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 FEEDBACK RESPONSE OF MEVALONATE: NADP oxidoreductase (acylating CoA; EC 1.1.1.34) in two varieties of hepatoma has been examined. In marked contrast to the feedback inhibition of this enzyme that is regularly observed in normal liver, the feedback control is completely lost in minimal-deviation hepatomas 9121 and 3924A. This finding provides the first specific biochemical localization of the defect in cholesterol feedback control, which has been shown previously to be a characteristic of all hepatomas.
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PMID:Loss of feedback control of hydroxymethylglutaryl coenzyme A reductase in hepatomas. 527 77

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

Significant changes in aldehyde dehydrogenase (ALDH) activity occur during rat hepatocarcinogenesis in vivo. An NADP-dependent tumor ALDH isozyme has been studied extensively. To better understand the nature, origin, and importance of this tumor-associated phenotypic change, we have examined the ALDH activity of five well-established rat hepatoma cell lines, H4-II-EC3, HTC, McA-RH7777, JM1, and JM2. HTC, JM1, and JM2 express the tumor ALDH phenotype, as indicated by elevated NADP-dependent, benzaldehyde-oxidizing activity, the appearance of new isozymes by electrophoresis, and characteristic histochemical localization of ALDH activity in situ. The tumor ALDH phenotype is not detected in McA-RH7777 cells. H4-II-EC3 has intermediate tumor ALDH activity. Thus, the 5 cell lines provide a spectrum of tumor ALDH activities representative of the range of activities seen in vivo. Benzo(a)pyrene, 3-methylcholanthrene, and phenobarbital induce hepatic ALDH activity after treatment in vivo. The ability of these compounds to induce ALDH in vitro was assessed in H4-II-EC3, McA-RH7777, HTC, JM1, and JM2. Treatment of cell cultures for 72 hr with 3-methylcholanthrene (1.0 mM) increases the NADP-dependent ALDH activity in H4-II-EC3 and McA-RH7777 cell lines up to 34- and 11-fold, respectively. Treatment with benzo(a)pyrene (1.0 mM) also increases the NADP-dependent ALDH activity in both lines up to 17- and 48-fold, respectively. Treatment with 3-methylcholanthrene or benzo(a)pyrene increases ALDH activity 2-fold in HTC and JM2 but does not increase NADP-dependent ALDH activity in JM1. Only marginal increases in NADP-dependent ALDH are observed after phenobarbital treatment in 4 of 5 cell lines. The induction of ALDH is blocked by actinomycin D, alpha-amanitin, and cycloheximide. These studies support our hypothesis that changes in ALDH activity observed in vivo are due to mutational events occurring in initiated cells. It appears that rat hepatoma cell lines will provide an in vitro model for studying genetic regulation of the tumor ALDH.
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PMID:Regulation of aldehyde dehydrogenase activity in five rat hepatoma cell lines. 648 82

The purification and kinetic characterization of an NAD(P)+-malic enzyme from 22aH mouse hepatoma mitochondria are described. The enzyme was purified 328-fold with a final yield of 51% and specific activity of 38.1 units/mg of protein by employing DEAE-cellulose chromatography and an ATP affinity column. Sephadex G-200 chromatography yielded a native Mr = 240,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a major subunit with Mr = 61,000, suggesting a tetrameric structure, and also showed that the preparation contained less than 10% polypeptide impurities. Use of the ATP affinity column required the presence of MnCl2 and fumarate (an allosteric activator) in the elution buffers. In the absence of fumarate, the Michaelis constants for malate, NAD+, and NADP+ were 3.6 mM, 55 microM, and 72 microM, respectively; in the presence of fumarate (2 mM), the constants were 0.34 mM, 9 microM, and 13 microM, respectively. ATP was shown to be an allosteric inhibitor, competitive with malate. However, the inhibition by ATP displayed hyperbolic competitive kinetics with a KI (ATP) of 80 microM (minus fumarate) and 0.5 mM (plus 2 mM fumarate). The allosteric properties of the enzyme are integrated into a rationale for its specific role in the pathways of malate and glutamate oxidation in tumor mitochondria.
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PMID:Purification, kinetic behavior, and regulation of NAD(P)+ malic enzyme of tumor mitochondria. 672 50

Accumulation of Ca2+ (+ phosphate) by respiring mitochondria from Ehrlich ascites or AS30-D hepatoma tumor cells inhibits subsequent phosphorylating respiration in response to ADP. The respiratory chain is still functional since a proton-conducting uncoupler produces a normal stimulation of electron transport. The inhibition of phosphorylating respiration is caused by intramitochondrial Ca2+ (+ phosphate). ATP + Mg2+ together, but not singly, prevents the inhibitory action of Ca2+. Neither AMP, GTP, GDP, nor any other nucleoside 5'-triphosphate or 5'-diphosphate could replace ATP in this effect. Phosphorylating respiration on NAD(NADP)-linked substrates was much more susceptible to the inhibitory effect of intramitochondrial Ca2+ than succinate-linked respiration. Significant inhibition of oxidative phosphorylation is given by the endogenous Ca2+ present in freshly isolated tumor mitochondria. The phosphorylating respiration of permeabilized Ehrlich ascites tumor cells is also inhibited by Ca2+ accumulated by the mitochondria in situ. Possible causes of the Ca2+-induced inhibition of oxidative phosphorylation are considered.
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PMID:Inhibition of oxidative phosphorylation in ascites tumor mitochondria and cells by intramitochondrial Ca2+. 676 37

Tissue contents of NADPH and NADP+ were measured in freeze-clamped samples of normal rat liver and in four transplantable rat hepatomas covering a wide range of growth rates. Lowry cycling procedures were employed for analysis, using alkaline extracts for NADPH and acid extracts for NADP+. The mean NADPH content in 33 normal livers was 515 nmol/g wet weight, and mean NADP+ content was 311 nmol/g wet weight. In the four hepatomas, the amounts of both NADPH and NADP+ were low, and the extent of decrease correlated with tumor growth rate. In the slowly growing hepatoma 9618A, total NADP was slightly decreased (63% control) and more extensive decreases were observed in the medium growth rate tumors 47C and 8999 (38% and 19%, respectively, of control). In the rapidly growing hepatoma 3924A, total NADP was drastically decreased to 3% of the control liver value. Measurement of NADPH and NADP+ recovery from extracts of hepatoma 3924A showed that there were no inhibitors that might have blocked the activity of the assay enzymes. The NADPH/NADP+ ratio was close to the normal liver value in all four hepatomas. A 30-sec period of ischemia did not cause significant change in NADPH, but gave 33% decrease in liver NADP+. A 5-min period of ischemia decreased NADP+ to 50% of the zero-time value in liver, and to 71% in hepatoma 3924A, but was without effect on NADPH.
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PMID:Decreased content of reduced and oxidized nicotinamide-adenine dinucleotide phosphate in rat hepatomas. 715 Oct 32

The mRNA for the novel aldehyde dehydrogenase 5 (ALDH5) gene was detected in HuH7 hepatoma cells. The cells also expressed cytosolic aldehyde dehydrogenase (ALDH1) mRNA, but no mitochondrial aldehyde dehydrogenase (ALDH2) mRNA. Extracts of the hepatoma cells contained an enzymatic activity with an isoelectric point similar to that of ALDH1. This enzyme activity was insensitive to inhibition by disulfiram, a potent inhibitor of ALDH1. The enzyme was active with short chain aldehydes (acetaldehyde and propionaldehyde) and NAD+, but not with NADP+, and the activity was higher in the mitochondrial pellet than other cell fractions. These studies demonstrate the expression of ALDH5 mRNA in a human hepatoma and suggest that the gene product is enzymatically active and probably resides in the mitochondria.
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PMID:The novel aldehyde dehydrogenase gene, ALDH5, encodes an active aldehyde dehydrogenase enzyme. 777 80

The development of hepatocellular carcinoma in rodents treated with different chemical compounds is associated with the appearance in the cytosol of neoplastic liver cells of an unusual aldehyde dehydrogenase isozyme of class 3 (ALDH-3) which is very active with aromatic aldehydes. This tumor-associated isozyme is readily detected by enzyme cytochemistry using the substrate benzaldehyde with NADP as coenzyme. To determine whether human hepatocellular carcinomas express ALDH-3, the activity of this isozyme was examined in frozen sections from 68 echo-guided human liver biopsies. In 54 cases the guided biopsy was performed on one or more nodules suggestive for hepatocellular carcinoma found at ultrasonography within the liver parenchyma. The remaining 14 patients were affected by chronic active hepatitis or cirrhosis. An intense enzymatic activity was ascertained in 5 out of 36 hepatocellular carcinomas. In non-neoplastic liver, in macroregenerative nodules and in metastatic adenocarcinomas enzymatic activity was not detectable. ALDH-3-positive tumors were typical hepatocellular carcinomas (histological grade II and III). These results suggest that ALDH-3 is a phenotype associated with malignancy in human liver tumors.
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PMID:Cytochemical detection of a class 3 aldehyde dehydrogenase in human hepatocellular carcinoma. 779 43

Supplemental glutamine prevents gut atrophy and enhances muscle protein synthesis in septic rats. This study investigated the effect of glutamine administration and mitomycin C treatment on protein turnover in tumor-bearing rats. AH109A rat ascites hepatoma cells (2 x 10(6)) were subcutaneously implanted in the back of male Donryu rats (n = 32, body weight 150-200 g) on Day 0. The animals were then fed rat chow ad libitum for 10 days. On Day 10, the rats were catheterized for TPN and randomized into four groups according to diet and treatment. The groups were: (i) standard total parenteral nutrition (STPN) + saline; (ii) glutamine-supplemented TPN (GTPN) + saline; (iii) STPN+mitomycin C (MMC); (iv) GTPN+MMC. GTPN was isocaloric (250 kcal/kg/day) and isonitrogenous (1.5 gN/kg/day) with STPN. The animals were maintained on TPN for 5 days and received mitomycin C (0.5 mg/kg) via the catheter every day. On the fifth day of TPN, [1-14C]leucine was given via a 5-hr continuous infusion (2.0 microCi/hr/rat) to determine the fractional synthesis rate of muscle, gut mucosa, liver, and tumor. Also, endogenous leucine production (not equal to whole body protein breakdown rate) was calculated. Body weight loss during TPN was reduced with GTPN. GTPN enhanced muscle FSR in untreated animals (STPN: 10.8 +/- 8.7%/day vs GTPN: 14.7 +/- 0.6%/day, P < 0.05) and in mitomycin C-treated animals (STPN+MMC: 9.6 +/- 0.9%/day, GTPN+MMC: 12.0 +/- 0.8%/day, P < 0.05). The whole body protein breakdown rate was reduced with GTPN. Mitomycin C reduced the mucosal fractional synthesis rate and GTPN did not prevent this reduction.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of glutamine and chemotherapy on protein metabolism in tumor-bearing rats. 804 Nov 29

The objectives of this study were to evaluate the effect of insulin-like growth factor I (IGF-I) on the fractional synthesis rate (FSR) of muscle and whole body protein breakdown rate (WPBR) during methionine-free total parenteral nutrition (MTPN). We also determined whether the inhibition of endogenous methionine availability reduced tumor protein synthesis. AH109A hepatoma cells were inoculated onto the backs of Donryu rats on day 0. On day 10, the rats were catheterized for TPN and assigned to one of four groups: 1) standard TPN (STPN), 2) STPN + IGF-I, 3) MTPN, or 4) MTPN + IGF-I. The addition of IGF-I to MTPN reduced the loss of body weight by both increasing muscle FSR and reducing WPBR. The tumor FSR did not differ between MTPN + IGF-I and MTPN. The methionine extraction ratio from the liver was negative with MTPN + IGF-I but positive in the other groups. We concluded that IGF-I blockage of endogenous methionine release from peripheral protein sites was associated with a shift to liver-derived methionine, with no change in tumor growth in MTPN-treated rats.
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PMID:Effect of methionine-free total parenteral nutrition and insulin-like growth factor I on tumor growth in rats. 925 74


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