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)

Previous work has shown that low-density lipoproteins (LDL) secreted by hepatoma-derived cell lines have an unusual composition compared to plasma LDL; rather than cholesteryl ester, the hepatoma cell-secreted LDL have a triacylglycerol core. We have found that they also have an increased negative charge, as judged by agarose electrophoresis. Since apolipoprotein B is a glycoprotein containing carbohydrate chains terminated with negatively charged sialic acid residues, we examined whether increased glycosylation of the apolipoprotein B from three hepatoma cell lines (Hep G2, Hep 3B and Huh 7) might account for the differences in LDL charge. The weight percent carbohydrate for Hep G2, Hep 3B and Huh 7 LDL-protein (1.1 +/- 0.2; 1.7 +/- 0.8; 0.4 +/- 0.1) was found to be extremely low compared with the 2.8-9% range we found for plasma LDL-protein, while the amount of LDL-lipid associated carbohydrate from hepatoma LDL was similar to that we found in plasma LDL. Furthermore, desialation of hepatoma cell-secreted LDL with neuraminidase did not normalize the negative charge to that of neuraminidase-treated plasma LDL. Western blots of thrombin proteolytic fragments indicated that, in addition to the T1-T4 fragments seen in plasma apolipoprotein B, apolipoprotein B of hepatoma-derived LDL produced four to five new fragments (T5-T9), suggesting increased exposure of proteolytic sites. Western blotting of the new fragments with antibodies specific for known apolipoprotein B sequences suggests that many of the new cleavage sites cluster in or near the putative LDL receptor recognition site.
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PMID:Unique structural properties of apolipoprotein B in low-density lipoproteins produced by several human hepatoma-derived cell lines. 217 71

Four murine MoAbs, KM191(IgM), KM206(IgM), KM230(IgG1) and KM231(IgG1), against human gastric cancer were generated using mice which underwent tolerance treatment to stomach tissues. They exhibited very similar high reactivities to stomach adenocarcinoma cells and low reactivities to normal cells in both membrane binding assay and immunohistochemical analysis. Their antigens were neuraminidase and protease sensitive and existed as macromolecules (1,000Kd) in body fluids. Binding of each antibody was inhibited by the others and KM231 showed the highest binding avidity. When they were used to detect the antigens shed in ascitic fluids and pleural effusions of cancer patients, KM231 allowed the most efficient detection of the antigen. The above results indicated that the four MoAbs bound to closely related epitopes on the same antigen and that the nature of its high binding avidity enabled KM231 to show the greatest efficiency in the detection of the antigen in body fluids. KM231 was applied to serum diagnosis and gave high positive percentages in pancreatic cancer(86%), hepatocarcinoma(87%), gall bladder cancer(50%), and gastric cancer(34%), whereas in healthy persons (0%) and benign diseases except for hepatitis(29%) the percentages were low. KM231 was similar to NS19-9, but quite different from NS19-9 in the high positive percentages of hepatocarcinoma in serum diagnosis.
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PMID:Comparative studies on monoclonal antibodies raised against human gastric cancer for application to serum diagnosis of cancer. 245 69

The lectin from the elderberry (Sambucus nigra L.) bark, shown to recognize the sequence neuraminic acid (alpha 2,6) galactose/N-acetylgalactosamine, was applied for detecting binding sites in Lowicryl K4M sections by light and electron microscopy. The lectin was used either directly complexed to colloidal gold or in a two-step cytochemical affinity technique. The lectin-gold complex proved to be superior and thus was extensively tested on rat liver, kidney and hepatoma cells as well as on sheep and bovine submandibular glands. Controls to establish specificity of lectin-gold binding included sugar and glycoprotein inhibition tests and enzymic removal of sialic acid. In agreement with biochemical data demonstrating the potentiating effect of sialic acid on the binding of the lectin to oligosaccharides, enzymic removal of sialic acid from liver sections resulted in abolition of lectin staining. However, in the submandibular glands, neuraminidase pretreatment of the sections had no effect on the subsequent lectin-gold binding. In rat kidney some structures became negative while others retained the lectin-gold staining due to binding to penultimate N-acetylgalactosamine exposed after sialic acid removal. In line with this, spot blot analysis demonstrated that the lectin-gold complex reacted with both fetuin and asialofetuin. Taken together, these results suggest that, for cytochemical staining, the sialic acid and the galactose/N-acetylgalactosamine lectin combining subsites of Sambucus nigra L. lectin are equally reactive with cellular glycoconjugates and that neuraminidase predigestion of tissue sections is of utmost importance to ensure specificity of staining for the sequence neuraminic acid (alpha 2,6) galactose/N-acetylgalactosamine.
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PMID:Elderberry bark lectin--gold techniques for the detection of Neu5Ac (alpha 2,6) Gal/GalNAc sequences: applications and limitations. 246 94

Biochemical characteristics of alpha-L-fucosidase (alpha-L-fucoside hydrolase, EC 3.2.1.51) were studied in tumorous and nontumorous human hepatocellular carcinoma (n = 14). Five parameters were studied: (i) specific activity, (ii) thermostability, (iii) enzyme affinity for an artificial substrate (Km), (iv) isoenzyme patterns of the glycosidase before and after neuraminidase treatment and (v) pH influence on enzyme activity. The specific activity of alpha-L-fucosidase was significantly decreased in tumoral liver when compared to nontumoral liver. The curve of pH activity constantly showed a broad optimum centered near pH 5, whereas two optima were always observed in nontumoral areas. In contrast, there was no modification of the thermostability, the substrate affinity and the isoenzyme patterns of alpha-L-fucosidase in hepatocellular carcinoma.
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PMID:Biochemical aspects of alpha-L-fucosidase in hepatocellular carcinoma. 253 49

Intracellular movement of cell surface 5'-nucleotidase was studied in H4S cells, a rat hepatoma cell line. Surface labelled cells were incubated for various periods at 37 degrees C and treated with neuraminidase at 0 degrees C. Removal of sialic acid residues from glycoproteins results in a change of their isoelectric points. Analysis with isoelectric focusing was then used to distinguish between cell surface and intracellular 5'-nucleotidase. Incubation of 125I-surface-labelled cells at 37 degrees C resulted in a gradual decrease of labelled 5'-nucleotidase at the plasma membrane until, at 60 to 90 min, a steady state was reached with 52% of the label on the cell surface and 48% intracellular. Pretreatment of the cells with the weak base primaquine had no influence on this distribution while at the same time uptake of iron via the transferrin receptor was inhibited. Using immunoelectron microscopy 5'-nucleotidase was found on the cell surface, in multivesicular endosomes and the Golgi complex. Preincubation of the cells in the presence of cycloheximide caused a reduction of labelling in the Golgi complex, whereas the label in the other compartments was retained. These results lead to the conclusion that 5'-nucleotidase does not recycle through the Golgi complex and that in contrast to the transferrin receptor the recycling of 5'-nucleotidase is not inhibited by primaquine.
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PMID:Recycling of 5'-nucleotidase in a rat hepatoma cell line. 285 Jan 62

gamma-Glutamyltransferase from human hepatoma and the surrounding non-neoplastic liver tissue was purified by immunoaffinity column chromatography and characterized with regard to molecular weight, isoelectric point (pI), amino acid composition, hexosamine content and affinity for various lectins. Both enzymes showed the same molecular weight (the heavy subunit 64 000; the light subunit 26 000) and pIs (3.7-3.9) on SDS-polyacrylamide gel electrophoresis and isoelectric focusing in polyacrylamide gel, respectively. After neuraminidase treatment, the pIs for both enzymes shifted to a more alkaline pH (pI 5.7). Both enzyme preparations exhibited similar amino acid compositions; however, the glucosamine content of the hepatoma enzyme was 362 nmol/mg protein, about 3-fold higher than that of the enzyme isolated protein from the non-neoplastic tissue. Binding of the two enzymes to lectins revealed that less of the hepatoma enzyme bound to Sepharose-conjugated wheat germ agglutinin, erythroagglutinating phytohemagglutinin and Ricinus communis agglutinin. These results suggest that the two enzymes possess similar peptide moieties and degree of sialylation, but differ with respect to other aspects of their heterosaccharide moieties.
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PMID:Comparison of the peptide and saccharide moieties of gamma-glutamyltransferase isolated from neoplastic and non-neoplastic human liver tissue. 286 19

gamma-Glutamyltransferase was purified to apparent homogeneity from human adult liver, fetal liver and hepatoma by deoxycholate extraction, immunoaffinity chromatography, papain digestion, phenyl-Sepharose chromatography and preparative polyacrylamide gel electrophoresis. The purified enzyme from all three sources had an apparent Mr of 82 000 by Sephadex G-150 gel filtration and on dodecyl sulphate/polyacrylamide gel electrophoresis two nonidentical subunits of Mr 57 000 and 23 000 were obtained. The pI of all three forms was 3.85 and after neuraminidase treatment they each gave at least five bands with pI values ranging over 5.9-6.6. Sialic acid content was 188 (adult liver), 182 (fetal liver) and 188 (hepatoma) nmol/mg protein. Total neutral sugar content was 702 (adult and fetal liver) and 700 (hepatoma) nmol/mg protein. The hexosamine content of the enzyme from all the three sources was the same (354 nmol/mg protein) and galactosamine was absent. Partially purified hydrophobic and hydrophilic forms of gamma-glutamyltransferase from all the three sources were precipitated by Concanavalin A, Ricinus communis agglutinin and wheat germ agglutinin. These results show that gamma-glutamyltransferase from human adult liver, fetal liver and hepatoma are structurally similar and that the elevated levels found in fetuses and hepatoma are only a quantitative increase and are not due to a new isoenzyme.
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PMID:Comparative structural and lectin-binding studies on gamma-glutamyltransferase from human adult liver, fetal liver and primary hepatoma. 286 57

In the rat, asialoorosomucoid and rat dimeric immunoglobulin A are both taken up by hepatocytes via receptor-mediated endocytosis. The fate of these two proteins, however, differs significantly. Rat dimeric IgA is taken up into smooth vesicles, transported to the bile canaliculus and secreted intact into the bile, whereas asialoglycoproteins are internalized via coated vesicles and transported to lysosomes for degradation. Recently, several studies both in the rat and in cultured human hepatoma cells have suggested that the receptor for asialoglycoproteins may play a role in the hepatic uptake and processing of human polymeric IgA. Using receptor-binding techniques, we have provided quantitative data for the competition of human monomeric, polymeric and secretory IgA with asialoorosomucoid for its receptor on liver plasma membrane preparations from rat, monkey and man. Some IgA molecules required desialylation with neuraminidase to enhance markedly their efficacy for asialoorosomucoid inhibition. Quantitatively, human IgA molecules showed an affinity for the ASOR receptor similar to that for asialoceruloplasmin. Rat dimeric IgA does not compete for this binding site. We conclude that human IgA can compete with ligands for the asialoglycoprotein receptor of rat, monkey and human liver. This receptor may provide an alternative pathway for the hepatic processing of IgA and IgA immune complexes when secretory component-mediated uptake is not available as in the monkey and man, particularly under pathological conditions where serum IgA concentrations accumulate to abnormally high levels.
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PMID:Hepatic asialoglycoprotein receptor-mediated binding of human polymeric immunoglobulin A. 291 27

To define the basis of the heterogeneity of angiotensinogen, we have characterized the immunoreactivity of high molecular weight (HMW) and low molecular weight (LMW) plasma angiotensinogen, the angiotensinogen precursor synthesized by cell-free translation, and angiotensinogen secreted by human hepatoma (Hep G2) cells. Angiotensinogen precursor synthesized by rabbit reticulocyte lysate primed with RNA prepared from liver or Hep G2 cells was compared with angiotensinogen secreted by Hep G2 cells by using immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). So as to assess the contribution of N-glycosylation of angiotensinogen, Hep G2 cells were incubated in the presence of tunicamycin. Glycosylation of secreted angiotensinogen was further characterized by using chromatography on concanavalin A-Sepharose, digestion with neuraminidase, and treatment with trifluoromethane sulfonic acid. In Sephadex G-200 column chromatography, HMW plasma angiotensinogen eluted just after the column void volume and was clearly separated from LMW angiotensinogen which eluted just before bovine serum albumin. Both HMW and LMW plasma angiotensinogen were shown to bind to monoclonal and polyclonal antibodies raised against pure LMW angiotensinogen. Only one angiotensinogen precursor (mol wt 50,000) was identified by cell-free translation which, after cleavage by renin, was reduced to mol wt 45,600. Angiotensinogen secreted by Hep G2 cells showed electrophoretic heterogeneity (mol wt 53,100-65,400). Tunicamycin-treated Hep G2 cells secreted five discrete forms of angiotensinogen, a predominant form of mol wt 46,200, with other forms (mol wt 46,800, 48,100, 49,200, and 49,600) representing 10% of secreted angiotensinogen. All five forms showed a similar reduction in molecular weight after cleavage by renin. The predominant 46,200-mol wt protein represented nonglycosylated angiotensinogen in that, after cleavage by renin, it had an electrophoretic mobility (mol wt 45,600) identical to the desangiotensin I-angiotensinogen resulting from renin cleavage of the angiotensinogen precursor. The other higher molecular weight forms of angiotensinogen secreted by tunicamycin-treated Hep G2 cells were shown to represent O-glycosylated angiotensinogen in that they were reduced to 46,200 mol wt by treatment with trifluoromethane sulfonic acid. Dexamethasone (10(-7) and 10(-6)M) stimulated angiotensinogen secretion by Hep G2 cells two- to fourfold, both in the absence and presence of tunicamycin. However, a small stimulatory effect of mestranol (10(-7) M) was evident only in the presence of tunicamycin. Neither dexamethasone nor mestranol influenced the electrophoretic pattern (SDS-PAGE) of angiotensinogen secreted by Hep G2 cells. However, when incubation media were chromatographed on Sephadex G-200 with subsequent immunoprecipitation of the column fractions, both dexamethasone and mestranol were shown to stimulate the secretion of HMW angiotensinogen (eluting just after the column void volume) which, on SDS-PAGE, migrated in a position identical to LMW angiotensinogen. From these studies, we conclude that all forms of human angiotensinogen are derived from a single precursor. The heterogeneity of secreted angiotensinogen represents differences in posttranslational processing of angiotensinogen. This processing includes both N- and O-glycosylation, and also the formation of HMW complexes (HMW angiotensinogen) through association either with other angiotensinogen molecules or with some other protein(s) whose secretion by hepatocytes is stimulated by glucocorticoids and estrogens.
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PMID:Characterization of precursor and secreted forms of human angiotensinogen. 298 36

The biosynthesis and post-translational processing of the insulin-like growth factor II (IGF-II) receptor has been studied in H-35 hepatoma cells using a specific polyclonal anti-receptor immunoglobulin preparation. Cells were pulse-labeled with [35S]methionine followed by incubation with excess unlabeled methionine (chase). Gel electrophoresis of the immunoadsorbed receptors shows that the receptor is first synthesized as a 245-kDa precursor which is transformed to the mature 250-kDa form with a half-time of about 2 h. The 245-kDa precursor could also be labeled biosynthetically with [3H]mannose, only one-half of which was ultimately found associated with the 250-kDa product. Neuraminidase converts the 250-kDa receptor species to a 245-kDa form. Whereas the 250-kDa receptor is insensitive to detectable cleavage by endoglycosidase H, digestion of the 245-kDa species with this enzyme produces a 232-kDa form. A similar 232-kDa receptor species accumulates in H-35 cells incubated with tunicamycin (2 micrograms/ml). This tunicamycin-induced aglyco-receptor is not further processed to the 250-kDa form. Monensin (50 nM) blocks receptor processing at the 245-kDa stage. Endoglycosidase H treatment of the monensin-induced 245-kDa species indicates that this is a mixture of partially processed precursors having equivalent Mr. No evidence was obtained for the presence of O-linked oligosaccharides on the IGF-II receptor. The IGF-II binding activity of the three different biosynthetic forms of the receptor was assessed by affinity cross-linking of 125I-IGF-II to the receptors using disuccinimidyl suberate. Both the mature 250-kDa receptor and the neuraminidase-digested 245-kDa form specifically bound 125-I-IGF-II. However, the 232-kDa aglyco-receptor had no detectable IGF-II binding activity using this method. In summary, these studies show: 1) that the H-35 cell IGF-II receptor is synthesized first as a 245-kDa precursor having 4-6 high-mannose oligosaccharide side chains, 2) processing of the receptor oligosaccharides by mannose removal and terminal sialylation converts the 245-kDa precursor to the 250-kDa mature product which has been previously identified as the functional receptor in the plasma membrane, 3) the apparent molecular mass of the receptor in the absence of N-glycosylation is 232-kDa, and 4) glycosylation of the IGF-II receptor is required for the acquisition of IGF-II binding activity.
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PMID:Biosynthesis and processing of the type II insulin-like growth factor receptor in H-35 hepatoma cells. 299 8


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