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

Tumor-specific antigen was extracted with 3 M KCl from line-10 guinea pig hepatoma cells. The yield of antigenic activity, estimated by production of delayed cutaneous hypersensitivity reactions in line-10 immune guinea pigs, was 10-30% of the antigen present in intact cells. By ultracentrifugation criteria, the extracted antigen was soluble. Gel filtration, ion exchange chromatography, and salting-out studies showed that the antigen was heterogeneous in size and net charge. The possibility that 3 M KCl extracted a homogeneous population of molecules associating into polymers of various sizes at low ionic strength was ruled out by heterogeneity on Sephadex G-200 chromatography at high ionic strength. After osmotic lysis of sucrose-loaded line-10 cells, whole plasma membranes or large membrane fragments were obtained in a yield of about 20%. The isolation procedure did not cause detectable loss of membrane antigenic activity. The membranes had 33 skin test U/mg membrane protein, compared to the intact cell value of 1.7 skin test U/mg cell protein. Extracts of plasma membranes had 10-20% of the antigenic activity of the starting membrane material. In contrast to the wide variety of proteins liberated from intact cells, much of the protein extracted from the membranes was in the molecular weight range above 250,000.
 ...
PMID:Extraction of tumor-specific antigen from cells and plasma membranes of line-10 hepatoma. 16 67

1. Mitochondrial and microsomal fractions were prepared from normal rat liver and the Morris 7777 hepatoma and characterized by the use of the marker enzymes, succinate dehydrogenase and rotenone-insensitive NADPH-cytochrome c reductase. 2. The phospholipid content per mg membrane protein of Morris 7777 hepatoma mitochondria was increased by 75% as compared with mitochondria from normal rat liver. Microsomes from this poorly-differentiated tumor were found to have a 45% decrease in the content of phospholipid. These abnormalities were independent of tumor size or age. 3. The percent phospholipid content of the subcellular fractions was determined, and revealed an increase in the percent sphingomyelin in both the microsomal and mitochondrial fractions of the tumor. Decreases in the percent phosphatidylcholine and phosphatidylethanolamine were noted in tumor microsomes as compared with normal liver. Diphosphatidylglycerol was not found in significant quantities in the microsomal fraction of this hepatoma line. 4. The content of the various phospholipid classes per mg protein in the respective mitochondrial and microsomal fractions was determined. Large increases in nearly all the major phospholipid classes were found in tumor mitochondria; tumor microsomes were characterized by an increased content of sphingomyelin but the content of nearly all other phospholipids was significantly decreased. These findings suggest the presence of disturbances in the regulation of phospholipid metabolism in subcellular organelle membranes of the Morris 7777 hepatoma.
 ...
PMID:Abnormal membrane phospholipid content in subcellular fractions from the Morris 7777 hepatoma. 18 53

Concentrations of trypsin that bring about aggregation of hepatoma tissue culture (HTC) cells also release from the cell surface an Mr = 55,000 glycopeptide fragment. This glycopeptide fragment also accumulates in the medium, including serum-free medium, as a normal consequence of membrane protein turnover. The trypsin-released glycopeptide is labeled when cells are grown in the presence of fucose or leucine before treatment of the cells with the protease. Similarly, the glycopeptide fragment can be labeled by reacting cells in situ by lactoperoxidase-catalyzed radioiodination or by tritiated borohydride reduction of cells treated first with neuraminidase and galactose oxidase. The tryptic glycopeptide fragment was purified by concanavalin A-Sepharose chromatography, and hydroxyapatite chromatography in the presence of dodecyl sulfate. The amino acid and carbohydrate composition was determined, as was the sensitivity of the purified glycopeptide to a variety of endo- and exoglycosidases. The purified glycopeptide contains an average of 17 sialic acid residues and hence, shows charge heterogeneity after electrophoresis in isoelectric focusing gels. The charge heterogeneity can be eliminated completely by treatment with neuraminidase. The glycopeptide after this treatment is homogeneous. The trypsin-sensitive membrane glycoprotein which is the source of the Mr = 55,000 glycopeptide was identified by two-dimensional gel electrophoretic analysis of labeled cells, treated or not treated with trypsin. This glycoprotein, which has an apparent molecular weight of 85,000 and forms a homodimer in the presence of calcium ions, was purified and its identity as the parent of the Mr = 55,000 glycopeptide was confirmed by showing that the same Mr = 55,000 fragment was released by trypsin from the purified glycoprotein as was released from the intact cells.
 ...
PMID:Effect of trypsin on the cell surface proteins of hepatoma tissue culture cells. Characterization of a carbohydrate-rich glycopeptide released from a calcium binding membrane glycoprotein. 43 68

We investigated biosynthesis, intracellular transport and release of beta-galactoside alpha-2,6-sialyltransferase in a dexamethasone-inducible rat hepatoma cell line. Confluent cells were induced by 10 microM dexamethasone for 24 h, and metabolically labelled with [35S]methionine/cysteine, followed by immunoprecipitation of sialyltransferase and electrophoretic/fluorographic analysis. The 35S-labelled enzyme was synthesized as a 46-kDa precursor, converted to an intermediate 47-kDa form after 1 h, and gradually to a mature form of 48 kDa within the following 3 h. By means of either tunicamycin inhibition of N-glycosylation or cleavage of N-glycans from isolated sialyltransferase using N-glycosidase F, the sizes of the precursor and the mature form were reduced to 41 kDa and 43 kDa, respectively. After a 4-h chase, treatment with endoglycosidase H revealed two distinct molecular forms of sialyltransferase, bearing either two N-acetyllactosamine-type or one oligomannose-type and one N-acetyllactosamine-type N-linked sugar chain. In addition, sialyltransferase became sensitive to neuraminidase digestion after a 4-h chase. The half-life of intracellular [35S]sialyltransferase was estimated at 3 h. A soluble form was detectable in the supernatant, 2 h after the pulse. Only 12% of the initially labelled sialyltransferase was found in the medium after 12 h, while 73% of the enzyme was degraded intracellularly. To characterize a possible intracellular degradation site, we studied intracellular transport in the presence of either secretion-blocking or acidotropic agents or protease inhibitors. Degradation was significantly delayed by all treatments. Our results show that sialyltransferase follows the secretory pathway as a membrane protein and is retained at a late Golgi stage. We suggest that the bulk of sialyltransferase in rat hepatoma cells is diverted to a post-Golgi degradation pathway. This route contrasts with the post-Golgi trafficking of beta-1,4-galactosyltransferase in HeLa cells, which is constitutively secreted [Strous, G. J. A. M. & Berger, E. G. (1982) J. Biol. Chem. 257, 7623-7628].
 ...
PMID:Biosynthesis and intracellular transport of alpha-2,6-sialyltransferase in rat hepatoma cells. 152 30

The in vitro and in vivo growth of Con8 cells, a single cell-derived subclone of the 13762NF-transplantable rat mammary adenocarcinoma, is strongly suppressed by glucocorticoid hormones. Hybrids were formed between glucocorticoid-suppressible Con8.hD6 mammary tumor cells (Con8 transfected with the histidinol dehydrogenase selectable marker) and either glucocorticoid-resistant 8RUV7 mammary tumor cells (derived from Con8) or MCT-HTC rat hepatoma cells. Both of the glucocorticoid-resistant 8RUV7 and MCT-HTC fusion partners express functional glucocorticoid receptors, since hormone-responsive genes such as plasminogen activator inhibitor are fully dexamethasone inducible. Karyotypic analyses revealed that the hybrid cell populations possessed the appropriate number of chromosomes for a fusion between the glucocorticoid-suppressible and either of the two resistant cell types. Moreover, Northern blots showed that the intertissue hybrids expressed transcripts for both the milk fat globule membrane protein gene originating from the parental Con8.hD6 mammary tumor cells as well as mouse mammary tumor virus glycoprotein sequences which had been transfected into the MCT-HTC hepatoma cells as a molecular tag. Analysis of DNA content and [3H]thymidine incorporation demonstrated that growth of both the intratissue (Con8.hD6 x 8RUV7) and intertissue (Con8.hD6 x MCT-HTC) hybrids was glucocorticoid suppressible, even though the absolute rates of proliferation differed depending on the parental cells. Analysis of conditioned medium isolated from glucocorticoid-treated and untreated Con8.hD6 cells indicated that the growth suppression response is not mediated through the elaboration of an extracellular growth inhibitor. Taken together, our results demonstrate that the glucocorticoid-suppressible phenotype of Con8 rat mammary tumor cells is dominant, suggesting the existence of intracellular regulatory factors under glucocorticoid control that may function as trans-acting suppressors of tumor cell growth.
 ...
PMID:Glucocorticoid growth suppression response in 13762NF adenocarcinoma-derived Con8 rat mammary tumor cells is mediated by dominant trans-acting factors. 193 66

A large number of hepatoma cell lines has been used to study expression and regulation of liver-specific function. However these cells, even the most differentiated, are morphologically far from hepatocytes. In no case is the typical hepatocyte cell polarity well maintained. Cell hybridization has been used as a potential means for turning on specific genes. From hybrids between well differentiated Fao rat hepatoma cells and WI 38 human fibroblasts, we have attempted to isolate segregated cells that are highly differentiated and polarized. Such cells, detected in aged cultures of only one hybrid (WIF12), were isolated by subcloning. One subclone, WIF12-1 was analyzed. Expression of liver-specific functions extinguished in the original hybrid is restored in all WIF12-1 cells at a very high level, similar to that of hepatocytes and 5-30 times higher that that of parental cells. Moreover human genes coding for liver-specific proteins (albumin, fibrinogen, and alcohol dehydrogenase) are actively expressed. WIF12-1 cells have acquired a polarized phenotype as attested by the presence of bile canaliculi between adjacent cells and by the asymmetrical localization of apical (Mg(2+)-ATPase, gamma-glutamyl transpeptidase) and basolateral membrane markers. The bile canaliculi formed are dynamic and functional structures, characterized by long periods of expansion followed by rapid contractions. The ability to polarize is a general and permanent property of WIF12-1 cells. These cells appear to constitute a valid model for the in vitro study of hepatocyte cell polarity, membrane domain formation and mechanisms of membrane protein sorting.
 ...
PMID:Hybrid cell lines constitute a potential reservoir of polarized cells: isolation and study of highly differentiated hepatoma-derived hybrid cells able to form functional bile canaliculi in vitro. 195 80

The mechanism of glucose transported (GT) expression on the plasma membranes of hepatoma cells in rats induced by 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) was studied. Cytochalasin B binding to plasma membrane fractions from control and 3'-MeDAB group in the absence of cold cytochalasin B showed 9,825 +/- 925 and 30,165 +/- 625 dpm/mg membrane protein. Scatchard plot analysis showed that the GTs present on the plasma membrane fractions in control and 3'-Me DAB groups were 5.0 and 16.0 pmol/mg membrane protein and their Kd values were 151 and 157 nM, respectively. These results suggest that the numbers of GTs in plasma membrane were increased in the 3'-Me DAB group compared to the control group. In contrast, the amounts of GTs in low density microsomal (LDM) fractions measured by a photoaffinity labeling technique using [3H]-cytochalasin B were 31,207 and 11,702 dpm/mg protein in the control and 3'-Me DAB group, respectively. These results suggest that GTs were translocated from LDM to plasma membranes during carcinogenesis. To confirm these results by an independent method 10% SDS-polyacrylamide gel electrophoresis was carried out. Gel slice No. 13 corresponding to MW of 45 kDa from plasma membrane fractions showed increased radioactivities in the 3'-Me DAB group compared to the control group. However, LDM fractions of the 3'-Me DAB group showed decreased radioactivities compared to the control group. Western blot analysis using anti-human RBC GT antibody present in the plasma membranes and LDM fractions from control and 3'-Me DAB groups did not show any significant difference, indicating low cross-reactivity between them. These results indicate that increased glucose transport seems to be more likely due to reciprocal redistribution of GTs between plasma membrane and LDM fractions.
 ...
PMID:A study on the regulation of translocation of glucose transporters during hepatocarcinogenesis induced by 3'-Me DAB. 207 56

Cellular influx kinetics of 4-50 microM bilirubin diglucuronide and sulfobromophthalein (BSP) by the human hepatoma cell line Hep G2 was examined at 37 degrees C. In confluent monolayer cultures, cellular influx of increasing concentrations of conjugated bilirubin and BSP revealed similar saturation kinetics with Km values of 9.9 and 12.1 microM, and Vmax values of 0.512 and 0.473 nmol.mg cell protein-1.min-1, respectively. Uptake of [3H]bilirubin diglucuronide was competitively inhibited by unlabeled BSP, and was temperature dependent with maximal cellular influx rates at 37 degrees C. When the confluent monolayer cultures were pretreated with a monospecific antibody to the rat liver BSP/bilirubin binding membrane protein, initial uptake rates of conjugated and unconjugated bilirubin as well as of BSP were significantly inhibited, whereas uptake of oleate was not affected. Furthermore, immunoblot analysis of the homogenate of Hep G2 cells with the same antibody revealed predominant reactivity with a 55 kDa protein. These data suggest that cellular uptake of bilirubin and related cholephilic organic anions by the human hepatoma cell line Hep G2 is mediated by a specific 55 kDa membrane BSP/bilirubin binding protein.
 ...
PMID:Cellular uptake of conjugated bilirubin and sulfobromophthalein (BSP) by the human hepatoma cell line Hep G2 is mediated by a membrane BSP/bilirubin binding protein. 215 59

To examine the cellular mechanism responsible for impaired insulin action in ageing, we determined various in-vitro parameters involved in the pathogenesis of insulin resistance, i.e. basal and insulin-stimulated [14C]3-O-methylglucose transport (3OMG), 125I-labelled insulin binding, activation of insulin receptor kinase (IRKA) in intact cells, and number and subcellular distribution of glucose transporters in subcellular membrane fractions of adipocytes from 6- (FR-6) and 24- (FR-24) month-old Fischer rats. Ageing had no effect on basal 3OMG (12 +/- 4 vs 13 +/- 3 fmol/5 x 10(4) cells, means +/- S.E.M.); in contrast, in FR-24 rats insulin-stimulated 3OMG was markedly decreased by 43% when compared with that in FR-6 rats (158 +/- 14 vs 90 +/- 8 fmol/5 x 10(4) cells; P less than 0.01). Insulin binding to adipocytes from FR-6 rats was 2.40 +/- 0.38% compared with 2.28 +/- 0.47% in FR-24 (P not significant). Moreover, ageing had no significant effect on IRKA, as determined by insulin-stimulated (0, 1, 4 and 500 ng insulin/ml) 32P-incorporation into histone 2B. In subcellular membrane fractions, low density microsomes and plasma membranes, glucose transporter numbers were determined using [3H]cytochalasin B binding and immunodetection using an antiserum against the C-terminal peptide of the hepatoma-G2-glucose transporter. Cytochalasin B binding revealed that in the basal state the intracellular pool of glucose transporters was depleted in FR-24 by about 39% compared with low density microsomes from FR-6: (48.6 +/- 7.2 vs 29.8 +/- 5.5 pmol/mg membrane protein; P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Potential mechanism of insulin resistance in ageing: impaired insulin-stimulated glucose transport due to a depletion of the intracellular pool of glucose transporters in Fischer rat adipocytes. 216 28

The inner mitochondrial membranes from bovine heart, rat liver, and Morris hepatoma 7777 all bound the mitochondrial isozymes of aspartate aminotransferase and malate dehydrogenase with comparable affinities and binding ratios (mg of enzyme bound per mg of membrane protein). A low molecular weight fraction separated from a detergent extract of the heart membrane by chromatography on Sephacryl S-300 contained most of the binding activity of the extract for the aminotransferase and had a dissociation constant for the aminotransferase of 0.2 microM. The protein component of the membrane binding sites for the aminotransferase was apparently present in this fraction because binding activity was largely eliminated by proteolysis with trypsin. When this fraction was chromatographed on an aminotransferase affinity column, only the portion that was bound and eluted by 0.25 M KCl associated with added aminotransferase. Unlike the membrane, which was markedly inhibited by the non-ionic detergent Genapol but was inhibited only 20% by trypsin, the binding activity of this subfraction was completely inhibited by trypsin but not by Genapol. This suggests, on the membrane, that the aminotransferase binds to the binding protein and is then transferred to lipids specifically associated with the binding protein. These putative lipids are presumably removed on the affinity column. Although the yield of the binding protein was low, there is probably ample binding protein in mitochondria to accommodate the aminotransferase. In every case, binding of the aminotransferase to the membrane inactivated the malate dehydrogenase binding site whereas malate dehydrogenase had little effect on the binding of the aminotransferase and only associated with the higher molecular weight fractions from the Sephacryl column that contained Complex I activity. Inactivation of the malate dehydrogenase site by the aminotransferase, but not vice versa, could result from aminotransferase associating with the binding protein and malate dehydrogenase with Complex I followed by association of the enzymes with lipids located in the same region of the membrane. However, since aminotransferase is more cationic, it is not displaced readily from the lipids by malate dehydrogenase. The relevance of these interactions to the organization of the enzymes is discussed.
 ...
PMID:Interactions among mitochondrial aspartate aminotransferase, malate dehydrogenase, and the inner mitochondrial membrane from heart, hepatoma, and liver. 224 39


1 2 3 4 5 6 7 8 9 10 Next >>