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)

Flunitrazepam (FNTZ), like other benzodiazepines, has a high affinity for the benzodiazepine receptor within the gama-aminobutyric acid (GABA) complex. These affinities correlate with the pharmacological and therapeutic potencies of the drug. FNTZ is a drug commonly abused by young adults. In humans, FNTZ is oxidized to the major metabolites N-demethylflunitrazepam (DM FNTZ) and 3-hydroxyflunitrazepam (3-OH FNTZ) and reduced to 7-aminoflunitrazepam (7A FNTZ). Human CYP2C19 and CYP3A4 are the principal P-450 cytochromes involved in DM FNTZ and 3-OH FNTZ formation. However, it is not clear which enzyme is responsible for the reduction of FNTZ to 7-aminoflunitrazepam (7A FNTZ). In this study, the involvement of NADPH-cytochrome P-450 reductase in the conversion of FNTZ to 7A FNTZ was investigated in two human hepatoma cell lines, human lymphoblast microsomes specifically expressing human NADPH-cytochrome P-450 reductase and purified recombinant human HADPH-cytochrome P-450 reductase. Significantly more FNTZ was converted to 7A FNTZ in Hep G2 than in Hep 3B cells, and this difference was associated with the catalytic activity and protein levels of NADPH-cytochrome P-450 reductase in these cells. In Hep G2 cells, conversion of FNTZ to 7A FNTZ was effectively inhibited by alpha-lipoic acid, an NADPH-cytochrome P-450 reductase inhibitor. In addition, formation of 7A FNTZ by the microsomal fraction of Hep G2 cells was specifically inhibited by antibody against NADPH-cytochrome P-450 reductase. Under hypoxia (N2 85%; CO2 5%; H2 10%), human lymphoblast microsomes specifically expressing human NADPH-cytochrome P-450 reductase and purified recombinant human NADPH-P-450 reductase catabolized FNTZ to 7A FNTZ in a concentration-dependent manner. These results suggest that NADPH-cytochrome P-450 reductase is involved in the reductive metabolism of FNTZ to 7A FNTZ under hypoxic conditions.
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PMID:NADPH-cytochrome P-450 reductase is involved in flunitrazepam reductive metabolism in Hep G2 and Hep 3B cells. 1467 1

CYP3A4, the most abundant form of cytochrome P450 in the human adult liver, shows wide interindividual variation in its activity. This variability is thought to be caused largely by transcriptional and genetic factors, yet the underlying mechanisms are poorly understood. The purpose of this study was to clarify the mechanisms controlling the CYP3A4 gene transcription and to search for genetic polymorphisms in the 5'-flanking region of the CYP3A4 gene. Transient transfection of human hepatoma HepG2 cells and of normal human hepatocytes with a series of CYP3A4 promoter-luciferase reporter plasmids revealed that a region from -11.4 to -10.5 kilobases, designated the constitutive liver enhancer module of CYP3A4 (CLEM4), was important for the constitutive activation of the CYP3A4 gene. Gel shift assay using nuclear extracts prepared from HepG2 cells showed that HNF-1alpha, HNF-4alpha, USF1, and AP-1 interacted with CLEM4. Furthermore, the introduction of mutations into their binding sites demonstrated that essentially all sites were required for the maximal enhancer activity. Screening for genetic polymorphisms within CLEM4 in genomic DNA from French persons, we identified the novel variant, TGT insertion between -11,129 and -11,128 (-11,129_-11,128insTGT), whose allele frequency was 3.1%. The -11,129_-11,128insTGT resulted in the disruption of USF1 binding and a 36% reduction of the enhancer activity. These results suggest that CLEM4 is a constitutive enhancer of the CYP3A4 gene in the liver and that -11,129_-11,128insTGT may at least partly contribute to the interindividual variability of CYP3A4 expression.
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PMID:Identification of a novel polymorphic enhancer of the human CYP3A4 gene. 1474 74

The expression of CYP3A4 gene is induced by a variety of structurally unrelated xenobiotics including the antibiotic rifampicin, pregnenolone 16-carbonitrile (PCN), and endogenous hormones, that might mediate through steroid and xenobiotic receptor (SXR) system. The molecular mechanisms underlying regulation of CYP3A4 gene expression have not been understood. In order to gain the insight of the molecular mechanism of CYP3A4 gene expression, study has been undertaken to investigate if the histone deacetylation is involved in the regulation of CYP3A4 gene expression by proximal promoter in human hepatoma HepG2 cells. Also we have investigated to see if SXR is involved in the regulation of CYP3A4 proximal promoter activity in human hepatoma HepG2 cells. HepG2 cells were transfected with a plasmid pCYP3A4-Luc containing approximately 1 kb of the CYP3A4 proximal promoter region (-863 to +64 bp) in front of a reporter gene, luciferase, in the presence or absence of pSAP-SXR. In HepG2 cells, CYP3A4 inducers, such as rifampicin, PCN and RU486 showed minimal stimulation of CYP3A4 proximal promoter activity in the absence of SXR and histone deacetylase (HDAC) inhibitors. 4-Dimethylamino-N-[4-(2-hydroxycarbamoylvinyl)benzyl]benzamide (IN2001), a new class HDAC inhibitor significantly increased CYP3A4 proximal promoter activity over untreated control cells and rifampicin concomitant treatment with IN2001 increased further CYP3A4 proximal promoter activity that was stimulated by IN2001. The results of this study demonstrated that both HDAC inhibitors and SXR are essential to increase of CYP3A4 proximal promoter activity by CYP3A4 inducers such as PCN, rifampicin, and RU486. Especially SXR seems to be important for the dose dependent response of CYP3A4 inducing chemicals to stimulate CYP3A4 proximal promoter activity. Also this data suggested that HDAC inhibitors seemed to facilitate the CYP3A4 proximal promoter to be activated by chemicals.
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PMID:Histone deacetylase inhibitor stimulate CYP3A4 proximal promoter activity in HepG2 cells. 1518 Mar 6

R126638 is a novel triazole with in vitro activity similar to that of itraconazole against dermatophytes, Candida spp., and Malassezia spp. In animal models of dermatophyte infections, R126638 showed superior antifungal activity. R126638 inhibits ergosterol synthesis in Candida albicans, Trichophyton mentagrophytes, Trichophyton rubrum, and Microsporum canis at nanomolar concentrations, with 50% inhibitory concentrations (IC(50)s) similar to those of itraconazole. The decreased synthesis of ergosterol and the concomitant accumulation of 14 alpha-methylsterols provide indirect evidence that R126638 inhibits the activity of CYP51 that catalyzes the oxidative removal of the 14 alpha-methyl group of lanosterol or eburicol. The IC(50)s for cholesterol synthesis from acetate in human hepatoma cells were 1.4 microM for itraconazole and 3.1 microM for R126638. Compared to itraconazole (IC(50) = 3.5 microM), R126638 is a poor inhibitor of the 1 alpha-hydroxylation of 25-hydroxyvitamin D(3) (IC(50) > 10 microM). Micromolar concentrations of R126638 and itraconazole inhibited the 24-hydroxylation of 25-hydroxyvitamin D(3) and the conversion of 1,25-dihydroxyvitamin D(3) into polar metabolites. At concentrations up to 10 microM, R126638 had almost no effect on cholesterol side chain cleavage (CYP11A1), 11 beta-hydroxylase (CYP11B1), 17-hydroxylase and 17,20-lyase (CYP17), aromatase (CYP19), or 4-hydroxylation of all-trans retinoic acid (CYP26). At 10 microM, R126638 did not show clear inhibition of CYP1A2, CYP2A6, CYP2D6, CYP2C8, CYP2C9, CYP2C10, CYP2C19, or CYP2E1. Compared to itraconazole, R126638 had a lower interaction potential with testosterone 6 beta hydroxylation and cyclosporine hydroxylation, both of which are catalyzed by CYP3A4, whereas both antifungals inhibited the CYP3A4-catalyzed hydroxylation of midazolam similarly. The results suggest that R126638 has promising properties and merits further in vivo investigations for the treatment of dermatophyte and yeast infections.
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PMID:The novel azole R126638 is a selective inhibitor of ergosterol synthesis in Candida albicans, Trichophyton spp., and Microsporum canis. 1532 84

Focusing on drug metabolism in liver, we constructed and evaluated a drug-metabolizing bioartificial liver (BAL) support system. In a previous study, we constructed ammonia-metabolizing CHO and hepatoma-derived HepG2 cell lines by recombination of the glutamine synthetase (GS) gene. For further mimicking of liver metabolism, the human hepatoma-derived cell line HepG2 was transformed by the pBudCE-GS-CYP3A4 vector, which contains GS and drug-metabolizing CYP 3A4 genes. The constructed GS-3A4-HepG2 cell line showed 3A4 activity higher than that of human primary hepatocytes. The drug-metabolizing activity of BAL (BAL clearance) was evaluated using this cell line. The estimated clearance was higher than that of the human hepatocyte system.
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PMID:Construction and evaluation of drug-metabolizing cell line for bioartificial liver support system. 1590 54

Cross-talk between nuclear receptors involved in the control of drug metabolism is being increasingly recognised as a source of drug side effects. Omeprazole is a well known activator of the aryl hydrocarbon receptor (AhR). We investigated the regulation of AhR by omeprazole-sulphide, a degradation metabolite of omeprazole, using CYP1A mRNA induction, reporter gene assay, receptor DNA binding, ligand binding, nuclear translocation, trypsin digests, and drug metabolism analysis in mouse Hepa-1c1c7, human HepG2 cells and primary human hepatocytes. Omeprazole-sulphide is a pure antagonist of AhR in Hepa-1c1c7 and HepG2 hepatoma cell lines. In Hepa-1c1c7 cells, omeprazole-sulphide is a ligand of AhR, inhibits AhR activation to a DNA-binding form, induces a specific pattern of AhR trypsin digestion and inhibits AhR nuclear translocation and subsequent degradation in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, in highly differentiated primary human hepatocytes treated with rifampicin an agonist of the pregnane X receptor (PXR), omeprazole-sulphide behaves as an agonist of AhR. Inhibition of drug metabolizing enzymes by ketoconazole restores the antagonist effect of omeprazole-sulphide. Metabolic LC/MS analysis reveals that omeprazole-sulphide (AhR antagonist) is efficiently converted to omeprazole (AhR activator) by cytochrome P450 CYP3A4, a target gene of PXR, in primary human hepatocytes but not in hepatoma cells in which PXR is not expressed. This report provides the first evidence for a cross-talk between PXR/CYP3A4 and AhR. In addition, it clearly shows that conclusions drawn from experiments carried out in cell lines may lead to erroneous in vivo predictions in man.
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PMID:Role of CYP3A4 in the regulation of the aryl hydrocarbon receptor by omeprazole sulphide. 1610 80

The human cytochrome P450 3A (CYP3A) enzymes, which metabolize 50% of currently used therapeutic drugs, exhibit great interindividual differences in activity that have a major impact on drug treatment outcome, but hitherto no genetic background importantly contributing to this variation has been identified. In this study we show that CYP3A4 mRNA and hnRNA contents with a few exceptions vary in parallel in human liver, suggesting that mechanisms affecting CYP3A4 transcription, such as promoter polymorphisms, are relevant for interindividual differences in CYP3A4 expression. Tanzanian (n=143) healthy volunteers were phenotyped using quinine as a CYP3A probe and the results were used for association studies with CYP3A4 genotypes. Carriers of CYP3A4*1B had a significantly lower activity than those with CYP3A4*1 whereas no differences were seen for five other SNPs investigated. Nuclear proteins from the B16A2 hepatoma cells were found to bind with less affinity to the CYP3A4*1B element around -392 bp as compared to CYP3A4*1. The data indicate the existence of a genetic CYP3A4 polymorphism with functional importance for interindividual differences in enzyme expression.
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PMID:Phenotype-genotype variability in the human CYP3A locus as assessed by the probe drug quinine and analyses of variant CYP3A4 alleles. 1617 83

We focused on the establishment of a trial procedure for the collection and distribution of Japanese liver tissues obtained from waste surgical resections for drug development and research use. The following procedures were prepared for this project: the pretreatment of liver tissues before storage, their storage at 4 degrees C, the transport of liver samples, the setting up of a communication network among the participating hospitals and laboratories and the approval of each ethics committee. Thirteen liver samples (1.6-7.6 g) obtained from patients whose livers were excised due to cirrhosis, hepatocellular carcinoma, cholangiocarcinoma, or metastasis from colorectal carcinoma and were donated for research. Informed consent was obtained from every patient. Freshly isolated human hepatocytes were prepared from nine liver samples (viability 34.3-86.1%). Four samples were unsuitable to prepare hepatocytes. The profile of testosterone metabolism as 6beta-, 2beta-, 16beta-, 16alpha- and 2alpha-hydroxytestosterone and androstenedione in freshly isolated hepatocytes was shown to be specific for human liver. The 6beta-hydroxylation activity catalyzed by CYP3A4/5 indicated a high level of metabolism (139-996 pmol/min/million cells). Levels of 7-ethoxycoumarin O-deethylation and glucronidation activities were sufficient for analysis in freshly isolated human hepatocytes. We conclude that liver tissues from waste surgical resections supplied from a participating hospital can constitute a valuable source of freshly isolated human hepatocytes for drug development and safety evaluation.
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PMID:[Network for the collection and distribution of Japanese liver tissues resected surgically for drug development and research use]. 1654 56

Steroid and xenobiotic receptor (SXR) or human pregnane X receptor (hPXR) dimerizes with retinoid X receptor (RXR) and regulates the transcription of genes encoding xenobiotic-metabolizing enzymes such as CYP3A4. Rifampin, the classical activator of CYP3A4, binds to SXR directly. It is unclear whether various natural and synthetic retinoids can regulate the expression of CYP3A4. To evaluate the effects of retinoids on the RXR/SXR-mediated pathway, transient transfection assays were performed on both CV-1 and human hepatoma Huh7 cells using a reporter construct containing multiple RXR/SXR consensus binding elements (an everted repeat with a 6-nucleotide spacer, ER-6). The results revealed that eight out of 13 retinoids screened significantly induced the RXR/SXR-mediated pathway in Huh7 cells. At an equal molar concentration, the acid forms (9-cis-RA, 13-cis-RA, and all-trans-RA) or aldehyde, the direct precursor of acid (9-cis-retinal and 13-cis-retinal), exhibited a greater or similar potency than rifampin. Depending on the ligands, RXR may serve as a silent or an active partner of SXR. Additionally, retinoids can increase CYP3A4 enzyme activity in Huh7 cells. To further evaluate the potential drug-drug interactions, which may be caused by retinoids, Huh7 cells were pretreated with 9-cis-RA and followed by acetaminophen. We showed that 9-cis-RA enhanced the covalent binding of N-acetyl-p-quinoneimine, a toxic intermediate of acetaminophen produced by phase I enzymes oxidation. This result suggested that drug-drug interaction might occur between 9-cis-RA and acetaminophen in human liver cells. Taken together, retinoids activate the RXR/SXR-mediated pathway and regulate the expression of CYP3A4. Thus, retinoids potentially can cause drug-drug interactions when they are administered with other CYP3A4 substrates.
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PMID:Retinoids activate the RXR/SXR-mediated pathway and induce the endogenous CYP3A4 activity in Huh7 human hepatoma cells. 1663 23

Two recent screens for copy-number variations in the entire human genome found 12.4 gene copy number variations per person, including 2.5% of individuals with gains between 7q21.1 and 7q22.1, the chromosomal location of CYP3A4. CYP3A4 is involved in the metabolism of approximately 50% of all drugs, including many cancer chemotherapeutic agents. CYP3A4 gene copy was determined in DNA from 143 individuals: normal human livers, primary and secondary liver tumors, human hepatic cell lines, and immortalized cell lines representing eight ethnically diverse populations. CYP3A4 gene copy was normal in all but one sample, a primary human hepatocellular carcinoma cell line (TONG/HCC). Southern blots of TONG/HCC DNA revealed an approximate 10-fold increase in CYP3A and a corresponding increase in CYP3A mRNA expression and catalytic activity. Fluorescent in situ hybridization of TONG/HCC revealed specific amplification of the CYP3A4 gene on chromosome 7q21 but no amplification of the MDR1 gene that localizes 11.9 Mb upstream of CYP3A4. High resolution analysis of DNA copy number by comparative genomic hybridization confirmed amplification at 7q21.3-7q22. The amplicon spanned 1.7 Mb and contained 30 known genes, including the entire CYP3A locus. To determine whether CYP3A4 expression affected chemotherapeutic toxicity, LLC-PK1 cells were transduced with adenoviruses expressing CYP3A4 and P450 reductase. CYP3A4 conferred resistance to taxol, vinblastine and topotecan. These studies demonstrate that CYP3A4 copy number differences do not contribute to the normal variation in CYP3A4 expression. Tumors with increased CYP3A copy number (via amplification or increased chromosome 7q) would be expected to show reduced cytotoxicity to some chemotherapeutic drugs and potentially an increase in the outgrowth of drug resistant tumors.
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PMID:Increased CYP3A4 copy number in TONG/HCC cells but not in DNA from other humans. 1670 50


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