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)

Glutamine synthetase (EC 6.3.1.2) activity of hepatoma tissue culture cells is elevated by corticosteroids and depressed by glutamine (Kulka, R.G., Tomkins, G.M. and Crook, R.B. (1972) J. Cell Biol., 54, 175--179). The transfer of cells from high (1--5 mM) to low (0.2--0.4 mM) concentrations of glutamine causes a marked increase in glutamine synthetase activity. The addition of a glutamine antagonist, methionine sulfone (1 mM) to cells suspended in high (1 mM) concentrations of glutamine also causes an increase of glutamine synthetase activity which is greater than that elicited by the transfer of cells to low concentrations of glutamine. Rates of synthesis of glutamine synthetase have been measured by radioimmunoprecipitation in hepatoma tissue culture cells incubated under various conditions. Incubation of cells with the synthetic corticosteroid hormone, dexamethasone, markedly stimulates the relative rate of glutamine synthetase biosynthesis. Glutamine, or its analogue, methionine sulfone, have no effect on the relative rate of synthesis of the enzyme. However, total protein and RNA synthesis increase markedly with increasing external glutamine concentration in the range 0--1 mM. Methionine sulfone (1 mM) inhibits the degradation of glutamine synthetase in the presence of 1 mM glutamine. The data are consistent with the conclusion that the corticosteroid, dexamethasone, elevates glutamine synthetase activity by stimulating its rate of synthesis, whereas methionine sulfone elevates glutamine synthetase activity by inhibiting the glutamine-stimulated degradation of preformed enzyme.
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PMID:Effects of glutamine, methionine sulfone and dexamethasone on rates of synthesis of glutamine synthetase in cultured hepatoma cells. 3 Nov 91

In studies in this and other laboratories, induction of hepatocardinoma by several different chemical carcinogens was enhanced in rats fed diets deficient in lipotropes (choline, methionine, folic acid), amino acids, and niacin, and high in fat. In some cases, specific supplementation with lipotropes blocked carcinogenesis. In studies reported here, specific supplementation of a marginally deficient diet that enhanced carcinogenesis in rats, with the amino acids or lipotropes in which it was deficient, significantly decreased induction of hepatocarcinoma by N-nitrosodiethylamine. Niacin supplementation decreased hepatocarcinoma incidence only slight; the addition of beef fat to an adequate diet did not enhance tumor induction. Rats fed the amino acid- or lipotrope-supplemented diets had an increased incidence of hepatic hemangioendothelial sarcomas, compared to deficient rats or to rats fed the adequate control diet. Methionine was contained in both the amino acid and the lipotrope supplement and probably was responsible for reducing hepatocarcinoma incidence. Methionine has been found to have an anticarcinogenic effect in other studies and also to block the depletion of hepatic folate stores that is induced by N-nitrosodiethylamine. Interactions between carcinogens, S-adenosylmethionine, and folate may be significant in hepatic or other tissue carcinogenesis. One of more hepatic microsomal oxidases were depressed in rats fed any of the high-fat diets but were not correlated with tumor incidence.
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PMID:Reduction of N-nitrosodiethylamine carcinogenesis in rats by lipotrope or amino acid supplementation of a marginally deficient diet. 6 28

The PLC/PRF/5 cell line derived from a human hepatoma produces hepatitis B surface antigen (HBsAg) in 22-nm particles of the same buoyant density as those found in the serum of infected patients. The HBsAg particles from this cell line were labeled with [35S]methionine and purified, and the polypeptides were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with those of serum-derived particles. The two major polypeptides of serum-derived HBsAg particles (p20 and p23) were found in the same relative amounts in the particles from the cell line. The three smallest of the five minor components observed in HBsAg particles from serum were present in particles from the cell line. These polypeptides (p31, p36, and p43), as well as p20 and p23, were precipitated with anti-HBs-containing serum. The two largest polypeptides of serum particles (p49 and p66) were not detected in particles from these cells. When the PLC/PRF/5 HBsAg particles were radiolabeled with tritiated sugars, p23, and not p20, was found to contain radioactivity, indicating that the pattern of polypeptide glycosylation is similar to that of serum HBsAg. None of the other possible gene products of hepatitis B virus was detected in the PLC/PRF/5-derived HBsAg particles, in the cells, or in the cell supernatants.
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PMID:Polypeptides of hepatitis B virus surface antigen produced by a hepatoma cell line. 9 75

Nucleoli isolated from Novikoff hepatoma cells of the rat were previously shown to carry out synthesis of predominantly ribosomal precursor RNA and methylation of this RNA in vitro. In order to develop in vitro systems for further detailed study of these processes and their interrelationships, isolated nucleoli were incubated in a complete RNA-synthesizing medium using (5-3H)cytidine 5'-triphosphate or S-adenoxyl(methyl-3H)methionine to measure the activities of RNA synthesis and methylation, respectively, under the same reaction conditions. Methylation of the ribose of the nascent ribosomal precursor RNA predominated. It occurred in close coordination with the transcriptional step by RNA polymerase as shown by the kinetic data, the analysis of labeled RNA in sucrose gradients, the inhibition by increased ionic strength or actinomycin D, and the release of labeled nucleotides by a 3'-exonuclease, venom phosphodiesterase. Methylation of the RNA bases occurred more slowly, continued longer after transcription ceased, and appeared to follow later in the processing of the RNA. Certain divalent cations (Mg2+, Mn2+, and Ca2+ at higher concentrations, and Zn2+ and Cu2+) inhibited both RNA synthesis and methylation to similar extents. RNase inhibitors (bentonite and dextran sulfate) at low concentration inhibited methylation while stimulating RNA synthesis, and pyrophosphate greatly decreased RNA synthesis with relatively little effect on methylation. These results indicated that RNA polymerase and ribosomal RNA methylases can function independently despite their close relationship. An exogenous substrate for the nucleolar rRNA methylases was found: nuclear RNA prepared from Novikoff hepatoma cells, cultured in the absence of methionine, served as a good substrate for methylation of both ribose and bases. Other exogenous RNAs, including cytoplasmic ribosomal RNA from these methionine-starved cells, nucleolar RNA from normal cells, and wheat germ ribosomal RNA were almost devoid of methyl-acceptor activity. A description of these parameters helps establish isolated nucleoli as a suitable system for further study of interaction of RNA polymerase, methylases, and nucleases in control of synthesis of ribosomal RNA.
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PMID:Interrelationships between synthesis and methylation of ribosomal RNA in isolated Novikoff Tumor nucleoli. 16 25

Parental and filial DNA strands were isolated from a Novikoff rat hepatoma cell line, synchronized by S-phase arrest with excess thymidine, that had completed up to one round of DNA replication in the presence of (14-C-methyl)methionine and (6-3-H) bromodeoxyuridine. Both strands were methylated, the proportion of total methyl label in parental DNA increasing slightly with time in S-phase. The studies were repeated with (14-C-methyl)methionine and (3-H)deoxycytidine to determine if parental methylation occurred on extant or repair-inserted cytosine residues. Both (14-C) and (3-H) were found in parental DNA. The (14-C)/(3-H) ration of parental DNA-5-methylcytosine was about twice that in filial DNA while the (3-H) data showed twice the concentration of 5-methylcytosine in parental compared to filial DNA. Thus parental methylation occurred on repair-inserted cytosine residues and resulted in overmethylation. That the DNA damage and repair was due to 5-phase arrest was shown by repeating the studies using a sequential mitotic-G1 arrest method. With this method little (14-C) or (3-H) was found in parental DNA. We conclude that S-phase arrest leads to DNA damage and repair with subsequent overmethylation of repair-inserted cytosines; that sequential mitotic-G1 arrest minimizes DNA damage; and, that the latter technique, suitable for synchronization of large quantities of cells, may prove useful in relatively artifact-free studies of eukaryotic DNA replication.
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PMID:Repair methylation of parental DNA in synchronized cultures of Novikoff hepatoma cells. 16 53

S-Adenosylmethionine-homocysteine methyltransferase, which catalyzes synthesis of methionine from homocysteine, with the use of S-adenosylmethionine as the methyl donor, is absent in tumor tissue such as rat ascites hepatoma and Morris hepatoma but is present in rat liver homogenate. Absence of the enzymatic activity in tumor cells is not due to the action of an inhibitor. S-Adenosylhomocysteine hydrolase, however, is present in both rat liver and hepatoma tissue.
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PMID:Deficiency of S-adenosylmethionine-homocysteine methyltransferase activity in hepatoma cells. 18 33

Individual yeast tRNAVal1 was used as a substrate for estimation of kinetic constants and study of site specificity of m5C-and m1A-methylases of Zajdela ascite hepatoma and rat liver. It was demonstrated that the rate of yeast tRNAVal1 methylation by hepatoma tRNA-methylases is 4--5 times higher than that induced by liver tRNA-methylases. The rates of 1-hour methyl groups incorporation into tRNAVal1 were 3.7 and 4.7 times higher in case of m5C-and m1A-methylases and 9.4 and 4.5 times higher in case of m1G-and m7G-methylases of hepatoma than the respective rates obtained for corresponding liver methylases. The main products of methylation were m5C and m1A containing about 90% of total radioactivity incorporated into tRNA. m5C-methylases of liver and hepatoma had similar affinity for S-Ad-Met. The Km value for both enzymes was 2.66 micronmole; the Km values for m1A-methylases of liver and hepatoma with respect to S-Ad-Met were the same and equal to 0,25 micronmole. m5C and m1A methylases of liver and hepatoma had adequate affinity for yeast tRNAVal1; their site specificity was the same, since they methylated in yeast tRNAVal1 cytosine in the tetracytidylic sequence of C49--C52 and adenine in the 59th position from the 5'-end of the molecule.
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PMID:[Estimation of kinetic constants and study of site specificity of Zajdela ascite hepatoma and rat liver tRNA-methylases]. 19 39

Two-dimensional gel electrophoresis revealed quantitative differences in the 35S-methionine labeled proteins synthesized in vitro in the wheat germ system containing poly A(+) mRNA of normal liver, regenerating liver or Novikoff hepatoma cells. A group of low molecular weight proteins which comigrated with proteins of 40S ribosomal subunits were synthesized in a much greater concentration with the poly A(+) mRNA from the latter two sources. This correlates with increased synthesis of ribosomal proteins in regenerating liver or tumors which is temporally coupled with the increased nucleolar synthesis of rRNA precursors.
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PMID:Evidence for coupled synthesis of mRNA for ribosomal proteins and rRNA. 20 72

Mitochondria were isolated from a slow-growing (9618A) and two intermediate-to-fast-growing (5123C, 5123tc) Morris hepatomas and host livers. The mitochondrial proteins were solubilized and fractionated on sodium dodecyl sulfate:polyacrylamide slab gels. One Coomassie blue-stained band was absent or reduced in amount in all tumors relative to host livers. In addition, a major mitochondrial enzyme present in normal liver, carbamyl phosphate synthetase, was missing or greatly reduced in the slow-growing, highly differentiated hepatoma 9618A, a tumor that is considered to be similar to normal liver in many biochemical and morphological respects. Incubation of mitochondria with [35S]methionine and a suitable amino acid incorporation system resulted in labeling of specific mitochondrial proteins. Autoradiography of the slab gels disclosed four prominently labeled fractions and a number of minor fractions. Preparations from hepatoma 5123tc demonstrated two labeled bands that were absent or greatly reduced in host liver. Host liver preparations displayed a minor band that was absent or greatly reduced in hepatoma 5123C. However, no single change in labeling pattern was common to all three tumors, suggesting the absence of a causal relationship between carcinogenesis and mutations in mitochondrial DNA.
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PMID:Differences in total mitochondrial proteins and proteins synthesized by mitochondria from rat liver and Morris hepatomas 9618A, 5123C, and 5123tc. 20 52

1. Naturally-occurring and synthetic analogues of phenylalanine, tyrosine, histidine, arginine, proline, tryptophan and the sulphur amino acids have beeen tested in rat reticulocytes and in the Reuber H35 hepatoma for effects on protein synthesis and protein degradation and on the heat lability of phosphoenolpyruvate carboxykinase (EC 4.1.1.32) in the hepatoma cells. The experiments were designed to test whether the analogues could be incorporated into mammalian proteins and whether the resultant proteins would be degraded at an accelerated rate. 2. Several analogues, including thiazolylanine, triazolalanine and selenocystine both stimulated protein synthesis and produced labile protein in reticulocytes. Other analogues, such as dihydroxyphenylalanine, thioproline and pipecolic acid accelerated protein breakdown but probably indirectly via an inhibition of protein synthesis. Azetidine-2-carboxylic acid had the largest effect on protein breakdown in reticulocytes. 3. Labile protein was produced in hepatoma cells incubated in the presence of azetidine-2-carboxylic acid, canavanine, indospicine, triazolalanine, 2-, 3- and 4-fluorophenylalanine. These same analogues, together with 3,4-dehydroproline, beta-2-thienylalanine, dihydroxyphenylalanine, histidinol, 5- and 6-fluorotryptophan, selenocystine and selenomethionine produced heat-labile phosphoenolpyruvate carboxykinase. Enzyme induced in the presence of selenomethionine or indospicine showed the largest increases in heat lability, and for these analogues equimolar concentrations of methionine and arginine respectively were needed to nullify the enzyme abnormality. 4. The toxicity of the same naturally-occurring analogues has been discussed in terms of their ability to be incorporated into cell proteins.
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PMID:Effects of amino acid analogues on protein synthesis and degradation in isolated cells. 21 95


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