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)

Initial velocity measurements of [3H]ADP and [3H]ATP uptake have been made with mitochondria isolated from Morris hepatomas of differing growth rates, and factors known to influence the rates of nucleotide exchange have been examined in an effort to determine whether the elevated rates of aerobic glycolysis in these tumors can be attributed to altered carrier activity. These studies included the determination of the apparent kinetic constants for nucleotide uptake as a function of the mitochondrial energy state and the dependence of transport rates on temperature. Also included in these studies were measurements of the mitochondrial levels of endogenous inhibitors, divalent cations and internal adenine nucleotides. Results obtained showed that with mitochondria isolated from the various tumor lines, the apparent kinetic constants for nucleotide uptake are different from those of control rat or regenerating liver mitochondria; the apparent Vmax values for both ADP and ADP uptake are significantly lower. Furthermore, under conditions of a high-energy state, the Km and Vmax values for ATP uptake are greater than the Km and Vmax value for ADP uptake but that under uncoupled conditions, the opposite is observed. Comparison of the levels of mitochondrial Ca2+, Mg2+, long-chain acyl-CoA ester and adenine nucleotide from the various mitochondria showed that important differences exist between liver and hepatoma mitochondria in the levels of Ca2+, long-chain acyl-CoA ester and AMP. Mitochondrial Ca2+ levels are elevated 3-5--fold in all tumor lines, and for Morris 7777 hepatoma (a rapidly growing tumor) by a remarkable 70-fold; whereas the levels of acyl-CoA ester and AMP are significantly lower in the more rapidly growing tumors. Arrhenius plots for nucleotide uptake in mitochondria from liver and hepatoma are characterized as being biphasic, having similar activation energies above and below the break point temperature (28-38 and 6-16 kcal/mol, respectively). However, the transition temperature for mitochondria from the various hepatomas is uniformly 4-5 degrees C lower than mitochondria from control liver. The latter difference may reflect a variation in membrane composition, most probably lipid components. It is concluded that the presence of elevated levels of Ca2+ and lower levels of AMP in hepatoma mitochondria and difference of membrane compositions may play an important role in limiting adenine nucleotide transport activity in vivo and that the impaired carrier activity may contribute to higher rates of aerobic glycolysis observed in these tumors.
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PMID:Adenine nucleotide transport in hepatoma mitochondria. Characterization of factors influencing the kinetics of ADP and ATP uptake. 683 Jul 67

Messenger RNA was extracted from polysomes of rat ascites hepatoma, AH 7974, which contains both beta- and gamma-actins, and was translated in nuclease-treated reticulocyte lysate. The isoactins, beta and gamma, synthesized in vitro were characterized by (1) a high affinity to DNAase I-agarose; (2) polymerization with actin purified from bovine brain; (3) coelectrophoresis with bovine brain actin on two-dimensional gel, and (4) peptide mapping of each isoactin by partial digestion with papain (EC 3.4.22.2) followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimum conditions with respect to the concentration of RNA, Mg2+, and K+ for the synthesis of beta- and gamma-isoactins were identical: 300 micrograms/ml, 1.5 mM, and 100 mM, respectively. Aurintricarboxylic acid and 7-methyl-GMP (7MeGMP) inhibited the synthesis of beta- and gamma-actins to the same extent. These results strongly suggest that there is very little possibility of differential translational control of each isoactin gene. When polysomal RNA was separated by sucrose gradient centrifugation, both beta- and gamma-actin mRNAs appeared as a sharp peak at the region slightly heavier than 18 S RNA.
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PMID:In vitro synthesis of beta- and gamma-isoactins by messenger RNA of rat ascites hepatoma. 689 86

The activity on ribosome monomers of dissociation factor preparations obtained by high salt wash from ribosomes and from the post-ribosomal supernatant (cytosol) of Yoshida rat ascites hepatoma and Ehrlich mouse ascites carcinoma cells and from the liver of control and tumor-bearing animals has been determined at different periods of intraperitoneal tumor growth. The concentration of the polyamines spermine, spermidine and putrescine has also been measured under the same conditions. Results here reported show the presence of an association factor activity on subunit ribosomes at low Mg2+ concentrations in the post-ribosomal supernatant fractions of Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during tumor growth. An association factor activity also takes place in the ribosomal high salt wash extracts of Yoshida ascites cells at the terminal stages of tumor growth. Since an increase of spermidine to putrescine ratios occurs during tumor growth the changes in the rate of ribosome monomer dissociation into units here observed might be attributable, at least in part, to changes in polyamine concentrations under the conditions studied.
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PMID:Reassociation of eukaryotic ribosomal subunits and polyamine concentration in Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during growth. 721 13

A cyclic-nucleotide independent heparin-sensitive nuclear protein kinase (NII) from the Morris hepatoma 3924A has been purified by a combination of ion exchange and affinity chromatographic procedures and velocity gradient centrifugation. The purified kinase had a molecular weight of 140,000 as determined by gel filtration. Two polypeptides (Mr = 42,000 and 25,600) were present in the purified preparation in approximately equimolar concentrations. The protein kinase employed Mg2+ and Co2+ as divalent ion and preferred the nonhistone proteins, casein or phosvitin, as protein acceptors. In the presence of Mg2+, it utilized both ATP and GTP as substrates and transferred the terminal nucleotide phosphate to serine and threonine residues of the protein acceptor. Phosphorylation of casein was stimulated by polyamines, particularly spermine. This polyamine preferentially enhanced phosphate transfer to threonine. The enzyme was inhibited by several compounds including heparin, the o-n-octyloxime of rifamycin (AF/013), 3'-dATP, o-phenanthroline, polynucleotides, and ADP. Of these inhibitors, heparin was the most potent and completely abolished kinase activity at a concentration of 0.1 micrograms/ml. The kinase could be autophosphorylated by incubation with Mg2+ and [gamma-32P]ATP; under these conditions phosphorylation was confined to the polypeptide of Mr = 24,600 and was completely inhibited by heparin. Based on the unique properties of NII protein kinase (ability to use GTP, stimulation by spermine, sensitivity to heparin), a selective assay was developed which could measure NII activity in the presence of other nuclear kinases. Under the optimal assay conditions, the nuclear extract of hepatoma 3924A was found to contain at least five times more NII kinase activity than that of normal adult liver. Analysis of extensively purified preparations from the two sources confirmed these results. After purification 11 times more NII protein kinase activity was obtained from hepatoma 3924A than from liver. Although hepatoma and liver protein kinases exhibited many common properties, they displayed distinct nucleotide saturation kinetics. The apparent Km for ATP was 10 microM for hepatoma protein kinase and 24 microM for the liver enzyme.
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PMID:A heparin-sensitive nuclear protein kinase. Purification, properties, and increased activity in rat hepatoma relative to liver. 725 4

The phosphorylation of endogenous membrane proteins by an endogenous protein kinase was studied in isolated plasma membranes from AH-66 hepatoma ascites cells using [gamma-32P]ATP as a precursor. The phosphorylation occurred very rapidly in the presence of 10 mM Mg2+ and reached a maximal level at 2 min. Ca2+ strongly inhibited the phosphorylation reaction and antagonized the activation produced by Mg2+. Neither cyclic AMP nor cyclic GMP had a significant effect on the phosphorylation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography showed that only membrane proteins ranging in molecular weight from 125,000 to 200,000 were heavily phosphorylated and those of less than 60,000 molecular weight were not phosphorylated at all. The protein kinase activity was readily extractable from the plasma membranes with 1 mM EDTA at pH 8.5. Among exogenous substrates, the extracted protein kinase catalyzed the phosphorylation of histone, protamine and phosvitin rather than casein. When the extracted protein kinase was subjected to chromatography on DEAE-Sepharose, a single major peak of cyclic AMP-independent protein kinase was eluted at a position quite different from those of the cytosolic protein kinases.
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PMID:Endogenous protein phosphorylation in isolated plasma membranes of AH-66 hepatoma ascites cells. 728 78

A nuclear protein kinase, designated NII, was purified essentially to homogeneity from the Morris hepatoma 3924A. In the presence of excess Mg2+, phosphorylation of casein by the kinase was stimulated by spermine (1-5 mM) and was inhibited completely by 0.1 microgram/ml heparin. The apparent Km for casein was reduced in the presence of spermine. Spermine preferentially augmented phosphorylation of threonine residues. The kinase was also associated with highly purified RNA polymerase I and appears to correspond to two polypeptides (Mr 42,000 and 24,600) of the polymerase. RNA polymerase I polypeptides of Mr 120,000 (S2), Mr 65,000 (S3) and Mr 24,600 (S5) were phosphorylated by the endogenous kinase. Spermine enhanced phosphorylation of the RNA polymerase I subunits as much as 20-fold. Phosphorylation activated RNA polymerase I; the phosphorylated enzyme synthesized longer product with no apparent effect on the number of RNA chains initiated.
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PMID:Spermine-mediated phosphorylation of RNA polymerase I and its effect on transcription. 733 1

Plasma membranes have been isolated from chicken liver and from Mc-29 virus induced transplantable hepatoma. The purity of membrane preparations has been checked by electron microscopy and by determination of the activity of some enzymes: 5'-nucleotidase, Na+, K+-ATP-ase, Mg2+-ATP-ase, alkaline beta-glycerophosphatase and glucose-6-phosphatase. In hepatoma membranes the activity of 5'-nucleotidase, Na+, K+-ATP-ase and Mg2+-ATP-ase was lower, that of alkaline phosphatase higher, than in liver membrane preparation. The incorporation rate of glucosamine-14C into UDP-N-acetylglucosamine and into plasma membrane glucosamine have been studied as well. The rate of synthesis of UDP-N-acetylglucosamine was faster in liver than in tumor cells. The labeling of hepatoma plasma membranes with glucosamine-14C occurred more slowly than that of liver ones. The rate of transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to membrane-bound glucosamine is lower in hepatoma, than in liver cells.
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PMID:Isolation and partial characterization of plasma membranes from chicken liver and from Mc-29 virus induced transplantable hepatoma. 745 56

The aim of this study was to selectively inhibit human mitochondrial aldehyde dehydrogenase (ALDH2) gene expression by triple helix assembly. Eight 21-mer oligodeoxyribonucleotides were designed to bind to two purine-rich sequences in the 5'-flanking region of the human ALDH2 gene. Gel mobility shift assays showed that triplex formation is sequence-specific for the target duplex and the third strand oligonucleotide. In the presence of Mg2+, but absence of K+, triplex-forming oligonucleotides bind to their target sites with apparent dissociation constants (Kd) in the 10(-7) to 10(-9) M range. Potassium cation virtually suppressed the triplex formation of G-C-rich duplex DNA with natural oligonucleotides, but did not prevent triplex formation with phosphorothioate-modified oligonucleotides. Phosphorothioate-modified oligonucleotides were delivered into human hepatoma Hep G2 cells by cationic liposomes. The reduction in ALDH2 mRNA levels in the cells was determined by the competitive reverse transcription-polymerase chain reaction. One of the phosphorothioate-modified oligonucleotides designed to forma an antiparallel triplex with a target in the 5'-flanking region of human ALDH2 gene (-105 to -125 from the translation initiation codon ATG) reduced by 80-90% the ALDH2 mRNA levels without affecting albumin mRNA levels. Data suggest that triple-helix formation may provide a means to selectively inhibit hepatic ALDH2 gene expression for therapeutic use.
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PMID:Inhibition of gene expression by triple helix formation in hepatoma cells. 749 44

For many years after Warburg's classic work, it was generally assumed that tumors produced large amounts of lactic acid and consequently had an acidic intracellular pHi. However, with the advent of Magnetic Resonance Spectroscopy (MRS), a non-invasive in vivo measure of tissue pH became available and demonstrated that in both human and animal tumors, pHi was higher (> 7.0) than pH epsilon (< 6.8), in contrast to normal tissues (e.g., liver) in which pHi (approximately 7.2) is lower than pH epsilon (approximately 7.4). This result has been confirmed in animal tumors using an MRS-visible extracellular marker, 3-aminopropyl phosphonate. The pH gradient across the tumor cell membrane is part of an interrelated system of ionic gradients and measurements made by both 31P MRS and by conventional analysis in Morris hepatoma 9618a and in livers demonstrated that the following ions also changed: compared with liver the Na+ content was 2-fold higher, K+ was 20% lower, total Ca2+ was 8-fold higher (7.4 mumol/g wet wt) and total Pi 2-fold higher (8.5 mumol/g wet wt), suggesting the presence of insoluble calcium phosphate, HCO3- was lower, total Mg2+ was similar in both tissues, but free [Mg2+] (calculated by two different methods) was approximately 5-fold lower in the hepatoma, as was [ATP]/[ADP][P(i)]. Because of an inadequate blood supply, tumors are often hypoxic with impaired Krebs cycle activity, low [ATP]/[ADP][P(i)] and rely mainly on glycolysis for energy. The rapid production and subsequent export of anionic lactate-from the tumor cell would be accompanied by H+. This would account for reversal of the proton gradient and activation of the Na+/H+ exchange. The elevated [Na+]i would decrease the Na+/Ca2+ exchange, which would in turn tend to cause the accumulation of Ca2+ (and P(i)). Such calcification is a very common feature of tumor pathology. The data indicate the change in gradient of one ion (H+) involves alterations in the linked equilibria of many ions and also of energy metabolites and offers new insights into properties of tumors important both diagnostically and therapeutically.
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PMID:Tumor metabolism: the lessons of magnetic resonance spectroscopy. 757 38

The oligonucleosomal pattern of DNA fragmentation is the best-characterized biochemical marker of apoptosis and believed to be generated by a, as yet unidentified, Ca2+, Mg(2+)-dependent endonuclease. All apoptotic cells fragment their genome. However, not every cell type undergoing apoptosis is capable of internucleosomal DNA cleavage. We have analyzed the endonuclease activities and patterns of DNA fragmentation in four established cell lines undergoing apoptosis following serum deprivation, i.e., rat 5123tc hepatoma and PC12 pheochromocytoma, as well as human MCF7 breast and DU145 prostatic carcinoma cells. Whereas apoptotic 5123tc and PC12 cells degraded their DNA into oligonucleosomes, the MCF7 and DU145 cells generated only > 50 kilobase pairs (kbp) DNA fragments. However, when isolated nuclei from all four cell lines were incubated with both Ca2+ and Mg2+ ions, their DNA was cleaved into internucleosomal fragments. Following washing with a low ionic strength buffer, the nuclei could only degrade DNA to > 50-kbp fragments. DNA ladders were produced again in these washed nuclei after reconstitution with the nuclear wash, which contained an endonucleolytic activity of approximately 97 kilodaltons. These experiments showed that cells maintain separate pools of endonucleolytic activities responsible for the high and low molecular mass DNA fragmentation, and depending on the cell type, one or both enzymatic pools become activated during apoptosis.
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PMID:Separate pools of endonuclease activity are responsible for internucleosomal and high molecular mass DNA fragmentation during apoptosis. 765 36


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