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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Normal as well as neoplastic cells traverse extracellular matrix barriers by mobilizing proteolytic enzymes in response to epidermal growth factor (EGF)-EGF receptor (EGFR) or hepatocyte growth factor/scatter factor (SF)-c-Met interactions. The plasminogen activator-plasminogen axis has been proposed to play a key role during cell invasion, but the normal development of plasminogen activator- as well as that of plasminogen-deficient mice supports the existence of alternate proteolytic systems that permit cells to traverse extracellular matrix barriers. To characterize the role that matrix-degrading proteinases play in EGF- or SF-stimulated invasion, a human squamous carcinoma cell line (UM-SCC-1) was triggered atop the matrices of type I collagen or human dermal explants in a three-dimensional culture system. During EGF- or SF-induced invasion, UM-SCC-1 cells expressed urokinase-type plasminogen activator (uPA) and uPA receptor as well as the matrix metalloproteinases (MMPs), membrane-type MMP-1, collagenase 1, stromelysin 1, and gelatinase B. Despite the presence of a positive correlation between uPA receptor-uPA expression and growth factor-stimulated invasion, UM-SCC-1 invasion was not affected by inhibitors directed against the plasminogen activator-plasminogen axis. In contrast, both recombinant and synthetic MMP inhibitors completely suppressed invasion by either EGF- or SF-stimulated cells without affecting either proteinase expression or cell motility across collagen-coated surfaces. These data demonstrate that MMPs, but not the plasminogen activator-plasmin system, can directly regulate the ability of either EGF- or SF-stimulated tumor cells to invade interstitial matrix barriers.
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PMID:Role of the plasminogen activator and matrix metalloproteinase systems in epidermal growth factor- and scatter factor-stimulated invasion of carcinoma cells. 982 36

A new human hepatocellular carcinoma (HCC) cell line with a highly metastatic potential was established from subcutaneous xenograft of a metastatic model of human HCC in nude mice (LCI-D20) by means of alternating cell culture in vitro and growth in nude mice. The line, designated MHCC97, has been cultivated for 18 months and subcultured for more than 90 passages. The line was showed to be of human origin by karyotype analysis. The cells were either grown as compact colonies (in clusters) or as a monolayered sheet with about 31 h of population-doubling time, exhibited typical malignant epithelial in morphology and were positive for alpha-fetoprotein (AFP). Flow cytometric analysis of the cell DNA content showed an aneuploid pattern, and its index was 1.5 as compared to that of normal human peripheral blood lymphocytes. Karyotypic analyses of G- and C-banding techniques revealed that all cells presented chromosome abnormalities in number and structure. The number of cell line MHCC97 chromosome ranged from 59 to 65 with a modal number of 60 and 61. At least two common chromosome markers, i(1q) and der(4)t(4;?)(4pter-->q35::?), were present in all cells, and deletion of Y chromosome also occurred in all cells. The subcutaneous and intrahepatic xenografts were formed and metastatic lesions in lungs were found after the cells were inoculated into nude mice. The rate of metastasis to lungs was 100% using orthotopic inoculation. Reverse transcription polymerase chain reaction products revealed positive expressions of integrin alpha5 and beta1, urokinase type plasminogen activator receptor (uPAR), vascular endothelial growth factor and nm23-H1 mRNAs of cell line MHCC97. Immunostaining of c-Met, uPAR showed strongly positive in both subcutaneous xenografts and lung metastatic lesions; while positive in xenografts and negative in metastatic lesions for integrin alpha5, beta1. E-cadherin and P53 was not expressed either in xenograft or in the metastatic lesions. PCR products of HBsAg and HBxAg were both positive. The cell line MHCC97 still retained some characteristic features of original tumour. Establishment of cell line MHCC97 should be beneficial to the studies of HCC metastatic mechanisms.
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PMID:New human hepatocellular carcinoma (HCC) cell line with highly metastatic potential (MHCC97) and its expressions of the factors associated with metastasis. 1055 51

Several lines of evidence indicate that hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, c-Met, may play an important role in progression of human glioma. In this study, effects of HGF/SF on urokinase- type plasminogen activator (uPA)-mediated proteolysis network were examined in c-Met-positive human glioma cell lines. Treatment of the glioma cells with various concentrations of HGF/SF resulted in an enhanced secretion of uPA proteins accompanying increased transcription of uPA mRNA in a dose dependent fashion. The levels of uPA receptor (uPAR) mRNAs were also elevated simultaneously upon HGF/SF stimulation, and the cell-surface associated uPA activity was also elevated by the treatment. Since concomitant expression of HGF and its receptor c-Met are frequently observed in malignant gliomas, these results suggest that HGF/SF participates in invasive process of malignant glioma cells not only by its motility-stimulating activity but also through enhanced degradation of the extracellular matrix induced by autocrine activation of uPA proteolysis network.
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PMID:Simultaneous up-regulation of urokinase-type plasminogen activator (uPA) and uPA receptor by hepatocyte growth factor/scatter factor in human glioma cells. 1108 86

Neuroblastoma is the most frequent solid childhood malignancy. Despite aggressive therapy, mortality is high due to rapid tumor progression to advanced stages. The molecules and mechanisms underlying poor prognosis are not well understood. Here, we report that cultured human neuroblastoma cells express the hepatocyte growth factor (HGF) and its receptor c-Met. Binding of HGF to c-Met triggers receptor autophosphorylation, indicating functional relevance of this interaction. HGF activates several downstream effectors of c-Met such as the mitogen-activated protein kinases extracellular signal-regulated kinase 1/extracellular signal-regulated kinase 2 and phospholipase C-gamma, whereas signal transducer and activator of transcription 3 is constitutively activated in neuroblastoma cells expressing c-Met. In addition, HGF is able to stimulate expression and proteolytic activity of matrix metalloproteinase-2 and tissue-type plasminogen activator in neuroblastoma cells, thereby promoting degradation of extracellular matrix components. We show that HGF stimulates invasion of neuroblastoma cells in vitro and in vivo, and it promotes the formation of angiogenic neuroblastomas in vivo. These processes can be blocked by specific inhibitors of the mitogen-activated protein kinase cascade, by inhibitors of phospholipase C-gamma, and also by the expression of a dominant negative signal transducer and activator of transcription 3 mutant. Our data provide the first evidence that the HGF/c-Met pathway is essential for invasiveness and malignant progression of human neuroblastomas. They further suggest that specific inhibitors of this pathway may be suitable as therapeutic agents to improve clinical outcome of neuroblastomas.
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PMID:Hepatocyte growth factor/c-Met signaling promotes the progression of experimental human neuroblastomas. 1534 94

The hepatocyte growth factor (HGF) is a multifunctional cytokine that is produced as latent scHGF (single chain HGF). Various proteases reportedly cleave scHGF to generate the active two-chain form (HGF), including u-PA (urokinase-type plasminogen activator), t-PA (tissue-type plasminogen activator), kallikrein, Factor XIa, Factor XIIa, HGF activator and matriptase. Considerable evidence indicates that, in vivo, u-PA activates scHGF in the liver; however, the in vivo results have not been uniformly supported by in vitro experiments. We now report that cleavage of scHGF by high-molecular-mass u-PA (abbreviated u-PA throughout) is sensitive to ionic strength. scHGF cleavage by u-PA was accelerated as the ionic strength was decreased. This result was equivalent irrespective of whether the predominant anion was chloride or acetate. Lmw-u-PA (low-molecular-mass u-PA) was ineffective at cleaving scHGF, regardless of ionic strength. Although scHGF shares homology with plasminogen, EACA (-amino-caproic acid) did not regulate u-PA-mediated scHGF cleavage. Soluble HGF receptor (MET) and soluble u-PAR (u-PA receptor) inhibited the scHGF cleavage. These results support a model in which the ability of u-PA to activate scHGF in vivo may be highly dependent on local conditions within the extracellular space.
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PMID:Activation of hepatocyte growth factor by urokinase-type plasminogen activator is ionic strength-dependent. 1586 63

Plasminogen activator inhibitor-1 (PAI-1) is an acute phase protein known to correlate with hepatic fibrosis. However, whether or not PAI-1 plays a causal role in this disease process had not been directly tested. Therefore, wild-type or PAI-1 knockout (PAI-1(-/-)) mice underwent bile duct ligation. Mice were sacrificed either 3 or 14 days after surgery for assessment of early (i.e., inflammation) and late (i.e., fibrosis) changes caused by bile duct ligation. Liver injury was determined by histopathology and plasma enzymes. Accumulation of extracellular matrix was evaluated by Sirius red staining and by measuring hydroxyproline content. Hepatic expression of PAI-1 was increased approximately 9-fold by bile duct ligation in wild-type mice. Furthermore, early liver injury and inflammation due to bile duct ligation was significantly blunted in PAI-1(-/-) mice in comparison with wild-type mice. Although PAI-1(-/-) mice were significantly protected against the accumulation of extracellular matrix caused by bile duct ligation, increases in expression of indices of stellate cell activation and collagen synthesis caused by bile duct ligation were not attenuated. Protection did, however, correlate with an elevation in hepatic activities of plasminogen activator and matrix metalloprotease activities. In contrast, the increase in tissue inhibitor of metalloproteases-1 protein, a major inhibitor of matrix metalloproteases, caused by bile duct ligation was not altered in PAI-1(-/-) mice compared with the wild-type strain. The increase in hepatic activity of urokinase-type plasminogen activator was also accompanied by more activation of the hepatocyte growth factor receptor c-Met. Taken together, these data suggest that PAI-1 plays a causal role in mediating fibrosis during cholestasis.
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PMID:Critical role of plasminogen activator inhibitor-1 in cholestatic liver injury and fibrosis. 1622 37

Extrahepatic cholestasis leads to complex injury and repair processes that result in bile infarct formation, neutrophil infiltration, cholangiocyte and hepatocyte proliferation, extracellular matrix remodeling, and fibrosis. To identify early molecular mechanisms of injury and repair after bile duct obstruction, microarray analysis was performed on liver tissue 24 hours after bile duct ligation (BDL) or sham surgery. The most upregulated gene identified encodes plasminogen activator inhibitor 1 (PAI-1, Serpine 1), a protease inhibitor that blocks urokinase plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) activity. Because PAI-1, uPA, and tPA influence growth factor and cytokine processing as well as extracellular matrix remodeling, we evaluated the role of PAI-1 in cholestatic liver injury by comparing the injury and repair processes in wild-type (WT) and PAI-1-deficient (PAI-1-/-) mice after BDL. PAI-1-/- mice had fewer and smaller bile infarcts, less neutrophil infiltration, and higher levels of cholangiocyte and hepatocyte proliferation than WT animals after BDL. Furthermore, PAI-1-/- mice had higher levels of tPA activation and mature hepatocyte growth factor (HGF) after BDL than WT mice, suggesting that PAI-1 effects on HGF activation critically influence cholestatic liver injury. This was further supported by elevated levels of c-Met and Akt phosphorylation in PAI-1-/- mice after BDL. In conclusion, PAI-1 deficiency reduces liver injury after BDL in mice. These data suggest that inhibiting PAI-1 might attenuate liver injury in cholestatic liver diseases.
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PMID:Transcriptional profiling after bile duct ligation identifies PAI-1 as a contributor to cholestatic injury in mice. 1625 54

Hepatocyte growth factor (HGF), its transmembrane tyrosine kinase receptor (c-Met), and urokinase type plasminogen activator (uPA) is a key protein in the plasminogen activation system, which plays a proteolytically important role in the invasion and metastasis of various types of cancers. However, the mechanisms by which HGF/c-Met signaling mediates cancer progression and metastasis are unclear. This study was designed to investigate the roles of HGF/c-Met in tumor progression and metastasis in HepG2 and Hep3B hepatoma cell lines. Treatment with HGF increased c-Met phosphorylation in a dose-dependent manner. Activity of c-Met phosphorylation peaked 1-3 min after HGF treatment and then declined. HGF enhanced the protein level and the activity of uPA in HepG2 and Hep3B cells, and the uPAR protein level also increased in a HGF dose-dependent manner. HGF increased cell invasion through the Matrigel. A monoclonal antibody against human uPA receptor, mAb 3936, inhibited HGF-mediated tumor cell invasion in a dose-dependent manner. Down-regulation of uPA using uPA-shRNA induced a decrease in in vitro cell invasion. These results suggest that hepatoma cells express functional c-Met, which may provide a target for a therapeutic basis to interfere with metastases of cancer cells by inhibiting uPA system-mediated proteolysis.
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PMID:Role of hepatocyte growth factor/c-Met signaling in regulating urokinase plasminogen activator on invasiveness in human hepatocellular carcinoma: a potential therapeutic target. 1799 75