion 1.8-fold (P < 0.05) and HEC-1A invasion 6.5-fold (P < 0.05). During exposure to endometrial stromal cell conditioned medium containing HGF as determined by ELISA, invasion of the KLE cell line was stimulated 2.5-fold (P < 0.05).

CONCLUSION

These results demonstrate that HGF stimulates the invasion of endometrial carcinoma cells in vitro. Since endometrial adenocarcinoma specimens express Met, these findings suggest that the HGF/Met pathway may play a role in the invasive progression of endometrial carcinoma.

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.

HGF-mediated apoptosis via p53/bax-independent pathway activating JNK1

Current studies have indicated both positive and negative roles for the hepatocyte growth factor (HGF)/c-met receptor signaling system in tumor development. Recently, we have shown that HGF has the capacity to induce both growth inhibition and programmed cell death in aflatoxin-transformed (AFLB8) rat liver epithelial cells. Using the same cell line, we have now investigated a potential mechanism for HGF-induced apoptosis. Immunoblot analysis of bcl-2 gene family member (bax, bcl-2, bclX-s/l) expression showed no correlation with HGF treatment, suggesting that HGF-mediated apoptosis is bax independent. Following HGF treatment retinoblastoma protein (pRB) was present in the hypophosphorylated state. HGF treatment increased cyclin A, cyclin G1 and nuclear transcriptional factor (NFkappaB) protein expression. However, electrophoretic mobility shift analysis showed that NFkappaB activity decreased with HGF treatment. Under these apoptotic conditions, c-Jun N-terminal kinase (JNK1) and extracellular signal-regulated kinase (ERK2) were activated with lower level activation of ERK2, while no involvement of phosphatidylinositol-3 kinase was observed. Epidermal growth factor (EGF) was not protective, and actually induced cells to undergo apoptosis to a level similar to that of HGF alone or EGF/HGF in combination. These results suggest the possibility of cross-talk between HGF/c-met and EGF/EGFR signaling pathways, and the involvement of JNK1 induction in HGF-mediated apoptotic cell death.

Regulation of the c-met proto-oncogene promoter by p53

In the present study, we have investigated the possible involvement of p53 in the transcriptional regulation of the c-met gene. Cotransfection of various c-met promoter reporter vectors with p53 expression plasmids demonstrated that only wild-type p53 but not tumor-derived mutant forms of p53 resulted in a significant enhancement of c-met promoter activity. Functional assays revealed that the p53 responsive element in the c-met promoter region is located at position -278 to -216 and confers p53 responsiveness not only in the context of the c-met promoter but also in the context of a heterologous promoter. Electrophoretic mobility shift assays using purified recombinant p53 protein showed that the p53 binding element identified within the c-met promoter specifically binds to p53 protein. Induction of p53 by UV irradiation in RKO cells that express wild-type p53 increased the level of the endogenous c-met gene product and p21(WAF1/CIP1), a known target of p53 regulation. On the other hand, in RKO cells in which the function of p53 is impaired either by stable transfection of a dominant negative form of p53 or by HPV-E6 viral protein, no induction of the endogenous c-met gene or p21(WAF1/CIP1) was noted by UV irradiation. These results suggest that the c-met gene is also a target of p53 gene regulation.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

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.

HGF/SF in mammary epithelial growth and morphogenesis: in vitro and in vivo models

HGF/SF is a multifunctional cytokine which through binding to its cellular receptor, c-MET, can elicit mitogenic, morphogenic and motogenic responses in target cells. Expression of HGF/SF and c-MET has been shown to be critical in early embryogenesis affecting development of many organs and tissues. The effects of HGF/SF4 on established human and mouse mammary cell lines have previously been reported. This review describes the source and targets for HGF/SF in both human and mouse mammary tissue and discusses the effects of HGF/SF on primary mouse and human mammary epithelial cells in vitro, detailing the individual response of the two epithelial sub-population of cells which comprise this organ. Additionally, the effects of HGF/SF overexpression on mouse mammary gland development in vivo, are summarized.

c-Src kinase activity is required for hepatocyte growth factor-induced motility and anchorage-independent growth of mammary carcinoma cells

Overexpression and amplification of hepatocyte growth factor (HGF) receptor (Met) have been detected in many types of human cancers, suggesting a critical role for Met in growth and development of malignant cells. However, the molecular mechanism by which Met contributes to tumorigenesis is not well known. The tyrosine kinase c-Src has been implicated as a modulator of cell proliferation, spreading, and migration; these functions are also regulated by Met. To explore whether c-Src kinase is involved in HGF-induced cell growth, a mouse mammary carcinoma cell line (SP1) that co-expresses HGF and Met and a nonmalignant epithelial cell line (Mv1Lu) that expresses Met but not HGF were used. In this study, we have shown that c-Src kinase activity is constitutively elevated in SP1 cells and is induced in response to HGF in Mv1Lu cells. In addition, c-Src kinase associates with Met following stimulation with HGF. The enhanced activity of c-Src kinase also correlates with its ability to associate with Met. Expression of a dominant negative double mutant of c-Src (SRC-RF), lacking both kinase activity (K295R) and a regulatory tyrosine residue (Y527F), in SP1 cells significantly reduced c-Src kinase activity and strongly blocked HGF-induced motility and colony growth in soft agar. In contrast, expression of the dominant negative c-Src mutant had no effect on HGF-induced cell proliferation on plastic. Taken together, our data strongly suggest that HGF-induced association of c-Src with Met and c-Src activation play a critical role in HGF-induced cell motility and anchorage-independent growth of mammary carcinomas and further support the notion that the presence of paracrine and autocrine HGF loops contributes significantly to the transformed phenotype of carcinoma cells.

Mammary fibroblast-derived hepatocyte growth factor stimulates growth and morphogenesis of mouse mammary tumor cells in primary culture

We have recently isolated a mammary growth factor from the conditioned medium of mouse mammary stromal fibroblasts and identified it as a mouse homologue of human HGF (hepatocyte growth factor). To elucidate the role of HGF in mouse mammary tumorigenesis, we produced recombinant mouse HGF and examined its effects on primary cultures of mouse mammary tumor cells in this study. HGF at concentrations above 20 ng/ml maximally stimulated the growth of mammary tumor cells in primary monolayer culture. HGF also stimulated the three-dimensional growth and branching morphogenesis of mammary tumor cells cultured inside collagen gels. A comparison of the growth-stimulating activity of HGF with that of EGF (epidermal growth factor) and KGF (keratinocyte growth factor) revealed that HGF is the most potent growth factor among the three. Immunological studies using an antibody against mouse HGF demonstrated that 74% of the growth-stimulating activity present in the mammary fibroblast-conditioned medium was abolished by the antibody, indicating that HGF is the major growth factor produced by the fibroblasts. These observations thus suggest a role for HGF as a mammary stromal fibroblast-derived factor which stimulates growth and morphogenesis of adjacent mammary tumor cells in vivo.

Establishment of a functional HGF/C-MET autocrine loop in spontaneous transformants of WB-F344 rat liver stem-like cells

A model of spontaneous malignant transformation was used to evaluate the molecular changes that take place in WB-F344 rat liver epithelial cells during neoplastic transformation and tumorigenesis. A comparison of wild-type low-passage WB-F344 cells to spontaneously transformed tumor cell lines revealed that the majority of the tumor cell lines have an increased capacity for autonomous proliferation and motility when maintained in serum-free media. In the current study, we show that c-met is expressed at some level in wild-type WB-F344 cells and in all of the spontaneously transformed tumor cell lines, and that 9/16 of the tumor cell lines have acquired hepatocyte growth factor (HGF) expression. In vitro growth of HGF-expressing tumor cell lines is inhibited as much as 68% by the addition of neutralizing antibodies to HGF or antisense HGF oligonucleotides, indicating that the production of HGF by the tumor cells is partially responsible for driving autonomous proliferation in a subset of tumor cell lines. Furthermore, conditioned media collected from HGF-expressing tumor cell lines stimulates DNA synthesis in wild-type WB-F344 cells, and this effect can be abrogated by pre-incubation of the conditioned media with neutralizing antibodies to HGF. Because HGF is a motility-promoting growth factor, all cell lines were evaluated to determine if expression of HGF stimulated motogenesis. All tumor cell lines (regardless of HGF expression) were highly motile in comparison with wild-type WB-F344 cells, with a 3.5-fold to 20-fold greater number of motile cells. The high basal rate of motility characteristic of the tumor cell lines is not a result of the production of HGF, because it is also a property of the cell lines that do not express HGF messenger RNA. Furthermore, tumor cell motility is not inhibited by antisense oligonucleotides or neutralizing antibodies. Establishment of an autocrine HGF/c-met loop in a subset of spontaneously transformed WB-F344 cell lines may influence development and/or expression of the tumorigenic phenotype by driving cellular proliferation.

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.

Possible involvement of p21/waf1 in the growth inhibition of HepG2 cells induced by hepatocyte growth factor

Hepatocyte growth factor (HGF) is a potent mitogen for a variety of cell types, but it is also known as an antimitogenic factor for several types of tumor cell lines. The biological processes by which HGF inhibits tumor cell growth remain poorly understood. Here we report a comparative study of HGF-mediated signal transduction events between two opposite responding types of human hepatoblastoma cell lines, HuH6 and HepG2. Following serum starvation, both cell lines were cultured in hepatocyte growth medium (HGM), a chemically defined medium, in the presence or absence of HGF. Under these culture conditions, cell growth in HuH6 was promoted by HGF, while it was inhibited in HepG2. Phosphorylation of p42/mitogen-activated protein (MAP) kinase was observed within 10 min after HGF stimulation in both cell lines. The level of phosphorylated MAP kinase in HuH6 declined to basal levels after 2 hr. However, in HepG2 the phosphorylated form was detectable at 6 hr. p21/waf1 was induced in both cell lines where levels peaked 4-6 hr after HGF stimulation. In HuH6, a marked decrease of p21/waf1 was observed at 8-12 hr, while a high level of p21/waf1 was sustained for at least 24 hr in HepG2. HGF treatment depressed cdk2 activity in a time-dependent manner in HepG2 while the activity increased in HuH6. When serum-starved HepG2 was growth stimulated with serum in the presence or absence of HGF, the cells treated with HGF underwent growth inhibition correlating with a sustained induction of p21/waf1 and a decrease of cdk2 activity. Immunoprecipitation analysis revealed accumulation of cdk2-associated p21/waf1 in the HGF-treated HepG2. Together, the results suggest that sustained induction of p21/waf1 mediates growth inhibition in HepG2 in the presence of HGF.

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.

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.

Hepatocyte growth factor-induced expression of ornithine decarboxylase, c-met, and c-myc is differently affected by protein kinase inhibitors in human hepatoma cells HepG2

Binding of hepatocyte growth factor (HGF) to its receptor Met induces autophosphorylation and activation of the tyrosine kinase activity. In HGF-treated HepG2 cells, we studied: (i) the expression patterns of early (c-myc, c-jun, and c-fos) and delayed-early (ornithine decarboxylase and c-met) response genes and (ii) the possible involvement of protein kinase transducers in the control of the expression of c-met and of other genes eventually induced downstream. c-met and c-myc mRNAs peaked 1-2 h after HGF, while c-jun and c-fos mRNAs slightly increased at 1 h. Ornithine decarboxylase activity was induced earlier (4 h) than the mRNA (8-10 h). The transducers involved in HGF-triggered gene inductions were investigated using different protein kinase inhibitors: genistein for the receptor tyrosine kinase, herbimycin A for the nonreceptor tyrosine kinase (pp60(c-src)), wortmannin for phosphatidylinositol 3-kinase (PI3K) and H7 for protein kinase C (PKC). The similarity of responses to PKC inhibition led to suppose that c-myc and ornithine decarboxylase mRNAs were induced sequentially along the same transduction pathway triggered by HGF. Ornithine decarboxylase activity seemed to be largely regulated by phosphorylation(s). The mRNA expression of c-jun was likely to undergo a negative regulation through a mechanism involving PI3K, while that of c-met seemed to be almost independent from various protein kinases (PI3K, pp60(c-src), and PKC).

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.

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.

Induction of apoptosis by hepatocyte growth factor/scatter factor and its augmentation by phorbol esters in Meth A cells

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional cytokine with mitogenic, motogenic, and morphogenic activities. In addition, HGF/SF inhibits the proliferation of some tumor cell lines, but its mechanism remains poorly understood. We determined in this study whether HGF/SF induces cell death of a Meth A mouse sarcoma cell line in vitro, whose proliferation is remarkably suppressed by HGF/SF. Inhibition of Meth A cell growth by HGF/SF was dose-dependent and maximal at a concentration of 30 ng/ml. The percentage of dead cells increased to 22% upon treatment with 30 ng/ml of HGF/SF for 96 h, whereas that in untreated cultures was less than 5%. Staining of these cells nuclei with Hoechst 33342 revealed condensation of the chromatin and nuclear fragmentation. Gel electrophoresis of DNA from HGF/SF-treated cells showed a typical ladder pattern. Cells with a fractional DNA content also increased five-fold in the HGF/SF-treated cultures as analyzed by flow cytometry after propidium iodide staining. These are features typical of apoptosis. Concurrent addition of 12-O-tetradecanoylphorbol 13-acetate (TPA) with HGF/SF augmented the apoptosis induced by the growth factor, while TPA alone caused little death. This enhancement was largely blocked by addition of the specific protein kinase C inhibitor GF 109203X. These results indicate that HGF/SF induced the apoptotic cell death of the Meth A sarcoma cell line and that protein kinase C activation augmented the growth factor-induced apoptosis.

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.

NK1, a natural splice variant of hepatocyte growth factor/scatter factor, is a partial agonist in vivo

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent mitogen, motogen, and morphogen for epithelial cells expressing its tyrosine kinase receptor, the c-met proto-oncogene product, and is required for normal development in the mouse. Inappropriate stimulation of Met signal transduction induces aberrant morphogenesis and oncogenesis in mice and has been implicated in human cancer. NK1 is a naturally occurring HGF/SF splice variant composed of only the amino terminus and first kringle domain. While the biological activities of NK1 have been controversial, in vitro data suggest that it may have therapeutic value as an HGF/SF antagonist. Here, we directly test this hypothesis in vivo by expressing mouse NK1 in transgenic mice and comparing the consequent effects with those observed for mice carrying an HGF/SF transgene. Despite robust expression, NK1 did not behave as an HGF/SF antagonist in vivo. Instead, NK1-transgenic mice displayed most of the phenotypic characteristics associated with HGF/SF-transgenic mice, including enlarged livers, ectopic skeletal-muscle formation, progressive renal disease, aberrant pigment cell localization, precocious mammary lobuloalveolar development, and the appearance of mammary, hepatocellular, and melanocytic tumors. And like HGF/SF-transgenic livers, NK1 livers had higher levels of tyrosine-phosphorylated complexes associated with Met, suggesting that the mechanistic basis for the effects of NK1 overexpression in vivo was autocrine activation of Met. We conclude that NK1 acts in vivo as a partial agonist. As such, the efficacy of NK1 as a therapeutic HGF/SF antagonist must be seriously questioned.

Expression of the hepatocyte growth factor and c-met in normal thyroid, non-neoplastic, and neoplastic nodules

We have examined the coexpression of hepatocyte growth factor (HGF) and its receptor (HGF-R or c-met) in an archival series of 63 paraffin-embedded thyroid specimens plus one lymph node metastasis. By immunocytochemistry, we found undetectable expression of both the ligand and the receptor in 10 normal thyroids and 9 nonpapillary malignant nodules [5 follicular carcinomas, 1 poorly differentiated (insular) carcinoma, 3 undifferentiated (anaplastic) carcinomas]. Of 10 non-neoplastic nodules (colloid nodules) and 17 benign neoplastic nodules, 3 of 10 colloid nodules, 2 of 10 follicular adenomas, and 2 of 7 oncocytic adenomas showed a weak but distinct staining (1+ score in a scale from 0 to 4+) of both HGF and c-met in a modest proportion of cells (1% to 3%). In these 7 cases, expression of HGF was always stromal and expression of c-met limited to the membrane of the follicular cells. Of 3 malignant nodules derived from aberrant growth of the parafollicular C cells (medullary thyroid cancer or MTC), 2 were positive (6% of cells). In these 2 cases, the expression of HGF (3+) was not stromal, but in both the membrane and cytoplasm of the parafollicular cells, while that of c-met (3+) was restricted to the membrane. In contrast to all of the above, of 14 papillary carcinomas (PTC) encompassing 5 histological variants (conventional; follicular; oncocytic; with foci of solid growth; diffuse sclerosing) plus 1 neck lymph node metastasis of 1 conventional PTC, 12 (86%) expressed HGF, and 13 (93%) expressed c-met. With the exception of 2 negative cases, HGF was detected in 15% to 46% of the cells. The highest percentage (46%) pertained to conventional PTC cases with abundant peritumoral lymphocyte infiltration, indicating that some lymphokine(s) may recruit PTC cells for HGF expression in a paracrine fashion. With the exception of one negative case, c-met was found in 43% to 80% of the cells, both at levels from intense (3+) to very intense (4+). The immunostaining for HGF was stromal in 25%, membranous in 8%, cytoplasmic in 8%, and both membranous and cytoplasmic in 59% of the PTC-positive cases. The immunostaining for c-met was membranous in 43% and both membranous and cytoplasmic in 57% of the PTC-positive cases. In the lymph node metastasis and in the diffuse sclerosing variant of PTC (the most aggressive variant), the coexpression of HGF/c-met was lost, in that only c-met was expressed on membranes in both cases. We conclude that the HGF/c-met system is activated (by overexpression of both components) in the vast majority of PTC. In most PTC the interaction of HGF and its receptor (c-met) is autocrine, not paracrine.

Induction of hepatocyte growth factor/scatter factor by interferon-gamma in human leukemia cells

Induction of hepatocyte growth factor/scatter factor (HGF/SF) may be one of the critical steps in organ regeneration, wound healing, and embryogenesis. We previously reported the production of HGF/SF from various human leukemia cell lines and a high level of the growth factor in blood and bone marrow plasma from patients with various types of leukemia. We determined here the effects of hematopoietic cytokines on HGF/SF production in human leukemia cell lines, KG-1, a myeloid cell line, and RPMI-8226, a B cell line. Interferon (IFN)-gamma remarkably stimulated HGF/SF production in both cell lines at concentrations of more than 0.1 or 1 IU/ml. IFN-alpha and IFN-beta were as effective as IFN-gamma in RPMI-8226 cells, but less than IFN-gamma in KG-1 cells. HGF/SF gene expression in KG-1 cells was also up-regulated by IFN-gamma. Granulocyte colony-stimulating factor (G-CSF), granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-5 and IL-6 had no effect on HGF/SF production in the 2 leukemia cell lines. We also determined the effects of HGF/SF inducers known for human fibroblasts on the growth factor production in leukemia cells. Out of phorbol 12-myristate 13-acetate (PMA), cholera toxin, IL-1 beta, and tumor necrosis factor (TNF)-alpha, the former three were as effective as IFN-gamma in KG-1 cells, but only TNF-alpha stimulated HGF/SF production in RPMI-8226 cells, whose effect was less than those of IFN-alpha, IFN-beta, and IFN-gamma. The effect of IFN-gamma in KG-1 cells was synergistic with that of PMA. In contrast with the effect in leukemia cells, HGF/SF induction by IFN-gamma in human skin fibroblasts was much less than that by PMA or cholera toxin. These results indicated that IFN-gamma is a potent inducer of HGF/SF in human leukemia cells. This finding suggests the presence of a homeostatic control mechanism in liver regeneration and repair: hepatic injury, DNA synthesis inhibition, or apoptosis caused by IFN-gamma is subsequently overcome by cytokine-induced HGF/SF, a potent promoter of liver DNA synthesis.

Co-expression of hepatocyte growth factor and its receptor in human prostate cancer

Hepatocyte growth factor acts differently depending on the organs or tumours involved. It may be produced simultaneously with its receptor, c-Met, in several types of malignant tumour cells and may exercise an autocrine regulation. To analyse the effect of hepatocyte growth factor in human prostate cancer, we conducted immunohistochemistry, in situ hybridization and the reverse transcriptase polymerase chain reaction. The first two techniques revealed the growth factor in prostate cancer cells, and the polymerase chain reaction confirmed this expression. c-Met is expressed in prostate cancer cells, but not in interstitial cells. Hepatocyte growth factor is expressed in interstitial cells, especially in hormone-treated cancer tissue, indicating that the growth factor pathway changes with the hormonal status. Low-grade tumours expressed c-Met at the plasma membrane. Higher grade tumours tended to express it in the cytoplasm, suggesting that the role of c-Met as the hepatocyte growth factor receptor was blocked in higher grade tumours. The relationship between the growth factor and its receptor is thus influenced by hormonal status and differentiation in prostate cancer and is not explained simply in terms of autocrine or paracrine action.

Hepatocyte growth factor stimulates motility, chemotaxis and mitogenesis in ovarian carcinoma cells expressing high levels of c-met

A proportion of ovarian carcinomas markedly overexpress the proto-oncogene c-met, which encodes the receptor for hepatocyte growth factor (HGF). HGF may either stimulate or inhibit the multiplication of its target cells, and may also promote motogenesis and morphogenesis. In this study, we established that the ovarian carcinoma-derived cell-line SK-OV-3 expressed about 20-fold higher levels of c-met protein than are expressed by a second line, CH1. This enabled us to test functional consequences of high-level expression of c-met in ovarian carcinoma cells. The addition of HGF to attached cultures of SK-OV-3 cells caused a change to a motile phenotype, that was evident after 4-6 hr and affected essentially all of the cells by 24 hr. When HGF was placed in the lower compartment of a migration chamber, it induced a 17-fold increase in the migration of SK-OV-3 cells to the lower surface of the filter. Finally, HGF stimulated the incorporation of [3H]-thymidine by cultures of SK-OV-3 cells incubated in medium containing either low (0.2%) or full (10%) FCS. None of these responses were obtained when HGF was added to CH1 cells. We conclude that high levels of c-met expression in ovarian cancer cells may lead to a range of responses to HGF that would promote tumour growth and dissemination.

Growth inhibition and induction of apoptosis by HGF in transformed rat liver epithelial cells

Recently we demonstrated in a transgenic mouse model that hepatocyte growth factor (HGF) inhibits c-myc dependent hepatocarcinogenesis. The inhibitory effects of HGF in carcinogenesis were further characterized using a series of rat liver epithelial (RLE) cell lines which were transformed in vitro with either aflatoxin or oncogenes, or spontaneously. HGF caused a cytostatic effect and enhanced cell motility in spontaneously and aflatoxin-transformed cells. In normal RLE cells HGF was slightly stimulatory and did not induce scattering. The HGF receptor was tyrosine phosphorylated in all cell lines, indicating that it is functionally active and capable of signaling events. In the aflatoxin transformed cells HGF also induced apoptosis, associated with constitutive c-myc expression and 1 Kb bax-alpha transcripts. These findings indicate that transformed RLE cell lines may provide a useful model to further examine the mechanism(s) by which HGF and its receptor modulate neoplastic development.

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.

Diverse tumorigenesis associated with aberrant development in mice overexpressing hepatocyte growth factor/scatter factor

Hepatocyte growth factor/scatter factor (HGF/SF) is a mesenchymally derived, multifunctional paracrine regulator possessing mitogenic, motogenic, and morphogenetic activities in cultured epithelial cells containing its tyrosine kinase receptor, Met. c-met has been implicated in oncogenesis through correlation of expression with malignant phenotype in specific cell lines and tumors. Paradoxically, however, HGF/SF can also inhibit the growth of some tumor cells. To elucidate the oncogenic role of HGF/SF in vivo, transgenic mice were created such that HGF/SF was inappropriately targeted to a variety of tissues. HGF/SF transgenic mice developed a remarkably broad array of histologically distinct tumors of both mesenchymal and epithelial origin. Many neoplasms arose from tissues exhibiting abnormal development, including the mammary gland, skeletal muscle, and melanocytes, suggesting a functional link between mechanisms regulating morphogenesis and those promoting tumorigenesis. Most neoplasms, especially melanomas, demonstrated overexpression of both the HGF/SF transgene and endogenous c-met, and had enhanced Met kinase activity, strongly suggesting that autocrine signaling broadly promotes tumorigenesis. Thus, subversion of normal mesenchymal-epithelial paracrine regulation through the forced misdirection of HGF/SF expression induces aberrant morphogenesis and subsequent malignant transformation of cells of diverse origin.

High expression of heparin-binding EGF-like growth factor in rat hepatocarcinogenesis

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a member of the EGF family and is highly expressed in hepatoma tissues but not in normal liver. However, it is unknown when HB-EGF is induced during hepatocarcinogenesis and what are the mechanisms underlying its high expression in hepatoma. To address this issue, the expression of HB-EGF was investigated during hepatocarcinogenesis in LEC (Long-Evans with a cinnamon-like coat color) rats, which spontaneously develop hepatitis and hepatoma. LEA (Long-Evans with an agouti coat color) rats were used as controls. Furthermore, the induction of HB-EGF mRNA by various agents was investigated in a rat hepatoma cell line and hepatocytes in primary culture. Expression of HB-EGF mRNA in the liver was very low at the stage of acute and chronic hepatitis and markedly increased at the stage of hepatoma in LEC rats. Non-involved tissues adjacent to hepatoma showed low expression of HB-EGF mRNA. Immunochemical studies revealed positive staining in hepatoma tissues. Induction of HB-EGF mRNA by several growth factors was observed in a hepatoma cell line but not in normal hepatocytes. Our results suggest that HB-EGF is associated with the early progression steps of hepatoma.

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.

Hepatocyte growth factor. A cytokine mediating endothelial migration in inflammatory arthritis

OBJECTIVE

Angiogenesis is an integral component of the vasculoproliferative phase of rheumatoid arthritis (RA). Recently, a heparin-binding cytokine termed hepatocyte growth factor (HGF), or scatter factor (due to its ability to disperse cohesive epithelial colonies), was described. We conducted this study to investigate the hypothesis that this cytokine was present in the milieu of the inflamed joint, and that it contributed to the chemotaxis of endothelial cells in the synovial tissue.

METHODS

We examined synovial fluid, synovial tissue, and peripheral blood from 91 patients with RA and other arthritides. We used 83 total samples in an enzyme-linked immunosorbent assay to quantitate the HGF in synovial fluids and peripheral blood. To determine whether the HGF was biologically active, an epithelial scatter factor assay was performed. Immunohistochemical analysis was used to determine localization in synovial tissues. To define a function for synovial HGF, we preincubated rheumatoid synovial fluids with neutralizing anti-HGF and measured the ability of these synovial fluids to induce endothelial chemotaxis.

RESULTS

Synovial fluid from patients with RA contained a mean +/- SEM HGF concentration of 2.0 +/- 0.3 ng/ml, while synovial fluid from patients with other arthritides (including inflammatory arthritis) contained 2.4 +/- 0.7 ng/ml HGF. Osteoarthritis (OA) patient samples contained the smallest quantities of synovial fluid HGF at 0.9 +/- 0.1 ng/ml. RA synovial fluid contained significantly more HGF than did RA peripheral blood (1.1 +/- 0.2 ng/ml) (P < 0.05). Rheumatoid synovial fluids induced more scattering of cells than did OA synovial fluids, suggesting a role for this cytokine in rheumatoid joint destruction. Interleukin-1 beta induced expression of rheumatoid synovial tissue fibroblast antigenic HGF and scatter factor activity. Immunohistochemically, HGF, as well as the HGF receptor (the met gene product), localized to significantly more rheumatoid synovial tissue lining cells than normal lining cells (P < 0.05). Both HGF and its receptor immunolocalized to subsynovial macrophages as well. Levels of synovial tissue immunoreactive HGF correlated positively with the number of synovial tissue blood vessels. Anti-HGF neutralized a mean of 24% of the chemotactic activity for endothelial cells found in 10 rheumatoid synovial fluid samples.

CONCLUSION

These results indicate that synovial HGF may contribute to the vasculoproliferative phase of inflammatory arthritides such as RA, by inducing HGF-mediated synovial neovascularization. These findings point to a newly described role for HGF in the fibroproliferative phase of RA-associated synovitis.

Plasma hepatocyte growth factor levels are increased in systemic inflammatory response syndrome

Interleukin-1 (IL-1), a cytokine released from macrophages by endotoxin stimulation, has been shown to upregulate the genetic expression of the hepatocyte growth factor (HGF). The present study was conducted to determine whether plasma HGF is increased in patients with systemic inflammatory response syndrome (SIRS). The plasma levels of HGF, endotoxin, and beta-glucan were measured in 41 surgical patients without hepatic diseases, 18 of whom had been diagnosed with sepsis, and 33, with nonseptic SIRS. The plasma HGF was found to be significantly increased in the 18 patients with sepsis, at 0.69 +/- 0.47 ng/ml (mean +/- SD), and in the 23 patients with nonseptic SIRS, at 0.49 +/- 0.37 ng/ml, compared to values in 40 normal controls, at 0.10 +/- 0.03 ng/ml (P < 0.001). No significant correlations were observed between the plasma levels of HGF and endotoxin (r = 0.02) or beta-glucan (r = -0.05) in any of the patients; however, plasma HGF was significantly correlated with the WBC count (r = 0.34, P < 0.05) and with total bilirubin (r = 0.45, P < 0.01). Plasma HGF was also strongly correlated with alanine transaminase (ALT) in 8 patients with ALT levels higher than 50 U/l (r = 0.70), but there was no such correlation in 33 patients with ALT levels of 50 U/l or less (r = 0.30). Thus, although the clinicopathologic significance of HGF is not well understood, the present findings indicate that plasma HGF increases in response to infection or inflammation.

Mediators, cytokines, and growth factors in liver-lung interactions

Multiple mediators have been implicated in the interactions between the liver and the lungs in various disease states. The best characterized mediator of liver-lung interaction is alpha 1-antitrypsin. Several cytokines and mediators may be involved in the pathogenesis of the hepatopulmonary syndrome and in the cytokine cascades that are activated in systemic inflammatory states such as acute respiratory distress syndrome. Hepatocyte growth factor or scatter factor is a recently described peptide with a broad range of biologic effects that may mediate lung-liver interactions.

Gene expressions of c-met and hepatocyte growth factor in chronic liver disease and hepatocellular carcinoma

BACKGROUND/AIMS

The roles of c-met proto-oncogene and hepatocyte growth factor in human livers have not been shown.

METHODS

Gene expressions of both c-met and hepatocyte growth factor were quantified in livers with chronic active hepatitis and in cirrhotic livers with hepatocellular carcinoma as well as in normal controls, using competitive reverse transcription polymerase chain reaction.

RESULTS

C-met expression was significantly increased in chronic active hepatitis compared with control livers, and c-met expression in chronic active hepatitis correlated with serum alanine aminotransferase levels. Hepatocyte growth factor expression was increased in some patients with chronic active hepatitis compared with controls, and there was a significant correlation between c-met expression and hepatocyte growth factor expression. On the other hand, in hepatocellular carcinoma tissues, c-met expression was increased in some cases, while that in the surrounding non-carcinomatous tissues was similar to normal controls. Hepatocyte growth factor expression was not detected in the hepatocellular carcinoma tissues and was low in the surrounding non-carcinomatous tissues.

CONCLUSIONS

These findings suggest that hepatocyte growth factor may be involved in the regeneration of hepatocytes via paracrine mechanism in chronic active hepatitis, while in regulation of c-met expression in hepatocellular carcinoma tissues may be independent of hepatocyte growth factor stimulation.