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 hypothesis was tested that the increased IMP dehydrogenase activity in human myelocytic leukemic cells, and along with it guanylate biosynthesis, might be a sensitive target to chemotherapy by tiazofurin. 1. IMP dehydrogenase activity in normal leukocytes was 3.1 +/- 0.5 (means +/- S.E.) nmol/hr/mg protein and in leukemic cells it was elevated 15- to 41-fold. The activity of guanine phosphoribosyltransferase in normal leukocytes was 389 +/- 27 nmol/hr/mg protein and in the leukemic cells it increased 2.8- to 6.8-fold. 2. IMP dehydrogenase was purified 4,900-fold to homogeneity from rat hepatoma 3924A with a yield of 30%. The kinetic properties of the hepatoma enzyme were similar to those of the enzyme in human myelocytic leukemic blast cells because of the similarity of the Km's for IMP (23 microM), NAD (44 and 65 microM); the Ki for TAD was 0.1 microM in both enzymes. 3. There was a selectivity of the in vitro response to tiazofurin in human normal and leukemic leukocytes. When labeled tiazofurin was incubated with leukocytes from normal, healthy volunteers and from leukemic patients, the leukemic leukocytes made 20- to 30-fold more TAD and the GTP content decreased as compared to normal leukocytes. This procedure proved to be a suitable predictive test in a clinical setting because patients with positive tests responded to tiazofurin whereas those with negative ones did not. 4. The National Cancer Institute approved a chemotherapeutic phase I/II trial which concentrates on treatment of refractory acute myelocytic leukemia. Tiazofurin is infused in a 60-minute period with a pump to insure uniform delivery. A novel aspect of the trial was that it was directed primarily by the biochemical impact of tiazofurin on IMP dehydrogenase activity and GTP concentration and the tiazofurin doses were to be adjusted accordingly. Patients received allopurinol as a routine precaution against possible accumulation of uric acid in the kidney. 5. In the first eight patients, there was one complete remission, two entered the chronic phase, two entered into partial remission, one did not respond, and two were not evaluable. In the five patients who responded, there was a rapid, profound decrease in IMP dehydrogenase activity of the blast cells and a gradual decline in GTP concentrations. The blast cell count followed the decrease in the GTP concentration. The white blood cell count was largely preserved. 6. Bone marrow aspirates and peripheral blood samples showed that with tiazofurin treatment there was an induced differentiation of the myelocytes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Enzyme-pattern-targeted chemotherapy with tiazofurin and allopurinol in human leukemia. 290 68

Hepatocarcinogenesis in rats treated with several chemicals is associated with changes in aldehyde dehydrogenase (AlDH) activity, particularly heterogeneous expression of a "tumor specific" phenotype that is very active with aromatic aldehydes, e.g., benzaldehyde (Bz). Objectives of this study were first, to determine if liver cancers in vinyl chloride-treated rats also expressed this AlDH phenotype, and second, to quantitate the NAD- and NADP-dependent AlDH activity for the substrates Bz and acetaldehyde (Ac) in the cancers and surrounding tissue. Small cubes of tissue containing well-differentiated hepatocellular carcinoma were obtained from five Sprague-Dawley rats exposed to 2500 ppm vinyl chloride for 55 weeks. An optimized procedure was developed for AlDH histochemistry. Frozen sections were preincubated in nitroblue tetrazolium/acetone and then incubated at 20 degrees C in viscous polyvinyl alcohol media containing buffer, phenazine methosulfate, sodium azide, substrate, coenzyme, and nitroblue tetrazolium. Background activity was evaluated by omission of substrate. Activity was quantitated by computer-assisted microscopic photometry. All five carcinomas had heterogeneous staining of NADP- and NAD-dependent BzDH and AcDH activity, with clusters of very high-activity cells. The magnitude of staining in the high-activity neoplastic cells was at least tenfold greater for BzDH-NADP and about twofold greater for BzDH-NAD, AcDH-NADP, and AcDH-NAD than the staining in other liver cells. More neoplastic cells had high BzDH than high AcDH activity. Only BzDH-NADP was localized predominantly to the carcinoma.
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PMID:Quantitative histochemistry of benzaldehyde dehydrogenase in hepatocellular carcinomas of vinyl chloride-treated rats. 300 81

Well coupled mitochondria were isolated from transplantable chicken hepatoma induced by MC-29 virus. The mitochondrial phosphate-dependent and phosphate-independent glutaminase activities were increased compared with those from normal chicken liver. Glutamate dehydrogenase was undetectable in the tumor mitochondria. Oxypolarographic tests showed the following: glutamine oxidation was prominent in the tumor mitochondria and was mediated through an NAD-linked reaction, while mitochondria from the liver showed a feeble glutamine oxidation; glutamine oxidation by tumor mitochondria was inhibited either by aminooxyacetate, inhibitor of transaminases, or prior incubation of mitochondria with DON (6-diazo-5-oxonorleucine), which inhibited mitochondrial glutaminases. Bromofuroate, inhibitor of glutamate dehydrogenase, had little or no effect; and glutamate oxidation was also inhibited by aminooxyacetate, while it was not affected by DON. These findings clearly show a high glutamate oxidation activity in the hepatoma and indicate that the product of glutamine hydrolysis, glutamate, is catabolized via transamination in the mitochondria to supply ATP.
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PMID:Prominent glutamine oxidation activity in mitochondria of avian transplantable hepatoma induced by MC-29 virus. 301 1

Aldehyde dehydrogenase (ALDH) activity was measured in primary cultures of normal human hepatocytes and of the human hepatoma cell line HepG2 after application of phenobarbital (PB) or 3-methylcholanthrene (MC) for 5 days. Treatment with PB alone resulted in a significant increase in both protein and DNA content at concentrations of 2 and 3 mM. Treatment with MC at a concentration as low as 5 microM led to a significant loss of cells when it lasted more than 5 days. Concentrations of 3-5 mM of PB in the media of HepG2 cell cultures caused a 2-fold enhancement of the activity of ALDH, as measured with NAD and propionaldehyde (P/NAD) or benzaldehyde (B/NAD). On the other hand, MC-treated cultures (5 microM) showed a 20-fold increase in enzyme activity measured with NADP and benzaldehyde (B/NADP), and a 2-fold increase in B/NAD activity. Combined treatment with both PB and MC led to an effect of dynamic synergism as far as B/NAD and B/NADP activities are concerned, suggesting a metabolite of MC as the mediator for the increase of ALDH activity. Normal human hepatocytes in primary cultures responded to PB (3 mM) in a similar way as HepG2 cells as far as DNA and protein content and ALDH activity are concerned. It is concluded, that HepG2 hepatoma cells behave similar to the normal hepatocytes in terms of ALDH regulation and can be used for studies on the activity of ALDH as modified by added xenobiotics.
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PMID:Effect of phenobarbital and 3-methylcholanthrene on aldehyde dehydrogenase activity in cultures of HepG2 cells and normal human hepatocytes. 303 38

We have tested the feasibility of targeting liposomes via interaction with specific ecto-enzymes, i.e., enzymes which have their active site oriented to the external surface of the cell. 3,4-Dimethylpyridine adenine dinucleotide, a competitive inhibitor of ecto-NAD+-glycohydrolase, was substituted at N6 with a hydrophilic spacer arm, functionalized with a sulfhydryl group, and covalently linked to performed liposomes containing 4-(p-maleimidophenyl)butyryl phosphatidylethanolamine. We show that compared to control vesicles, the binding of the conjugated liposomes was greatly increased (up to 5-fold) to cells presenting ecto-NAD+-glycohydrolase activity (Swiss 3T3 fibroblasts, mouse peritoneal macrophages); in contrast, no specific binding was detected with hepatoma tissue culture cells, which lack this enzyme. Specific binding was found to depend on the ligand/lipid molar ratio of the vesicles and on the length of the arm. High concentrations of free 3,4-dimethylpyridine adenine dinucleotide virtually abolished the specific binding to cells of the targeted liposomes. Analysis of binding revealed that the ligand conjugated to the liposomes presented a functional affinity for 3T3 fibroblasts 15-fold superior to that of the free ligand.
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PMID:Targeting of liposomes by covalent coupling with ecto-NAD+-glycohydrolase ligands. 307 76

Exposure of murine hepatoma (Hepa 1c1c7) cells to a variety of chemical agents known to protect animals against the neoplastic, mutagenic, and other toxic effects of chemical carcinogens results in dose- and time-dependent inductions of NAD(P)H:quinone reductase (EC 1.6.99.2). This enzyme protects against quinone toxicity by promoting obligatory two-electron reductions that divert quinones from oxidative cycling or direct interactions with critical nucleophiles. Quinone reductase levels are stable in culture, are easily measured, and are useful markers for the inductive effects of chemoprotective agents. The Hepa 1c1c7 system responds to chemoprotective compounds such as phenolic antioxidants (e.g., BHA [3(2)-tert-butyl-4-hydroxyanisole], BHT (3,5-ditert-butyl-4-hydroxytoluene), and tert-butylhydroquinone), lipophilic azo dyes belonging to the 1,1'-azonaphthalene, Sudan I (1-phenylazo-2-naphthol), and Sudan III [1-(4-phenylazophenylazo)-2-naphthol] families, polycyclic aromatic hydrocarbons, coumarin and various other lactones, flavonoids, and certain sulfur compounds (e.g., benzylisothiocyanate, dithiolthiones, and dithiocarbamates), all of which are recognized enzyme inducers and chemoprotectors in vivo. Quinone reductase induction in Hepa 1c1c7 cells therefore provides a simple, versatile, and reliable system for the evaluation of the potency, kinetics, and mechanism of action of anticarcinogens.
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PMID:Induction of NAD(P)H:quinone reductase in murine hepatoma cells by phenolic antioxidants, azo dyes, and other chemoprotectors: a model system for the study of anticarcinogens. 308 Jul 50

NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase in extracts of mitochondria from the highly malignant AS-30D rat hepatoma cell line demonstrate Ca2+ sensitivities and affinities for substrates similar to those of normal liver mitochondria. However, the maximal activities of NAD+- and NADP+-dependent isocitrate dehydrogenase were found to be 8 and 3.5 fold higher in hepatoma mitochondrial extracts than those of liver mitochondria, whereas maximal activities of succinate and 2-oxoglutarate dehydrogenases were similar in the two tissues. At pyridine nucleotide concentrations giving the lowest physiological NADH/NAD+ ratio, NAD+-isocitrate dehydrogenase activity in hepatoma mitochondrial extracts was completely inhibited at subsaturating concentrations of Ca2+, substrate, and NAD+, in contrast to rat liver mitochondrial extracts which retained significant activity.
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PMID:Calcium sensitive isocitrate and 2-oxoglutarate dehydrogenase activities in rat liver and AS-30D hepatoma mitochondria. 320 22

We describe a rapid and direct assay of NAD(P)H:(quinone-acceptor) oxidoreductase (EC 1.6.99.2) activity in cultured cells suitable for identifying and purifying inducers of this detoxication enzyme. Hepa 1c1c7 murine hepatoma cells are plated in 96-well microtiter plates, grown for 24 h, and exposed to inducing agents for another 24 h. The cells are then lysed and quinone reductase activity is assayed by the addition of a reaction mixture containing an NADPH-generating system, menadione (2-methyl-1,4-naphthoquinone), and MTT [3-(4,-5-dimethylthiazo-2-yl)-2,5-diphenyltetrazolium bromide]. Quinone reductase catalyzes the reduction of menadione to menadiol by NADPH, and MTT is reduced nonenzymatically by menadiol resulting in the formation of a blue color which can be quantitated on a microtiter plate absorbance reader. The reaction is more than 90% dicoumarol inhibitable and menadione dependent. The results are comparable to those obtained by harvesting cells from larger plates, preparing cytosols, and carrying out spectrophotometric measurements.
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PMID:Direct measurement of NAD(P)H:quinone reductase from cells cultured in microtiter wells: a screening assay for anticarcinogenic enzyme inducers. 338 6

Anticarcinogenic enzyme inducers are of two types: (a) bifunctional inducers [2,3,7,8-tetrachlorodibenzo-p-dioxin, polycyclic aromatics, azo dyes, beta-naphthoflavone] that elevate both Phase II enzymes [e.g., glutathione S-transferases, UDP-glucuronosyltransferases, and NAD(P)H:(quinone-acceptor) oxidoreductase] and certain Phase I enzymes [e.g., aryl hydrocarbon hydroxylase (AHH)]; and (b) monofunctional inducers [e.g., diphenols, thiocarbamates, 1,2-dithiol-3-thiones, isothiocyanates] that elevate primarily Phase II enzymes without significantly affecting AHH. Since Phase I enzymes such as AHH may activate precarcinogens to ultimate carcinogens whereas Phase II enzyme induction suffices to achieve chemoprotection, an understanding of the molecular mechanisms that regulate these enzymes is critical for devising methods for chemoprotection. We report a systematic analysis of the inductions of aryl hydrocarbon hydroxylase (AHH) and NAD(P)H:quinone reductase (QR) by seven monofunctional and eight bifunctional inducers, singly or in combination, in a murine hepatoma cell line (Hepa 1c1c7) and two mutants defective in either Ah (Aryl hydrocarbon) receptor function (BPrc1) or in AHH expression (c1). We have also examined such inductions in genetically defined mouse strains with high affinity (C57BL/6J) and low affinity (DBA/2J) Ah receptors. The combination of our earlier model for the induction of Phase I and Phase II enzymes (H. J. Prochaska, M. J. De Long, and P. Talalay, Proc. Natl. Acad. Sci. USA, 82: 8232, 1985) with mechanism(s) for autoregulation of AHH (O. Hankinson, R. D. Anderson, B. W. Birren, F. Sander, M. Negishi, and D. W. Nebert, J. Biol. Chem., 260: 1790, 1985) is compatible with our results. Thus, induction of QR by monofunctional inducers does not depend on a competent Ah receptor or AHH activity and appears to involve an electrophilic chemical signal. In contrast, bifunctional inducers require competent Ah receptors to induce both AHH and QR, although the latter process appears to be regulated by more than one mechanism. It is our view that bifunctional inducers bind to the Ah receptor thereby enhancing transcription of genes encoding both AHH and QR. Metabolizable bifunctional inducers are then converted by the induced AHH to products that resemble monofunctional inducers and are capable of generating the aforementioned chemical signal. The existence of mechanism(s) for AHH autoregulation that also affect Phase II enzyme expression would account for the high basal activities of QR in the AHH-defective mutant (c1).
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PMID:Regulatory mechanisms of monofunctional and bifunctional anticarcinogenic enzyme inducers in murine liver. 340 19

Fundamental differences were previously discovered in the ADP-ribosylation of proteins from metaphase chromosomes and interphase nuclei of HeLa cells. The number of modified nonhistone species was found to be dramatically reduced for metaphase chromosomes. An investigation has therefore been made of factors which could influence, and therefore be responsible for, this change in ADP-ribosylation during the cell cycle. Modified proteins were detected by autoradiography of sodium dodecyl sulfate-polyacrylamide gels containing mitotic and interphase samples from permeabilized cells that had been incubated with [32P]NAD. Whole cells showed a difference between interphase and metaphase similar to that for isolated nuclei and chromosomes. Chromosome expansion, disruption of chromosomes or nuclei, DNA nicking, and cellular growth activity significantly changed the incorporation of 32P label. Inhibitors of protein, RNA, and DNA synthesis did not, however, greatly affect ADP-ribosylation. The pattern of labeled species was not altered by the presence of nonradioactive NAD, though the extent of labeling declined. The results were not artifactually due to the procedure used to arrest cells in mitosis. Similar results were found with Novikoff rat hepatoma cells, demonstrating that the difference between metaphase and interphase is not confined to HeLa cells.
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PMID:Factors influencing ADP-ribosylation differences between chromosomal proteins of interphase and metaphase HeLa cells. 349 64


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