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)

Amino acid starvation causes an adaptive increase in the initial rate of transport of selected neutral amino acids in an established line of rat hepatoma cells in tissue culture. After a lag of 30 min, the initial rate of transport of alpha-aminoisobutyric acid (AIB) increases to a maximum after 4 to 6 h starvation of 2 to 3 times that seen in control cells. The increased rate of transport is accompanied by an increase in the Vmax and a modest decrease in the Km for this transport system, and is reversed by readdition of amino acids. The enhancement is specific for amino acids transported by the A or alanine-preferring system (AIB, glycine, proline); uptake of amino acids transported by the L or leucine-preferring system (threonine, phenylalanine, tyrosine, leucine) or the Ly+ system for dibasci amino acids (lysine) is decreased under these conditions. Amino acids which compete with AIB for transport also prevent the starvation-induced increase in AIB transport; amino acids which do not compete fail to prevent the enhancement. Paradoxically threonine, phenylalanine, tryptophan, and tyrosine, which do not compete with AIB for transport, block the enhancement of transport upon amino acid starvation. The starvation-induced enhancement of amino acid transport does not appear to be the result of a release from transinhibition. After 30 min of amino acid starvation, AIB transport is either unchanged or slightly decreased even though amino acid pools are already depleted. Furthermore, loading cells with high concentrations of a single amino acid following a period of amino acid starvation fails to prevent the enhancement of AIB transport, whereas incubation of the cells with the single amino acid for the entire duration of amino acid starvation prevents the enhancement; intracellular amino acid pools are similar under both conditions. The enhancement of amino acid transport requires concomitant RNA and protein synthesis, consistent with the view that the adaptive increase reflects an increased amount of a rate-limiting protein involved in the transport process. Dexamethasone, which dramatically inhibits AIB transport in cells incubated in amino acid-containing medium, both blocks the starvation-induced increase in AIB transport, and causes a time-dependent decrease in transport velocity in cells whose transport has previously been enhanced by starvation.
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PMID:Derepression of amino acid transport by amino acid starvation in rat hepatoma cells. 1 7

AH-66 rat ascites hepatoma cells incorporated [14C]leucine into the AFP fraction. In a cell-free system, hepatoma ribosomes were found to be active in AFP synthesis whereas the supernatant fraction from hepatoma had no specific effect on AFP production. The amount of [14C]leucine incorporated in AFP by membrane-bound polysomes was 20 to 90 times higher than that by free polysomes, suggesting that AFP is mainly synthesized on membrane-bound polysomes. DBcAMP inhibited the growth of hepatoma cells. However, the incorporation of [14C]leucine into the AFP fraction as well as into total proteins was stimulated by DBcAMP.
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PMID:Synthesis of alpha-fetoprotein by rat ascites hepatoma cells. 5 30

Five monkeys were treated ip with N-nitrosodiethylamine (DENA), and one was treated with 1-nitrosopiperidine (PIP), starting within 2 months of birth, until hepatocellular carcinoma (HCC) developed. All animals except the PIP-treated monkey had much elevated serum alpha-fetoprotein (AFP) values. Fresh, minced, biopsy-derived tumor was cultured with L-[14C]leucine and L-[14C]lysine. Synthesis of AFP was determined by radioimmunoassay and by specifically precipitable [14C]AFP. Good agreement between these two parameters was obtained for the 4 DENA-induced tumors synthesizing AFP in culture. Tumor from 1 DENA-treated monkey did not synthesize AFP. In addition, neither normal liver nor tumor from the PIP-treated monkey showed AFP synthesis. Rates of synthesis were 0.37-5.50 ng AFP/mg tumor/day, or 0.0012-0.0183 pg AFP/cell/day (if one assumes 3.0 X 10(5) cells/mg tissue) over 48 or 72 hours. Different nodules from the same animal had similar rates of synthesis. For tumors that synthesized AFP in culture, a positive correlation was generally found between rate of synthesis and serum AFP level. The rate of in vitro AFP synthesis observed was lower than that of immunoglobulin synthesis in human myeloma or of AFP synthesis in a rat HCC, but it was close to the estimated rate of AFP synthesis in a monkey HCC line in long-term culture.
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PMID:In vitro alpha-fetoprotein synthesis by monkey hepatocellular carcinoma. 7 69

The present report is a continuation of our previous studies on the observations of macromolecule precursors incorporated into the liver of newborn (1-10 days), infant (11-21 days) and young adult (41-50 days) old mice C57BLfemale X C3Hmale Fl and 3-hour interval circadian rhythm in livers of 15 day-old mice. 3H thymidine, 3H uridine and 3H leucine were used for studying incorporation into the macromolecules. DNA, RNA and protein were prepared by a modified Kirby's procedure. The data obtained indicate fluctuation of DNA activity approximately at 5-day intervals with a decreasing tendency up to 50 days of age. In 15-day-old mice, the peak of synthetic DNA activity was observed at 9.00 a.m. and the lowest values were found the next day at 6.00 a.m. Our results should provide fundamental data from which it would be possible to speculate whether the hepatocarcinogenic effect of different compounds with or without a special affinity to induce hepatoma may be correlated to different macromolecular synthetic activity.
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PMID:Inter and intra diurnal variations of DNA, RNA and protein synthetic activity in newborn, infant and young adult mouse livers. 13 83

The effect of a serum factor purified from normal rat serum on growth and incorporation of 3-H-thymidine and 3-H-leucine was investigated with the use of 3T3 and L cells. The factor was not present in serum of hepatoma-bearing animals at a time when the weight of the hepatomas was equal to or greater than liver weight. The factor disappeared gradually from the serum of hepatoma-bearing animals, and the disappearance was proportional to the increase in the size of the hepatomas. Diminished amounts of the factor could be detected as early as 10 days after hepatoma transplant, and the factor was absent at 30 days after hepatoma transplant from the serum of rats bearing hepatoma 7777. Medium supplemented with 5% normal rat serum supported incorporation of lavel into 3T3 and L cells and growth of these cells, as did medium supplemented with 10% calf serum. Serum from hepatoma-bearing animals was only approximately equal to 50% as efficient as normal rat serum in supporting growth and label incorporation. The addition of purified factor to the serum from hepatoma-bearing animals restored the ability of the serum to support growth and label incorporation to between 70 and 90% of that found with normal rat serum as a medium supplement. The factor also enhanced incorporation of 3-H-thymidine following release of 3T3 cells from contact inhibition.
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PMID:Effect of a normal serum protein absent from hepatoma-bearing animals on cell cultures. 16 13

1. Reuber H35 hepatoma cells incorporate the arginine analogue canavanine into cell protein when arginine is omitted from the incubation medium. 2. By labelling arginine-containing proteins with (14-C)leucine and then canavanine-containing proteins with (3-H)leucine in the same cells, it is possible to measure the degradation of both types of protein during a subsequent 'chase' period. With this technique it has been shown that canavanine-containing proteins are degraded at a rate severalfold greater than normal proteins. Comparable results were found when 6-fluorotryptophan was used as an analogue to tryptophan. 3. Control experiments in which the labelling order was reversed or where the animo acid and its analogue were incubated in separate cell cultures support the conclusion that abberrant proteins are rapidly degraded in vivo.
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PMID:Increased degradation rates of protein synthesized in hepatoma cells in the presence of amino acid analogues. 16 23

A cobalamin-binding protein has been purified by affinity chromatography from plasma of a patient with hepatoma and a 10,000-fold increase in the concentration of the plasma cobalamin-binding capacity. The protein behaved as normal transcobalamin I in gel filtration, agar gel electrophoresis, immunoelectrophoresis, precipitation by ammonium sulphate, and cobalamin-binding studies. The protein contained 38 per cent carbohydrate, and the relative molecular mass based on amino acid and carbohydrate analyses was 69,000. The molar absorption coefficient of cyanocobalamin bound to the protein was determined to be 36,000 at 362 nm. On amino acid sequencing, one amino terminal was found, and the first 13 residues were determined as Glu-Ile-Ser/Cys-Glu-Val-Ser/Cys-Glu-Glu-Asx-Tyr-Ile-Arg-Leu/Ile.
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PMID:Characterization of a cobalamin-binding plasma protein from a patient with hepatoma. 17 88

The turnover of the plasma membrane proteins of hepatoma tissue culture cells was examined by three different methods--loss of polypeptides labeled in situ by lactoperoxidase-catalyzed iodination, loss of membrane polypeptides labeled with amino acid precursors, and loss from the membrane of fucose-labeled polypeptides. In both logarithmically growing and density-inhibited cells the proteins of the membrane are degraded with a half-life of about 100 hours. This is longer than the half-life of total cell protein, 50 to 60 hours, and longer than the doubling time of the cells, about 30 hours. Similar values for the rate of degradation of the membrane proteins were obtained by each of the three techniques. The same fucose-labeled polypeptides are present in the microsomal and the plasma membrane fractions of hepatoma tissue culture cells as analyzed by electrophoresis in dodecyl sulfate-acrylamide gels. But the fucose-labeled polypeptides were lost from the microsomal fraction at a faster rate than from the plasma membrane. Autoradiographic and double labeling techniques using 125I and 131I, or [3H]leucine and [14C]leucine were used to measure the relative rates of degradation of the proteins in the plasma membrane. All of the leucine-labeled polypeptides and the iodinated polypeptides had similar rates of degradation. These results support a model for the biogenesis of the plasma membrane in which the proteins are incorporated and removed in large structural units.
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PMID:Turnover of the plasma membrane proteins of hepatoma tissue culture cells. 17 63

Ornithine decarboxylase has been induced in log phase hepatoma cells grown in suspension culture. Induction with N6, O2'-dibutyryl cyclic adenosine 3':5'-monophosphate produced a 4-fold increase in enzyme activity by 3 hours which was followed by a return to base levels by 6 hours. Induction with dexamethasone, a potent synthetic glucocorticoid, exhibited a slow steady rate of increase in enzyme activity, reaching a plateau level of approximately 5- to 6-fold stimulation by about 12 hours. Induced cell and regenerating rat liver ornithine decarboxylase were shown to be indistinguishable by titration with antibody monospecific to the latter and by heat stability. L-[14C]Leucine incorporation into immunoprecipitable enzyme protein after induction in vitro or partial hepatectomy showed an increase which, when coupled with the increase in enzymatic activity, indicated de novo synthesis of enzyme protein. Physiological concentrations of the naturally occurring polyamines, spermidine and spermine, abolish cyclic AMP induction whereas they have no effect on dexamethasone induction. Both inductions were abolished by cycloheximide; in contrast, inhibition by actinomycin D was complete for dexamethasone induction and only partial with respect to cyclic AMP induction. The different time pattern of induction seen with cyclic AMP and dexamethasone, the partial inhibition of the cyclic AMP induction seen with actinomycin D, as well as the absence of inhibition of the dexamethasone induction by polyamines, indicate that these inducers might affect different aspects of the control of the same enzyme.
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PMID:Stimulation of ornithine decarboxylase synthesis and its control by polyamines in regenerating rat liver and cultured rat hepatoma cells. 18 26

1. Rates of degradation of normal and abnormal protein were measured in hepatoma cells after labelling first for 16h with [14C]leucine plus L-arginine and then for 3h with [3H]-leucine plus the arginine analogue, L-canavanine. 2. Over the first 2h of the degradation period, canavanine-containing proteins were degraded at approximately 5 times the average degradation rate of normal proteins. 3. Degradation of normal proteins was inhibited by about 30% by insulin, cycloheximide, puromycin, leupeptin, antipain and foetal calf serum, whereas these agents had a negligible effect on the breakdown of canavanine-containing proteins. 4. Other compounds inhibited degradation of both classes of protein to equal extents. 5. Combination experiments showed no additional inhibitory effects on the degradation of normal proteins over degradation measured in the presence of a single selective inhibitor. 6. In contrast with the results with a 16 h labelling period, the degradation of normal proteins labelled for only 3 h was not inhibited by insulin. 7. These results are explained by a model with two distinct pathways of protein turnover. The first of these pathways involves the formation of autophagic vacuoles and would be completely inhibited by each of the selective inhibitors. Normal and canavanine-containing proteins would be catabolized by this pathway at equal rates. We propose that degradation by a second pathway is not regulated by the agents tested, but by the inherent stability of each protein.
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PMID:Selective control of the degradation of normal and aberrant proteins in Reuber H35 hepatoma cells. 18 57


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