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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insulin receptors of Fao hepatoma cells were labelled with a 125I-labelled photoreactive insulin analogue or by surface iodination catalysed by lactoperoxidase. Cells were then incubated at 37 degrees C, and the cellular localization of the labelled receptors was assessed by limited exposure of intact cells to trypsin. The results show that: (1) photolabelled insulin-receptor complexes are internalized and recycled in Fao hepatoma cells; (2) the dynamics of photolabelled insulin receptors (internalization and recycling) is similar before and after down-regulation; (3) the unoccupied receptors labelled by surface iodination are internalized and recycled similarly to covalent insulin-receptor complexes; (4) insulin does not induce internalization of surface-iodinated insulin receptors. We conclude that internalization and recycling of insulin receptors are independent of receptor occupancy by insulin in Fao hepatoma cells.
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PMID:Internalization and recycling of insulin receptors in hepatoma cells. Absence of regulation by receptor occupancy. 638 54

Heparitinase [EC 4.2.2.8, heparitin sulfate lyase] was prepared from an extract of cultured cells of Flavobacterium heparinum. Purification of the enzyme was achieved by repeating the hydroxyapatite column chromatography. The enzyme was used to degrade heparan sulfate occurring on the surfaces of ascites hepatoma cells, AH 66. From the supernatant of the enzyme-treated cells, breakdown products from heparan sulfate could be detected by paper chromatography. The heparitinase was found to be more effective than trypsin in removing heparan sulfate from the cells. Furthermore, on analyzing glycosaminoglycans and glycopeptides from the enzyme-treated cells and control cells, it was concluded that heparan sulfate was exclusively present on the cell surface and accessible to the heparitinase whereas other cell surface complex carbohydrates remained intact.
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PMID:Degradative removal of heparan sulfate from the surface of an ascites hepatoma, AH 66, by heparitinase. 645 48

When their membrane proteins were labeled with 125I by lactoperoxidase, dividing hepatoma cells lost radioactivity to the medium in a biphasic manner (T1/2 = 16-26 h, greater than 40 h). Lysosomotropic weak bases, chloroquine, and NH4Cl inhibited the rapid phase by 59%. More than 50% of the radioactivity which accumulates in the media from dividing cells during the first 4 h after labeling was trichloroacetic acid-soluble, and was identified as iodotyrosine. Iodotyrosine release from labeled membrane proteins was 60-71% inhibited by lysosomotropic agents chloroquine and NH4Cl as well as the sodium-proton ionophore, monensin. The inhibitory effect of NH4Cl and monensin was reversible. Inhibitors of microtubule and microfilament function and transglutamination had no effect on release of iodotyrosine to the medium, but trypsin-like protease inhibitors, p-aminobenzamidine, tosyl-L-lysine/chloromethylketone, and phenylmethylsulfonyl fluoride, as well as the cathepsin B inhibitor, leupeptin, inhibited by 21-24%. Iodotyrosine release showed a biphasic Arrhenius plot with an activation energy of 17 kcal/mol above but 27 kcal/mol below 20 degrees C. These results indicate that cell membrane polypeptides require a temperature-limiting event as well as passage through an ion-sensitive compartment prior to their complete degradation to constituent amino acids. In contrast to other lysosomal-mediated events, however, iodinated membrane proteins of dividing cells are degraded in a manner insensitive to agents which disrupt the cytoskeleton.
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PMID:Degradation of surface-labeled hepatoma membrane polypeptides: effect of inhibitors. 648 99

1. Plasma membranes from rat liver or kidney inhibited the growth of hepatoma (AH-130) cells in vitro. AH-130 plasma membranes or erythrocyte ghosts inhibited the growth of AH-130 cells less effectively. The inhibitory activity of liver plasma membranes was lost by heat treatment, or mild protease (papain or bromelin, but not trypsin or pronase) treatment, whereas it was retained after sialidase treatment of delipidation by ethanol/ether. 2. Proteoglycan (proteoheparan sulfate) prepared from liver plasma membranes inhibited the growth of AH-130 cells, but heparan sulfate was less active. The inhibitory activity of liver plasma membranes seemed, however, not to be ascribable solely to proteoheparan sulfate associated with plasma membranes. 3. Preliminary investigation suggested that the molecular weight 40 000 component may be a major inhibitory principle in liver plasma membranes.
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PMID:Liver plasma membranes and proteoglycan prepared therefrom inhibit the growth of hepatoma cells in vitro. 702 39

We have found that a murine hepatoma displays a considerable phenotypic diversification in culture, which depends upon the substratum utilized, and is manifested by the formation of multicellular structures of differing geometry: Monolayer on glass and plastic, thick multilayer pads on Gelfilm, and spheroids on agar and agarose. These multicellular morphological phenotypes were assayed without disruption to ascertain their antigenicity in vitro and their tumorigenicity in vivo and to obtain quantitative information on the effect of the spatial arrangement of the hepatoma cells upon the ability of each multicellular structure to interact, as a whole, with molecules and cells in its surroundings. The antigenicity of the multicellular structures was determined with calibrated probes and a methodology that measures the total antigenicity, as well as antigenicity per unit of surface area. Antigenicity was found to differ in the following decreasing order: Monolayer on plastic greater than spheroids on agarose greater than spheroids on agar greater than multilayer on Gelfilm. At least part of these antigenic variants arise from different degrees of masking of the structures' surface determinants by a trypsin-sensitive material. The multicellular phenotypes also differed in tumorigenicity. When assayed in syngeneic hosts under comparable conditions, agar-grown spheroids produced the fewest tumors, whereas Gelfilm-grown multilayers produced the most. These two independent sets of data show that the various geometries that a tumor tissue is induced to acquire by the culture substratum are accompanied by a distinctive combination of surface and biological properties.
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PMID:Phenotypic diversification of a cultured tumor line as a function of substratum. 702 95

A major cell surface sialoglycoprotein with Concanavalin A receptor activity has been isolated from rat Zajdela ascites hepatoma cells. The sialic acid residues of the plasma membrane glycoproteins were specifically labeled by oxidation and NaIO4 followed by reduction with NaB3H4. Surface-labeled glycoproteins were released by short incubations with TPCK-trypsin at 37 degrees C and then separated by gel filtration on Sepharose 6B column. The predominantly labeled fraction, GP II2, was then purified by chromatography on DEAE-cellulose equilibrated with 0.05 M phosphate buffer, pH 7.5, and eluted with increasing molarities of NaCl. It was shown to be homogeneous by protein and carbohydrate staining on SDS-polyacrylamide gels, isoelectric focusing, rechromatography on DEAE-cellulose and immunoelectrophoresis. It has an apparent molecular weight of 110,000 daltons. The location of GP II2 on the cell surface was confirmed by the fact that it could be labeled metabolically with D-(3H) glucosamine and externally through the nonpenetrating periodate-NaB3H4 system. GP II2 could not be removed from the cell surface by high salt concentrations, chelator, or chaotropic agents but was released from the membrane by detergents. This suggests that GP II2 could be an integral protein. Analysis of the carbohydrate composition of GP II2 revealed galactose, N-acetylglucosamine, N-acetylgalactosamine, and sialic acid as major constituents and mannose as a minor one. This suggests that it contains carbohydrate chains both O- and N-linked to the polypeptide chain, most of them being O-linked. Finally, GP II2 has a potent Concanavalin A receptor activity. It inhibits the interaction between Concanavalin A and hepatoma cells and suppresses its effects on hepatoma cell proliferation.
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PMID:Purification and characterization of a major cell surface glycoprotein in Zajdela ascites hepatoma cells which displays a potent concanavalin A receptor activity. 706 81

The complement-dependent cytotoxicity of antibodies in tumour-bearer serum (TBS) from rats carrying the chemically induced D23 hepatoma was investigated. Target cells were D23 cells from solid tumours (D23sol), from ascites tumours (D23asc), or from in vitro growing cell cultures (D23cc). The D23asc and D23cc cells were not lysed when used as target cells in the assay, although they evoke cytotoxic antibodies when growing in vivo. The D23 ascites cells became susceptible to complement-dependent lysis after trypsin treatment. This was, however, not due to unmasking of target antigens, since untreated D23 ascites cells absorbed cytotoxic antibodies as efficiently as trypsinized cells. No increase in susceptibility to complement-dependent lysis was observed after trypsin treatment of D23cc cells. Absorption of cytotoxic antibodies with D23cc cells showed no or very low antigen expression on the surface of these cells. They did, however, contain the antigen(s), since 3 M KCl extracts of the D23cc cells could inhibit the complement-dependent cytotoxicity of D23sol TBS against D23sol cells. From these data it was concluded that the susceptibility of hepatoma cells for antibody-mediated complement lysis is not only correlated with antigen expression, as was the case with the in-vitro-cultivated cells, but is also dependent on increased lytic susceptibility after trypsin treatment of the cells.
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PMID:Cytotoxicity of tumour-bearer serum to D23 hepatoma cells derived from solid tumours, ascites or in vitro cultures. 708 87

Using the principle of relief of self-quenching of carboxyfluorescein [Weinstein, J. N., Yoshikami, S., Henkart, P., Blumenthal, R., & Hagins, W. A. (1977) Science 195, 489-492] upon leakage of the dye from the interior of lipid vesicles, we investigated the integrity of sonicated small unilamellar vesicles in the presence of isolated hepatocytes, Zajdela ascites hepatoma cells, and plasma membranes of either cell type. We observed that cells as well as plasma membranes induce leakage of carboxyfluorescein from vesicles. Two parameters (initial rate and maximal level of induced leakage) were determined to quantitate the leakage events and were found to depend on cell density, vesicle concentration, and vesicle lipid composition. The magnitude of both parameters is shown to increase with cell density and to decrease with increasing vesicle lipid concentration and seems to be proportional to the number of vesicles found in close contact with the cell. For vesicles made of phosphatidylcholine and cholesterol, the degree of induced leakage increases steeply with cholesterol contents increasing from 30 to 40 mol %. In the case of simultaneous presence of 10 mol % phosphatidylserine, induced leakage can be observed at cholesterol contents exceeding 20 mol %. We show that leak-inducing activity resides in the plasma membrane and that it can be considerably reduced by treatment of the plasma membranes with neuraminidase or trypsin, suggesting the involvement of cell-surface glycoprotein(s). Release of activity from intact cells and isolated plasma membranes into the medium occurs spontaneously (at a slow rate) but can be facilitated by freezing and thawing; the activity can subsequently be recovered in a soluble form from the medium.
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PMID:Cell-induced leakage of liposome contents. 721 93

A protein showing lower electrophoretic mobility in acidic urea polyacrylamide gels than did the usual histone H1 subfractions has been detected among the H1 histones extracted from chromatin of a transplantable hamster hepatoma, originally induced by Kirkman and Robbins. It was proved to be a true H1 histone subfraction. It differs from the remaining ones by the total chain length, amino acid composition, and isoelectric point value. It is not a phosphorylated or phosphoribosylated metabolic form of another subfraction. Its proteolytic degradation products (obtained by thrombin and trypsin digestion) closely resembled those obtained from other H1 subfractions. The investigated hepatoma seems to provide an interesting model of neoplastic cells showing a distinct difference in histone composition from the homologous normal tissue.
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PMID:A low-electrophoretic-mobility H1 histone subfraction from Kirkman-Robbins hamster hepatoma. 723 41

1. The inactivation of cytosol enzymes in liver extracts was carried out by several subcellular fractions, with plasma membranes having the highest specific activity. Rough and smooth microsomal fractions were both active, whereas lysosmal inactivation capacity appeared to be derived entirely from contaminating plasma-membrane fragments. 2. Inactivation capacity in liver fractions was derived from parenchymal cells. Of the non-liver cells tested, plasma membranes from H35 hepatoma cells were able to inactivate glucose 6-phosphate dehydrogenase (EC 1.1.1.49), adipocyte "ghosts" showed slight activity and erythrocyte and reticulocyte "ghosts" were inactive. 3. Liposomes prepared from pure lipids with net negative, positive or neutral charge did not possess inactivation capacity. 4. Liver plasma-membrane inactivation capacity was destroyed by heating at 50 degrees C. 5. Inactivation factor solubilized from membranes by trypsin plus Triton X-100 treatment was partially purified by (NH4)2SO4 fractionation, gel filtration, ion-exchange chromatography and hydroxyapatite chromatography. 6. Partially purified inactivation factor analysed by gel electrophoresis gave a major protein band that co-migrated with capacity for inactivation of glucose 6-phosphate dehydrogenase. 7. It is concluded that inactivation factor is a membrane protein whose intracellular distribution and other properties are consistent with a possible role for this activity in the initial step of protein degradation.
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PMID:Distribution and partial purification of a liver membrane protein capable of inactivating cytosol enzymes. 737 65


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