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)

This research demonstrates how the chemical reaction interface mass spectrometry (CRIMS) approach works for a study of amino acid metabolism in cell culture. 15N-selective chromatograms from both the culture medium and the cytosol of human hepatoma Hep G2 cells that were incubated in the presence of either 12 mM (alpha-15N)glutamine or (alpha-15N)asparagine have been produced. The time course of the distribution of 15N among different amino acids, as well as the enrichment for each amino acid, were observed over a 144 h period. Labeled glutamine was quickly converted into glutamate. After 144 h of incubation, the total amount of 15N was distributed primarily among alanine (50%), proline (28%) and glutamate (21%). The 15N enrichment of alanine and proline reached 44% and 41% respectively. Asparagine was only slowly metabolized by the cells. In addition to the 82% that was retained in asparagine, the remaining 15N in the media at 144 h was found primarily in alanine (8%), glutamate (6.8%) and proline (2.2%). Their enrichments were 20%, 36% and 19% respectively. The minimum detectable amount was 17 pg of 15N entering the CRI. CRIMS appears to be a powerful, facile approach for 15N-tracer experiments.
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PMID:Tracing 15N with chemical reaction interface mass spectrometry: a demonstration using 15N-labeled glutamine and asparagine substrates in cell culture. 784 Dec 9

Infection with hepadnaviruses and exposure to dietary aflatoxin are considered major risk factors in the development of hepatocellular carcinoma (HCC) both in humans and in animals. Recently, a broad range of mutations in the p53 tumor suppressor gene has been reported in human HCCs, predominantly from hepatitis B virus carriers in areas with either high or low levels of exposure to dietary aflatoxin. To determine whether p53 mutations are common to HCCs of hosts infected with related hepadnaviruses with and without treatment with aflatoxin, we studied the occurrence of mutations in the p53 gene in HCCs of ground squirrels and woodchucks with history of infection with ground squirrel hepatitis virus (GSHV) and woodchuck hepatitis virus, respectively. Sequencing of wild type p53 genes from ground squirrels and woodchucks revealed remarkable homology between the two species with only a few amino acid differences in exons 4, 8, and 9. Using direct polymerase chain reaction sequencing, we analyzed the state of the p53 gene (exons 4-9) in 20 HCCs from ground squirrels (2 uninfected, 7 with past, and 11 with ongoing infection with GSHV) and in 11 HCCs from woodchucks persistently infected with woodchuck hepatitis virus. Five GSHV carrier and two uninfected ground squirrels received i.p. administration of aflatoxin B1. We detected only one mutation in the p53 gene of the tested animals. This mutation was located in codon 176 of exon 5 in the HCC of a GSHV-positive ground squirrel treated with aflatoxin. Mutation was caused by a G to T transversion in the second position of the codon, resulting in the replacement of cysteine with phenylalanine, and was accompanied by a tumor-specific loss of heterozygosity. p53 allelic amino acid variation with sequences coding for aspartic acid or asparagine was present in codon 61 in the variable region of exon 4 in both HCCs and nonneoplastic tissues of ground squirrels. In view of the considerably lower apparent rate of mutations in comparison to human HCCs, we suggest a less important role for aflatoxin in the induction of p53 mutations in HCCs of ground squirrels. Alternatively, etiological factors other than p53 mutations may be of greater significance in the development of HCC in ground squirrels and woodchucks.
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PMID:State of the p53 gene in hepatocellular carcinomas of ground squirrels and woodchucks with past and ongoing infection with hepadnaviruses. 792 76

The naturally occurring nullHong Kong variant of human alpha 1-antitrypsin is truncated at its carboxyl terminus, and is retained and degraded in a pre-Golgi compartment of stably transfected murine hepatoma cells (Le, A., Graham, K. S., and Sifers, R. N. (1990) J. Biol. Chem. 265, 14001-14007). Long-term metabolic radiolabeling with [35S]methionine or [32P]orthophosphate in combination with low stringency immunoprecipitation of the nullHong Kong variant has resulted in the co-precipitation of a radiolabeled 90-kDa protein designated p90. Several criteria, including mobility in SDS-polyacrylamide gel electrophoresis, absence of asparagine-linked oligosaccharides, and immunoreactivity with peptide-specific antiserum, have indicated that co-precipitating p90 is identical to calnexin, a calcium-binding phosphoprotein of the endoplasmic reticulum membrane (Wada, I. W., Rindress, P. H., Ou, W.-J., Doherty, J. J., Louvard, D., Bell, A. W., Dignard, D., Thomas, D. Y., and Bergeron, J. J. M. (1991) J. Biol. Chem. 266, 19599-19610). Finally, results from co-immunoprecipitation analyses and velocity sedimentation experiments have verified that approximately 30% of the retained nullHong Kong variant polypeptides are associated with calnexin in a 1:1 molar ratio and can be dissociated with either deoxycholate or chelation of calcium ions at 37 degrees C. Overall, these findings may extend our current understanding of the molecular pathogenesis of serum alpha 1-antitrypsin deficiency.
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PMID:Association between calnexin and a secretion-incompetent variant of human alpha 1-antitrypsin. 812 71

The asparagine-linked sugar chains in serum transferrin purified from patients with hepatocellular carcinoma (n = 13), healthy individuals (n = 5) and patients with liver cirrhosis (n = 6) were compared. Sugar chains released with N-glycanase from desialylated and pepsin-digested transferrin were derivatized by reductive pyridylamination. Analysis of the sugar chains by high performance liquid chromatography in combination with exoglycosidase digestion revealed an increase of a biantennary complex-type sugar chain with a fucosylated trimannosyl core; Gal beta 1-4GlcNAc beta 1-2Man alpha 1-6(Gal beta 1-4GlcNAc beta 1-2Man alpha 1-3) Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-6)GlcNAc in 7 of 13 cancer patients and an increase of a sugar chain with a fucosylated trimannosyl core and bisecting N-acetylglucosamine; Gal beta 1-4GlcNAc beta 1-2Man alpha 1-6(GlcNAc beta 1-4) (Gal beta 1-4GlcNAc beta 1-2Man alpha 1-3)Man beta 1-4GlcNAc beta 1-4(Fuc alpha 1-6)GlcNAc in one of the 13 cancer patients. Further, the fucosylated alteration of the sugar chain was detected also in alpha 1-antitrypsin, hemopexin, alpha 1-acid glycoprotein and alpha 2-HS glycoprotein from one of the patients with increased fucosylated transferrin.
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PMID:Alteration of asparagine-linked glycosylation in serum transferrin of patients with hepatocellular carcinoma. 817 73

In two recently reported cases, integrated hepatitis B virus (HBV) DNAs cloned from hepatocellular carcinoma were found to express a transcriptional transactivator from 3'-terminally truncated HBV surface (preS/S) genes. In this study, we characterized the transactivator at the protein level. Expression of a 3'-truncated preS2/S gene in Spodoptera frugiperda (Sf9) insect cells resulted in a C-terminally truncated middle surface protein of 76 amino acids (MHBst76), which was found to be associated with membranes of the endoplasmic reticulum and retained from Golgi processing and secretion. Accordingly, the microsome fraction of MHBst76-expressing Sf9 cells displayed transactivator activity after electric field-mediated transfer into Chang liver cells. In contrast to full-length MHBs, MHBst76 is unglycosylated, and glycosylation is not required for transactivation as shown by mutation of the glycosylation site at asparagine-4. Since highly purified MHBst76 derived from an E. coli expression system also showed transactivator activity, it is concluded that unglycosylated MHBst76 protein is the authentic transactivating factor. As the transactivator protein derives from inactive MHbs by rearrangements of integrated HBV DNA, it may be important for HBV-associated liver carcinogenesis.
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PMID:ER-localization and functional expression of the HBV transactivator MHBst. 824 38

Sequence-specific resonance assignments provide the basis for interpreting multidimensional NMR spectra and for determining 3D structures of proteins from these data. We have developed an improved strategy for determining these sequence-specific NMR assignments in small proteins and applied this method in determining proton and nitrogen resonance assignments for an 8.2-kDa engineered domain (the Z-domain) of the cell wall protein A of Staphylococcus aureus. First, HCCNH-TOCSY [Lyons, B. A. & Montelione, G.T. (1993) J. Magn. Reson. 101B, 206] data were used together with 2D 2QF-COSY, TOCSY, and 15N-HSQC data to identify amino acid spin systems. Most asparagine and glutamine spin systems were also identified uniquely from these triple-resonance data. Next, complementary HCC(CO)-NH-TOCSY [Montelione, G. T., et al. (1992) J. Am. Chem. Soc. 114, 10975] data were used to identify sequential connections from the aliphatic H alpha, H beta, H gamma, H delta, and H epsilon resonances of residue i to the amide and nitrogen resonances of residue i + 1. By combined analysis of HCCNH-TOCSY and HCC(CO)NH-TOCSY spectra we have determined most of the proton and nitrogen resonance assignments for the Z-domain. This represents the first example of the use of this triple-resonance technique to determine extensive resonance assignments in a small protein.
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PMID:An improved strategy for determining resonance assignments for isotopically enriched proteins and its application to an engineered domain of staphylococcal protein A. 839 17

During growth stimulation of cells, Ca2+ and amino acids of the A, ASC and N transport systems are important for the induction of ornithine decarboxylase (ODC, L-ornithine carboxylase, EC 4.1.1.17). In order to clarify the relationship between Ca2+ and amino acids, we studied the induction of ODC by asparagine under three different Ca2+ states in H-35 rat hepatoma cells. First, in normal cells, extracellular Ca2+ above 0.1 mM and 10 mM asparagine separately stimulated ODC activity and their effects were approximately additive. In these normal cells, asparagine could act in the absence of medium Ca2+. TMB-8, a sequestered-Ca2+ release antagonist, had no effect on ODC induction whilst the asparagine action is sensitive to treatment with W7, a Ca-calmodulin antagonist, or lanthanum, a Ca2+ antagonist. Secondly, in cells treated with 0.5 mM EGTA in Ca(2+)-free medium, the asparagine action on ODC induction was blocked but the inhibition could be reversed by the addition of Ca2+ to the medium. Thirdly, ionomycin treatment in the absence of medium Ca2+ did not block the asparagine effect. Furthermore, in ionomycin-treated cells, the presence of high levels of medium Ca2+ increased ODC activity, but this increase was additive to, and could not replace, the action of asparagine. Our results indicate that the asparagine action does not depend on an increase of intracellular free-Ca2+.
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PMID:Independent actions of asparagine and high levels of free Ca2+ in the induction of ornithine decarboxylase. 843 91

Purified gamma-glutamyl hydrolase secreted from rat H35 hepatoma cells has been characterized as a diffuse band of 55 kDa on SDS-polyacrylamide gel electrophoresis that is converted to bands of 35 and 33 kDa after enzymatic removal of N-linked carbohydrate. Polyclonal antibodies against 55-kDa gamma-glutamyl hydrolase captured the enzyme activity and recognized the glycosylated and both deglycosylated forms of gamma-glutamyl hydrolase. A complete cDNA sequence of gamma-glutamyl hydrolase was obtained using degenerate oligonucleotides derived from peptide sequences, screening of a rat hepatoma cDNA library, and reverse transcription polymerase chain reaction. Based upon the deduced amino acid sequence the peptide component of gamma-glutamyl hydrolase had a molecular weight of 33,400. The results of amino acid analysis of the purified protein agreed with the deduced amino acid sequence in which there are seven potential asparagine-containing glycosylation sites.
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PMID:Identification, cloning, and sequencing of a cDNA coding for rat gamma-glutamyl hydrolase. 862 74

Hepatitis delta virus (HDV) is a defective virus requiring the hepatitis B virus (HBV) to provide hepatitis B surface antigens as the envelope protein. The hepatitis B surface antigens are posttranslationally modified by N-linked glycosylation, and its significance in HDV assembly was investigated with a cotransfection system using human hepatoma cell line Huh-7. After the N-linked glycosylation of HBsAg was blocked by tunicamycin treatment, the packaging of HDV in the culture system could be suppressed to a level as low as 5-10% of the untreated control. The extent of inhibition correlated with the increased concentrations of tunicamycin. In contrast, the loss of HBsAg glycosylation did not affect the efficiency of assembly of HBV particles. When the N-linked glycosylation site of small HBsAg at amino acid 146 was mutated from asparagine to glutamine, the mutant HBsAg packaged only a modest amount of HDV particles. The quantity and kinetics of formation of HDV particles in culture system were reduced by the depletion of HBsAg glycosylation. Therefore HDV, similar to influenza and vesicular stomatitis viruses, depends on glycosylation of the envelope proteins as a signal for envelope protein maturation and for virion formation.
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PMID:N-linked glycosylation of hepatitis B surface antigens is involved but not essential in the assembly of hepatitis delta virus. 865 25

Among various kinds of tumor markers, alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) are very important and widely used in the clinical medicine. AFP is a specific marker for diagnosis of hepatocellular carcinoma (HCC). AFP is a glycoprotein composed of 590 amino acid residues and has one asparagine-linked sugar chain at the 232nd position from N-terminal of the AFP molecule. A difference exists between the sugar chain of HCC AFP and the chain from a cirrhotic patient. This difference is easily detected by a lectin-binding analysis using LCA or PHA-E4. This technique enabled us to predict a risk of tumor occurrence in patients with a high probability of HCC development. Exciting progress in molecular biology has been made in the field of AFP and CEA research. The gene structures and the regulatory mechanism of synthesis of AFP and CEA has been elucidated successively. These results may provide a clue to the solution of the mechanism of carcinogenesis and may provide more sensitive tools for detection of tumors as well as practical therapies.
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PMID:[Carcino-fetal antigens]. 869


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