UMLS:C0019204 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UMLS:C0019204 (hepatocellular carcinoma)
71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gene regulatory functions of the human IL-2 receptor (IL-2R) were reconstituted in transiently transfected hepatoma cells. The combination of IL-2R beta and -gamma mediated a strong stimulation via the cytokine response element of the alpha 1-acid glycoprotein gene and the hematopoietin receptor response element, but none via the IL-6 response element or the sis-inducible element. IL-2R alpha enhanced 10-fold the sensitivity of the IL-2R beta.gamma complex to respond to IL-2 or IL-15, but did not modify the specificity or the magnitude of maximal gene regulation. A homodimerizing chimeric receptor G-CSFR-IL-2R beta could mimic the IL-2R action. The IL-2R-mediated gene regulation was similar to that seen with receptors for IL-4 and IL-7, but differed from that for IL-6 type cytokines, thrombopoietin, erythropoietin, and growth hormone. The activation of STAT proteins by the IL-2R was assessed in transfected L-cells and COS-1 cells. Although IL-2R subunits were highly expressed in these cells, no STAT protein activation was detectable. Transient overexpression of JAK3 was unable to change the signaling specificity of the hematopoietin receptors in rat hepatoma, L-, and COS cells, but established a prominent activation of the IL-6 response elements by the IL-2R and IL-4R in HepG2 cells. The data support the model that the IL-2R and related hematopoietin receptors produce at least two separate signals which control gene expression.
...
PMID:The action of interleukin-2 receptor subunits defines a new type of signaling mechanism for hematopoietin receptors in hepatic cells and fibroblasts. 771 38

We describe a highly efficient calcium phosphate transfection protocol capable of achieving 100% transfection efficiency of reporter genes transiently expressed in the human hepatoma cell lines HuH7 and HepG2. This procedure, a modification of that described by Chen and Okayama, is reliable, reproducible, and eliminates the requirement for the inclusion of cotransfected internal control plasmids. While Chen and Okayama described the pH of the 2x BBS (N,N-bis[2-hydroxyethyl]-2-aminoethanesulfonic acid-buffered saline) and DNA concentration as being critical factors for optimal transfection efficiency, we show that a reduced and strictly monitored standing time of the DNA/CaCl2/2x BBS cocktail prior to addition to cultured cells is essential for a particular combination of pH and DNA concentration. We also show that the inclusion of internal control plasmids can inhibit reporter gene activity in a promoter- and dose-dependent manner. The method so described is also applicable for the transfection of other mammalian cell lines including COS and HeLa, and conceivably for the generation of stable transfectants at high frequency.
...
PMID:Optimization of experimental variables influencing reporter gene expression in hepatoma cells following calcium phosphate transfection. 781 89

We have previously shown that two remote glucocorticoid-responsive units (GRUs) of the rat tyrosine aminotransferase (TAT) gene contain multiple binding sites for several transcription factor families, including the glucocorticoid receptor (GR). We report here the identification of two novel binding sites for members of the Ets family of transcription factors in one of these GRUs. One of these binding sites overlaps the major GR-binding site (GRBS), whereas the other is located in its vicinity. Inactivation of the latter binding site leads to a twofold reduction of the glucocorticoid response, whereas inactivation of the site overlapping the GRBS has no detectable effect. In vivo footprinting analysis reveals that the active site is occupied in a glucocorticoid-independent manner, in a TAT-expressing cell line, even though it is located at a position where there is a glucocorticoid-dependent alteration of the nucleosomal structure. This same site is not occupied in a cell line that does not express TAT but expresses Ets-related DNA-binding activities, suggesting the existence of an inhibitory effect of chromatin structure at a hierarchical level above the nucleosome. The inactive Ets-binding site that overlaps the GRBS is not occupied even in TAT-expressing cells. However, this same overlapping site can confer Ets-dependent stimulation of both basal and glucocorticoid-induced levels when it is isolated from the GRU and duplicated. Ets-1 expression in COS cells mimics the activity of the Ets-related activities present in hepatoma cells. These Ets-binding sites could participate in the integration of the glucocorticoid response of the TAT gene with signal transduction pathways triggered by other nonsteroidal extracellular stimuli.
...
PMID:Participation of Ets transcription factors in the glucocorticoid response of the rat tyrosine aminotransferase gene. 791 Sep 45

As a putative mechanism of hepatitis B virus (HBV) uptake into hepatocytes the interaction between HBV and the hepatic, human-derived asialoglycoprotein receptor (ASGPR) was investigated. Sera from patients with different variations of hepatitis B surface antigen-(HBsAg) positive chronic hepatitis, HBV particles isolated from HBV carriers with high-titre viraemia and commercial HBsAg served as sources of HBV. ASGPR was affinity-purified from human liver. HBV that had bound to isolated ASGPR was either detected by radioimmunoassay using solid-phase bound ASGPR or enzyme immunoassay with biotin-ASGPR bound to immobilized HBV. Furthermore, binding and uptake of purified, 125I-labelled HBV particles into human hepatoma cell lines (HepG2 and HuH7), which constitutively express functional ASGPR molecules, were compared to that of ASGPR-negative COS cells. As a result HBV was found to bind to purified human ASGPR in two different assays. Circulating virus particles from sera with high titre viraemia showed the highest attachment activity to ASGPR. HBV binding to purified ASGPR was saturable and inhibitable by an excess of D-galactose-bearing ligands, by EDTA and anti-receptor immunoglobulin. Lysis of particles by adding detergent abolished immunodetectable HBV binding to purified ASGPR. Commercial HBsAg did not adhere to solid phase-immobilized ASGPR. Monoclonal anti-preS1 antibody (MA18/7) but not anti-preS2 antibody (Q19/10) inhibited virus attachment. Purified and radiolabelled HBV particles showed binding to HepG2 and HuH7 cells but to much lesser degree to COS cells. Cellular binding of HBV was significantly inhibited by blocking of ASGPR function. Both ASGPR ligands and rabbit anti-ASGPR immunoglobulin but not non-immune rabbit serum inhibited uptake of radiolabelled HBV particles into HepG2 cells or HuH7 cells, respectively. This study suggests that HBV virions may enter human hepatocytes via ASGPR molecules by attachment of viral preS1-related envelope binding sites to this receptor.
...
PMID:The asialoglycoprotein receptor mediates hepatic binding and uptake of natural hepatitis B virus particles derived from viraemic carriers. 796 11

In order to clone novel diacylglycerol kinase (DGK) isozymes, we first obtained a DGK-related cDNA fragment by polymerase chain reaction using the human hepatoma cell line HepG2 mRNA and degenerated primers. The amplified fragment was subsequently used as a probe for screening the cDNA library from HepG2 cells. We obtained a cDNA clone coding for a novel DGK isozyme (designated DGK gamma) comprised of 791 amino acid residues. The amino acid sequence of DGK gamma was 52 and 62% identical to those of previously sequenced porcine 80-kDa and rat 90-kDa enzymes, respectively. DGK gamma, although initially cloned from the HepG2 cDNA libraries, was unexpectedly expressed in the human retina abundantly and to a much lesser extent in the brain. Other human tissues, including the liver and HepG2 cells, contained extremely low levels of DGK gamma mRNA. Furthermore, HepG2 cells and most of the human tissues except for the retina and brain expressed a truncated DGK gamma with an internal deletion of 25 amino acid residues (Ile451-Gly475). When transfected into COS-7 cells, the nontruncated cDNA gave phosphatidylserine-dependent DGK activity with no apparent specificity with regard to the acyl compositions of diacylglycerol. In contrast the truncated cDNA failed to give DGK activity in spite of the expression of its mRNA and enzyme protein in COS cells, thus demonstrating that the truncated DGK gamma is catalytically inactive. The sequence comparison of the three cloned DGKs revealed the presence of four highly conserved regions including the two sets each of EF-hand and zinc finger structures. Although the implication of the catalytically inactive form of DGK gamma remains unknown, this work further demonstrates the occurrence of multiple animal DGK isozymes with a conserved basic structure but with markedly different expression patterns depending on the cell types.
...
PMID:Molecular cloning of a diacylglycerol kinase isozyme predominantly expressed in human retina with a truncated and inactive enzyme expression in most other human cells. 803 97

We constructed an SV40-derived expression vector containing a mutated albumin minigene of Nagase analbuminemic rats (NAR), and introduced it into cultured cells. Transient expression of the minigene mRNA was determined by RT-PCR. Three kinds of aberrant mRNAs were expressed by the non-hepatic cells COS-1, and the undifferentiated human hepatoma cells HLE, transfected with the minigene. Their predominant mRNA lacked exon H (delta H), while mRNAs lacking exons H and I, or exons G and H were less abundant. This pattern of the mRNAs was similar to that of albumin mRNAs in the liver of old NAR. In contrast, a differentiated type of human hepatoma cell line, HepG2, expressed only delta H mRNA, like young NAR. These findings indicate that the expression system of the mutated minigene in cultured hepatoma cells is useful for understanding two-exon-skipping of albumin pre-mRNA of NAR.
...
PMID:Cell type specific patterns of mRNA splicing in hepatoma cells transfected with the mutated albumin minigene of Nagase analbuminemic rats. 806 20

In this report, cDNAs for mouse liver Ugt1.6 and rabbit liver UGT1.6 have been cloned and characterized. The predicted amino acid sequence of mouse Ugt1.6 is 93% and 78% similar to the rat and human UGT1.6 sequences, respectively, while the rabbit UGT1.6 is 79% and 83% similar to the rat and human UGT1.6 sequences, respectively. To examine the substrate specificities of the proteins encoded by the mouse Ugt1.6 and rabbit UGT1.6 cDNAs, the recombinants were expressed in monkey kidney COS-1 cells. Transfection of the mouse and rabbit recombinants allowed for the expression of the UGT1.6 proteins as determined by immunoprecipitation of newly synthesized protein. The expressed UGTs conjugated small planar phenolic molecules such as 4-nitrophenol, 1-naphthol, and 4-methylumbelliferone. While the bulky phenol 4-hydroxybiphenyl was not a substrate for the enzymes, 2-hydroxybiphenyl was an excellent substrate. Androgens and estrogens were not conjugated by either mouse Ugt1.6 or rabbit UGT1.6. In rodents, UGT1.6 mRNA is expressed constitutively and induced when the animals are treated with the Ah receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Using wild-type mouse hepatoma cells and the Ah receptor deficient class II cells, it was demonstrated that induction of mouse Ugt1.6 was dependent upon a functional Ah receptor complex. However, when New Zealand white rabbits were treated with TCDD and liver mRNA was examined by Northern blot analysis, it was shown that TCDD had no effect on the induction of UGT1.6 mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Cloning and characterization of cDNAs encoding mouse Ugt1.6 and rabbit UGT1.6: differential induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin. 806 91

Phosphatidylethanolamine N-methyltransferase catalyzes the synthesis of phosphatidylcholine from phosphatidylethanolamine and is most active in liver. A cDNA for this enzyme from a rat liver cDNA library has been cloned, sequenced, and expressed in COS-1 cells, McArdle-RH7777 rat hepatoma cells, and Sf9 insect cells. The expressed protein was capable of converting phosphatidylethanolamine into phosphatidylcholine in intact COS-1 cells, which normally have very low methyltransferase activity. The calculated molecular mass of the methyltransferase protein is 22.3 kDa, which is equivalent to that of the pure protein isolated from rat liver. Comparison of the sequence of the cloned rat liver methyltransferase with the yeast phosphatidylethanolamine methyltransferase PEM2 gene product revealed 44% identical amino acids and 68% similarity in the two predicted protein sequences. A polyclonal antibody was raised against a synthetic peptide corresponding to the carboxyl-terminal region of the enzyme and was affinity purified. The antibody recognized a single protein with a molecular mass of approximately 20 kDa when either rat liver proteins or proteins derived from the transfected COS-1 cells were electrophoresed on polyacrylamide gels containing sodium dodecyl sulfate. Surprisingly, the antibody exhibited no reactivity with endoplasmic reticulum proteins, even though the major phosphatidylethanolamine methyltransferase activity resides on this subcellular organelle. Instead, the antibody specifically recognized a protein in a unique subcellular membrane fraction purified from a crude mitochondrial preparation on a Percoll gradient. Immunocytochemical examination by electron microscopy showed positive labeling only in unique regions of the hepatocytes. The data suggest that this phosphatidylethanolamine methyltransferase is a specific marker for this unique membrane fraction.
...
PMID:Cloning and expression of a novel phosphatidylethanolamine N-methyltransferase. A specific biochemical and cytological marker for a unique membrane fraction in rat liver. 834 45

A human hepatitis B virus (HBV) gene, which encodes the major surface antigen protein (S protein) carrying the hepatocyte receptor-binding site, was constructed with site-directed mutagenesis and in vitro recombination. When expressed in monkey kidney cell line COS-M6, this gene product (S309 protein) formed surface antigen (HBsAg) particles and secreted from the cells. It was stable within the cells and in the culture medium and could be immunoprecipitated with antisera directed against plasma-derived HBsAg or synthetic preS1 polypeptide. Isopycnic CsCl gradient centrifugation showed that the density of S309 protein particles (1.25 g/ml) was slightly higher than that of S protein particles. The S309 protein was readily secretable from hepatoma cell lines, and the amount secreted was comparable to that of the S protein. By contrast, only about 10% of the S309 protein was secreted from COS-M6 cells, and its appearance in culture medium was delayed. The efficiency of the secretion of the S309 protein can be improved when it is coexpressed with the S protein.
...
PMID:The properties of an HBV surface antigen protein carrying the binding site for the receptor of hepatocytes--its formation of surface antigen particles and secretion from discrete cell lines. 836 32

Dihydrotachysterol (DHT), a reduced vitamin D analog in which the A-ring has been rotated through 180 degrees is a biologically active molecule which can be used to study the structural requirements for the calcemic and cell differentiating properties of the vitamin D hormone, 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3), as well as to investigate the specificity of the enzyme systems that catalyze the formation of this hormone. In this study we showed that dihydrotachysterol was metabolized in vivo into a significant polar metabolite observed on straight-phase high performance liquid chromatography (HPLC) which subsequently split into two peaks on reverse-phase HPLC. These two metabolites were identified by HPLC and gas chromatography-mass spectrometry techniques as 1 alpha,25-(OH)2DHT and 1 beta,25-(OH)2DHT. This pair of metabolites was formed from either DHT2 or DHT3. Standard 1 alpha,25-(OH)2DHTs were generated in vitro from chemically synthesized 1-hydroxydihydrotachysterol precursors using a liver hepatoma cell system. Both 1 alpha,25-(OH)2D2 and 1 alpha,25-(OH)2DHT3 showed a binding affinity to the mammalian vitamin D receptor only 50-100 less than 1 alpha,25-(OH)2D3 whereas 1 beta,25-(OH)2DHTs showed poor binding. On the other hand 1 beta,25-(OH)2DHT3 bound to the rat vitamin D transport protein (DBP) with stronger affinity than did 1 alpha,25-(OH)2DHT3. When tested in a COS-1 cell transfection assay system using a rat osteocalcin vitamin D responsive element coupled to a growth hormone reporter gene, 1 alpha,25-(OH)2DHT3 showed a biological activity only 10 times lower than 1 alpha,25-(OH)2D3. It is therefore suggested that 1 alpha,25-(OH)2DHT probably represents the metabolite of DHT responsible for some of its in vivo effects although we cannot rule out in vivo effects of other metabolites identified. Our studies suggest that 1 alpha,25-dihydroxylated DHTs represent a promising novel group of vitamin D analogs worthy of study for cell differentiation as well as calcemic properties.
...
PMID:In vivo metabolism of the vitamin D analog, dihydrotachysterol. Evidence for formation of 1 alpha,25- and 1 beta,25-dihydroxy-dihydrotachysterol metabolites and studies of their biological activity. 838 Jan 56

<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>