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)

Galactose was introduced to poly(L-lysine) (PLL) with an average molecular weight of 13,000 to develop a hepatocyte-specific carrier for gene drugs. The pharmacokinetic characteristics of a model plasmid, pCAT (plasmid DNA encoding chloramphenicol acetyltransferase reporter gene), complexed with galactosylated PLL (Gal-PLL) was studied in mice in relation to its physicochemical properties. pCAT/Gal-PLL complex at a ratio of 1:0.6 (w/w) has a zeta potential of -20 mV and a mean particle size of about 180 nm. After intravenous injection, [32P]pCAT/Gal-PLL was rapidly eliminated from the circulation and preferentially taken up by the liver's parenchymal cells. The hepatic uptake of [32P]pCAT/Gal-PLL was significantly inhibited by prior administration of Gal-bovine serum albumin, suggesting that the uptake was mediated by the asialoglycoprotein receptors on hepatocytes. In vitro transfection experiments using a hepatoma cell line expressing the asialoglycoprotein receptor revealed that pCAT/Gal-PLL gave a high CAT gene expression whereas pCAT complexed with unmodified PLL failed to transfect the cells.
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PMID:Targeted delivery of plasmid DNA complexed with galactosylated poly(L-lysine). 974 38

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) is inducible by genotoxic stress. MGMT induction results from transcriptional activation of the MGMT gene which is a specific response to DNA damage. A possible factor involved in triggering MGMT induction might be p53, because both p53 and MGMT are activated by DNA breaks. To study the effect of p53 on induction of the MGMT gene, we compared the presence of functional wild-type (wt) and mutant p53 with MGMT expression level in various mouse fibroblasts and rat hepatoma cell lines upon genotoxic treatment. Cells which responded to ionizing radiation (IR) by MGMT induction displayed functional p53, whereas in cells not expressing wt p53, MGMT induction was not observed. Also, the cloned MGMT promoter was inducible by IR upon transfection into p53 wt cells, but not in cells deficient for p53. Thus, expression of wt p53 appears to be required for induction of MGMT mRNA and protein by IR. On the other hand, transfection of a MGMT-promoter-CAT construct together with p53 (either wt or mutant) in cells expressing wt p53 markedly reduced the basal activity of the MGMT promoter whereas cotransfection with a p53 antisense construct slightly increased MGMT promoter activity. Furthermore, cotransfection of MGMT promoter with wt or mutant p53 in p53 wt cells reduced radiation evoked MGMT promoter induction. Thus, transfection mediated high level expression of p53 has inhibitory effect both on basal MGMT promoter activity and its activation by IR. The results give evidence for involvement of p53 in DNA damage-induced MGMT promoter activation.
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PMID:p53 is involved in regulation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT) by DNA damaging agents. 978 1

Induction of phase II enzymes is an important mechanism of chemoprevention. In our search for novel cancer chemopreventive agents, 4'-bromoflavone (4'BF) was found to significantly induce quinone reductase (QR) activity in cultured murine hepatoma 1c1c7 cells (concentration to double activity: 10 nM) and effectively induce the alpha- and mu-isoforms of glutathione S-transferase in cultured H4IIE rat hepatoma cells with no observed toxicity. In short-term dietary studies, 4'BF was also shown to increase QR activity and glutathione levels in rat liver, mammary gland, colon, stomach, and lung in a dose-dependent manner. Induction mediated by 4'BF was bifunctional (induction of both phase I and phase II enzymes) and regulated at the transcriptional level, as revealed by transient transfection studies with plasmid constructs (pDTD-1097CAT, XRE-CAT, and ARE-CAT) and reverse transcription-PCR-based analysis of QR mRNA. In studies conducted with female Sprague Dawley rats, the effects of 4'BF on the relative induction levels of phase I and phase II enzyme activities were investigated in liver and mammary gland. Treatment with 4'BF and 7,12-dimethylbenz[a]anthracene (DMBA) or 4'BF alone did not significantly alter DMBA-induced cytochrome P4501A1 activity (phase I enzyme), but it significantly increased QR activity (phase II enzyme), compared with the DMBA treatment group. In addition, 4'BF was found to be a potent inhibitor of cytochrome P4501A1-mediated ethoxyresorufin-O-deethylase activity, with an IC50 of 0.86 microM. Furthermore, in studies conducted with cultured HepG2 or MCF-7 cells, 4'BF significantly reduced the covalent binding of metabolically activated benzo[a]pyrene to cellular DNA. On the basis of these results, a full-term cancer chemoprevention study was conducted with DMBA-treated female Sprague Dawley rats. Dietary administration of 4'BF (2000 and 4000 mg per kg of diet, from 1 week before to 1 week after DMBA) significantly inhibited the incidence and multiplicity of mammary tumors and greatly increased tumor latency. In summary, 4'BF can be viewed as a relatively simple, readily available, inexpensive compound that is a highly effective cancer chemopreventive agent. The full mechanism of action remains to be defined, but enhancement of detoxification pathways appears to be important.
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PMID:Cancer chemopreventive activity mediated by 4'-bromoflavone, a potent inducer of phase II detoxification enzymes. 997 3

Synergism between exposure to chemical carcinogens and infection with the hepatitis B virus (HBV) has been implicated in the high incidence of hepatocellular carcinoma. In this study we report that the HBV protein HBx, inhibits cellular DNA repair capacity in a p53-independent manner. Two alternative assays were used: the host cell reactivation assay, which measures the cell's capacity to repair DNA damage in a reporter plasmid, and unscheduled DNA synthesis, which measures the overall DNA repair capacity in damaged cells. Two p53-proficient cell lines, the hepatocellular carcinoma cell line HepG2 and liver epithelial cell line CCL13, were co-transfected with the pCMV-HBx reporter plasmid and the pCMV-CAT plasmid damaged with UVC radiation. Compared with cells transfected with control plasmid, the presence of HBx resulted in approximately 50% inhibition of the cell's capacity to reactivate CAT activity of UVC-damaged plasmid, and approximately 25% inhibition of unscheduled DNA synthesis in cells treated with either aflatoxin B1 epoxide or UVC radiation. Using the p53-deficient cell line Saos-2, we demonstrated that expression of HBx also resulted in diminished overall cellular DNA repair of damage induced by both aflatoxin B1 epoxide and UVC radiation, using both the host cell reactivation and unscheduled DNA synthesis assays. In summary, this study provides evidence for p53-independent regulation of DNA repair by HBx.
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PMID:Downregulation of DNA excision repair by the hepatitis B virus-x protein occurs in p53-proficient and p53-deficient cells. 1019 May 65

Previous studies demonstrated that the -82 to +87 nucleotides (nt) 5'-upstream region of the chicken apolipoprotein (apoAI) gene are necessary for maximum reporter chloramphenicol acetyl transferase (cat) gene activation in chicken hepatocarcinoma (LMH) cells [Bhattacharyya, N., Chattapadhyay, R., Oddoux, C., Banerjee, D., 1993. Characterisation of the chicken apolipoprotein A-I gene 5'-flanking region. DNA Cell Biol. 12, 597-604]. The -82 to +87nt contain the 5'-untranslated nt, part of the first intron, and the upstream regulatory sequences. In this study, we examined the role of the first intron in the transcriptional regulation of the chicken apoAI gene. Six different reporter cat gene constructs with or without part of the first intron were prepared and transfected into LMH, normal rat kidney (NRK) and human hepatocarcinoma (HepG2) cells. Cell extracts were prepared from each transfected cell line, and CAT activities were measured. All three cell-lines readily expressed CAT, indicating that transcriptional regulatory sequences are present within the first intron region of the chicken apoAI gene. In an enhancer assay, the first intron containing cat construct exhibited a 5.4-fold increase of reporter activity in NRK cells when compared to a SV 40 promoter containing cat plasmid, suggesting the presence of a moderate enhancer element within +29 to +87nt of the first intron. DNase I protection assays, electrophoretic mobility shift assays and binding experiments with nuclear proteins isolated from different chicken tissues and LMH cells showed interaction with +29 to +87nt. Nuclear proteins isolated from tissues like liver and intestine, that actively express apoAI gene, failed to interact with +29 to +87nt, whereas nuclear proteins isolated from tissues that are less active in apoAI gene expression readily interacted with this region. To show the binding of the LMH-specific trans-acting factors to the +50 to +68nt intron region, DNA-affinity chromatography step was performed by using 3H-labeled nuclear proteins. These studies demonstrate that the first intron region of the apoAI gene interacts with trans-acting proteins and plays an important role in transcriptional regulation of the apoAI gene.
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PMID:Transcriptional regulatory sequences within the first intron of the chicken apolipoproteinAI (apoAI) gene. 1039 11

We have previously shown that a mixture of dietary conjugated derivatives of linoleic acid (conjugated linoleic acid, CLA) induces peroxisome proliferator-responsive enzymes and modulates hepatic lipid metabolism in vivo. The present studies demonstrate that CLA is a high affinity ligand and activator of peroxisome proliferator-activated receptor alpha (PPARalpha) and induces accumulation of PPAR-responsive mRNAs in a rat hepatoma cell line. Using a scintillation proximity assay (SPA), CLA isomers were shown to be ligands for human PPARalpha with a rank order of potency of (9Z,11E)>(10E,12Z)>(9E,11E)> furan-CLA (IC(50) values from 140 nm to 400 nm). Levels of acyl-CoA oxidase (ACO), liver fatty acid-binding protein (L-FABP), and cytochrome P450IVA1 (CYP4A1) mRNA were induced by CLA in FaO hepatoma cells. Even though linoleate and CLA were incorporated into lipids of hepatoma cells to the same extent, linoleate had little or no effect on ACO, CYP4A1, or L-FABP mRNA. In agreement with its binding potency, (9Z,11E)-CLA was the most efficacious PPARalpha activator in the mouse PPARalpha-GAL4(UAS)(5)-CAT reporter system. These data indicate that CLA is a ligand and activator of PPARalpha and its effects on lipid metabolism may be attributed to transcriptional events associated with this nuclear receptor. Also, (9Z,11E)-CLA is one of the most avid fatty acids yet described as a PPARalpha ligand.
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PMID:Conjugated linoleic acid is a potent naturally occurring ligand and activator of PPARalpha. 1042 78

Infection by HBV of a cell already infected with other viral species or vice versa has been suggested as being involved in hepatocellular carcinoma. Using the CAT assay method, we investigated the interactive roles of HBx and potentially oncogenic and transactivating viral early proteins such as Ad5 E1A, HPV-16 E6, and SV40 T ag. In the presence of HBx, only HPV-16 E6 showed significant synergistic transactivation of EnI. We further investigated the function of the HPV-16 E6 using deletion, heterologous promoter, and mutation analyses on the EnI promoter. The results showed that the synergistic effect was mediated through the AP1 site of the E element in EnI by the direct activation of AP1 and support the idea that the infection by HBV of the cell with other viral species such as HPV-16 could increase the transcription activity of the HBV and other oncogenes containing an AP1 site in the promoter.
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PMID:The synergistic transactivation of the hepatitis B viral (HBV) pregenomic promoter by the E6 protein of human papillomavirus type 16 (HPV-16 E6) with HBV X protein was mediated through the AP1 site of E element in the enhancer I (EnI) in human liver cell. 1054 91

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

During a series of transfection experiments, the pRSV-luc plasmid used as an internal control was found to be sensitive to cotransfection with expression vectors for several members of the steroid/thyroid/retinoid superfamily of nuclear receptors. Therefore, a survey of the effect of these expression vectors on the activity of four reporter plasmids was conducted. In CV-1 cells, the activity of pRSV-luc, which contains the P. pyralis luciferase gene, was repressed by co-transfection of PPARalpha and ARP-1 and was activated by COUP-TFI. Expression of pSV40-luc, containing the same luciferase gene, was repressed by PPARalpha and HNF-4 and activated by both COUP-TFI and ARP-1. All four of these expression vectors reduced the expression of the pRL-TK plasmid, which contains the luciferase gene from Renilla reniformis. RXR expression vectors had no effect on luciferase activity in CV-1 cells but induced luciferase activity in H4IIEC3 hepatoma cells. This activation was blocked by the addition of ligand, 9-cis retinoic acid. pSV2-CAT, which contains the chloramphenicol acetyltransferase gene, was insensitive to all receptor expression vectors tested. Both the P. pyralis and R. reniformis luciferase genes appear to contain sequences that render them responsive to steroid/thyroid/retinoid nuclear receptors.
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PMID:Sensitivity of virally-driven luciferase reporter plasmids to members of the steroid/thyroid/retinoid family of nuclear receptors. 1062 8

Hepatocyte Growth Factor (HGF) exerts its biological effects via binding and activating a transmembrane protein tyrosine kinase receptor known as c-Met. Previous studies from our laboratory demonstrated that c-met gene expression is inducible by its own ligand (HGF). However, the molecular mechanism(s) involved in this process are unknown. The present study was carried out to address this question. Transfection of various c-met-CAT promoter constructs into the mouse hepatocellular carcinoma cell line Hepa 1-6 in combination with electrophoretic mobility shift assays (EMSA) identified the responsive element as an activated protein-1 (AP-1) binding site (TGAGTCA) within the c-met core promoter region at position -158 to -152. The c-met AP-1 element binds specifically to AP-1 protein as verified by supershift assays. EMSA studies and mutational analyses of the promoter region also revealed that the members of the Sp family of transcription factors (Sp-1 and Sp-3) bind to the c-met Sp-1 element (located at position -124) which is adjacent to the AP-1 site. We show that Sp binding dampens binding of AP-1 to its cognate site in the c-met promoter region. Stimulation of Hepa 1-6 cells with HGF resulted in a rapid and dramatic enhancement of the AP-1 binding activity as well as an overall increase in the level of AP-1 protein. Cotransfection of AP-1 expression vectors (c-Fos plus c-Jun) with c-met promoter constructs resulted in stimulation of c-met promoter activity. We found that transactivation of the c-met promoter by AP-1 can be blocked by Curcumin, an inhibitor of AP-1. Moreover, we found that the induction of the endogenous c-met gene by HGF is inhibited by the addition of Curcumin. The results demonstrate that the HGF-induced transcription of the c-met gene by HGF is, at least in part, due to activation of the AP-1 pathway.
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PMID:Transcriptional activation of the hepatocyte growth factor receptor (c-met) gene by its ligand (hepatocyte growth factor) is mediated through AP-1. 1071


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