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)

Improvements in the technique of ultramicroinjection of macromolecules into animal cells are described. The method is based on the Sendai virus-induced fusion of animal cells with erythrocyte ghosts containing trapped macromolecules. Fusion of hepatoma tissue culture (HTC) cells with ghosts prepared by hemolysis of erythrocytes in the presence of cytochrome C is much more efficient than fusion with ghosts prepared in the presence of bovine serum albumin (BSA) as in previous investigations. La+++ is more fficient in promoting fusion and less toxic to cells than Mn++, which was used previously. Thus in all subsequent experiments, erythrocytes were hemolyzed in the presence of cytochrome C plus other macromolecules to be trapped, and the resultant ghosts fused in the presence of La+++. The percentage of HTC cells which fused with ghosts reached 80% in many experiments. Ghosts containing 125I-BSA were used to measure the number of BSA molecules injected into HTC cells. About 10(6) BSA molecules were injected per fused cell. The overall efficiency of injection was low (about 0.02% of the starting material).
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PMID:A quantitative study of ultramicroinjection of macromolecules into animal cells. 18 74

In mouse hepatoma Hepa-1c1c7 cultures, polycyclic aromatic compounds such as benzol[a]pyrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; dioxin) activate the Cyp1a-1 (cytochrome P(1)450) and Nmo-1[NAD(P)H:menadione-oxidoreductase] genes, two members of the aromatic hydrocarbon (Ah)-responsive gene battery. Mevinolin is known to inhibit 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase (EC 1.1.1.34), the rate-limiting step in cholesterol biosynthesis. We show here that in the absence of TCDD, mevinolin markedly increases Cyp1a-1 transcription, CYP1A1 mRNA and protein levels and enzyme activity, and NMO1 mRNA concentrations. Addition of mevalonate, the product of HMG-CoA reductase activity, fails to reverse the effects of mevinolin. In fact, when used at high concentrations, mevalonate activates Cyp1a-1 transcription. Mevinolin-induced Cyp1a-1 gene activation: (1) occurs independently of the lipid content of the growth medium, (2) is not suppressed by adding 25-hydroxycholesterol, which blocks MHG-CoA reductase activity, and (3) requires a functional Ah receptor and unimpaired nuclear translocation of the receptor. It is possible that an unknown metabolite (or metabolites) of mevinolin activates Cyp1a-1 expression and that high concentrations of mevalonate act via the same mechanism. Using chimaeric plasmids that contain different lengths of Cyp1a-1 5' flanking regions fused to the bacterial neomycin (neo) gene, we find that the mevinolin effect on Cyp1a-1 induction requires the 5' flanking sequences between -1647 and -824, which are also needed for TCDD induction. Mevinolin, however, is not a ligand for the Ah receptor. Gel mobility shift assays revealed that Cyp1a-1 activation caused by mevinolin does not involve the ligand-dependent formation of a functional Ah receptor-dependent DNA-binding complex, but instead appears to be correlated with release of a putative repressor from its cognate DNA site. Our results suggest that the basel level of Cyp1a-1 transcription is maintained by an unknown negative regulatory factor. We propose that Cyp1a-1 transcriptional activation can result not only from induction by polycyclic aromatic compounds but also from derepression by mevinolin, independent of HMG-CoA reductase inhibition.
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PMID:Transcriptional derepression of the murine Cyp1a-1 gene by mevinolin. 131 Dec 72

Hepatic resection can be performed safely in carefully selected patients with cirrhosis. To minimize morbidity and mortality, it is essential to reliably estimate functional hepatic reserve and the extent of tumor before resection is performed. Child's classification is a reliable predictor of long term survival, but a more sensitive measure of hepatic function is needed to predict early morbidity and mortality. Child's classification can also be used to stratify patients and exclude those at high risk from hepatic resection. Promising predictors of operative mortality focus on the mitochondrial function of hepatocytes and include cytochrome a (+a3) contents and the redox tolerance index. Patients with advanced cirrhosis are not candidates for extensive hepatic resection and require careful evaluation before consideration for any hepatic resection. In patients with well-compensated cirrhosis and unifocal tumors, the procedure of choice is an anatomic resection of the tumor. If tumor size and location allows, a segmentectomy offers the best outcome, minimizing postoperative liver dysfunction while offering a long term outcome not dissimilar to a major liver resection. In highly selected patients with incidental tumors, a central tumor and perhaps in patients with multifocal hepatocellular carcinoma, hepatic transplantation may be of benefit. By using the appropriate predictors of hepatic function, refined surgical techniques and optimal postoperative care, a mortality rate of less than 10 per cent is achievable in cirrhotic patients with hepatocellular carcinoma who require resection.
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PMID:Hepatic resection in patients with cirrhosis and hepatocellular carcinoma. 131 68

Transcriptional activation of the murine Cyp1a-1 (cytochrome P(1)450) gene by inducers such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (dioxin) requires the aromatic hydrocarbon (Ah) receptor and the interaction of an inducer-receptor complex with one or more of the Ah-responsive elements (AhREs) located about 1 kb upstream from the transcriptional initiation site. We find that treatment of mouse hepatoma Hepa-1 cells with 2-aminopurine, an inhibitor of protein kinase activity, inhibits CYP1A1 mRNA induction by TCDD as well as the concomitant increase in CYP1A1 enzyme activity. Formation of DNA-protein complexes between the Ah receptor and its AhRE target is also inhibited by 2-aminopurine, as determined by gel mobility shift assays. Phosphorylation is required for the formation of Ah receptor-specific complexes, since in vitro dephosphorylation of nuclear extracts from TCDD-treated Hepa-1 cells abolishes the capacity of the Ah receptor to form specific complexes with its cognate AhRE sequences. To determine whether any one of several known protein kinases was involved in the transcriptional regulation of the Cyp1a-1 gene, we treated Hepa-1 cells with nine other protein kinase inhibitors prior to induction with TCDD; nuclear extracts from these cells were analyzed for their capacity to form specific DNA-protein complexes. Only extracts from cells treated with staurosporine, a protein kinase C inhibitor, were unable to form these complexes. In addition, staurosporine completely inhibited CYP1A1 mRNA induction by TCDD. Depletion of protein kinase C by prolonged treatment with phorbol ester led to the complete suppression of CYP1A1 mRNA induction by TCDD. We conclude that (i) phosphorylation is necessary for the formation of a transcriptional complex and for transcriptional activation of the Cyp1a-1 gene; (ii) the phosphorylation site(s) exists on at least one of the proteins constituting the transcriptional complex, possibly the Ah receptor itself; and (iii) the enzyme responsible for the phosphorylation is likely to be protein kinase C.
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PMID:Dioxin-dependent activation of murine Cyp1a-1 gene transcription requires protein kinase C-dependent phosphorylation. 131 72

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a potent tobacco-specific carcinogen in animals, has been linked to tobacco-related cancers in humans. The cytochrome(s) P-450 (P-450) responsible for the metabolic activation of NNK in humans has not been identified. The present work investigated the ability of human lung and liver microsomes and 12 forms of human P-450, expressed in Hep G2 (hepatoma) cells, to metabolize NNK. Of the 12 P-450 forms, P-450 1A2 had the highest activity in catalyzing the conversion of NNK to the keto alcohol, 4-hydroxy-1-(3-pyridyl)-1-butanone. P-450s 2A6, 2B7, 2E1, 2F1, and 3A5 also had measurable activities in the formation of keto alcohol. The apparent Km and Vmax for the formation of keto alcohol in the P-450 1A2-expressed Hep G2 cell lysate were 309 microM and 55 pmol/min/mg protein, respectively. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol, a reductive product, was the major metabolite formed, whereas the formation of keto alcohol and its aldehyde and acid derivatives (all alpha-hydroxylation products) constituted approximately 1% of the initial amount of NNK in P450-expressed Hep G2 cell lysate. A similar metabolite pattern was observed with human lung or liver microsomes. In human lung microsomes, the apparent Kms for the formation of 4-hydroxy-4-(3-pyridyl)butyric acid, 4-oxo-1-(3-pyridyl)-1-butanone, NNK-N-oxide, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol were 526, 653, 531, and 573 microM, respectively; the formation of keto alcohol was not observed. For human lung microsomes, there was no sex-related difference in NNK metabolism. Carbon monoxide (90% atmosphere) significantly inhibited the metabolism of NNK in human lung and liver microsomes. 7,8-Benzoflavone, an inhibitor of P-450s 1A1 and 1A2, had no effect on NNK metabolism in human lung microsomes but decreased the formation of keto alcohol by 47% in human liver microsomes. Similarly, antibodies against human P-450s 1A2 and 2E1 decreased keto alcohol formation by 42% and 53%, respectively, in human liver microsomes but did not affect NNK metabolism in lung microsomes. Inhibitory antibodies against P-450s 2A1, 2C8, 2D1, or 3A4 had little or no effect on the metabolism of NNK in human liver or lung microsomes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in human lung and liver microsomes and cytochromes P-450 expressed in hepatoma cells. 131 98

Effects of human interleukin-6 (hIL-6), the major acute phase inducer, on the expression of transcripts encoding cytochrome P450s were examined in human hepatoma-derived cells. Using reverse-transcription polymerase chain reaction, it was demonstrated that three hepatoma cell lines, HepG2, HepG2f and Hep3B, express P450 mRNAs encoding IA1, IA2 and IIIA3, the major P450 isozymes involved in carcinogen metabolism, and that they also show induction responses to treatment with their specific inducers. When hepatoma cells were treated with hIL-6, the levels of IA1, IA2 and IIIA3 mRNAs were markedly suppressed. These findings suggest that significant down regulation of cytochrome P450s may occur during the acute phase reaction, which may result in alterations in drug biotransformation.
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PMID:Interleukin-6 down regulates the expression of transcripts encoding cytochrome P450 IA1, IA2 and IIIA3 in human hepatoma cells. 137 45

The environmental contaminant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces the expression of a number of genes. The biochemical process of the induction of aldehyde dehydrogenase (ALDH-3) was investigated in rat H4IIE hepatoma cells in culture. The kinetics of ALDH-3-induction exhibited parallel increases in the rate of transcription, mRNA, protein, and enzyme activity, all reaching a plateau at 36-48 h after addition of TCDD. Half maximal and maximal inductions occurred at 0.1 and 1 nM of TCDD, respectively. No significant changes in the half-life of ALDH-3 mRNA (14 h) were observed in the cells exposed to three different concentrations of TCDD. Other inducers of xenobiotic metabolism, such as 3-methylcholanthrene and beta-naphthoflavone, also induced ALDH-3 mRNA to a similar level as TCDD, whereas antioxidants or electrophiles, such as tert-butylhydroquinone and dimethyl fumarate, did not show any induction of ALDH-3 mRNA. To examine the involvement of the aryl hydrocarbon receptor (Ah receptor) in the induction of ALDH-3, mouse variant cell lines defective in cytochrome P450IA1-induction and a parental wild type cell line (Hepa1c1c7) were studied. ALDH-3 mRNA and the transcription of its gene were detected in TCDD-treated wild type cells, but not in the treated and untreated variant cells. These results demonstrate that TCDD induces transcription of the ALDH-3 gene via its binding to the Ah receptor.
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PMID:Regulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin-inducible expression of aldehyde dehydrogenase in hepatoma cells. 141 78

Human hepatoma HEPG2 cells were infected with recombinant vaccinia virus vectors containing cDNAs encoding both known and variant rat cytochromes P450 (CYP). CYP2B1 and CYP2B2 cytochromes were equally well expressed (110-140 pmol/mg of microsomal protein) and catalyzed metabolism of 7,12-dimethylbenz[a]anthracene (DMBA). Their regioselectivity for DMBA metabolism paralleled that of the respective purified rat liver enzymes and reproduced previously reported regioselective differences between CYP2B1 and CYP2B2 [Wilson et al. (1984) Carcinogenesis 5, 1475-1483]. CYP2A1 and CYP2A2 expressed in HEPG2 microsomes exhibited nearly equal DMBA-metabolizing activities that closely matched that of purified CYP2A1. Although purified rat liver CYP2B1 was 3 times more active than purified rat liver CYP2B2, the expressed recombinant microsomal CYP2B1 (rCYP2B1) was 20 times less active than rCYP2B2, where activity matched that of the purified cytochrome. Microsomal suppression of rCYP2B1 catalytic activity was also observed for benzo[a]pyrene. Specific amino acid substitutions at equivalent positions of the completely homologous NH2-terminal halves of rCYP2B1 and rCYP2B2 changed this suppression effect. Thus, a L58----F, I114----F double mutant exhibited 3 times the normal activity for rCYP2B1 while remaining inhibitory for rCYP2B2. The single substitutions produced very different effects. The L58----F substitution prevented expression of rCYP2B1, while the I114----F substitution was inhibitory for both rCYP2B1 and rCYP2B2 (40 and 70%). A single E282----V mutation produced a stimulation of rCYP2B1 activity comparable to that of the L58----F, I114----F double substitution.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Selective suppression of the catalytic activity of cDNA-expressed cytochrome P4502B1 toward polycyclic hydrocarbons in the microsomal membrane: modification of this effect by specific amino acid substitutions. 154 25

The expression of cytochrome P450IA1 was examined in hepatic lesions of mummichog (Fundulus heteroclitus), a small, non-migratory teleost fish collected from a site in the Elizabeth River, VA, heavily contaminated with polycyclic aromatic hydrocarbons (PAH) of creosote origin. Immunoblot ('Western' blot) analysis using monoclonal antibody (MAb 1-12-3) to P450IA1 of the marine fish Stenotomus chrysops indicated that cytochrome P450IA1 levels in hepatocellular carcinoma and in foci of cellular alteration were 28-85% lower than those of adjacent non-neoplastic tissue. P450IA1-dependent monooxygenase activity, measured as ethoxyresorufin O-deethylase (EROD), exhibited a similar trend with EROD activity in lesions being 15-77% lower than activity in non-neoplastic tissue. Immunohistochemical examination of liver sections revealed general low intensity P450IA1-associated staining in hepatocellular carcinoma, exocrine pancreatic tissue, bile ducts and cholangiocellular proliferative lesions. Staining intensity of non-neoplastic hepatic parenchyma varied considerably and was focally distributed. In one case intense staining was observed in an altered hepatocellular focus (putative preneoplastic lesion). The results indicate important similarities in the expression of P450IA1 in neoplasms of fish and mammals and suggest an adaptive response of a wild population to carcinogen exposure.
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PMID:Cytochrome P450IA1 in hepatic lesions of a teleost fish (Fundulus heteroclitus) collected from a polycyclic aromatic hydrocarbon-contaminated site. 154 43

The Ah receptor regulates induction of cytochrome P450IA1 and mediates certain toxicities of polyhalogenated aromatics such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). It has been characterized previously in continuous cell lines, notably the mouse hepatoma line Hepa 1, the human squamous cell carcinoma line A431, and the human liver cell line Hep G2. The present work extends our knowledge of the Ah receptor in continuous human liver cell lines. Ah receptor can be detected in Mz-Hep-1, a hepatitis B virus-negative cell line derived from a Thorotrast-induced hepatocellular carcinoma. The mean concentration of Ah receptor in Mz-Hep-1 cells was 341 +/- 22 fmol/mg cytosol protein (mean +/- SEM, nine separate determinations). This is equivalent to approximately 30,000 sites per cell. The concentration of Ah receptor in Mz-Hep-1 cells is similar to that in Hepa 1 cells and approximately three times higher than that in Hep G2 cells. The Mz-Hep-1 Ah receptor sedimented in continuous sucrose gradients at approximately 9 S. Specificity of binding by [3H]TCDD was demonstrated by competitive binding of non-radiolabeled 2,3,7,8-tetrachlorodibenzofuran, 3-methylcholanthrene (MC), and dibenz[a,h]anthracene in 50-fold molar excess. Phenobarbital, which is not a substrate for P450IA1, did not compete with [3H]TCDD for binding to Mz-Hep-1 Ah receptor. Dexamethasone and estradiol also did not compete with [3H]TCDD for binding, suggesting non-identity of Ah receptor with glucocorticoid or estrogen receptor. In separate experiments, glucocorticoid receptor was identified in Mz-Hep-1 cells. By Scatchard plot analysis, the apparent equilibrium dissociation constant (Kd) for binding of [3H]TCDD to Mz-Hep-1 Ah receptor was estimated to be 4.4 nM, compared to 0.8 nM in Hepa 1 cells. By Woolf plot analysis the Kd was 5.4 nM, compared to 1.2 nM in Hepa 1 cells. The [3H]TCDD.Ah receptor complex extracted from nuclei of Mz-Hep-1 cells incubated with [3H]TCDD in culture at 37 degrees sedimented at approximately 6 S under conditions of high ionic strength. Aryl hydrocarbon hydroxylase (AHH) activity was detectable in Mz-Hep-1 cells after pretreatment with inducing chemicals. Mz-Hep-1 cells have the highest concentrations of Ah receptor in any continuous human liver cell line thus far investigated. The Mz-Hep-1 Ah receptor is similar physicochemically to that described in murine systems. AHH activity is inducible in Mz-Hep-1 cells.
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PMID:Ah receptor mediating induction of cytochrome P450IA1 in a novel continuous human liver cell line (Mz-Hep-1). Detection by binding with [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin and relationship to the activity of aryl hydrocarbon hydroxylase. 165 Feb 14


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