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 increase in tyrosine aminotransferase activity which occurs in rat hepatoma tissue culture (HTC) cells in response to cyclic AMP analogs has been shown to be an enzyme induction, similar to the larger response observed in certain other hepatoma cells and in liver. A specific antibody to tyrosine aminotransferase has been used to show that the number of enzyme molecules and the rate of enzyme synthesis are increased by N6,O2'-dibutyryl cyclic AMP in HTC cells. The effect on tyrosine aminotransferase is also produced by various 8-substituted derivatives of cyclic AMP and occurs whether or not the enzyme has been preinduced with a glucocorticoid. The response of the enzyme is greater when HTC cells are maintained in monolayer than in suspension cultures. Neither cell growth nor serum is required for the response.
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PMID:The influence of culture conditions on the induction of tyrosine aminotransferase by cyclic nucleotides in rat hepatoma cells. 1 19

1. Plasma membranes were isolated from ascites hepatoma AH-130 and rat livers with or without partial hepatectomy or bile duct ligation. Reciprocal manifestations of two marker enzymes for plasma membranes were observed in these membrane preparations; alkaline phosphatase activity was found much higher in the hepatoma membrane than in any preparations of the liver membranes, whereas 5'-nucleotidase activity was much lower in the former than in the latter. 2. Effects of lectins and anti-plasma membrane antiserum on these two marker enzymes were examined. The results showed that about 50% of apparent activity of 5'-nucleotidase found in the hepatoma membrane was exhibited by alkaline phosphatase. 3. Localizations of alkaline phosphatase and 5'-nucleotidase in polyacrylamide gels after electrophoresis were demonstrated using 5'-AMP and 5-Br, 4-Cl-indoxylphosphate as substrate. There was a difference in electrophoretic mobility between the alkaline phosphatase of the hepatoma and that of the liver.
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PMID:Contrast manifestation of alkaline phosphatase and 5'-nucleotidase in plasma membranes isolated from rat liver and ascites hepatoma. 2 Sep 52

Asparagine synthetase (L-aspartate:ammonia ligase (AMP-forming, EC 6.3.1.1) activity in rat liver increased when the animals were put on a low casein diet. The enzyme was purified about 280-fold from the supernatant of rat liver homogenate by a procedure comprising ammonium sulfate fractionation. DEAE-Sepharose column chromatography, and Sephadex G-100 gel filtration. The optimal pH of the enzyme was in the range 7.4-7.6 with glutamine as an amide donor. The molecular weight was estimated to be approximately 110,000 by gel filtration. Chloride ion was required for the enzyme activity. The apparent Km values for L-aspartate, L-glutamine, ammonium chloride, ATP, and Cl- were calculated to be 0.76, 4.3, 10, 0.14, and 1.7 mM, respectively. The activity was inhibited by L-asparagine, nucleoside triphosphates except ATP, and sulfhydryl reagents. It has been observed that the properties of asparagine synthetase from rat liver are not so different from those of tumors such as Novikoff hepatoma and RADA 1.
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PMID:Purification and properties of asparagine synthetase from rat liver. 2 63

Analogs of cyclic AMP elevate the synthesis of tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase; EC 2.6.1.5) in cultured hepatoma cells and rat liver at a post-transcriptional level but have no discernible effect on total soluble protein synthesis. In order to determine whether cyclic AMP exerts its effect on a step before or after initiation of the synthesis of this enzyme, we have analyzed the ribosomal transit times for both the aminotransferase and total soluble protein in hepatoma cells incubated in the presence or absence of N(6),O(2)'-dibutyryl cyclic AMP. The time required for one ribosome to translate one subunit of the "average" soluble protein (transit time) was about 2 min in cells incubated with or without the cyclic AMP analog. In contrast, the transit time for tyrosine aminotransferase was found to be reduced from 5-8 min under basal conditions to as low as 45 sec after exposure to dibutyryl cyclic AMP. Although the degree of effect varied from experiment to experiment, the relative rate of aminotransferase nascent chain elongation was found to be proportional to the stimulation of its activity. In contrast, dexamethasone did not alter the rate of aminotransferase elongation even though it elevated enzyme activity between 5- and 10-fold. These data are consistent with the hypothesis that induction of tyrosine aminotransferase with cyclic AMP analogs occurs by stimulation of the rate at which ribosomes translate pre-existing mRNA in contrast to adrenal steroids which act by increasing the level of translatable mRNA coding for this enzyme.
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PMID:Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP. 2 12

Alkaline phosphatase was purified from plasma membranes of rat ascites hepatoma AH-130, the homogenate of which had 50-fold higher specific activity than that found in the liver homogenate. The presence of Triton X-100, 0.5%, was essential to avoid its aggregation and to stabilize its activity. The purified enzyme, a glycoprotien, was homogeneous in polyacrylamide gel electrophoresis. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate indicated a protein molecular weight of 140,000. The addition of beta-mercaptoethanol caused the dissociation of the alkaline phosphatase into two subunits of identical molecular weight, 72,000. Isoelectric focusing revealed that the pI of this enzyme is 4.7. The pH optimum for the purified enzyme was 10.5 or higher with p-nitrophenylphosphate, and slightly lower pH values (pH 9.5--10.2) were obtained when other substrates were used. Of the substrates tested, p-nitrophenylphosphate (Km-0.3 mM) was most rapidly hydrolyzed. Vmax values of other substrates relative to that of p-nitrophenylphosphate were as follows; beta-glycerophosphate, 76%; 5'-TMP, 82%; 5'-AMP, 62%; 5'-IMP, 43%; glucose-6-phosphate, 39%; ADP, 36% and ATP, 15%. More than 90% of the activity of the purified enzyme was irreversibly lost when it was heated at 55 degrees C for 30 min, or exposed either to 10 mM beta-mercaptoethanol for 10 min to 3 M urea for 30 min, or to an acidic pH below pH 5.0 for 2 h. Of the effects by divalent cations, Mg2+ activated the enzyme by 20% whereas Zn2+ strongly inhibited it by 95% at 0.5 mM. EDTA at higher than 1 mM inactivated the enzyme irreversibly, although the effect of EDTA at lower than 0.1 mM was reversible by the addition of divalent cations, particularly by Mg2+. The enzyme was most strongly inhibited by L-histidine among the amino acids tested, and also strongly inhibited by imidazole. These results suggest that alkaline phosphatase of rat hepatoma AH-130 is very similar to that of rat liver in most of the properties reported so far.
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PMID:Purification and characterization of alkaline phosphatase from plasma membranes of rat ascites hepatoma. 2 78

Tyrosine adminotransferase (EC 2.6.1.5) has been found to be phosphorylated in intact rat hepatoma cells in culture. Incorporation of [32p]i into the enzyme is rapid and is exclusively found as phosphoserine. Cycloheximide treatment reduced phosphorylation of the aminotransferase only slightly and in the presence of three different inducers of this enzyme, dexamethasone, insulin, and dibutyryl cyclic AMP, [32P]I incorporation was increased. It is concluded that [32p]i incorporation into this enzyme probably reflects turnover of phosphate groups associated with pre-existing enzyme molecules catalyzed by a cyclic AMP-independent protein kinase.
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PMID:Relationship between phosphorylation of tyrosine aminotransferase and regulation of its synthesis by cyclic AMP and hormones. 2 2

Adenylate cyclase activity as well as intracellular content of sAMP were decreased 2.5-4-fold, as compared with normal state, in plasmatic membranes (PM) of hepatoma 22 and of Ehrlich ascites carcinoma--the tumors characterized by high level- of malignancy. Activity of cAMP phosphodiesterase exceeded distinctly the normal value in all the tumors studied. In less malignant hepatoma 48 the adenylate cyclase activity and content of cAMP were similar to those found in normal liver cells. The guanylate cyclase activity did not differ markedly from values found in normal liver cells in PM of all the tumors studied and in liver tissue of the tumor-bearing animals. Distinct alterations were not found in content of cGMP in the tumors, except of hepatomas 60 and 22, in which the nucleotide level exceeded 2-fold the normal value. The ratio cAMP/cGMP was decreased in the most malignant tumors. At the same time, the ratio was distinctly elevated in tumors with the middle level of malignancy (hepatomas 60 and 61).
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PMID:[Concentration of cyclic nucleotides, activity of adenylate cyclase, 3',5'-AMP phosphodiesterase and guanylate cyclase in plasma membranes from liver and hepatomas of different degrees of malignancy]. 3 Feb 12

Activity of 5'-nucleotidase was significantly lower in plasmatic membranes of highly malignant hepatoma 22 as compared with the activity found in normal liver tissue. The optimal activity of the enzyme from hepatoma 22 was found at pH 8.5 with AMP as a substrate. Decrease of pH value from 8.5 to 7.4 did not affect the enzymatic activity in homogenates and plasmatic membranes in the normal liver tissue. In all the experiments activity of 5'-nucleotidase was lower towards CMP as compared with AMP. The additive effect of the both substrates was observed only in experiments with hepatoma 22.
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PMID:[Comparison of the activity and properties of 5'-nucleotidase in the homogenates and plasma membranes of the normal liver, hepatomas and of the liver in mice with inoculated hepatomas of varying degrees of malignancy]. 4 19

Intracellular and extracellular levels of 3':5'-cyclic GMP and 3':5'-cyclic AMP were studied in synchronized Novikoff rat hepatoma cells. Intracellular levels of cyclic GMP increased spontaneously from 2-fold (without colcemid) to 10-fold (with colcemid), in proportion to the number of cells in mitosis. As cells entered mitosis, cellular cyclic AMP declined simultaneously with the rise in cyclic GMP. These reciprocal changes in cyclic nucleotide levels were reversed as cells passed out of metaphase and through anaphase. Maximum cyclic AMP and minimum cyclic GMP concentrations occurred during G-1. Less marked reciprocal fluctuations in both cyclic nucleotides were also found in S-phase and early G-2, where the ratio of cyclic AMP to cyclic GMP concentrations first fell and then increased. These changes in cyclic nucleotide ratios were closely correlated with major cell-cycle transitions at the boundaries between G-1/S-phase, S-phase/G-2, G-2/prophase, and metaphase/anaphase. Most, but not all, of the extracellular cyclic nucleotides were extruded when cells traversed mitosis. Colcemid or vinblastine completely prevented the appearance of extracellular cyclic AMP but augmented the appearance of extracellular cyclic GMP in parallel with the accumulation of mitotic cells. These results reflected changes in intracellular cyclic nucleotides and indicated that increased intracellular turnover of cyclic GMP and cyclic AMP occurred before and after metaphase, respectively. Elevated cyclic GMP levels during mitosis and S-phase are consistent with potential modulatory roles for this cyclic nucleotide in proliferation.
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PMID:Cell-cycle-related changes of 3':5'-cyclic GMP levels in Novikoff hepatoma cells. 6 82

Three ascites hepatoma cells of the rat, AH-41B, AH-34, and AH-64B, which had been determined in vivo as alpha-fetoprotein-negative, were cultivated in vitro in a medium containing adenosine 3',5'-cyclic monophosphate (cyclic AMP), cyclic dibutyryl-AMP, or theophylline. The concentration of alpha-fetoprotein in culture media was measured by the 125 I-radioimmunoassay. Results demonstrated that the AH-41B cells produced alpha-fetoprotein in vitor, the concentration of which being elevated in the media with three substances, while the remaining AH-34 and AH-64B cells did not. A comment was made on the producibility of alpha-fetoprotein in the so-called alpha-fetoprotein-negative hepatoma cells.
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PMID:Production of alpha-fetoprotein by cultured rat ascites hepatoma cells determined in vivo as alpha-fetoprotein-negative. 7 15


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