Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have reported previously that derivatives of adenosine cyclic 3':5'-monophosphate dramatically stimulate the activity of plasminogen activator (PA), an arginine-specific serine protease, in HTC rat hepatoma cells. We report here that these derivatives also cause striking alterations in hepatoma tissue culture cell morphology. Because PA has been shown to alter cell morphology in other cell lines, we investigated whether the morphological changes induced by cyclic nucleotides were mediated by the stimulation of PA activity. Alterations in PA activity, measured by the plasminogen-dependent solubilization of 125I-labeled fibrin, and in cell morphology, detected by evaluation of cell flattening and process extension with phase-contrast microscopy, were assessed in the same cultures under various experimental conditions. Several lines of evidence clearly dissociate these two adenosine cyclic 3':5'-monophosphate-mediated phenomena. (a) The morphological changes precede increases in either cell-associated or extracellular PA activity. (b) Upon removal of the effectors, the morphological effects are completely reversed at a time when PA activity is still considerably elevated. (c) when protein synthesis is inhibited by the addition of cycloheximide, the stimulation of PA activity by cyclic nucleotides is blocked completely, whereas the induction of morphological alterations still occurs. (d) An exogenous PA, urokinase, does not elicit the characteristic changes in cell shape. We conclude that the morphological alterations induced by adenosine cyclic 3':5'-monophosphate derivatives in HTC cells are not mediated by the stimulation of PA activity and that these two membrane-associated properties are regulated independently.
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PMID:Role of plasminogen activator in the morphological alterations induced by derivatives of adenosine cyclic 3':5'-monophosphate in hepatoma tissue culture cells. 631 21

Incubation of HTC rat hepatoma cells with dexamethasone causes a rapid decrease in cellular plasminogen activator (PA) activity. Mixing experiments show the presence of an inhibitor of PA in dexamethasone-treated cells. This study investigates whether the decrease in PA activity is secondary to the induction of an inhibitor by glucocorticoids, to a decrease in the amount of PA, or to a combination of both mechanisms. PA and its inhibitor are dissociated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under non-reducing conditions, and both activities are then recovered and quantitated. HTC cells have two major forms of PA with Mr values of 110,000 and 64,000. Although PA activity in the unfractionated extracts from dexamethasone-treated cells is inhibited by 90% relative to control, there is no decrease in the total activity of sodium dodecyl sulfate-dissociated PA activity, suggesting that dexamethasone causes no decrease in the amount of the enzyme. PA inhibitor activity migrates as a single band of Mr = 50,000. The total activity of inhibitor increases in a time-dependent fashion, reaching a maximum of greater than 10 times control after a 4-6-h incubation with 0.1 microM dexamethasone. The induction of inhibitor requires both RNA and protein synthesis and shows a dependence on dexamethasone concentration identical to that for responses known to be mediated by glucocorticoid receptors. We conclude that dexamethasone inhibits PA activity by inducing the synthesis of an inhibitor rather than by decreasing the amount of PA.
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PMID:Dexamethasone induction of an inhibitor of plasminogen activator in HTC hepatoma cells. 642 25

Dexamethasone induces an inhibitor of plasminogen-dependent fibrinolysis in rat hepatoma (HTC) cells. The specificity of the inhibitor for urokinase and plasmin was investigated using both fibrinolytic and esterolytic assays. Urokinase, but not plasmin, was inhibited by serum-free conditioned medium from cells incubated with 0.1 microM dexamethasone. The specificity of the inhibitor for plasminogen activator was demonstrated directly by the inhibition of the urokinase-catalyzed activation of 125I-plasminogen to 125I-plasmin. The inhibitory activity was stable to pH 3 for 2 h at 37 degrees C, a condition which inactivated fibrinolytic inhibitors in serum, suggesting a cellular origin for the inhibitor. Further evidence for the cellular origin was the constant daily production of inhibitor throughout a 4-day incubation with dexamethasone in serum-free medium. SF HTC-H1 cells, selected for their ability to grow in serum-free medium (Thompson, E. B., Anderson, C. U., and Lippman, M. E. (1975) J. Cell Physiol. 86, 403-412), were grown for 76 days (at least 30 generations) in the presence or absence of serum; dexamethasone induced equivalent amounts of inhibitory activity in cells which had been grown under both conditions. We conclude that the dexamethasone-induced inhibitor from HTC cells is a cellular product which is specific for the inhibition of plasminogen activation and which differs from other reported fibrinolytic inhibitors.
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PMID:The dexamethasone-induced inhibitor of fibrinolytic activity in hepatoma cells. A cellular product which specifically inhibits plasminogen activation. 646 54

The adherent human hepatoma cell line Hep G2 exhibits receptor mediated endocytosis and catabolism of tissue-type plasminogen activator.plasminogen activator inhibitor type-1 (t-PA.PAI-1) complexes formed when exogenous t-PA combines with endogenous PAI-1 in the extracellular matrix. To determine whether the other major PA, urokinase (u-PA), which also complexes with PAI-1, is metabolised via the same mechanism, 125I-labelled high (hmw) and low (lmw) molecular weight forms of u-PA were incubated with Hep G2 cells at 4 degrees C for 2 hr in the absence and presence of a 100-fold excess of unlabelled ligand in order to detect specific binding. Both hmw and lmw 125I-u-PA formed complexes with PAI-1 and these bound specifically and with high affinity (apparent Kd 3.9 and 4.1 nM, with Bmax 78 x 10(3) and 83 x 10(3) binding sites/cell respectively). Binding by each form of radiolabelled u-PA was inhibited in a dose-dependent fashion by unlabelled t-PA, hmw-u-PA, lmw-u-PA, and by monoclonal anti-PAI-1 antibody. At 37 degrees C, bound hmw and lmw 125I-u-PA.PAI-1 complexes were internalised and degraded rapidly. These findings indicate that the specificity of the previously described receptor which mediates PAI-1 dependent catabolism of t-PA by Hep G2 cells extends to complexes of u-PA with this inhibitor.
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PMID:Urokinase binding and catabolism by Hep G2 cells is plasminogen activator inhibitor-1 dependent, analogous to interactions of tissue-type plasminogen activator with these cells. 748 38

HGF is a powerful mitogen for both rat and human hepatocytes, epithelial cells and endothelial cells in vitro, and is angiogenic in vivo. It has considerable homology with plasminogen and has been shown to upregulate urokinase-type plasminogen activator (u-PA) in endothelial cells as well as u-PA and its receptor in kidney epithelial cells. In this study, we report that human recombinant HGF stimulates expression of plasminogen activator inhibitor type 1 (PAI-1) and tissue factor (TF) in the human hepatoma cell line HepG2. PAI-1 antigen as determined by a specific enzyme-linked immunosorbent assay increased up to threefold in conditioned media of HepG2. This increase was dose dependent with maximum stimulation achieved with a concentration of 50 ng/mL of hepatocyte growth factor (HGF). PAI-1 antigen also increased up to fourfold in the extracellular matrix in HGF treated HepG2. The production of the PAI-1 binding protein vitronectin (Vn) was not affected by HGF. In contrast, TF activity in HepG2 treated with HGF increased up to twofold. As determined by Northern blotting, PAI-1 and TF-specific mRNA were increased significantly in the presence of HGF, whereas Vn mRNA was not affected. The increase in PAI-1 and TF mRNA was also seen when HepG2 were incubated with HGF in the presence of cycloheximide, thereby indicating that de novo protein synthesis is not required to mediate the effect. u-PA could be detected neither in unstimulated or HGF-stimulated HepG2 cells on the antigen level nor on the mRNA level. In conclusion, our data give evidence that HGF, in addition to its proliferative effect for different cell types, is also involved in the local regulation of fibrinolysis and coagulation. One could speculate that HGF might modulate processes requiring matrix degradation by increasing the expression of the protease u-PA in one cell type and by upregulating the expression of the serine protease inhibitor PAI-1 in a different cell type. Because u-PA has been shown to activate latent HGF to the active form, it could furthermore be speculated that by upregulating PAI-1, which in turn could inhibit u-PA, HGF might regulate its own activation.
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PMID:Hepatocyte growth factor stimulates expression of plasminogen activator inhibitor type 1 and tissue factor in HepG2 cells. 751 5

Culture medium conditioned by human SK-Hep1 hepatoma cells or mouse S180 sarcoma cells rapidly up-regulates endothelial cell expression of basic fibroblast growth factor (bFGF) and induces formation of capillary-like structures by vascular endothelial cells grown on three-dimensional fibrin gels (in vitro angiogenesis). Incubation of endothelial cells with the tumor cell-conditioned media also results in increased expression of urokinase plasminogen activator (uPA), a key component of the proteolytic system required for cell invasion and capillary formation. Although the tumor cell-conditioned media contain no bFGF, addition of anti-recombinant bFGF IgG abolishes the up-regulation of uPA and blocks in vitro angiogenesis. This indicates that both the increase in uPA production and formation of capillary-like structures are mediated by endogenous bFGF expressed by the endothelial cells. Both the bFGF/uPA-inducing activity and the angiogenic activity of SK-Hep1 cell-conditioned medium copurify with a relatively acid-resistant peptide that has moderate affinity for heparin and M(r) < 18 kDa > 3.5 kDa. Known cytokines with similar biochemical features do not possess the same biological activity. These findings indicate that angiogenesis can be mediated by endothelial cell bFGF through an autocrine mechanism and that the bFGF-inducing peptide may represent a novel tumor-derived angiogenic factor that modulates in endothelial cells the concerted expression of cytokines and proteolytic enzymes required for capillary formation.
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PMID:Tumor cells secrete an angiogenic factor that stimulates basic fibroblast growth factor and urokinase expression in vascular endothelial cells. 752 24

We measured urokinase-type plasminogen activator (u-PA) plasma levels in patients with various chronic liver diseases, including hepatocellular carcinoma (HCC), also measuring these levels in healthy volunteers. Plasma u-PA levels in the group of patients with decompensated liver cirrhosis (mean modified Pugh score of 14 points) were markedly elevated and significantly higher than those in the patients with decompensated liver cirrhosis with HCC (modified Pugh score of 10 points), those with compensated liver cirrhosis with HCC, and those with compensated liver cirrhosis. Patients in all these three latter groups had moderately and significantly elevated u-PA levels compared to levels in the chronic hepatitis group and the healthy volunteers, but the levels were not significantly different from each other. There was no relationship between u-PA plasma level and the type of HCC tumor invasion or number or size of tumors. Significant correlations were found between u-PA plasma levels and the results of seven different liver function tests in three groups without associated HCC; u-PA antigen and prothrombin time (%), hepaplastin test (%), serum cholinesterase, serum albumin, serum total cholesterol, and indocyanine green clearance correlated negatively, while u-PA antigen and serum total bilirubin correlated positively. These results suggest that plasma u-PA is associated with deterioration of liver function but not with HCC invasion.
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PMID:Elevated urokinase-type plasminogen activator plasma levels are associated with deterioration of liver function but not with hepatocellular carcinoma. 787 70

The glycoprotein tissue-type plasminogen activator (t-PA) is subject to hepatic clearance in humans. Here, the interaction of t-PA with a well-differentiated hepatoma cell line (HepG2) was examined. Suspended HepG2 cells bound 125I-t-PA in a specific, saturable, and reversible fashion through a Ca(2+)-dependent, active site-independent mechanism. Binding isotherms indicated a high affinity system with a single class of saturable binding sites (Kd 39 nM; maximum binding capacity 493,000 sites per cell). Bound t-PA was rapidly degraded at 37 degrees C in a manner inhibited by lysosomotropic agents or metabolic inhibitors. Pretreatment of t-PA with monoclonal antibodies against the EGF/fibronectin finger domain, but not kringle 2 or kringle 1, reduced total binding by 86%. Binding of 125I-t-PA to HepG2 cells was inhibited by monosaccharides fucose and galactose and by the neoglycoprotein fucosyl-albumin. Enzymatic removal of alpha-fucose residues, but not alpha-galactose, high mannose, or complex oligosaccharide from 125I-t-PA, reduced specific binding by 60 +/- 5%. Binding was also inhibited by high, but not low, molecular weight urokinase, which contains an EGF-based threonine-linked alpha-fucose homologous to that of t-PA. These data suggest that EGF-associated O-linked alpha-fucose may mediate t-PA binding and degradation by HepG2 cells. This mechanism may be relevant to other proteins with analogous structures.
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PMID:alpha-Fucose-mediated binding and degradation of tissue-type plasminogen activator by HepG2 cells. 811 82

The role of plasminogen activator inhibitor type 1 (PAI-1) in the clearance of tissue-type plasminogen activator (t-PA) by hepatocyte-like cells was studied. Rat (Novikoff) hepatoma cells were able to bind and degrade t-PA in a PAI-1 independent fashion, but PAI-1 markedly increased the rate of degradation and t-PA/PAI-1 was a more efficient inhibitor of 125I-t-PA or of 125I-t-PA/PAI-1 degradation than free t-PA. Competition studies revealed that the effect of PAI-1 is unlikely to involve determinants located on the PAI-1 part of the complex: 1) an excess of free PAI had no effect on the rate of degradation of 125I-t-PA/PAI-1.2) Complexes of PAI-1 with urokinase-type PA or with a t-PA mutant lacking the finger and growth factor domains were unable to compete for the binding and degradation of free or PAI-1-complexed 125I-t-PA.3) t-PA KHRR296-299AAAA, a mutant which reacts 2 orders of magnitude slower with PAI-1 than wild type t-PA, behaved similar to wild type t-PA. The clearance via both the PAI-1-dependent and the PAI-1-independent mechanisms was inhibited by the receptor-associated protein, a general inhibitor of clearance mediated by the LDL receptor-related protein. We conclude that t-PA can be cleared by rat hepatoma cells in a PAI-1 independent fashion, but after complex formation with PAI-1, binding of t-PA to the cells is increased and clearance accelerated. Both mechanisms seem to involve the same receptor.
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PMID:The role of plasminogen activator inhibitor type 1 in the clearance of tissue-type plasminogen activator by rat hepatoma cells. 811 17

Type 1 plasminogen activator inhibitor (PAI-1) is the major physiological inhibitor of plasminogen activation, inhibiting both tissue- and urokinase-type plasminogen activators. In HTC rat hepatoma cells, glucocorticoids increase PAI-1 activity, antigen and mRNA accumulation 3- to 5-fold; this increase is due solely to an increase in the rate of PAI-1 gene transcription. We have identified the cis-acting sequences in the 5'-flanking sequence of the HTC PAI-1 gene that mediate this induction. Analysis of a series of hybrid genes containing various portions of the PAI-1 5'-flanking region fused to the chloramphenicol acetyltransferase reporter gene transfected into HTC cells localized the region involved in the transcriptional regulation by glucocorticoids to between -1237 and -764. Electrophoretic mobility shift assays and DNase-I protection assays showed that a glucocorticoid response element (GRE) 15-mer located at -1212 bound the glucocorticoid receptor DNA-binding domain protein in a concentration-dependent manner. Mutations created within this GRE eliminated its ability both to confer a glucocorticoid response and to bind the glucocorticoid receptor. When placed upstream of a heterologous promoter in either orientation, this GRE conferred glucocorticoid inducibility. We, therefore, conclude that the sole cis-acting sequence required for the glucocorticoid response of the PAI-1 gene in rat HTC hepatoma cells is the GRE at -1212.
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PMID:Mechanism of glucocorticoid induction of the rat plasminogen activator inhibitor-1 gene in HTC rat hepatoma cells: identification of cis-acting regulatory elements. 824 19


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