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 specificity of protein labeling by an affinity label of glucocorticoid receptors, dexamethasone 21-mesylate (Dex-Mes), was investigated using bovine serum albumin (BSA) as a model. During the early stages of [3H]Dex-Mes labeling at pH 8.8, approximately 90% of the covalent bond formation occurred at the one non-oxidized cysteine (Cys-34) of BSA. The nonspecific labeling was equally distributed over the rest of the BSA molecule. [3H]Dex-Mes labeling of Cys-34 was totally, and specifically inhibited by nearly stoichiometric amounts of the thiol-specific reagent methyl methanethiolsulfonate (MMTS). Thus both Dex-Mes and MMTS appear to react very selectively with thiols under our conditions. In reactions with hepatoma tissue culture (HTC) cell glucocorticoid receptors, MMTS was equally efficient in preventing [3H]dexamethasone binding to receptors and [3H]Dex-Mes labeling of the 98-kDa receptor protein. These results indicate that Dex-Mes labeling of the glucocorticoid receptor involves covalent reaction with at least one cysteine in the steroid binding site of the receptor. Small (approximately 1600-dalton) fragments of the [3H]Dex-Mes-labeled 98-kDa receptor were generated by limit proteolysis with trypsin, chymotrypsin, and Staphylococcus aureus V8 protease under denaturing conditions. Data from these fragments on 15% sodium dodecyl sulfate-polyacrylamide gels were consistent with all of the covalent [3H] Dex-Mes being located on one or a few cysteines in one approximately 15-residue stretch of the receptor. Further studies revealed no differences in the limit protease digestion patterns of activated and unactivated [3H]Dex-Mes-labeled receptors with trypsin, chymotrypsin, or V8 protease under denaturing conditions. These data suggest that activation does not cause any major covalent modifications of the amino acids immediately surrounding the affinity-labeled cysteine(s) of the steroid binding site.
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PMID:Selective covalent labeling of cysteines in bovine serum albumin and in hepatoma tissue culture cell glucocorticoid receptors by dexamethasone 21-mesylate. 359 34

In order to elucidate the correlation between cell surface lectin binding sites and the degree of cell adhesiveness, quantitative lectin binding assays were performed using three types of rat ascites hepatoma cell lines (free cell, mixed cell, and island-forming cell types). The lectin binding site patterns showed no remarkable differences among the intact tumor cell lines, but treatment of the cells with L-1-tosylamide-2-phenylethyl chloromethyl ketone (TPCK)-trypsin or neuraminidase induced remarkable differences in the modulation of the number of lectin binding sites. TPCK-trypsin treatment caused a marked decrease in the number of peanut agglutinin binding sites on the island-forming and mixed cell types, concomitant with disaggregation of the cells, showing that trypsin sensitive binding sites are involved in the cell-cell adhesion. Neuraminidase treatment caused a decrease in wheat germ agglutinin binding sites and an increase in castor bean agglutinin binding sites, and these effects were greater for the free cell type. These results indicated that alpha-sialyl-beta-D-galactosyl residues are more abundant on the cell surface of the free cell type than the other cell types. Therefore, it was suggested that electrostatic repulsion due to negative charges of the cell surface sialic acid contributes to the low cell adhesiveness of the free cell type.
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PMID:Lectin binding sites related with rat ascites hepatoma cell adhesion. 382 89

Phosphorylation of the insulin receptor was studied in intact well differentiated hepatoma cells (Fao) and in a solubilized and partially purified receptor preparation obtained from these cells by affinity chromatography on wheat germ agglutinin agarose. Tryptic peptides containing the phosphorylation sites of the beta-subunit of the insulin receptor were analyzed by reverse-phase high performance liquid chromatography. Phosphoamino acid content of these peptides was determined by acid hydrolysis and high voltage electrophoresis. Separation of the phosphopeptides from unstimulated Fao cells revealed one major and two minor phosphoserine-containing peptides and a single minor phosphothreonine-containing peptide. Insulin (10(-7) M) increased the phosphorylation of the beta-subunit of the insulin receptor 3- to 4-fold in the intact Fao cell. After insulin stimulation, two phosphotyrosine-containing peptides were identified. Tyrosine phosphorylation reached a steady state within 20 s after the addition of insulin and remained nearly constant for 1 h. Under our experimental conditions, no significant change in the amount of [32P]phosphoserine or [32P]phosphothreonine associated with the beta-subunit was found during the initial response of cells to insulin. When the insulin receptor was extracted from the Fao cells and incubated in vitro with [gamma-32P]ATP and Mn2+, very little phosphorylation occurred in the absence of insulin. In this preparation, insulin rapidly stimulated autophosphorylation of the receptor on tyrosine residues only and high performance liquid chromatography analysis of the beta-subunit digested with trypsin revealed one minor and two major phosphopeptides. The elution position of the minor peptide corresponded to that of the major phosphotyrosine-containing peptide obtained from the beta-subunit of the insulin-stimulated receptor labeled in vivo. In contrast, the elution position of one of the major phosphopeptides that occurred during in vitro phosphorylation corresponded to the minor phosphotyrosine-containing peptide phosphorylated in vivo. The other major in vitro phosphotyrosine-containing peptide was not detected in vivo. Our results indicate that: tyrosine phosphorylation of the insulin receptor occurs rapidly following insulin binding to intact cells; the level of tyrosine phosphorylation remains constant for up to 1 h; the specificity of the receptor kinase or accessibility of the phosphorylation sites are different in vivo and in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Differences in the sites of phosphorylation of the insulin receptor in vivo and in vitro. 384 33

The degradation of insulin receptors was studied in cultured Zajdela hepatoma cells (ZHC). Receptor distribution within the cell was evaluated by estimating: i) surface receptor level on entire cells, ii) total cell receptors solubilized by Triton from cell membranes and iii) intracellular receptors solubilized from cells whose surface receptors had been inactivated with trypsin. In the absence of insulin, 80-90% of the insulin binding sites were located on the cell surface. When insulin was added, a rapid decrease of surface receptors was observed. After 2 h, their level was reduced nearly by half; this reduction was accounted for by an actual receptor loss from the cell without an increase in the intracellular pool. These results indicate that insulin enhanced the rate of receptor degradation within the cell. Basal receptor inactivation was studied by using tunicamycin which inhibits new receptor synthesis. The surface receptor number was decreased with a half-life of 7 h, while the level of internal sites remained unchanged. Both basal and insulin-activated receptor degradation were markedly slowed down by chloroquine or dansylcadaverine, indicating the importance of endocytic pathways in this process. Similarly, when de novo protein glycosylation was inhibited for 24 h by tunicamycin, both basal and insulin-activated receptor inactivation were precluded.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Degradation of insulin receptors by hepatoma cells: insulin-induced down-regulation results from an increase in the rate of basal receptor degradation. 390 17

Immunolocalization of type III procollagen (pro III) in normal and cirrhotic human liver was studied using rabbit antiserum specific for bovine type III procollagen aminopeptide. The material examined was deparaffinized, trypsin-treated hepatic tissue sections from 28 autopsy cases, including 19 cirrhotic and 9 normal liver donors. Immunostaining, performed by the unlabeled peroxidase-antiperoxidase antibody technique demonstrated that extracellular matrices corresponding to perisinusoidal reticulin, collagen in periportal areas, and blood vessel walls were the common sites of pro III antigenicity in both normal and cirrhotic liver. Moreover, in the cirrhotic liver, the fibrous septa of pseudolobules, and cytoplasm of hepatocytes and sinusoidal cells were positive when stained for pro III peptide. The differential counts of pro III positive cells in cirrhotic liver, however, revealed that the average ratio of these hepatocytes to sinusoidal cells was 25 to 1, indicating complete dominance of hepatocytes with respect to stainability for pro III peptide compared to sinusoidal cells. In hepatocellular carcinomas coexisting with cirrhosis, neoplastic cells also displayed pro III antigenicity. These data suggest that hepatocytes of cirrhotic liver and hepatocellular carcinoma cells play a significant role in type III collagen synthesis in vivo.
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PMID:Localization of type III procollagen aminopeptide antigenicity in hepatocytes from cirrhotic human liver. 393 61

The alpha-chain of the fourth component of complement (C4) contains tyrosine sulfate (Karp, D.R. (1983) J. Biol. Chem. 258, 12745-12748). Here we have determined the site and stoichiometry of sulfation of C4 secreted by the human hepatoma-derived cell line Hep G2. C4 was labeled with [35S]sulfate and isolated from culture medium by immunoprecipitation. C4 digested with trypsin and chymotrypsin and analyzed by reverse-phase high-performance liquid chromatography contained a single sulfate-labeled peptide. Digestion of C4 with trypsin alone yielded two major sulfate-labeled peptides, suggesting that there may be some sequence variability in C4 near the site of sulfation. Sequential Edman degradation of tryptic peptides labeled with [3H]tyrosine and [35S]sulfate detected tyrosine residues at positions 5, 13, 16, and 18. Chymotrypsin cleaved 5 residues off the NH2-terminal end of tryptic peptides, yielding a peptide with tyrosine at positions 8, 11, and 13. Comparison of the position of tyrosine residues with the reported sequence of C4 identified the sites of sulfation as tyrosine residues at positions 738, 741, and 743 in the alpha-chain of C4. All 3 of these tyrosine residues appeared to be sulfated. When sulfation of C4 was partially inhibited by addition of catechol to culture medium, three different forms of the peptide were resolved by high-performance liquid chromatography, consistent with peptides containing 1, 2, or 3 sulfates. Comparison of the quantities of tyrosine and tyrosine sulfate in C4 which had been labeled with [3H]tyrosine and digested with Pronase also indicated that C4 contained an average of 2-3 residues of tyrosine sulfate/molecule. These results suggest that the biologically active form of the protein is sulfated.
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PMID:Identification of the site of sulfation of the fourth component of human complement. 394 9

In primary monolayer cultures of mature rat hepatocytes, cell growth and hepatocyte-specific functions were mediated by a cell surface component (named the cell surface modulator) via cell-cell contact. The modulator activity was heat-labile and trypsin-sensitive. Activity was also found in plasma membranes from kidney, brain, lung, and erythrocytes. The modulator was solubilized by 4% octylglucoside plus 4M guanidine HCl from liver membranes. The molecular weight of the modulator was 670KD determined by Sephacryl S-400 gel filtration. Hepatoma cells established from Reuber and Morris hepatoma did not show any cell density-dependency on either cell growth or hepatocyte-specific function. However, these hepatoma cells had strong cell surface modulator activity. These results suggest that hepatoma cells have lost their cell density-dependent regulation because they have lost the ability to respond to the cell surface modulator. Characterization of the cell surface modulator and its mechanism of transmitting a signal for gene regulation would be helpful in understanding the process by which cells assemble into tissues in vivo and the mechanism of changes in gene expression in tissue during development, regeneration and carcinogenesis.
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PMID:[Reciprocal regulation of growth and differentiation in hepatocytes by cell surface modulator and loss of regulation during carcinogenesis]. 398 39

The antiproteinase activities against trypsin, chymotrypsin, elastase, papain and rat leucocyte proteinases were determined in plasma from control and Morris hepatoma-bearing rats. Bovine trypsin and chymotrypsin were similarly inhibited by the two types of plasma whereas porcine pancreatic elastase, papain and rat leucocyte neutral proteinases were more efficiently inhibited by plasma from tumour-bearing rats. The increased plasma concentrations of some proteinase inhibitors, as determined by rocket immunoelectrophoresis, are suggested to be responsible for the observed differences in inhibition. The highest increases in plasma of tumour-bearing rats were observed for alpha 2-macroglobulin and alpha 1-acute-phase globulin. The synthesis and secretion of six proteinase inhibitors: antithrombin III, alpha 1-proteinase inhibitor, alpha 1-macroglobulin, alpha 2-macroglobulin, alpha 1-acute-phase globulin and haptoglobin, as well as albumin, were measured in tissue slices from rat liver and Morris hepatoma after incubation with [14C]leucine. Local inflammation inflicted upon the tumour-bearing rats increased formation of acute-phase proteins in liver slices but not in hepatoma slices.
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PMID:Plasma proteinase inhibitors in Morris hepatoma-bearing rats: changes in the blood level and synthesis in tissue slices. 407 27

Tightly coupled mitochondria from the well-differentiated hepatoma 7800 failed to exhibit a significant 2,4-dinitrophenol-activated ATPase activity at concentrations of uncoupler sufficient to completely inhibit oxidative phosphorylation. ATPase activity could not be maximally activated by uncoupling agents more potent than 2,4-dinitrophenol, such as carbonylcyanide p-trifluoromethoxyphenylhydrazone and 5-chloro, 3-tert-butyl, 2'-chloro, 4'-nitrosalicylanilide, nor by Mg(++) after the following treatments: sonication, freezing, detergent lysis, and digestion with trypsin. Gel electrophoresis patterns of the membrane proteins of the hepatome mitochondria revealed neither an absence of any one of the three different types of ATPase subunits characteristic of the homogeneous enzyme purified from normal liver mitochondria, nor a deficiency of the oligomeric molecule. Taken together, these data strongly suggest that the supramolecular structure of the membrane ATPase complex of mitochondria from hepatoma 7800 is altered in such a way that its capacity for ATP hydrolysis is severely diminished.
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PMID:Deficiency of uncoupler-stimulated adenosine triphosphatase activity in tightly coupled hepatoma mitochondria. 432 1

Trypsin treatment, which is frequently used in the field of immunocytochemistry to faciliate conjugated antibody penetration through the cell membrane, was applied for the immunoradiographic demonstration of alpha-fetoprotein in ascites hepatoma cells using 125I-labeled anti rat alpha-fetoprotein antibody. No significant number of silver grains were detectable in the group without trypsin treatment, while numerous silver grains were recognizable in the ascites hepatoma cells after trypsin treatment. This indicates that trypsin treatment is effective for the immunoradiographic demonstration of alpha-fetoprotein and contributes to the quantitative immunoradioautographic investigation.
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PMID:Immunoradioautographic study of alpha-fetoprotein in hepatoma cells. 615 5


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