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)

We measured both pyridine nucleotide levels and ribonucleotide reductase-specific activity in Yoshida ascites hepatoma cells as a function of growth in vivo and during recruitment from non-cycling to cycling state in vitro. Oxidized nicotinamide adenine dinucleotide (NAD+) and reduced nicotinamide adenine dinucleotide (NADP) levels remained unchanged during tumour growth, while NADP+ and reduced nicotinamide adenine dinucleotide phosphate (NADPH) levels were very high in exponentially growing cells and markedly decreased in the resting phase. Ribonucleotide reductase activity paralleled NADP(H) (NADP+ plus NADPH) intracellular content. The concomitant increase in both NADP(H) levels and ribonucleotide reductase activity was also observed during G1-S transition in vitro. Cells treated with hydroxyurea showed a comparable correlation between the pool size of NADP(H) and ribonucleotide reductase activity. On the basis of these findings, we suggest that fluctuations in NADP(H) levels and ribonucleotide reductase activity might play a critical role in cell cycle regulation.
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PMID:Relationship between pyridine nucleotide levels and ribonucleotide reductase activity in Yoshida ascites hepatoma AH130. 353 72

The highly active alcohol dehydrogenase (EC 1.1.1.1) in rat hepatic tumor cells (HTC) was purified 120-fold by chromatography on DEAE-Sepharose and AMP-Agarose to yield an enzyme with a specific activity of 88 mumole/min/mg protein, assayed with 1.7 mM NAD+ and 0.55 M ethanol at pH 9 and 30 degrees C. (By comparison, purified, normal rat liver enzyme has an activity of about 1 unit/mg.) Based on its physical and kinetic properties, we conclude that the HTC isozyme is the same as the enzyme from rat stomach and another rat hepatoma (Cederbaum AI, Pietruszko R, Hempel J, Becker FF, and Rubin E (1975) Arch Biochem Biophys 171:348-360). The kinetics of the HTC enzyme are consistent with the Ordered Bi Bi mechanism. The kinetic constants are generally much larger for the HTC enzyme than for the normal rat liver enzyme. The Michaelis constants for ethanol and acetaldehyde (Kb = 1100 mM, Kp = 260 mM) are 1000-fold larger, and the constants for NADH are 10 to 50-fold larger. Although the HTC enzyme has low catalytic efficiency (V/Kb) on ethanol, it has much better activity on longer chain alcohols, but no activity on cyclohexanol. The pH dependence of V/Kb with ethanol is unusual in that it appears to be a linear function of pH, increasing with a slope of 0.56. Thus, the active sites of the liver and HTC enzymes may be different, although the HTC enzyme is inactivated by bromoacetate and bipyridine as is found for the liver enzyme. The HTC (stomach) enzyme may function to oxidize high concentrations of ingested ethanol or longer chain alcohols.
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PMID:Characterization of alcohol dehydrogenase from cultured rat hepatoma (HTC) cells. 361 21

The 1,2-dithiol-3-thiones are a class of five-membered cyclic sulfur compounds which have chemotherapeutic and chemoprotective properties. The parent 1,2-dithiol-3-thione nucleus and a series of six substituted analogs all induced NAD(P)H: quinone reductase (EC 1.6.99.2) activity and elevated glutathione levels in Hepa 1c1c7 murine hepatoma cells in culture thereby enhancing detoxification potential. These analogs included monosubstituted derivatives with phenyl, p-methoxyphenyl or 2-pyrazinyl groups at C-4 or C-5, and disubstituted compounds bearing phenyl or 2-pyrazinyl moieties at C-5 and an additional methyl group at C-4. This system can be used as an in vitro model for the study of the specificity and mechanism of action of the 1,2-dithiol-3-thiones as already demonstrated for several other classes of chemoprotective agents. The 1,2-dithiol-3-thiones also elevated quinone reductase and glutathione levels in the Hepa 1c1c7 cell mutants (BPrc1 and TAOBPrc1) that are defective in aryl hydrocarbon receptor functions. We conclude that the 1,2-dithiol-3-thiones are largely concerned with the stimulation of metabolic inactivation of electrophiles.
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PMID:1,2-Dithiol-3-thione analogs: effects on NAD(P)H:quinone reductase and glutathione levels in murine hepatoma cells. 370 58

A study was made of the effect of poly(ADP-ribosylation) of proteins on the formation and repair of single-strand DNA breaks in gamma-irradiated (50 Gy) permeable Zajdela ascites hepatoma cells permeabilized by the treatment with 0.05% triton X-100. Incubation of gamma-irradiated permeable cells in conditions promoting DNA synthesis and providing ADP-ribosylation (in the presence of 1 mM NAD) did not cause any substantial changes in the formation of single-strand DNA breaks and did not influence their repair.
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PMID:[Relation of the poly(ADP-ribosylation) of proteins to the formation and repair of DNA single-strand breaks in gamma-irradiated permeable Zajdela hepatoma cells]. 377 78

The purpose of this investigation was to examine factors which regulate the reprogramming of gene expression in tumors responsible for resistance to tiazofurin. To study the resistance phenomenon drug-induced tumor lines were selected and examined for the mechanism of resistance. A comparison of the biochemical expression of resistance to tiazofurin in drug-induced resistant lines of hepatoma 3924A, leukemias L1210 and P388 revealed that the 3 lines expressed similar genetic alterations related to reduced TAD content, decreased NAD pyrophosphorylase activity and increased synthesis of guanylates from salvaging preformed guanine indicating that these 3 factors play an important role in the resistance to tiazofurin. Resistance was stable in the leukemia lines and did not require drug to maintain resistance. Hepatoma 3924A resistant line reverted to sensitive state in the absence of drug selection pressure. NAD pyrophosphorylase activity was substantially deleted in the tiazofurin resistant leukemia lines, but was only significantly decreased in the hepatoma resistant line. Extensive biochemical alterations including enhanced activity of IMP dehydrogenase, increased inosinate and guanylate pools, and reduced uptake of tiazofurin were found in the hepatoma line resistant to tiazofurin. To examine the applicability of these results to naturally sensitive and spontaneously resistant tumors, murine tumors were examined. In murine tumors, TAD accumulation, ratios of enzyme activities responsible for the synthesis and degradation of TAD, and the ratios of perturbation of inosinate and guanylate pools following tiazofurin challenge demonstrated significant correlation with the sensitive or resistant nature of the tumors. To extrapolate these observations to human tumor systems, cytotoxicity of tiazofurin and its metabolic effects were compared in 6 human lung cancer cell lines derived from cancer patients with small cell lung cancer (4 lines) and lung adenocarcinoma (2 lines). Cell lines exhibiting greater sensitivity to tiazofurin accumulated significantly larger amounts of TAD and showed significant reduction of guanylate pools following tiazofurin incubation. The activity of the enzyme responsible for the formation of TAD, NAD pyrophosphorylase, did not correlate with responsiveness to tiazofurin but the enzyme which hydrolyzes TAD, TADase, correlated positively with the status of resistance.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Biochemical mechanisms of resistance to tiazofurin. 383 25

Induction of detoxification enzymes is a major mechanism whereby a wide variety of chemical agents protect rodents against neoplastic, mutagenic, and other toxicities of carcinogens. The enzyme NAD(P)H:(quinone acceptor) oxidoreductase (EC 1.6.99.2) can protect against the toxicities of quinones and is a useful marker for protective enzyme induction. Quinone reductase can be induced in murine Hepa 1c1c7 hepatoma cells and 3T3 embryo fibroblasts by compounds that are chemoprotectors in vivo, including some phenolic antioxidants, azo dyes, aromatic diamines, and aminophenols. Structurally dissimilar catechols (1,2-diphenols) and hydroquinones (1,4-diphenols) induce quinone reductase in these systems, but resorcinol (1,3-diphenol) and its substituted analogues are inactive. Furthermore, only aromatic 1,2- and 1,4-diamines and aminophenols are inducers, whereas the 1,3-diamines are completely inactive. These findings suggest that the functional capacity to form quinones or quinone-diimines, rather than the precise structure, is essential for inductive activity and that the generation of the signal for enzyme induction depends upon oxidation-reduction lability. The observations that some chemoprotective compounds (e.g., azo dyes, beta-naphthoflavone) induce both cytochromes P-450 and quinone reductase, whereas others (e.g., tert-butylhydroquinone) induce only quinone reductase, can be reconciled by the fact that inducers of the first type are metabolized by P-450 enzymes to form products that are functionally similar to compounds of the second type.
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PMID:On the mechanisms of induction of cancer-protective enzymes: a unifying proposal. 393 71

An electrochemical technique is described for measurement of intracellular NAD(P)H production. This technique involves an auxiliary redox system taken up by the cells which is then measured voltammetrically after reduction by NAD(P)H. The redox system used was 2, 6-dichlorophenolindophenol (DCPIP). It was shown to undergo a quasi-reversible two-electron transfer at the rotating gold disc electrode serving as an indicator electrode. The anodic wave of the reduced form of DCPIP was taken to indicate the amount of NAD(P)H produced by metabolic processes with glucose as substrate for a given number of cells. The following types of cell were investigated in suspension: Morris hepatoma 3924, a hepatocyte-derived cell line, and normal hepatocytes. Marked differences between normal and transformed cells were found under aerobic compared to anaerobic conditions. These were explained in terms of alterations in carbohydrate metabolism, e.g., Pasteur effect occurring on cell transformation.
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PMID:Investigation of the carbohydrate metabolism of normal and neoplastic hepatocytes using 2,6-dichlorophenolindophenol as a probe for NAD(P)H production measured by voltammetry. 405 62

The biochemical properties of ALDH isozymes have been examined in human tissues and one set, designated ALDH3, has been studied in detail. These components occur at highest levels in lung and stomach, but were not expressed in fetal tissues, or in blood, hair roots and fibroblasts. The ALDH3 isozymes show optimal activity with benzaldehyde and can use either NAD or NADP as cofactor. Antiserum against a partially purified ALDH3, from stomach, selectively precipitates this isozyme from human tissues and selectively recognizes an homologous component in the rat. Human and rodent ALDH3 were not immunoprecipitated by anti-ALDH1 or anti-ALDH2 antisera. High levels of expression were found in human-rodent hybrids, constructed using rat hepatoma cells, and these hybrids were used to assign the human ALDH3 gene to chromosome 17.
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PMID:Chromosome assignment, biochemical and immunological studies on a human aldehyde dehydrogenase, ALDH3. 407 32

Erthrocytes from African blacks with primary hepatoma were incubated with physiological amounts (1.64 microM) of nicotinamide-14C (NM-14C) and it was found that these erythrocytes could synthesize NAD from NM. After 3-hr incubation with NM-14C, a large percentage of the 14C was found in NMN, nicotinamide riboside (NR) and NAD, but was undetectable in nicotinic acid nucleotides (NAMN and NAAD). This suggested that the NAD synthesized from NM was not through the Preiss-Handler pathway. After 6-plus hr incubation, the 14C found in NAMN and NAAD suggested the NAD synthesized was being broken down and reutilized through Preiss-Handler pathway for synthesis of NAD. This reutilization pathway was confirmed by incubating nicotinic acid-14C (NA-14C) with erythrocytes. Apparently the metabolites from the breakdown of NAD were deaminated. The metabolism of NM-14C was slower than NA-14C. However, after 24 hr incubation with NM-14C, 72.26% of 14C was found in NAD. A high percentage of 14C in NR at the initial incubation and a later drop suggested that NR was another intermediate in the pathway.
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PMID:Pyridine nucleotide metabolism in the erythrocyte of South African blacks with primary hepatoma. 629 91

Aldehyde dehydrogenase subcellular distribution and activity were studied in the Yoshida hepatoma AH-130 and rat liver. NAD+- and NADP+-dependent dehydrogenase activities were lower in all hepatoma subfractions (except the cytosol) than in liver subfractions. In the presence of 0.025 mM substrate 78-80% of the liver NAD+- or NADP+-dependent aldehyde dehydrogenase was found in the mitochondria. With 10 mM substrate the enzyme activity was primarily in the mitochondria and microsomes. In the hepatoma a sharp increase of the soluble aldehyde dehydrogenase (either NAD+- or NADP+ dependent) was observed at all substrate concentrations. The Km of the different isoenzymes (either identified by their localization or coenzyme dependency) were of the same order for liver and hepatoma. However, a high Km enzyme was present in liver mitochondria outer membranes but not in hepatoma. Hepatoma acetaldehyde dehydrogenase was inhibited, as was the liver enzyme, by diethyldithiocarbamate. The return of activity was slower for the hepatoma and neonatal liver than for the adult liver enzyme.
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PMID:The subcellular distribution and properties of aldehyde dehydrogenase of hepatoma AH-130. 630 66


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