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 role of nuclear protein phosphorylation in intracellular signal transduction of tumor-necrosis factor-alpha (TNF-alpha) in the human hepatoma cell line PLC(PRF/5) was investigated. TNF-alpha, which displays cytolytic activity against PLC hepatoma cells, elevated the in vitro phosphorylation of two nuclear proteins (21 kDa and 34 kDa) 16 h after treatment. The cytotoxicity and enhanced nuclear protein phosphorylation by TNF-alpha treatment decreased in the presence of dexamethasone. Both the 21-kDa and 34-kDa proteins were extracted with 2.2 M NaCl from nuclear pellets and phosphorylated in kinase reaction mixtures containing a high concentration of salt. By phosphoamino acid analysis, the specificity of the nuclear kinase was found to be directed toward serine residues. The protein kinase inhibitors H7, staurosporine and herbimycin A, inhibited the phosphorylation of the 21-kDa and 34-kDa proteins in vitro, but calphostin C and heparin did not. The treatment of cells with 4 beta-phorbol 12-myristate 13-acetate or okadaic acid did not affect the in vitro phosphorylation of the two nuclear proteins. An anti-Fas antibody increased the phosphorylation of the 21-kDa and 34-kDa proteins in PLC cells. DNA fragmentation was observed in PLC cells treated with TNF-alpha and anti-Fas antibody after 24 h treatment. These data suggest an involvement of nuclear protein kinase in signal-transduction pathways of apoptotic cell damage triggered by TNF-alpha in PLC hepatoma cells.
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PMID:Enhanced phosphorylation of nuclear 21-kDa and 34-kDa proteins in hepatoma cell death induced by tumor-necrosis factor-alpha. 755 42

Expression of the gene encoding the mitochondrial fatty acid. beta-oxidation enzyme, medium-chain acyl-CoA dehydrogenase (MCAD), is regulated among tissues during development and in response to alterations in substrate availability. To identify and characterize cis-acting MCAD gene promoter regulatory elements and corresponding transcription factors, DNA-protein binding studies and mammalian cell transfection analyses were performed with hjman MCAD gene promoter fragments. DNA:protein binding studies with nuclear protein extracts prepared from hepatoma G2 cells, 3T3 fibroblasts, or Y-1 adrenal tumor cells identified three sequences (nuclear receptor response element 1 or NRRE-1, NRRE-2, and NRRE-3) that bind orphan members of the steroid/thyroid nuclear receptor superfamily including chicken ovalbumin upstream promoter transcription factor and steroidogenic factor 1. Sp1 binding sites (A-C) were identified in close proximity to each of the NRREs. NRRE-3 conferred cell line-specific transcriptional repression by interacting with chicken ovalbumin upstream promoter transcription factor or activation via steroidogenic factor 1. In contrast, the Sp1 binding site A behaved as a transcriptional activator in all cell lines examined. We propose that multiple nuclear receptor transcription factors interact with MCAD gene promoter elements to differentially regulate transcription among a variety of cell types.
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PMID:The human medium chain Acyl-CoA dehydrogenase gene promoter consists of a complex arrangement of nuclear receptor response elements and Sp1 binding sites. 759 84

NAD(P)H:quinone oxidoreductase1 (DT-diaphorase or NQO1) is a flavoprotein that promotes obligatory two-electron reduction of quinones, preventing their participation in redox cycling, oxidative stress, and neoplasia. NQO1 is ubiquitously expressed. However, a large amount of variation in NQO1 gene expression was noticed among various human tissues. NQO1 gene is upregulated in livers of hepatocarcinoma patients, and its expression is induced in response to a variety of compounds, including planar aromatic hydrocarbons, phenolic antioxidants/chemoprotectors, tumor promoters, and hydrogen peroxide. Deletion mutagenesis in the NQO1 gene promoter identified several cis-elements including antioxidant response element (ARE), xenobiotic response element, and AP2 element, which regulate the expression and induction of the NQO1 gene. Among these DNA elements, ARE is the most important cis-element required for high basal expression of the NQO1 gene in tumor tissues, as compared to the normal tissues of the same origin, and for its induction in response to xenobiotics and antioxidants. Nucleotide sequence analysis of the ARE indicated presence of three AP1/AP1-like elements and a GCA box. Mutational analysis indicated a requirement of two AP1/AP1-like elements arranged as inverse repeats at the interval of three base pairs for the ARE activity. The GCA box in the ARE was required for optimum basal and induced expression. ARE is a novel cis-element because a single AP1/AP1-like element did not stimulate gene expression in response to xenobiotics and antioxidants. Band shift and supershift assays identified Jun, Fos, and novel proteins in the hARE-nuclear protein complexes that mediate regulation of the NQO1 gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:NAD(P)H:quinone oxidoreductase1 (DT-diaphorase): expression, regulation, and role in cancer. 762 Feb 21

"Spot 14" is a nuclear protein that is rapidly induced by thyroid hormone (T3) and dietary carbohydrate in liver. We used an antisense oligonucleotide to inhibit induction of spot 14 protein by T3 and glucose in primary cultures of rat hepatocytes to test the hypothesis that the protein could function in the regulation of lipid synthesis. Spot 14 protein was undetectable in hepatocytes maintained in 5.5 mM glucose without T3, and was induced within 4 h after addition of 27.5 mM glucose and 50 nM T3 to the culture medium, reaching a maximal level within 24 h. Accumulation of spot 14 protein was markedly inhibited in hepatocytes transfected with a spot 14 antisense oligonucleotide, but not in those treated with a control oligonucleotide. Transfection of the antisense, but not control, oligonucleotide also abrogated the increase in lipogenesis induced by T3 and glucose. Reduced triglyceride formation accounted for the diminished net lipid synthesis. In contrast to lipogenesis, glucose uptake was not significantly affected by the transfections. Antisense transfection inhibited the induction of both ATP-citrate lyase and fatty acid synthase immunoreactivities, as well as malic enzyme activity, indicating that the observed reduction in lipogenesis could be explained by diminished cellular content of lipogenic enzymes. Reduced malic enzyme activity in antisense-transfected hepatocytes was accompanied by lowered relative abundance of malic enzyme mRNA, suggesting that the antisense effects on lipogenic enzymes were mediated at the pretranslational level. The oligonucleotides did not significantly affect lipogenesis in a rat hepatoma cell line that does not express detectable spot 14 mRNA or protein. These data directly implicate the spot 14 protein in the transduction of hormonal and dietary signals for increased lipid metabolism in hepatocytes.
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PMID:Direct evidence for a role of the "spot 14" protein in the regulation of lipid synthesis. 762 69

Fibronectin (FN) is a widely distributed extracellular matrix protein that is essential for cell adhesion in a variety of biological processes such as wound healing, tissue development and remodeling and oncogenic transformation. Appropriate FN levels are obtained by induction or repression of the FN gene in response to specific factors or circumstances in vivo. In order to identify regulatory regions involved in tissue-specific expression of FN, we have examined the transcriptional activity of overlapping fragments, within 4 kb upstream of the rat FN gene, following transfection into different cell types. Two regions conferred increases in transcription. The region between -1.08 and -2.6 displayed tissue-specificity and was active in fibroblasts but not hepatoma cells. The second region, between -3.2 and -3.9, was active in both cell types. Further characterization of the -1.08 to -2.6 segment demonstrated that it acts as an enhancer. Exonuclease III deletions of the 3' and 5' ends of the enhancer localized essential sequences between -1.5 and -1.7 and indicate that this fragment acts in concert with other sites between -1.08 and -2.6 to provide maximum enhancer activity. Gel mobility shift assays demonstrated fibroblast-specific binding of nuclear protein(s) to a 65 bp fragment within the essential region and DNase I footprinting localized this binding to a 27 bp sequence. Deletion of the sequence abolished the activity of the 1.5 kb enhancer. These studies show that a novel DNA sequence at -1688 is involved in regulating transcription of the FN gene in fibroblasts.
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PMID:Identification of an enhancer involved in tissue-specific regulation of the rat fibronectin gene. 766 11

In previous studies, we identified a 21 bp palindrome (-794 to -774) located within the negative regulatory element of the human CYP1A1 gene consisting of an 8 bp inverted repeat and 5 bp spacer. This element specifically binds protein(s) present in HepG2 nuclear extract preparations and is capable of down-regulating heterologous promoters and enhancers in transient expression assays. Conserved guanine/cytosine-rich regions which flank the palindrome also were implicated in this activity. In the present study, we examined similar regions from the rat (-881 to -746) and mouse (-822 to -683) CYP1A1 genes for their ability to bind nuclear protein and down-regulate heterologous promoters and enhancers. These rodent DNA fragments contain the conserved guanine/cytosine-rich sequences, as well as half-sites similar to those found in the human CYP1A1 palindrome. However, each half-site is separated by approximately 40 bp. DNase I footprint analyses revealed the presence of rat and mouse nuclear proteins which gave a similar protection pattern as that observed with nuclear proteins from the human cell line, HepG2. Electrophoretic mobility shift assays with the human negative regulatory element demonstrated the formation of specific DNA-protein complexes with rat and mouse nuclear protein(s). Interestingly, two specific DNA-protein complexes were observed with rodent extracts as compared to the single specific complex seen with human extract. Specific binding was not observed with either the orthologous rat or mouse fragments using human or rodent extracts. In transient expression assays, the rat and mouse fragments were unable to down-regulate enhancer/promoter activity. This absence of negative regulatory activity occurred whether transfections were performed in human, rat or mouse hepatoma cell lines. The human negative regulatory element, which was previously shown to down-regulate heterologous enhancers/promoters approximately 70% in human cells, did not exhibit this activity in rodent cell lines. UV cross-linking and southwestern blot analyses indicated a high degree of similarity between human and rodent NRE binding proteins, although some differences also were apparent. The possible implications of these findings with regards to species differences in the regulation of CYP1A1 expression are discussed.
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PMID:In vitro binding and functional studies comparing the human CYP1A1 negative regulatory element with the orthologous sequences from rodent genes. 785 71

The connexin 32 (Cx32) gene, a member of a multigene family, is expressed preferentially in the liver. The basal promoter complex of the rat Cx32 gene was previously localized to a 146-bp region (map positions [mp] -179 to -34) immediately upstream of the first exon. To investigate the biochemical factors contributing to the basal promoter activity, nuclear protein-DNA complexes within this region (mp -177 to -106) were investigated by using a DNA mobility shift assay. Three DNA-protein binding activities, termed Cx32-B1, Cx32-B2, and Cx32-B3, were identified with nuclear protein extracts from hepatoma cell lines, HuH7 and FAO-1. However, only Cx32-B2 binding activity was detected in nuclear protein extract from normal rat liver tissue. This activity was significantly more abundant in rat liver tissue than in hepatoma cell lines and tissues from various other organs. By using methylation interference footprinting, the Cx32-B2 complex was localized to the region between mp -152 and -127 and a DNA probe containing this region bound to a 60-kDa protein in rat liver nuclear extracts. Mutation of two nucleotides in the Cx32-B2 binding site abrogated the formation of the Cx32-B2 protein-DNA complex and significantly reduced the transcriptional activity of the Cx32 promoter. These results indicate that the Cx32-B2 complex is an essential component of the rat Cx32 basal promoter and is likely a major factor in the preferential expression of this gene in the liver.
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PMID:Basal promoter of the rat connexin 32 gene: identification and characterization of an essential element and its DNA-binding protein. 786 37

A genomic clone encoding the hamster CYP1A1 gene was isolated from a hamster EMBL-3 genomic library and characterized. The CYP1A1 gene contained seven exons including the noncoding first exon as determined for CYP1A1 of other species. DNA sequence analysis up to -2307 bp of the CYP1A1 gene revealed the occurrence of five consensus xenobiotic responsive elements (XREs) and one basal transcription element (BTE) in addition to the canonical TATA box. For functional analysis, transfection experiments were performed in human hepatoma HepG2 cells with reporter gene constructs consisting of fragments with various lengths of the 5'-flanking region of the CYP1A1 gene and bacterial chloramphenicol acetyltransferase (CAT) gene. External deletion of the upstream region from the reporter gene resulted in a stepwise decrease of the CAT activity, suggesting that XREs were responsible for inducible expression of CYP1A1 gene by 3-methylcholanthrene (MC). A negative regulatory element (NRE) was also identified in the 5'-flanking region at -833 to -642. Removal of the NRE from the CYP1A1-CAT fusion gene resulted in about 3-fold increase of MC-inducible CAT activity. Using gel retardation assays with HepG2 nuclear extract, we demonstrated the presence of a specific protein which bound to the NRE fragment. Further competition analysis and methylation interference assays revealed that the nuclear protein bound to a 22-base fragment (from -688 to -709) of the NRE region, whose sequences were conserved among hamster, human, and rat CYP1A1 genes.
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PMID:Characterization of hamster CYP1A1 gene: inducible expression and negative regulation. 788 54

C-reactive protein is a serum acute-phase reactant that increases several thousand-fold in concentration during inflammation in most mammals. However, mouse C-reactive protein is considered to be a minor acute-phase reactant, since its blood level increases only from approx. 0.1 to 1-2 micrograms/ml. A mouse genomic clone of approximately 5 kb was obtained to determine the molecular basis for the regulation of the expression of mouse C-reactive protein. Several cis-acting elements in the 5' flanking region that potentially regulate transcription were identified: two glucocorticoid-responsive elements, two CCAAT-enhancer-binding protein C (C/EBP) consensus elements that are required for the interleukin-1 responsiveness of some acute-phase reactant genes, an interleukin-6-responsive element, two hepatocyte nuclear factor-1 (HNF-1) elements and a single heat-shock element. Transfection of the hepatoma cell line Hep 3B.2 with a pCAT expression vector containing the 5' flanking sequence from -1083 to -3 bp from the transcriptional start site, and truncations of this sequence, localized elements that control the tissue-specific expression of mouse C-reactive protein to the two HNF-1 elements and a C/EBP, interleukin-1-responsive element located between -220 and -153, and -90 and -50 bp from the transcriptional start site. A constitutive nuclear protein from mouse-liver hepatocytes specifically binds to the HNF-1 elements. These findings explain the tissue-specific expression of the gene, as well as its limited expression during the acute-phase response.
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PMID:Cloning and tissue-specific expression of the gene for mouse C-reactive protein. 791 20

MnSOD is an antioxidant enzyme whose decrease in activity appears involved in tumorigenesis. We had previously reported the production of a monoclonal antibody, named 35.8, against rat MnSOD. In the present paper we show that it recognizes human and mouse MnSODs, although with different detection limits. We also use the antibody for immunofluorescence studies and observed that the antibody yields a positive staining of a non-nuclear protein, in rat and human organs where high concentration of MnSOD activity have been reported, and a lack of staining in rat kidney where MnSOD activity is decreased. Two tumors, an experimental rat hepatocarcinoma and a human liver metastasis from a gastrointestinal adenocarcinoma, are found negative for immunostaining.
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PMID:Monoclonal antibody 35.8 recognizes human, mouse and rat MnSODs in western blot and immunostaining. 808 Dec


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