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)

As part of a continuing program aimed at developing nonpolyglutamylatable inhibitors of dihydrofolate reductase that are less toxic and more specific in their action, we herein report the therapeutic efficacy and toxicity of gamma-methylene-10-deazaaminopterin (MDAM) in athymic nude mice bearing advanced human HCT-8 ileocecal xenografts and its antitumor activity in C57BL/6 x DBA/2 F1 (hereafter called B6D2F1) mice bearing P388 murine leukemia. For the xenograft study, MDAM was administered at the maximum tolerated dose by the following dose schedules: (a) 5-day continuous i.v. infusion at 1.0 mg/kg/day (schedule I); and (b) i.v. push, daily for 5 days at 50 mg/kg/day (schedule II). The maximum tolerated dose values for methotrexate (MTX) under these conditions were 0.2 and 1.0 mg/kg/day for schedule I and schedule II, respectively. MTX did not exhibit any significant antitumor activity in this model system by both schedules; however, MDAM induced complete responses of 13 and 25% and partial responses of 25 and 50% by schedules I and II, respectively. MDAM also exhibited antitumor activity significantly superior to that of MTX in the P388 tumor model. One of the enantiomers of MDAM, which possesses the natural configuration at the gamma-methyleneglutamate moiety (l-MDAM), has been shown to be a better inhibitor of human recombinant dihydrofolate reductase and H35 hepatoma cell growth than D,L-MDAM. L-MDAM inhibited the uptake of radiolabeled folinic acid to H35 hepatoma cells eight times more efficiently than MTX. The results indicate that the superior activity of MDAM relative to MTX may be partially due to a combination of enhanced transport to tumor cells and slower deactivation by aldehyde oxidase.
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PMID:Polyglutamylation of the dihydrofolate reductase inhibitor gamma-methylene-10-deazaaminopterin is not essential for antitumor activity. 981 21

The cellular metabolism of 4-hydroxy-2-nonenal (4-HNE), a cytotoxic and genotoxic product of oxidative stress-induced lipid peroxidation, was investigated in rat H35 hepatoma cells. Previous studies from our laboratory (1) have characterized the degree to which oxidative, reductive, and conjugative metabolic pathways function simultaneously during hepatocellular metabolism of 4-HNE to rapidly eliminate the compound from suspensions of freshly isolated rat hepatocytes. In the current studies, we have extended the investigation of 4-HNE metabolism to examine the pharmacokinetic parameters of 4-HNE elimination and export in a hepatoma cell line and determined that the ensuing oxidative and conjugative metabolites of 4-HNE are rapidly and efficiently transported out the cell. Low concentrations of 4-HNE (25 microM) were used in an attempt to simulate physiologically relevant conditions. The H35 hepatoma cell line studied was first evaluated for enzymes known to play important roles in the metabolism of 4-HNE and were found to possess activities for glutathione S-transferase, aldehyde dehydrogenase (ALDH), and alcohol dehydrogenase of 24.00 +/- 1.12, 3. 45 +/- 0.17, and 6.44 +/- 0.29 nmol min-1 mg-1 protein, respectively. Hepatoma cells were incubated with 25 microM 4-HNE and metabolites in intra- and extracellular fractions were quantitated by reversed-phase HPLC over the time course of treatment. Reduced glutathione (GSH) and the GSH metabolites of 4-HNE were quantitated by reversed-phase HPLC as the dinitrobenzene derivatives. Uptake of 4-HNE from the extracellular medium occurred with an estimated rate of 0.398 +/- 0.181 min-1 10(6) hepatoma cells-1. The oxidative metabolite of 4-HNE, 4-hydroxy-2-nonenoic acid (HNA), produced by ALDH, appeared rapidly in the intracellular fraction achieving concentrations of 0.28 HNA nmol 10(6) hepatoma cells-1 and was efficiently eliminated with a first-order rate constant of 0.988 min-1. The GST-mediated conjugative metabolite, 3-glutathionyl-4-hydroxy-2-nonanal (4-HNE-SG), rapidly reached maximal intracellular concentrations of 1.88 +/- 0.44 nmol 10(6) hepatoma cells-1 and was eliminated at a rate of 0.101 +/- 0.033 min-1. Extracellular rates of formation, representing export, for HNA and 4-HNE-SG were 0.247 +/- 0.045 and 0.044 +/- 0.009 min-1 10(6) hepatoma cells-1, resulting in maximal extracellular concentrations for HNA and 4-HNE-SG of 0.70 +/- 0.10 and 3.03 +/- 0. 84 nmol 10(6) hepatoma cells-1. Approximately 75% of the administered concentration of 4-HNE was converted to measurable metabolites, with the 4-HNE-GSH conjugate accounting for 61% of total administered 4-HNE and HNA accounting for 14%. Collectively, these results demonstrate that oxidative and conjugative pathways are primarily responsible for elimination of 4-HNE at low concentrations in the hepatoma cell line evaluated and that the 4-HNE metabolites resulting from these pathways are rapidly and efficiently exported out of the cell.
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PMID:Formation and export of the glutathione conjugate of 4-hydroxy-2, 3-E-nonenal (4-HNE) in hepatoma cells. 988 35

Hepatoma cells have a below-normal content of polyunsaturated fatty acids; this reduces lipid peroxidation and the production of cytotoxic and cytostatic aldehydes within the cells. In proportion to the degree of deviation, hepatoma cells also show an increase in the activity of Class-3 aldehyde dehydrogenase, an enzyme important in the metabolism of lipid peroxidation products and also in that of several drugs. When hepatoma cells with different degrees of deviation were enriched with arachidonic acid and stimulated to peroxidize by ascorbate/iron sulphate, their growth rate was reduced in proportion to the quantity of aldehydes produced and to the activity of aldehyde dehydrogenase. Therefore, 7777 cells, less deviated and with low Class-3 aldehyde dehydrogenase activity, were more susceptible to lipid peroxidation products than JM2 cells. It is noteworthy that repeated treatments with prooxidant also caused a decrease in mRNA and activity of Class-3 aldehyde dehydrogenase, contributing to the decreased growth and viability. Thus, Class-3 aldehyde dehydrogenase could be considered relevant for the growth of hepatoma cells, since it defends them against cell growth inhibiting aldehydes derived from lipid peroxidation.
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PMID:Inhibition of class-3 aldehyde dehydrogenase and cell growth by restored lipid peroxidation in hepatoma cell lines. 989 24

Polyunsaturated fatty acids (PUFA) are important constituents of membrane phospholipids, whose levels are decreased in some tumor cells. This deficiency may cause alterations in signal transduction and an interruption of normal cellular events. The enrichment of tumor cells with PUFA may stimulate or inhibit tumor growth, probably depending on the type of PUFA and the cellular concentration of aldehydes derived from restored lipid peroxidation. We examined the effect of several doses of prooxidant on the growth of hepatoma cells with different aldehyde dehydrogenase activities, enriched with arachidonic acid. Two doses of prooxidant were sufficient to reduce growth of hepatoma cells with low aldehyde dehydrogenase activity, whereas three doses were necessary for those with high enzyme activity. In both cases, lipid peroxidation products blocked the cells in the S phase.
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PMID:Dose-dependent inhibition of cell proliferation induced by lipid peroxidation products in rat hepatoma cells after enrichment with arachidonic acid. 1047 28

The mouse cytosolic aldehyde dehydrogenase ALDH3A1 (encoded by the Aldh3a1 gene) has previously been shown in cell culture to be markedly inducible by 2,3,7,8,-tetrachlorodibenzo-p-dioxin (TCDD; dioxin), downregulated by the metabolism of functional CYP1A1/1A2 enzymes, and upregulated by a gene on Chr 7 that leads to endogenous oxidative stress. In order to study the regulation of Aldh3a1 gene expression, we isolated two overlapping genomic sequences from a B6/CBA mouse genomic library that included the entire Aldh3a1 gene, along with considerable 5' and 3' flanking sequences. The Aldh3a1 gene was shown to span approximately 10 kb and comprise 11 exons including a noncoding first exon. The sequence of 3.18 kb upstream of exon 1 reveals numerous consensus transcription factor-binding sites, some of which were shown to be important in the positive and negative control of Aldh3a1 gene expression; these include seven aromatic hydrocarbon response elements (AHREs), an electrophile response element (EPRE), and AP-1, C/EBP beta, c/EBP alpha, NF-kappaB, Sp1, and NF-1 putative binding sites. Deletion fusion constructs containing regions of the Aldh3a1 gene 5' flanking sequence, ligated to chloramphenicol experiments suggested that the 5' flanking region of the gene contains a strong promoter, at least four functional AHREs appear to act cooperatively in causing dioxin-mediated upregulation, and a putative negative regulatory element (NRE) controls basal gene expression independent of dioxin inducibility. The dioxin-mediated upregulation of Aldh3a1 expression in mouse hepatoma Hepa-1c1c7 cell cultures was shown to depend exclusively on the aromatic hydrocarbon receptor. acetyltransferase (CAT) or luciferase (LUC) reporter genes, were studied. Transient transfection experiments suggested that the 5' flanking region of the gene contains a strong promoter, at least four functional AHREs appear to act cooperatively in causing dioxin-mediated upregulation, and a putative negative regulatory element (NRE) controls basal gene expression independent of dioxin inducibility. The dioxin-mediated upregulation of Aldh3a1 expression in mouse hepatoma Hepa-1c1c7 cell cultures was shown to depend exclusively on the aromatic hydrocarbon receptor.
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PMID:Mouse cytosolic class 3 aldehyde dehydrogenase (Aldh3a1): gene structure and regulation of constitutive and dioxin-inducible expression. 1059 37

Tumor-associated aldehyde dehydrogenase (T-ALDH) is strongly expressed in hepatocellular carcinoma (HCC) but undetectable in normal liver. In the present study, this enzyme from human HCC, HCC T-ALDH, was purified and the partial amino acid sequences (384 residues) determined by direct protein sequencing matched the amino acid sequence (453 residues) deduced from cloned HCC T-ALDH cDNAs with an open reading frame. The coding sequences of HCC T-ALDH cDNA, human stomach ALDH3A1 cDNA [Hsu et al., J. Biol. Chem. 267 (1992) 3030-3037] and human squamous cell carcinoma (SCC) T-ALDH cDNA (Schuuring et al., GenBank I.D. M74542) matched one another except for discrepancies at four positions, with consequent P12R, I27F and S134A substitutions. R and A were found in HCC and SCC T-ALDHs, whereas P and S were present in stomach ALDH3A1. To confirm that these discrepancies would have general occurrence, coding sequences of HCC T-ALDH cDNAs from six patients and stomach ALDH3A1 cDNAs from two individuals were examined and all were found to encode ALDH3A1 having R, I and A at protein positions 12, 27 and 134, respectively, indicating HCC T-ALDH to be variant ALDH3A1 which is common in human stomach tissues.
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PMID:Primary structure of human hepatocellular carcinoma-associated aldehyde dehydrogenase. 1101 24

Fatty acids are ligands for the peroxisome proliferator-activated receptor alpha (PPAR alpha). Fatty acid levels are increased in liver during the metabolism of ethanol and might be expected to activate PPAR alpha. However, ethanol inhibited PPAR alpha activation of a reporter gene in H4IIEC3 hepatoma cells expressing alcohol-metabolizing enzymes but not in CV-1 cells, which lack these enzymes. Ethanol also reduced the ability of the PPAR alpha ligand WY14,643 to activate reporter constructs in the hepatoma cells or cultured rat hepatocytes. This effect of ethanol was abolished by the alcohol dehydrogenase inhibitor 4-methylpyrazole and augmented by the aldehyde dehydrogenase inhibitor cyanamide, indicating that acetaldehyde was responsible for the action of ethanol. PPAR alpha/retinoid X receptor extracted from hepatoma cells exposed to ethanol or acetaldehyde bound poorly to an oligonucleotide containing peroxisome proliferator response elements. This effect was also blocked by 4-methylpyrazole and augmented by cyanamide. Furthermore, in vitro translated PPAR alpha exposed to acetaldehyde failed to bind DNA. Thus, ethanol metabolism blocks transcriptional activation by PPAR alpha, in part due to impairment of its ability to bind DNA. This effect of ethanol may promote the development of alcoholic fatty liver and other hepatic consequences of alcohol abuse.
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PMID:The transcriptional and DNA binding activity of peroxisome proliferator-activated receptor alpha is inhibited by ethanol metabolism. A novel mechanism for the development of ethanol-induced fatty liver. 1102 51

We have previously shown that expression of the Class 3 aldehyde dehydrogenase gene (ALDH3) is abrogated by hypoxia. This phenomenon occurs in rat hepatoma systems in which ALDH3 expression is xenobiotic-inducible as well as in rat primary corneal epithelial cells that exhibit high constitutive ALDH3 expression. We have begun to test various segments of the ALDH3 5' flanking region for elements that may mediate this effect using CAT reporter gene constructs. In addition, although the involvement of the Ah receptor nuclear translocator (ARNT) in xenobiotic induction of ALDH3 is well established, the role of ARNT in constitutive ALDH3 expression is not clear. Moreover, ARNT is also a component of the hypoxia inducible factor-1 (HIF-1) bipartite transcription factor complex that mediates hypoxic induction of a variety of genes. Concomitant activation of the xenobiotic and hypoxia pathways results in cross-talk and functional interference. It has been hypothesized that this interference is due to limiting levels of ARNT. To examine if ARNT levels are limiting during hypoxic and xenobiotic induction in the context of ALDH3 expression and to examine possible roles of ARNT in constitutive expression of ALDH3 in corneal epithelial cells we co-transfected rat corneal epithelial cells and H4-II-EC3 rat hepatoma cells with ALDH3 5' UTR-CAT reporter genes and expression vectors containing either wild type or dominant negative forms of ARNT. Our results indicate that during hypoxia and xenobiotic induction of ALDH3 in H4-II-EC3 cells ARNT is not the limiting transcription factor. Further, neither wild type nor dominant negative ARNT had effects on constitutive ALDH3 expression in corneal epithelial cells.
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PMID:Aldehyde dehydrogenase 3 gene regulation: studies on constitutive and hypoxia-modulated expression. 1130 47

A mutation in the gene encoding for the liver mitochondrial aldehyde dehydrogenase (ALDH2-2), present in some Asian populations, lowers or abolishes the activity of this enzyme and results in elevations in blood acetaldehyde upon ethanol consumption, a phenotype that greatly protects against alcohol abuse and alcoholism. We have determined whether the administration of antisense phosphorothioate oligonucleotides (ASOs) can mimic the low-activity ALDH2-2 Asian phenotype. Rat hepatoma cells incubated for 24 h with an antisense oligonucleotide (ASO-9) showed reductions in ALDH2 mRNA levels of 85% and ALDH2 (half-life of 22 h) activity of 55% equivalent to a >90% inhibition in ALDH2 synthesis. Glutamate dehydrogenase mRNA and activity remained unchanged. Base mismatches in the oligonucleotide rendered ASO-9 virtually inactive, confirming an antisense effect. Administration of ASO-9 (20 mg/kg/day for 4 d) to rats resulted in a 50% reduction in liver ALDH2 mRNA, a 40% inhibition in ALDH2 activity, and a fourfold (P < 0.001) increase in circulating plasma acetaldehyde levels after ethanol (1 g/kg) administration. Administration of ASO-9 to rats by osmotic pumps led to an aversion (-61%, P < 0.02) to ethanol. These studies provide a proof of principle that specific inhibition of gene expression can be used to mimic the protective effects afforded by the ALDH2-2 phenotype.
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PMID:Eliciting the low-activity aldehyde dehydrogenase Asian phenotype by an antisense mechanism results in an aversion to ethanol. 1153 26

Alcoholic fatty liver is the earliest and most common response of the liver to alcohol and may be a precursor of more severe forms of liver injury. The mechanism by which ethanol causes fatty liver and liver injury is complex. We found that in both rat H4IIEC3 and McA-RH7777 hepatoma cell lines, ethanol induced transcription of a sterol regulatory element-binding protein (SREBP)-regulated promoter via increased levels of mature SREBP-1 protein. This effect of ethanol was blocked by addition of sterols. This effect is likely mediated by acetaldehyde, because the effect was only seen in cell lines expressing alcohol dehydrogenase, and inhibition of ethanol oxidation by 4-methylpyrazole blocked the effect in the hepatoma cells. Furthermore, the aldehyde dehydrogenase inhibitor cyanamide enhanced the effect of ethanol in the hepatoma cells. Consistent with these in vitro findings, feeding mice a low fat diet with ethanol for 4 weeks resulted in a significant increase in steady-state levels of the mature (active) form of SREBP-1. Activation of SREBP-1 by ethanol feeding was associated with increased expression of hepatic lipogenic genes as well as the accumulation of triglyceride in the livers. These finding suggest that metabolism of ethanol increased hepatic lipogenesis by activating SREBP-1 and that this effect of ethanol may contribute to the development of alcoholic fatty liver.
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PMID:Ethanol induces fatty acid synthesis pathways by activation of sterol regulatory element-binding protein (SREBP). 1203 55


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