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)

The Ah (aromatic hydrocarbon) receptor mediates induction of aryl hydrocarbon hydroxylase (AHH; an enzyme activity associated with cytochrome P450IA1) by polycyclic aromatic hydrocarbon carcinogens such as 3-methylcholanthrene (MC) and benzo[a]pyrene (BP) and the halogenated toxin 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Until recently the AhR seemed to be present only at very low levels in human cells and tissue. With a modified assay (the presence of sodium molybdate and a reduction in the amount of charcoal used to adsorb "excess" ligand) we found that cytosol from LS180 cells contains a high concentration of AhR (400-500 fmol/mg cytosolic protein) when detected by [3H]TCDD or [3H]MC. Cytosolic receptor also was detected with [3H]BP but at a level that was 35% of that detected with [3H]TCDD or [3H]MC. These levels are similar to those found in mouse Hepa-1 hepatoma cells in which AhR has been extensively characterized. The apparent binding affinity (Kd) of the cytosolic receptor for [3H]TCDD and for [3H]MC was about 5 nM. As with Hepa-1, the human LS180 cytosolic AhR sedimented at about 9 S on sucrose gradients when detected with [3H]TCDD, [3H]BP or [3H]MC. The nuclear-associated ligand.receptor complex recovered from cells incubated in culture with [3H]TCDD sedimented at about 6.2 S. The 9.8 S cytosolic form corresponds to a multimeric protein of a relative molecular mass (Mr) of about 285,000 whereas the 6.2 S nuclear receptor corresponds to a multimeric protein of Mr 175,000. The smallest specific ligand-binding subunit (detected by sodium dodecyl sulfate-polyacrylamide electrophoresis under denaturing conditions of receptor photoaffinity labeled with [3H]TCDD) was about Mr 110,000. AHH activity was induced in cells exposed in culture to TCDD or benz[a]anthracene (BA). The EC50 was 4 x 10(-10) M for TCDD and 1.5 x 10(-5) M for BA. For both inducers the EC50 in LS180 cells was shifted about one log unit to the right as compared to the EC50 for AHH induction in mouse Hepa-1 cells. The lower sensitivity of the LS180 cells to induction of AHH activity by TCDD or BA is consistent with the lower affinity of TCDD and MC for binding to human AhR. The ligand-binding properties, physicochemical properties, and mode of action of the AhR in this human cell line are therefore very similar to those of the extensively characterized AhR in rodent cells and tissues.
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PMID:Detection and characterization of the Ah receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin in the human colon adenocarcinoma cell line LS180. 165 65

Two distinct classes of cell surface FGF-binding proteins have been identified. These receptors differ in both mode of interaction and in affinity for the FGFs. cDNAs that encode the low-affinity receptor were isolated from a hamster kidney cell line cDNA library by expression cloning. Transfected cells that contained these heparan sulfate proteoglycan FGF receptor cDNAs were enriched for by panning on basic FGF-coated plates. The analogous human cDNA was isolated from a hepatoma cell line cDNA library. The homology of our hamster cDNAs to the previously described murine integral membrane proteoglycan syndecan, together with an exact amino acid sequence match of our human-cDNA-encoded product to human syndecan, clearly indicates the identity of these independently isolated proteoglycans. Further confirmation that the expressed molecule serves as a proteoglycan core protein was achieved by immunoprecipitation of 35SO4-labeled material from solubilized transfected cells. Nitrous acid treatment and chondroitinase digestion revealed that 77% of the label was associated with heparan sulfate chains and 22% with chondroitin sulfate chains. These heparan sulfate chains contributed to the fivefold increase in the total heparan sulfate found to be present on the surface of the transfected cells compared with cells transfected with a vector lacking the cDNA insert.
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PMID:The molecular biology of heparan sulfate fibroblast growth factor receptors. 166 83

The elongated mutant of alpha 2-plasmin inhibitor (alpha 2 PI) designated as alpha 2 PI-Nara is caused by a frameshift mutation found near the 3' end of the coding region of the alpha 2 PI gene. To elucidate the mechanism by which this molecular abnormality leads to alpha 2 PI deficiency in plasma, we transfected an expression plasmid for alpha 2 PI-Nara into a monkey kidney cell line COS-7 or human hepatoma cell line HepG2 synthesizing alpha 2 PI, and analyzed the secretory process of the expressed alpha 2 PI-Nara by radioimmunoprecipitation followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and fluorography. The results obtained showed that the recombinant alpha 2 PI-Nara was retained within the cells for prolonged periods as an endoglycosidase H-sensitive precursor form, and only a small portion of the recombinant protein was secreted into the medium as a neuraminidase-sensitive mature form. These results suggest that instead of being secreted from the cells, most of the alpha 2 PI-Nara undergoes degradation within the cells while its transport is retarded in the intracellular secretory pathway; thus, alpha 2 PI-Nara should lead to the alpha 2 PI deficiency primarily by causing a block in the intracellular transport from the endoplasmic reticulum to the Golgi complex.
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PMID:Impaired secretion of mutant alpha 2-plasmin inhibitor (alpha 2 PI-Nara) from COS-7 and HepG2 cells: molecular and cellular basis for hereditary deficiency of alpha 2-plasmin inhibitor. 168 97

A two-cycle immunoprecipitation procedure is described that markedly reduces nonspecific protein contamination occurring during the precipitation of hepatic lipase from rat H4 hepatoma cells. In this method, the precipitation of immune complexes during both cycles is achieved by utilizing a sodium dodecyl sulfate (SDS)-washed preparation of lyophilized Staphylococcus aureus cells (Staph A); this washed preparation effectively removes Staph A contaminants without compromising the ability to bind immune complexes. Following initial immunoprecipitation of the antigen, the Staph A/IgG/antigen complex containing coprecipitated nonspecific proteins was dissociated with SDS. Triton X-100 was added to the dissociated immunoprecipitate at a concentration (by weight) of at least 5 parts Triton X-100 to 1 part SDS. A second cycle of immunoprecipitation was then initiated by addition of fresh antibody, followed by Staph A precipitation of immune complexes and analysis by SDS-polyacrylamide gel electrophoresis. The two-cycle procedure is shown to be reproducible and suitable for the quantitative determination of relative amounts of hepatic lipase. The procedure described here is generally applicable to the immunoprecipitation of other antigens.
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PMID:A two-cycle immunoprecipitation procedure for reducing nonspecific protein contamination. 175 Jun 92

Highly sulfated, heparinlike species of heparan sulfate proteoglycans, with heparinlike glycosaminoglycan chains, are extracellular matrix components that are plasma membrane bound in growth-arrested liver cells. Heparins were found to inhibit the growth and lower the clonal growth efficiency of HepG2, a minimally deviant, human hepatoma cell line. Heparan sulfates, closely related glycosaminoglycans present in the extracellular matrix around growing liver cells, had no effect on the growth rate or clonal growth efficiency of HepG2 cells. Neither heparins nor heparan sulfates had any effect on the growth rate or clonal growth efficiency of two poorly differentiated, highly metastatic hepatoma cell lines, SK-Hep-1 and PLC/PRF/5. Heparin's inhibition of growth of HepG2 cells correlated with changes in the mRNA synthesis and abundance of insulinlike growth factor II (IGF II) and transforming growth factor beta (TGF beta). HepG2 cells expressed high basal levels of mRNAs encoding IGF II and TGF beta that were inducible, through transcriptional and posttranscriptional mechanisms, to higher levels by specific heparin-hormone combinations. For both IGF II and TGF beta, the regulation was multifactorial. Transcriptionally, IGF II was regulated by the additive effects of insulin, glucagon, and growth hormone in combination with heparin; TGF beta was regulated primarily by the synergistic effects of insulin and growth hormone in combination with heparin. Posttranscriptionally, the mRNA abundance of the IGF II 4.5- and 3.7-kb transcripts was affected by insulin. Heparin induction of all IGF II transcripts was also dependent on triiodotyronine and prolactin, but it is unknown whether their induction by heparin was via transcriptional or posttranscriptional mechanisms. Heparin-insulin combinations regulated TGF beta posttranscriptionally. The poorly differentiated hepatoma cell lines PLC/PRF/5 and SK-Hep-1 either did not express or constitutively expressed low basal levels of IGF I, IGF II, and TGF beta, whose mRNA synthesis and abundance showed no response to any heparin-hormone combination. We discuss the data as evidence that matrix chemistry is a variable determining the expression of autocrine growth factor genes and the biological responses to them.
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PMID:Heparin and hormonal regulation of mRNA synthesis and abundance of autocrine growth factors: relevance to clonal growth of tumors. 184 19

Dramatic cellular changes that occur during hepatocarcinogenesis are associated with major alterations in extracellular matrix formation and in the relationships between cells and their microenvironment. We have studied the expression of laminin, the major noncollagenous glycoprotein of basement membrane, and the laminin receptor 32 kD laminin-binding protein in two rat (Faza 967 and HTC) and two human (HepG2 and HBGC2) hepatoma cell lines that express a variety of liver-specific functions. Laminin was found in the rough endoplasmic reticulum of these cells when the indirect immunoperoxidase method and electron microscopic examination were used. Radiolabeled laminin, immunoprecipitated from both media and cell extracts, was resolved by electrophoresis on sodium dodecyl sulfate gel in two major polypeptides that comigrated with the A and B subunits from Engelbreth-Holm-Swarm tumor laminin. Immunoblot analysis showed that the Mr = 400,000 polypeptide did not correspond to the A subunit of laminin. Northern blot analyses demonstrated large amounts of B1 and B2 mRNAs but no A chain mRNA. We conclude that the tumor cells produce the laminin B chains only. In contrast, normal adult hepatocytes from either man or rat lacked laminin mRNAs, whereas in 1-day primary culture, B chain mRNAs became detectable. The steady-state level of 32 kD laminin-binding protein mRNA was 10-fold and threefold higher in rat hepatoma cells than in freshly isolated and 1-day cultured normal rat hepatocytes, respectively. In human hepatocytes, the steady-state levels of 32 kD laminin-binding protein mRNAs varied depending on the donor and never reached the level of the human hepatoma cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Expression of laminin and its receptor LBP-32 in human and rat hepatoma cells. 184 49

To identify proteins involved in the hepatocellular uptake of loop diuretics, [3H]bumetanide was photoactivated by light flash in the presence of either intact isolated rat hepatocytes, rat liver basolateral plasma membranes or integral membrane proteins extracted from the basolateral plasma membranes. Proteins of 52-54, 48, 33, 27, 25 and 23 kDa in sodium dodecyl sulfate (SDS) gel electrophoresis were radiolabeled on intact hepatocytes. On liver basolateral plasma membranes a 50-52 kDa protein was the most intensely labeled protein. After separation into integral and associated membrane proteins by extraction with Triton X-114, radioactive labeling was only found in integral membrane proteins with a molecular weight of 50-52 kDa. Photoactivated bumetanide irreversibly inhibited the hepatocellular uptake of cholate, taurocholate but not of serine. Binding proteins for photoactivated bumetanide were absent on AS 30-D ascites hepatoma cells. Labeling of all proteins was sodium dependent in intact hepatocytes but was sodium independent in plasma membranes. Labeling was prevented by non-labeled bumetanide and by the loop diuretics piretanide and furosemide. Labeling protection was further achieved with organic anions such as bromosulfophthalein, rifampicin, probenecid and by the bile acids taurocholate, deoxycholate and dehydrocholate. The radiolabeled proteins did not belong to the bumetanide-sensitive NaCl/KCl co-transport system which apparently does not occur in intact isolated rat hepatocytes.
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PMID:Photoaffinity labeling of plasma membrane proteins involved in the transport of loop diuretics into hepatocytes. 193 29

Cytosolic extracts prepared from perfused whole liver or purified hepatocytes of C57BL/6 mice inhibited interleukin-2--and concanavalin A--induced spleen cell proliferation in vitro. In contrast, cytosolic extracts from purified nonparenchymal liver cells had no effect. Arginase and very-low-density lipoprotein were previously identified as two immuninhibitory substances present in liver cytosolic extracts. We demonstrated, however, that inhibitory activity remained after removal of very-low-density lipoprotein and arginase from liver cytosolic extract by repeated ultracentrifugation and gel filtration chromatography, respectively, suggesting the presence of another inhibitor. Further purification by anion-exchange chromatography and chromatofocusing led to the isolation of a novel liver-derived immunohibitory factor. This liver-derived immunoinhibitory factor is sensitive to pronase digestion and heat and acid treatment; it has an estimated isoelectric point of 8.25. The Mr of liver-derived immunoinhibitory factor is 28 kD as estimated from its migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which is identical under both reducing and nonreducing conditions, indicating a monomeric nature of this protein. Amino acid composition analysis discloses that liver-derived immunoinhibitory factor is relatively rich in glycine and proline residues. Interleukin-2--induced spleen cell proliferation in vitro is inhibited by ths liver-derived immunoinhibitory factor, with a 50% inhibitory dose of 1.4 nmol/L. Furthermore, the biological activity of the liver-derived immunoinhibitory factor is not confined to mouse spleen cells, since the growth of B16 mouse melanoma and H35 rat hepatoma cells is also inhibited. A comparison with other liver-derived immunoinhibitors reported previously supports our claim that the liver-derived immunoinhibitory factor is a novel inhibitory protein.
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PMID:Isolation and characterization of a novel liver-derived immunoinhibitory factor. 193 91

Homogeneous (7.5%) and gradient (10-15%) ultrathin nondenaturating miniaturized polyacrylamide gels (Pharmacia PhastGel media) were used to separate glycogen phosphorylase isoforms from rabbit muscle, rat liver and brain, MH 3924A cells, a dedifferentiated hepatocellular carcinoma of the rat, and C1I cells, a nontumorigenic epithelial rat liver cell line. The enzymes were detected by in situ phosphorylase assay and by immunoblotting. Phosphorylase proteins from the brain, MH 3924A, and C1I exhibited similar electrophoretic mobility, which was different from that of the enzymes from the muscle and normal liver. Molecular weight determination from sodium dodecyl sulfate gels yielded similar data for the subunits of muscle and liver enzymes (98,000 and 96,000), respectively, on one hand, and brain, MH 3924A tumor, and nontumorigenic C1I cells (93,000, 93,000 and 92,000), respectively, on the other. In the native gels the enzymes migrated as dimers: for muscle phosphorylase a, a tetramer was also observed. The a and b forms of the enzymes could not be resolved. An antibody raised against rat liver phosphorylase reacted only with the liver enzyme, whereas an antibody raised against brain phosphorylase stained the brain enzyme and the enzymes from MH 3924A and C1I cells. This indicates that hepatoma cells and immortalized nontumorigenic epithelial liver cells express a phosphorylase isoenzyme that is different from the liver type but similar to the brain type. The PhastSystem provides a rapid, sensitive, and highly reproducible method to resolve the different isoenzymes of glycogen phosphorylase.
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PMID:Resolution of glycogen phosphorylase isoenzymes in precast PhastSystem polyacrylamide gels. 207 Jul 85

Glycosaminoglycans were investigated in surgically removed human liver and kidney tumours by applying biochemical methods. Four liver adenoma, 6 focal nodular hyperplasia and 9 primary hepatocellular carcinoma samples were compared with normal liver from autopsy cases and also with liver tissue adjacent to PHC. The studies on kidney included 14 renal cell carcinoma and 4 wilms' tumour samples. Three findings emerged from the quantitative and qualitative characterization of the tumours with epithelial origin. 1) The rise in the amount of total GAG was not limited to the malignant lesion. Similar increase was observed in benign liver tumours and also in the tissue adjacent to liver or kidney malignant tumours. 2) The dominant type of the GAG subclasses varies with the histology of the tumours. In benign liver tumours dermatan sulfate, in PHC and renal cell carcinoma chondroitin sulfate, but in Wilms' tumour hyaluronate was the prominent GAG subclass. 3) In all tumour-affected tissues dermatan and chondroitin sulfates had lower degree of sulfation. However, in the histologically different tumours various disaccharides showed reduced level of sulfation. The GAG alteration in renal cell carcinoma was compared with the prognostic factors of each individual case. This analysis showed a good correlation between HS/CS ratio and the prognostic factors of the kidney tumour cases.
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PMID:Alterations of glycosaminoglycans in human liver and kidney tumors. 213 May 24


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