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)

A promoter sequence between nucleotide -51 and nucleotide -10 in the human alcohol dehydrogenase gene ADH2 has been shown to bind the transcription factor CCAAT/enhancer-binding protein (C/EBP). A series of 5'-end deletions of the ADH2 promoter was cotransfected with a C/EBP expression plasmid in a human hepatoma cell line, and trans activation by C/EBP was seen when at least 171 base pairs of 5'-flanking DNA was present. Mutations in the ADH2 promoter indicate that the mechanism of C/EBP trans activation involves two binding sites, one located just upstream of the TATA box and one located in an unusual location between the TATA box and the transcription start point.
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PMID:trans activation of human alcohol dehydrogenase gene expression in hepatoma cells by C/EBP molecules bound in a novel arrangement just 5' and 3' to the TATA box. 216 45

The 5'-flanking region of the human gene encoding beta-alcohol dehydrogenase (ADH2) was shown by DNase I footprinting to contain three tandem binding sites for purified glucocorticoid receptor. The three binding sites lie very close together between nucleotide (nt) positions -245 and -171 with respect to the transcription start point. DNase I footprinting using a rat liver nuclear extract indicated a lack of protection of the glucocorticoid receptor binding sites, but protection of a sequence between nt -209 and -191 which partially overlaps the glucocorticoid receptor binding sites I and II. This site has homology with the known binding site for hepatocyte nuclear factor 1 (HNF1). ADH2 promoter DNA fragments containing various lengths of 5'-flanking sequences were fused upstream from the gene encoding chloramphenicol acetyltransferase (cat) and transfected into the HepG2 human hepatoma cell line. The resulting cat expression was subject to induction by dexamethasone in constructions containing ADH2 DNA between nt -272 and -171. This indicates that the glucocorticoid receptor binding sites identified by footprint analysis function as a glucocorticoid response element (GRE) in a liver cell line. Heterologous ADH-cat fusions, in which the ADH2-GRE was fused to the adenovirus major late promoter, exhibited glucocorticoid induction of cat expression in CV-1B cells when cotransfected with a glucocorticoid receptor expression vector. Glucocorticoid regulation in CV-1B was observed when either all three glucocorticoid receptor binding sites (sites 0, I, II) or the two distal sites (sites 0, I) were present. Overall, these results indicate that the ADH2 gene possesses a functional GRE which can potentially regulate expression transcriptionally.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A hormone response element upstream from the human alcohol dehydrogenase gene ADH2 consists of three tandem glucocorticoid receptor binding sites. 221 Mar 83

The human alcohol dehydrogenase gene ADH2 is expressed at high levels in the liver. At least five different complexes between nuclear proteins from mouse liver or rat hepatoma cells and the proximal promoter region extending from nucleotides -188 to +31 are detected by gel retardation assays. Using oligonucleotides to compete for the binding, and also as the probes, allowed localization of sequences within this region that bind nuclear proteins. Mutated oligonucleotides did not bind or compete. Nucleotides which are contacted by the proteins have been localized by methylation interference assays to two regions homologous to the related mouse Adh-1 gene. One maps between nucleotides -94 and -84; the other is from nucleotides -72 through -64. The 5' region of the human ADH2 gene is capable of directing accurate in vitro transcription in extracts from hepatoma cells. Deletion analysis indicates that the smallest portion of the proximal promoter region capable of directing significant transcription extends to nucleotide -93, which just contains both of the identified contact regions. The longer promoter fragments do not work as well, suggesting the presence of negative elements. In vitro transcription assays using oligonucleotides and mutated oligonucleotides as competitors demonstrate that both of the cis-acting sequences identified here are important to efficient initiation of transcription from the ADH2 promoter.
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PMID:cis-acting sequences involved in protein binding and in vitro transcription of the human alcohol dehydrogenase gene ADH2. 229 48

Fatty acid ethyl esters are a family of neutral lipids that are the products of esterification of fatty acids with ethanol. Unlike other pathways of ethanol metabolism, ethyl esters are present in numerous human organs which are the targets of ethanol-induced damage. In the present study, we have shown that fatty acid ethyl esters are synthesized by a hepatoma cell line in tissue culture when exposed to ethanol concentrations easily attained by man during social drinking. Unlike alcohol dehydrogenase, the enzyme(s) responsible for synthesis of ethyl esters are membrane-bound and concentrated in the microsomal fraction of rat hepatocytes. In addition, fatty acid ethyl esters are hydrolyzed to free fatty acids and ethanol by membrane-bound enzyme(s) that are enriched in the microsomal and mitochondrial-lysosomal fractions. Intracellular hydrolysis of fatty acid ethyl esters release free fatty acids which are preferentially incorporated into cellular cholesterol esters. Thus, we have shown that a hepatocellular line exposed to concentrations of ethanol easily achieved in man by social drinking utilize endogenous fatty acids to form long-lived ethanol metabolites, fatty acid ethyl esters. Importantly, this family of neutral lipids may act as biochemical mediators of ethanol-induced cell damage, including the changes in cholesterol metabolism noted in chronic alcoholics.
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PMID:Synthesis and degradation of fatty acid ethyl esters by cultured hepatoma cells exposed to ethanol. 235 65

The increase in serum gamma-glutamyl transpeptidase (GGT) is a well known marker of chronic alcoholism in man. We have previously shown that ethanol (180 mM) induces GGT activity 2-3-fold in the C2 rat hepatoma cell line. In this study, we have analyzed the interaction of ethanol with steroid hormones and drugs in this well defined cell culture system. Dexamethasone (100 nM), a synthetic glucocorticoid agonist, completely prevented the induction of GGT by ethanol, but had no effect when added alone. This inhibitory effect was also observed with other corticosteroids, but not with sex steroids; it was prevented by RU 486, a glucocorticoid antagonist. These observations suggest that dexamethasone acts through a high affinity glucocorticoid receptor. Conversely, ethanol did not interfere with the glucocorticoid induction of alanine aminotransferase in the same cell. We have analyzed the metabolism of ethanol in the C2 cells. These cells lack significant alcohol dehydrogenase activity as well as any cytochrome P-450 Alc immunoreactivity. Dexamethasone did not modify the disappearance of ethanol in the culture medium of those cells. We conclude that glucocorticoid hormones interact with ethanol at the cellular level, and that this interaction does not involve a modification of alcohol metabolism.
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PMID:Glucocorticoid hormones prevent the induction of gamma-glutamyl transpeptidase by ethanol in a rat hepatoma cell line. 256 56

The mouse alcohol dehydrogenase-encoding gene, Adh-1, is expressed at high levels in adult liver. We have begun analysis of the regulation of this gene, focusing upon specific DNA-protein interactions. Preliminary deletion mapping of the 5' region indicated that a 521-bp fragment extending from nucleotide (nt) -468 to +53 (relative to the transcription start point) could direct chloramphenicol acetyl transferase synthesis in hepatoma cells. We therefore focused upon this -468 to +53 fragment. Using the gel mobility-shift assay, we detected at least four different complexes between proteins extracted from nuclei of mouse liver or hepatoma cells and regions within the -468 to +53 fragment. Two of the DNA-protein complexes can be competed with a 43-bp region from nt -90 to -48, and an oligodeoxyribonucleotide spanning this region forms two complexes. The strongest of these two DNA-protein complexes has been localized by methylation interference experiments to the palindromic sequence CACGTG located between nt -57 and -62. This region is identical in the related human ADH2 gene, and may represent a novel regulatory sequence.
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PMID:Protein-DNA interactions in the 5' region of the mouse alcohol dehydrogenase gene Adh-1. 277 84

Serum albumin gene expression is generally extinguished in hepatoma x fibroblast hybrids. To define the genetic basis of this phenomenon, we screened a panel of hepatoma hybrids retaining different fibroblast chromosomes for albumin production by immunofluorescence. We report that albumin extinction in these clones was strictly correlated with the retention of mouse chromosome 1. Furthermore, albumin was systematically reexpressed in chromosome 1 segregants. These data define a tissue-specific extinguisher locus (Tse-2) that affects albumin gene expression in trans. Two other liver genes, those encoding liver alcohol dehydrogenase and liv-10, were coordinately extinguished with albumin in monochromosomal hybrids that specifically retained mouse chromosome 1.
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PMID:Tse-2: a trans-dominant extinguisher of albumin gene expression in hepatoma hybrid cells. 277 64

We have studied a short term effect (96 hr) of ethanol on hormone-stimulated DNA synthesis in a primary rat hepatocyte culture system. Studies were also performed with respect to total RNA and protein synthesis as well as albumin secretion measured by a solid-phase radioimmunoassay. We found that ethanol, when added to cultured hepatocytes, resulted in a substantial reduction in hormone-stimulated hepatocyte DNA synthesis and this effect was concentration dependent and occurred in serum-free medium. Ethanol also had an inhibitory effect on total RNA synthesis but protein synthesis and albumin secretion remained essentially unchanged. We determined that hepatocytes exposed to ethanol during the first 24 hr of culture were the most susceptible to inhibition of DNA synthesis. During the first 24 hr, alcohol dehydrogenase (ADH) activity was present in the cells at higher levels than at 48 and 72 hr. In human hepatoma cell lines and differentiated primary and secondary chick fibroblasts, no ADH activity was demonstrable; such cells were not inhibited by 100 mM ethanol additions and DNA synthesis rates were similar to untreated cultures. Other alcohols found to be metabolized by hepatocyte ADH were inhibitory towards hormone-stimulated DNA synthesis whereas those with less metabolism had little effect. Hepatocytes treated with 4-methylpyrazole, an inhibitor of ADH, were partially protected from ethanol effects. Taken together our results are consistent with the hypothesis that a major physiological effect of ethanol on the hepatocyte is a direct impairment of DNA synthesis and that alcohol metabolism is required.
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PMID:Ethanol-induced inhibition of liver cell function: I. Effect of ethanol on hormone stimulated hepatocyte DNA synthesis and the role of ethanol metabolism. 305 77

Liver alcohol dehydrogenase activity was present in rat H4IIE hepatoma cells. Dexamethasone increased the enzyme activity two- to fourfold in these cells, but not in HepG2 cells. Enzyme induction was observed at dexamethasone concentrations as low as 10(-9) M, and the induction was maximal at 3 days. The increase in enzyme activity was accompanied by an increase in alcohol dehydrogenase mRNA on Northern blots and a two- to fourfold increase in alcohol dehydrogenase mRNA levels as estimated from cytoplasmic dot blots. There was no effect of dexamethasone on alpha-tubulin mRNA levels. Insulin, triiodothyronine, and growth hormone had no effect on alcohol dehydrogenase activity or mRNA levels. The induction of alcohol dehydrogenase mRNA by dexamethasone could be blocked by actinomycin D, but not by protein synthesis inhibitors. Superinduction of the mRNA (approximately twofold) was observed with dexamethasone in the presence of cycloheximide. Southern blots of genomic DNA from rat liver and H4IIE cells revealed no differences in alcohol dehydrogenase gene structure. The induction of alcohol dehydrogenase activity and mRNA levels by dexamethasone may be due to an increase in the rate of transcription of the alcohol dehydrogenase gene.
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PMID:Induction of alcohol dehydrogenase activity and mRNA in hepatoma cells by dexamethasone. 336 66

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


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