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 subcellular distribution and properties of four aldehyde dehydrogenase isozymes (I-IV) identified in 2-acetylaminofluorene-induced rat hepatomas and three aldehyde dehydrogenase (I-III) identified in normal rat liver are compared. In normal liver, mitochondria (50%) and microsomes (27%) possess the majority of the aldehyde dehydrogenase (AlDH), with cytosol possessing little activity. Isozymes I-III can be identified in both fractions and can be differentiated on the basis of substrate and coenzyme specificity, substrate Km, inhibition by disulfiram and anti-hepatoma aldehyde dehydrogenase sera, and/or isoelectric point. Hepatomas possess considerable cytosolic AlDH (20%), in addition to mitochondrial (23%) and microsomal (35%) activity. Although isozymes I-III are present in tumor mitochondria and microsomes, little isozyme I or II is found in cytosol. Hepatoma cytosolic AlDH is composed (50%) of a hepatoma-specific isozyme (IV), differing in several properties from isozymes I-III; the remainder of the tumor cytosolic activity is due to isozyme III (48%). The data indicate that expression of the tumor-specific aldehyde dehydrogenase phenotype requires both qualitative and quantitative changes involving cytosolic and microsomal aldehyde dehydrogenase. The qualitative change requires the derepression of a gene for an aldehyde dehydrogenase expressed in normal liver only following exposure to potentially harmful xenobiotics. The quantitative change involves both an increase in activity and change in subcellular location of a basal, normal liver AlDH isozyme.
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PMID:Properties of aldehyde dehydrogenas from chemically-induced rat hepatomas and normal rat liver. 742 44

Naturally processed self-peptides bound to human histocompatibility leukocyte antigens (HLA) class I molecules of human hepatocellular carcinoma tissues (HLA-A2.1, -B44, -B13) in vivo were isolated for sequence analysis. Acid-eluted peptides were subjected to reversed-phase high-performance liquid chromatographic separation and single-fraction sequencing was performed by Edman degradation. The peptides were found to be octamers or nonamers and they were derived from the processing of intracellular proteins. Three independent sequences were obtained from HLA-A2.1 molecules. One of the peptides showed sequence homology to the hepatitis B virus (HBV) pre-S protein, one to aldehyde dehydrogenase, and the other to no known protein. Two independent sequences were obtained from HLA-B44, B13 molecules: one showed sequence homology to the human c-abl protein, the other showed no homology to any known protein. A synthetic biotinylated peptide based on the HBV pre-S peptide sequence was confirmed to bind to HLA-A2.1 gene-transfected L cells. These data suggested that peptides potentially recognized by cytotoxic T cells can bind to HLA class I molecules on tumor cells in vivo.
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PMID:Analysis of naturally processed human histocompatibility leukocyte antigen class I-bound peptides from hepatocellular carcinoma tissues in vivo. 749 16

The aim of this study was to selectively inhibit human mitochondrial aldehyde dehydrogenase (ALDH2) gene expression by triple helix assembly. Eight 21-mer oligodeoxyribonucleotides were designed to bind to two purine-rich sequences in the 5'-flanking region of the human ALDH2 gene. Gel mobility shift assays showed that triplex formation is sequence-specific for the target duplex and the third strand oligonucleotide. In the presence of Mg2+, but absence of K+, triplex-forming oligonucleotides bind to their target sites with apparent dissociation constants (Kd) in the 10(-7) to 10(-9) M range. Potassium cation virtually suppressed the triplex formation of G-C-rich duplex DNA with natural oligonucleotides, but did not prevent triplex formation with phosphorothioate-modified oligonucleotides. Phosphorothioate-modified oligonucleotides were delivered into human hepatoma Hep G2 cells by cationic liposomes. The reduction in ALDH2 mRNA levels in the cells was determined by the competitive reverse transcription-polymerase chain reaction. One of the phosphorothioate-modified oligonucleotides designed to forma an antiparallel triplex with a target in the 5'-flanking region of human ALDH2 gene (-105 to -125 from the translation initiation codon ATG) reduced by 80-90% the ALDH2 mRNA levels without affecting albumin mRNA levels. Data suggest that triple-helix formation may provide a means to selectively inhibit hepatic ALDH2 gene expression for therapeutic use.
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PMID:Inhibition of gene expression by triple helix formation in hepatoma cells. 749 44

Induction of Phase II enzymes of the [Ah] gene battery by L-buthionine (S,R)-sulfoximine (BSO) and other agents was examined in mouse hepatoma Hepa-1c1c7 cells. BSO, a nonelectrophilic inhibitor of gamma-glutamylcysteine synthetase (GCS), is routinely used to examine the toxicological implications of GSH depletion. Exposure to BSO for 24 h produced a 75-85% depletion of GSH levels, proportional to the inhibition of GCS activity, as well as small increases in the UDP-glucuronosyltransferase (UGT, 60%) and glutathione transferase (GST, 30%) enzyme activities in Hepa-1 wild-type (wt) cells. However, for the NAD(P)H:menadione oxidoreductase (NMO1) and cytosolic aldehyde dehydrogenase class 3 (AHD4) enzyme activities, BSO produced larger increases (110% and 170%, respectively). The mechanisms of NMO1 and AHD4 induction were examined further. In Hepa-1 wt cells, NMO1 and AHD4 activities were increased by the aromatic hydrocarbon inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and by the electrophile tert-butylhydroquinone (tBHQ), known inducing agents for these enzymes. However, NMO1 and AHD4 were induced in Ah receptor nuclear translocation-defective mutant (c4) cells by BSO and tBHQ, but not by TCDD, suggesting that the induction by BSO and tBHQ is not Ah receptor-mediated. In wt cells, N-acetylcysteine produced a concentration-dependent increase in intracellular cysteine levels, but not GSH levels, in the absence or presence of BSO. Furthermore, N-acetylcysteine had no effect on NMO1 activity under any conditions examined, suggesting that GSH levels per se, rather than change in overall thiol status, might be mediating increased NMO1 activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enzyme induction by L-buthionine (S,R)-sulfoximine in cultured mouse hepatoma cells. 757 30

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

The mouse hepatoma cell line Hepa-1 is inducible by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for both CYP1A1 (aryl hydrocarbon hydroxylase, AHH) and class 3 aldehyde dehydrogenase (ALDH3) enzymes. To test the hypothesis of a common regulatory mechanism, several AHH deficient mutants of Hepa-1 were studied for their ALDH3 activities and specific mRNA levels before and after TCDD treatment. The recessive (with respect to the wild-type Hepa-1) mutants have defects in Cypla-1 structural gene (mutant c1) or in the Ah (aryl hydrocarbon) receptor (mutants c2 and c6 with decreased levels of Ah receptor; mutant c4 defective in the DNA binding of the Ah receptor). The results with these mutants suggested that Ah receptor nuclear translocator protein, ARNT, is needed for ALDH3 expression. Two dominant mutants, one of which is characterized by preventing the binding of the Ah receptor complex to DNA, were also studied. Surprisingly, these mutants possessed elevated levels of ALDH3 mRNA and enzyme activities which were also inducible by TCDD. The binding of Ah receptor-ligand complex to DNA was thus not needed for the expression of ALDH3. A dominant repressor for Cypla-1 gene transcription did not prevent the derepression or induction of ALDH3. The results thus suggest that Aldh-3 gene is regulated by a mechanism independent of the Ah receptor.
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PMID:Comparison of expression of aldehyde dehydrogenase 3 and CYP1A1 in dominant and recessive aryl hydrocarbon hydroxylase-deficient mutant mouse hepatoma cells. 782 19

The murine aromatic hydrocarbon ([Ah]) gene battery consists of at least six genes that code for two functionalizing (Phase I) enzymes and four non-functionalizing (Phase II) enzymes. These enzymes are induced by compounds such as aromatic hydrocarbons and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) that bind to the cytosolic Ah receptor protein. Studies in rodents indicate that certain enzymes of this battery, namely cytochrome P4501A1 (CYP1A1), UDP-glucuronosyltransferase (UGT1*06) and NAD(P)H: quinone acceptor oxidoreductase (NMO1) are induced by the synthetic antioxidant 5,10-dihydroindeno[1,2-b]indole (DHII). The induction of [Ah] gene battery enzymes and the levels of reduced glutathione (GSH) were examined in mouse Hepa-1c1c7 hepatoma wild-type cells (wt), a CYP1A1 metabolism-deficient mutant (c37) and an Ah receptor nuclear translocation-defective mutant (c4). DHII and TCDD increased the activities of ethoxyresorufin O-deethylase, an indicator of CYP1A1 activity, as well as NMO1, UGT1*06, cytosolic aldehyde dehydrogenase class 3 and glutathione S-transferase form A1 in wt cells, but had little or no induction effect in c37 or c4 cells. DHII and TCDD differed in their effects on GSH levels; while DHII increased GSH levels 3-fold in wt, but not at all in c37 or c4 cells, TCDD had no effect on GSH levels in any cell type. However, GSH levels were enhanced in both wt and c4 cells by tert-butyl hydroquinone (TBHQ). L-Buthionine S,R-sulfoximine, an inhibitor of gamma-glutamylcysteine synthetase, prevented DHII-induced increases in wt cell GSH. The increase in GSH levels occurred after 8 h, while the induction of enzymes occurred within 4 h. The induction of the higher GSH levels in wt cells by DHII and TBHQ correlated with increases in intracellular levels of the GSH precursor thiol cysteine, as well as with increased activities of gamma-glutamylcysteine synthetase, the rate-limiting enzyme of GSH synthesis. However, TBHQ-mediated GSH increases in c4 cells were accompanied by increased gamma-glutamylcysteine synthetase activity with no change in intracellular cysteine concentration. The results suggest that DHII induction of [Ah] gene battery enzymes requires a functional Ah receptor, but not the functional gene product CYP1A1. Furthermore, metabolism, possibly via CYP1A1, appears to be required for DHII to enhance intracellular levels of cysteine and GCS activity that result in higher GSH levels.
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PMID:Regulation of [Ah] gene battery enzymes and glutathione levels by 5,10-dihydroindeno[1,2-b]indole in mouse hepatoma cell lines. 795 76

It is well established that many types of tumor cells have reduced lipid peroxidation capacity compared to their normal counterparts. Changes in the activity of enzymes metabolizing aldehydes produced by lipid peroxidation have also been reported in a variety of tumor cells. We have investigated the relationship between changes in lipid peroxidation and changes in aldehyde-metabolizing enzymes in normal hepatocytes and two representative rat hepatoma cell lines, McA-RH-7777 and JM2. Compared to hepatocytes, both 7777 and JM2 cells have significantly lower basal and prooxidant-induced levels of lipid peroxidation than normal hepatocytes. Using 4-hydroxynonenal (4-HNE) as substrate, both cell lines also have significantly reduced activities of alcohol dehydrogenase (ADH) and glutathione S-transferase (GST) compared to hepatocytes. JM2 cells have significantly increased aldehyde dehydrogenase (ALDH) and aldehyde reductase (ALRD) activities with 4-HNE. In 7777 cells the ALDH and ALRD activities are not different from hepatocytes. The changes in enzyme activity are inversely correlated with the sensitivity of cells to 4-HNE. JM2 cells, with increased ALDH and ALRD and decreased ADH and GST, are much more resistant to the toxic effects of 4-HNE than 7777 cells. Normal hepatocytes and JM2 cells are approximately equally resistant to 4-HNE even though hepatocytes rely primarily on GST-mediated aldehyde conjugation to metabolize 4-HNE. Coupled with previous results from our laboratories, the overall increased sensitivity of certain hepatoma cells to lipid aldehydes appears due to decreased ability of these hepatoma cells to remove toxic products of lipid peroxidation. Moreover, hepatoma cells with increased levels of aldehyde dehydrogenase and aldehyde reductase appear most like hepatocytes in their ability to metabolize lipid aldehydes.
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PMID:Role of aldehyde metabolizing enzymes in mediating effects of aldehyde products of lipid peroxidation in liver cells. 803 12

We have cloned and sequenced the murine AHD4 cDNA encoding the 'Class 3' cytosolic aldehyde dehydrogenase (ALDH-3c). The cDNA is 1722 bp in length, excluding the poly(A+) tail, and has 5' and 3' nontranslated regions of 174 bp and 186 bp, respectively. AHD4 encodes a protein of 453 amino acids, including the first methionine (M(r) = 50,466). The murine AHD4 protein is 91% and 80% similar to the rat and human ALDH3c proteins, respectively, 64% identical to the rat microsomal ALDH3 protein, and < 28% similar to ALDH 'Class 1' and 'Class 2' proteins. Surprisingly, in contrast to the rat gene that is expressed in both cell cultures and the intact liver, the murine Ahd-4 gene is inducible by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) or benzo[a]pyrene in cell cultures but not in liver of the intact adult or newborn mouse. Southern hybridization analysis of mouse DNA probed with the full-length cDNA reveals that the Ahd-4 gene is likely to span less than a total of 15 kb, and was mapped to chromosome (Chr) 11 between the Mgat-1 and Shbg loci by analysis of two multilocus crosses. AHD4 mRNA levels are strikingly elevated in the untreated mouse hepatoma Hepa-1c1c7 mutant line c37 lacking CYP1A1 (aryl hydrocarbon hydroxylase) activity and in the untreated 14CoS/14CoS mouse cell line having a homozygous deletion of about 1.2 cM on Chr 7. Our data suggest that the Ahd-4 gene in murine cell cultures is regulated by three distinct mechanisms: Ah receptor-mediated induction by TCDD or benzo[a]pyrene, CYP1A1 metabolism-dependent repression, and Chr 7-mediated putative derepression.
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PMID:Mouse dioxin-inducible cytosolic aldehyde dehydrogenase-3: AHD4 cDNA sequence, genetic mapping, and differences in mRNA levels. 814 69


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