UMLS:C0019204 - FACTA Search

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

Previous studies have resulted in conflicting data regarding the recovery of the nuclear enzymes topoisomerase (topo) II and topo I in the nuclear matrix fraction. In the present study we have assessed the effect of systematically altering a single extraction procedure on the distribution of these enzymes during the subfractionation of nuclei from HTC hepatoma tissue culture cells. When nuclear monolayers (prepared by treating attached cells in situ with the neutral detergent Nonidet-P40 at 4 degrees C) were isolated in the presence of the irreversible sulfhydryl blocking reagent iodoacetamide, subsequent treatment with DNase I and RNase A followed by 1.6 M NaCl resulted in structures which were extensively depleted of intranuclear components as assessed by phase contrast microscopy and conventional transmission electron microscopy. These structures contained 12 +/- 4% of the total protein present in the original nuclear monolayers. The lamins and polypeptides with molecular weights comparable to those of actin and vimentin were the predominant polypeptides present on SDS-polyacrylamide gels. Western blotting revealed that less than 5% of the total nuclear topo II molecules were present in these structures. In contrast, when the sulfhydryl cross-linking reagent sodium tetrathionate (NaTT) was substituted for iodoacetamide, the same extraction procedure yielded structures containing components of the nucleolus and an extensive intranuclear network. These structures contained a wide variety of nonlamin, nonhistone nuclear polypeptides including 23 +/- 4% of the total nuclear topo II. SDS-polyacrylamide gel electrophoresis performed under nonreducing conditions revealed that topo II in these nuclear matrices was present as part of a large disulfide cross-linked complex. Treatment of these structures with reducing agents in 1.6 M NaCl released the topo II. In contrast, topo I did not form disulfide cross-linked oligomers and was not detectable in any of these nuclease- and salt-resistant structures prepared at 4 degrees C. To assess the effect of in vitro heat treatment on the distribution of the topoisomerases, nuclear monolayers (isolated in the absence of iodoacetamide and NaTT) were heated to 37 degrees C for 1 h prior to treatment with nucleases and 1.6 M NaCl. The resulting structures (which retained 26 +/- 5% of the total nuclear protein) were morphologically similar to the NaTT-stabilized nuclear matrices and contained 15 +/- 4% of the total nuclear topo II. High-molecular-weight disulfide cross-linked oligomers of topo II were again demonstrated. Attempts to demonstrate these disulfide cross-linked oligomers in intact cells were unsuccessful.
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PMID:Association of topoisomerase II with the hepatoma cell nuclear matrix: the role of intermolecular disulfide bond formation. 184 38

We have previously demonstrated [Rihs, H.-P. and Peters, R. (1989) EMBO J., 8, 1479-1484] that the nuclear transport of recombinant proteins in which short fragments of the SV40 T-antigen are fused to the amino terminus of Escherichia coli beta-galactosidase is dependent on both the nuclear localization sequence (NLS, T-antigen residues 126-132) and a phosphorylation-site-containing sequence (T-antigen residues 111-125). While the NLS determines the specificity, the rate of transport is controlled by the phosphorylation-site-containing sequence. The present study furthers this observation and examines the role of the various phosphorylation sites. Purified, fluorescently labeled recombinant proteins were injected into the cytoplasm of Vero or hepatoma (HTC) cells and the kinetics of nuclear transport measured by laser microfluorimetry. By replacing serine and threonine residues known to be phosphorylated in vivo, we identified the casein kinase II (CK-II) site S111/S112 to be the determining factor in the enhancement of the transport. Either of the residues 111 or 112 was sufficient to elicit the maximum transport enhancement. The other phosphorylation sites (S120, S123, T124) had no influence on the transport rate. Examination of the literature suggested that many proteins harboring a nuclear localization sequence also contain putative CK-II sites at a distance of approximately 10-30 amino acid residues from the NLS. CK-II has been previously implicated in the transmission of growth signals to the nucleus. Our results suggest that CK-II may exert this role by controlling the rate of nuclear protein transport.
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PMID:The rate of nuclear cytoplasmic protein transport is determined by the casein kinase II site flanking the nuclear localization sequence of the SV40 T-antigen. 184 77

The cDNA for a 54-kDa nuclear protein (p54) has been cloned from a human hepatoma expression library. Contained within p54 is an arginine/serine-rich region similar to segments of several proteins that participate in pre-mRNA splicing including the 70-kDa component of U1 small nuclear and "suppressor-of-white-apricot" proteins. The arginine/serine-rich region is dominated by a series of 8-amino acid imperfect repetitive motifs (consensus sequence, Arg-Arg-Ser-Arg-Ser-Arg-Ser-Arg). Antibodies raised against synthetic peptides of p54 react with an approximately 70-kDa protein on immunoblots of HeLa cell and rat liver nuclear proteins. This apparent discrepancy in mass is also observed when p54 mRNA is translated in vitro. Indirect immunofluorescence studies in HeLa cells show that p54 is distributed throughout the nucleus in a speckled pattern, with an additional diffuse labeling of the nucleus excluding the nucleoli. Double immunofluorescence experiments indicate that these punctate regions are coincident with the speckles seen in cells stained with antibodies against several constituents of the pre-mRNA splicing machinery. Sedimentation analysis of HeLa cell extracts on sucrose gradients showed that p54 migrates at 4-6 S, indicating that the protein is not a tightly associated component of snRNPs. Although the function of p54 is not yet known, our structure and immunolocalization data suggest that this protein may have a role in pre-mRNA processing.
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PMID:Primary structure of a human arginine-rich nuclear protein that colocalizes with spliceosome components. 189 67

alpha 1-Inhibitor III (alpha 1 I3), a broad range plasma proteinase inhibitor, is synthesized with striking tissue specificity in rat livers. The gene is expressed strongly in periportal hepatocytes of healthy adults and less abundantly in regions near the centrilobular vein. This expression pattern is suggestive of a concentration gradient of a blood-borne hormone that enters through the portal vein and diffuses across the lobe toward the centrilobular vein. The alpha 1 I3 gene was known to be regulated both by glucocorticoids and interleukin 6, and therefore the hypothesis was tested that the normal constitutive expression of this gene depended on glucocorticoids. alpha 1 I3 mRNA levels in the livers of hypophysectomized rats with low endogenous glucocorticoid levels were only about 20% of those in control rat livers. Injection of exogenous glucocorticoids reconstituted hepatic alpha 1 I3 mRNA levels up to 64% of their original values in a dose-dependent manner. Similarly, treatment of FAZA rat hepatoma cells with the synthetic glucocorticoid dexamethasone induced alpha 1 I3 mRNA levels in a dose-dependent manner. Taken together these data suggested that glucocorticoids are required for the constitutive high level expression of this gene in normal adult rat livers. A series of 5' deletion constructs and linker scanning mutants of the promoter upstream region were produced and transfected into FAZA cells. A functional glucocorticoid response element was mapped between -168 and -151 base pairs 5' of the transcription start site. This element conforms with an inverted consensus glucocorticoid response element (GRE) but differs in two positions essential for protein DNA interaction between the GRE and the glucocorticoid receptor (GR). The induction of alpha 1 I3 gene promoter region constructs by dexamethasone was abolished by the receptor antagonist RU486, indicating that the GR participated in the activation of the alpha 1 I3 gene. In DNase I footprinting experiments with nuclear protein extracts from untreated and dexamethasone-treated FAZA cells, similar extents of alpha 1 I3 promoter upstream sequences were protected, indicating that proteins capable of binding in the glucocorticoid response-mediating element (GME) region were present before and after arrival of the hormonal signal. However, a purified recombinant fragment of the GR which contained essentially only its DNA binding domain was unable to bind at the GME although it interacted strongly with a consensus GRE sequence.
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PMID:Identification of a glucocorticoid response element contributing to the constitutive expression of the rat liver alpha 1-inhibitor III gene. 191 55

The nuclear Ah receptor from mouse hepatoma (Hepa-1c1c9) cells is a 176-kDa multimeric protein which is stable under conditions of up to 1 M KCl. Under denaturing conditions, the Hepa-1 nuclear receptor can be dissociated into a ligand-binding subunit of Mr approximately 91,000. The identity of subunits that compose the nuclear Ah receptor is currently unknown. We used partial proteolysis under nondenaturing conditions as an approach to study the domain organization of the nuclear form of Ah receptor from Hepa-1c1c9 cells treated with [3H]2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in culture. Low concentrations of trypsin (0.5 microgram/mg nuclear protein) generated heterogeneous fragments with the main fragment having a Stokes radius (Rs) approximately 6 nm. More discrete ligand-binding fragments of Mr approximately 84,000 (Rs approximately 4 nm/approximately 5 S) and Mr approximately 16,000 (Rs approximately 2 nm/approximately 2 S) could be generated using higher concentrations of trypsin (5 micrograms/mg nuclear protein). The relative concentration of the 84 and 16-kDa fragment was dependent on duration of protease treatment; formation of the 16-kDa fragment was accompanied by some loss in [3H]TCDD binding. Treatment of nuclear Ah receptor with alpha-chymotrypsin (1 microgram/mg nuclear protein) generated a single, apparently homogeneous ligand-binding fragment of Mr approximately 101,000 (Rs approximately 5 nm/approximately 5 S). When analyzed by DNA-cellulose chromatography, the chymotryptic fragment eluted at a significantly higher KCl concentration (462 mM) compared to native untreated nuclear Ah receptor (385 mM). Despite this increased affinity for DNA-cellulose columns, the ligand-binding fragment generated by chymotrypsin treatment was unable to interact with a dioxin responsive element in a gel retardation assay. DNA-cellulose binding ability, therefore, does not appear to be a reliable indicator of specific DNA interactions for these protease-modified fragments.
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PMID:Nuclear Ah receptor from mouse hepatoma cells: effect of partial proteolysis on relative molecular mass and DNA-binding properties. 217 30

The effects of androgen withdrawal and replacement on the concentrations of androgen receptor (AR) protein and AR mRNA were investigated in rat ventral prostate and seminal vesicles and in cultured human hepatoma (HepG2) cells. AR mRNA concentrations were determined by Northern blotting with single stranded AR cRNA as the hybridization probe, whereas antibodies raised against two synthetic 17-amino acid long peptides corresponding to the N-terminal and steroid-binding regions of the AR were employed in immunological receptor assays. AR mRNA levels in both prostate and seminal vesicles increased about 2-fold within 24 h after castration and continued to rise within the next 48 h to values that were 9- to 11-fold higher than those in intact controls. Administration of pharmacological doses of testosterone (400 micrograms steroid/day) to 1-day castrated animals for 24-48 h brought about a decrease in AR mRNA levels in accessory sex organs to levels in intact controls. Similar results were obtained in cultured HepG2 cells where a switch to serum- and steroid-free medium elicited a rapid increase (approximately 4-fold in 10 h) in the AR mRNA level, which was prevented by inclusion of 10(-7) M testosterone in culture medium. Similar, but quantitatively less marked, changes occurred in the AR protein concentration in prostate, seminal vesicles, and HepG2 cells, as determined by immunoblotting using antibodies against AR peptides. In addition, immunohistochemical studies showed that AR is a nuclear protein of the prostatic epithelial cells in both intact and castrated rats, and suggested that short term castration increases the concentration of nuclear AR in the prostate. Taken together, these data indicate that androgens down-regulate the concentration of AR protein and AR mRNA in a variety of target tissues.
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PMID:Regulation of androgen receptor protein and mRNA concentrations by androgens in rat ventral prostate and seminal vesicles and in human hepatoma cells. 217 37

The technique of protein blotting was used to study nuclear protein interaction with the alpha-fetoprotein (AFP) gene. The DNA-binding specificity was optimized by varying the amount of competitor DNA and the ionic strength. The specific binding of AFP gene DNA was observed for a set of Morris hepatoma 7777 nuclear proteins. Similar specificity was not seen for these same proteins in liver. In normal rat livers, however, two unique proteins were observed which displayed specific binding. The speculated involvement of these proteins in AFP gene regulation is discussed.
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PMID:alpha-Fetoprotein gene DNA-binding proteins. 241 63

A specific alpha-fetoprotein (AFP) gene binding nuclear protein (Mol. Wt. 149,000) was determined in Morris hepatoma 7777 cells by the protein blotting technique. This protein is not present in normal adult rat liver and non-AFP producing Morris hepatoma 5123tc. Neoplasia induced in rats fed the hepatocarcinogen 3'-methyl-4-dimethylaminoazobenzine enhanced AFP gene activity and re-expressed specific AFP gene binding nuclear protein. The precise role of this protein in AFP gene regulation remains to be determined.
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PMID:A specific alpha-fetoprotein gene binding protein in alpha-fetoprotein producing rat hepatomas. 243 86

DNase I footprinting and gel mobility shift analysis showed that an HuH-7 hepatoma nuclear protein, termed AFP1, binds specifically to an AT-rich sequence, TGATTAATAATTACA, in domain B of the human alpha-fetoprotein enhancer. No such binding activity was found in HeLa cell nuclei. Transient transfection studies showed that a 54-base-pair region corresponding to the AFP1-binding site could stimulate the simian virus 40 early promoter to express a linked chloramphenicol acetyltransferase gene in an orientation-independent and cell-specific manner. The correlation between the binding of AFP1 and the stimulation of chloramphenicol acetyltransferase gene expression strongly suggests that specific interaction of AFP1 with the AT motif is important for cell-specific transcriptional enhancement. Competition gel mobility shift analysis revealed that similar AT-rich sequences with high affinities to AFP1 were also present in the promoters of the alpha-fetoprotein and albumin genes. These results suggest that AFP1 may function as a common regulatory factor in the transcription of the alpha-fetoprotein and albumin genes.
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PMID:Interaction of a hepatoma-specific nuclear factor with transcription-regulatory sequences of the human alpha-fetoprotein and albumin genes. 246 95

Thirty-two cases of primary liver neoplasms comprising 12 benign, 15 malignant, and 5 cases with equivocal histopathological features between benign and malignant have been investigated using monoclonal antibody (MoAb) Ki67, which reacts with a nuclear protein expressed in the G1, G2, S, and M phases of the cell cycle. The Ki67 score (positive cells/total neoplastic cells) seems to correlate to the classes of lesions tested. In the hepatocellular carcinoma (HCC) group, the percentage of labelled nuclei, ranging from 15 to 50 per cent, showed a good correlation with Edmondson-Steiner's histological tumour grade. A percentage of positive cells similar to that of the proved low-grade HCCs was detected in the five neoplastic lesions in which the routine histopathological criteria of malignancy were not fulfilled. The benign neoplasms showed a very low growth fraction, similar to that of normal or cirrhotic tissues. The use of the Ki67 score seems to offer useful information about the biological behaviour of some liver masses and may help in the differential diagnosis of hepatocellular adenoma versus carcinoma.
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PMID:Primary liver neoplasms: evaluation of proliferative index using MoAb Ki67. 254 43

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