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

Normal human liver tissue and cultured human hepatocytes are valuable models to study xenobiotic metabolism and toxicity, but they only have a limited in vitro life-span and are not readily available. This report describes the establishment of replicative cultures of human adult liver epithelial cells in serum-free medium. The longevity of three of these cultures, derived from different donors, was extended by introduction of the simian virus 40 large T antigen gene. Two cell lines, THLE-2 and -3, established with a recombinant simian virus 40 large T antigen virus have undergone > 100 population doublings, are nontumorigenic when injected into athymic nude mice, have near-diploid karyotypes, and do not express alpha-fetoprotein. The cells express cytokeratin 18 and albumin in early passage, whereas higher-passage cells in logarithmic-phase growth also express cytokeratin 19. THLE-2 and -3 cells metabolize benzo[a]pyrene, N-nitrosodimethylamine, and aflatoxin B1 to their ultimate carcinogenic metabolites that adduct DNA, which indicates functional cytochrome P450 pathways. Other enzymes involved in metabolism of chemical carcinogens, such as epoxide hydrolase, NADPH cytochrome P450 reductase, superoxide dismutase, catalase, glutathione S-transferases, and glutathione peroxidase are also retained by THLE cells. Thus, these immortalized human liver cells constitute an in vitro model for pharmacotoxicological studies and for the investigation of etiology and pathogenesis of human hepatocellular carcinoma.
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PMID:Simian virus 40 large tumor antigen-immortalized normal human liver epithelial cells express hepatocyte characteristics and metabolize chemical carcinogens. 768 15

The cytokeratin 18 related molecules of human hepatocellular carcinoma have been previously recognized through a series of biochemical and immunological approaches. It is suggested that these molecules undergo modulation from human hepatocyte cytokeratin 18. To prove whether these molecules are produced by modulation or protein degradation, we checked the cytokeratin profile of human hepatoma cell line PLC/PRF/5 with the methods used before. These results revealed that the PLC cells have the same cytokeratin 18 related molecules as human hepatocellular carcinoma tissue. The gene expression of the cytokeratin 18 in non-tumor liver tissues, hepatocellular carcinoma and PLC/PRF/5 cells were investigated. First, the mRNAs of non-tumor liver tissues, hepatocellular carcinoma tissues and PLC/PRF/5 cells were collected by the acid guanidinium thiocyanate phenol chloroform method. After transcription into cDNA by reverse transcriptase polymerase chain reaction, the cDNAs of each specimen were amplified by PCR and then digested by SmaI and BamHI restriction enzymes. The digested cDNA fragments were electrophoresed in agarose gel and the base pairs were found to be the same in length between neoplastic and non-neoplastic hepatocytes.
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PMID:The alteration of cytokeratin 18 molecule and its mRNA expression during tumor transformation in hepatoma. 926 84

During experiments to identify putative hepatic receptors for thrombin-antithrombin (TAT) complexes, a 45-kDa protein was identified by ligand blotting. Following gel purification, amino acid sequencing revealed the 45-kDa TAT-binding polypeptide to be cytokeratin 18 (CK18). The presence of CK18 on the surface of intact rat hepatoma cells was demonstrated by binding of 125I-anti-CK18 antibodies. Anti-CK18 antibodies reduced the binding and internalization of 125I-TAT by rat hepatoma cells. Immunocytochemical analysis, to determine the location of CK18 in vivo, revealed a periportal gradient of CK18 staining; with hepatocytes around the portal triads demonstrating striking pericellular staining. In addition, anti-CK18 IgG associated with perfused livers to a significantly greater extent than preimmune IgG. Taken together, these data provide evidence that CK18 is found on the extracellular surface of hepatocytes and could play a role in TAT removal. Finally, these data, in conjunction with recent reports of CK8 (Hembrough, T. A., Li, L., and Gonias, S. L. (1996) J. Biol. Chem. 271, 25684-25691) and CK1 cell membrane surface expression (Schmaier, A. H. (1997) Thromb. Hemostasis 78, 101-107), indicate a novel role for these proteins as putative cellular receptors or cofactors to cellular receptors.
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PMID:Cytokeratin 18 is expressed on the hepatocyte plasma membrane surface and interacts with thrombin-antithrombin complexes. 935 22

Aflatoxin B1 (AFB1) is one of the major causative factors of hepatocellular carcinoma. In this study, the combined effects of AFB1 activated by human cytochrome p450 IA2 and c-myc in transformation of rat hepatocytes were investigated in an in vitro primary culture system. The expression vectors, Xm-6/c-myc was first constructed and their expression possibilities were examined in Alexander cells by immunocytochemistry. Then both c-myc and human cytochrome p450 IA2 expression vectors were sequentially transfected into newborn rat liver cells in serum-free primary culture. Results showed that p450 IA2 could activate AFB1 at concentrations as low as 5 ng/ml, and the activated AFB1 coupled with exogenous c-myc could induce rat hepatocytes to survive and grow beyond two-month limit in primary culture. During long-term in vitro culturing including four-month in crisis, one of the randomly selected transformed hepatocytes with the growth advantage became immortalized. Immunocytochemical assays for CK-18 and rat albumin plus observed electron microscopic features clearly confirmed these cells derived from epithelial hepatocytes. Further characterization showed that the process of immortalization was associated with chromosomal abnormalities and elevated expression of TGF alpha.
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PMID:[Transformation of rat hepatocytes in an in vitro primary culture by aflatoxin B1]. 1045 45

The epithelium in kidneys and urinary bladders contain CK18 as in liver cells. The modulation of cytokeratin 18 during tumor transformation in hepatoma had been previously recognized through a series of biochemical and immunological approaches. A 14 KD hepatoma related molecules was found in the previous studies. We would like to utilize the hepatoma transformation model to study the changes in CK18 in transitional cell carcinoma, using immunoblotting and western blotting techniques. The result is that transitional cell carcinoma retain their CK18 molecule. Furthermore, CK18 related molecules similar to those seen in hepatoma also present in transitional cell carcinoma. The conclusions are transitional cell carcinoma contains CK18 related proteins similar to those seen in hepatoma tissues. We suggest that this element would be responsible for the change during the malignant transformation processes.
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PMID:The expression of cytokeratin 18 in transitional cell carcinoma comparing with hepatoma. 1085 Mar 64

The cytoskeleton plays important roles in cell function and is therefore implicated in the pathogenesis of many human liver diseases, including malignant tumors. The stability of cytokeratin proteins during tumor transformation in human hepatocellular carcinoma has been studied with a molecular approach previously. The results demonstrate that the cytokeratin is modulated in human hepatocellular carcinoma. Besides this, three low molecular weight cytokeratin molecules (named HCC CK) are found. This indicates that these HCC CKs have undergone modulation from the human hepatocyte cytokeratin 18. We also checked the cytokeratin profile of the human hepatoma cell line PLC/PRF/5 with the same methods to ensure the HCC CK molecules are produced by modulation but not protein degradation. The stability of cytokeratin molecules was studied by a different approach. The cytokeratin compositions of human liver cells (Chang cell line) were analysed under the effects of microtubule-disrupting drug (colchicine) by SDS-PAGE, Western blot, immunoprecipitation using a commercially available monoclonal anti-cytokeratin 18 antibody and immunofluorescent staining. Within 1 h of treatment, the microtubule began to collapse and the filamentous structure was shortening. The microtubule had almost collapsed and became fragmented to form a lattice-like network after 24 h of treatment. The cytokeratin was modulated after long-term (24 h) treatment of colchicine, and the molecular weight became 14 kD and the antigenicity was lost. The stability of cytokeratin molecules was related to the intact microtubule network, after disruption of the microtubule the cytokeratin would be modulated. The intact microtubule network was a stabilizing factor of cytokeratin 18 in human liver cells.
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PMID:The stability of cytokeratin 18 in human liver cells during colchicine-induced microtubule disruption. 1125 54

The modulation of cytokeratin 18 during tumor transformation in hepatoma had been previously recognized through a series of biochemical and immunological approaches. Expression of cytokeratin 18 in transitional cell carcinoma comparing with hepatoma was investigated using the hepatoma transformation model. CK18 related molecules were found. In the present study, we design various epithelial cancers with the same model. CK18 related molecules were all evident. Therefore, we suggest that CK18 related proteins would play an important role in tumorigenesis of epithelial cancers.
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PMID:Do the CK18 related proteins change in general in epithelial cancers? 1191 16

Desmosomes are prominent cell adhesion structures that are major stabilizing elements, together with the attached cytoskeletal intermediate filament network, of the cytokeratin type in epithelial tissues. To examine desmosome dynamics in tightly coupled cells and in situations of decreased adhesion, fluorescent desmosomal cadherin desmocollin 2a (Dsc2a) chimeras were stably expressed in human hepatocellular carcinoma-derived PLC cells (clone PDc-13) and in Madin-Darby canine kidney cells (clone MDc-2) for the continuous monitoring of desmosomes in living cells. The hybrid polypeptides integrated specifically and without disturbance into normal-appearing desmosomes that occurred in association with typical cytokeratin filament bundles. Tracking of labeled adhesion sites throughout the cell cycle by time-lapse fluorescence microscopy revealed that they were immobile and that they maintained their structural integrity for long periods of time. Time-space diagrams further showed that desmosomal positioning was tightly controlled, even during pronounced cell shape changes, although the desmosomal arrays extended and contracted, suggesting that they were interconnected by a flexible system with intrinsic elasticity. Double-fluorescence microscopy detecting Dsc2a chimeras together with fluorescent cytokeratin 18 chimeras revealed the association and synchronous movement of labeled desmosomes and fluorescent cytokeratin filaments. Only a minor destabilization of desmosomes was observed during mitosis, demonstrated by increased diffuse plasma membrane fluorescence and the fusion of desmosomes into larger structures. Desmosomes did not disappear completely at any time in any cell, and residual cytokeratin filaments remained in association with adhesion sites throughout cell division. On the other hand, a rapid loss of desmosomes was observed upon calcium depletion, with irreversible uptake of some desmosomal particles. Simultaneously, diffusely distributed desmosomal cadherins were detected in the plasma membrane that retained the competence to nucleate the reformation of desmosomes after the cells were returned to a standard calcium-containing medium. To examine the molecular stability of desmosomes, exchange rates of fluorescent chimeras were determined by fluorescence recovery after photobleaching, thereby identifying considerable Dsc2a turnover with different rates of fluorescence recovery for PDc-13 cells (36+/-17% recovery after 30 minutes) and MDc-2 cells (60+/-20% recovery after 30 minutes). Taken together, our observations suggest that desmosomes are pliable structures capable of fine adjustment to functional demands despite their overall structural stability and relative immobility.
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PMID:Desmosomes: interconnected calcium-dependent structures of remarkable stability with significant integral membrane protein turnover. 1195 Aug 89

Fetal rat hepatocytes treated with transforming growth factor beta (TGF-beta) die by apoptosis. However, a subpopulation of them survives and undergoes an epithelial mesenchymal transition (EMT). This transition also occurs upon incubation with fetal bovine serum. We have isolated the subpopulations that undergo EMT (TGF-beta-treated-fetal hepatocytes: TbetaT-FH; serum-treated-fetal hepatocytes: ST-FH) and show that they present high levels of vimentin and Snail expression and lack cytokeratin 18 and E-cadherin. Both TbetaT-FH and ST-FH cells require mitogens to grow and maintain the response to TGF-beta in terms of growth inhibition. However, they lack differentiation markers such as the liver-enriched transcription factors hepatocyte nuclear factor 4 (HNF-4) or HNF-1alpha and express the progenitor marker OV-6. Interestingly, the EMT process confers them resistance to the apoptotic effect of TGF-beta, with cells showing higher levels of active AKT and Bcl-x(L) than fetal hepatocytes. In summary, these cells are refractory to the apoptotic effects of TGF-beta, showing characteristics of liver progenitors and of some hepatocellular carcinoma cells.
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PMID:The epithelial mesenchymal transition confers resistance to the apoptotic effects of transforming growth factor Beta in fetal rat hepatocytes. 1249 70

The ubiquitin-proteasome system is involved in a variety of biological processes. Inclusion bodies associated with intermediate filaments (IFs) and ubiquitin are observed in various diseases; however, the precise mechanisms of formation and the pathological significance of inclusion bodies have not been fully understood. We examined the effect of proteasome inhibitors on the structure of IF using anti-cytokeratin antibodies or transfection of green fluorescent protein-fused cytokeratin 18 in a hepatoma cell line, Huh7. Intracellular organelles were visualized by immunofluorescent and electron microscopies. Proteasome inhibitors induced IF inclusions associated with ubiquitin. Electron microscopic examination revealed inclusion bodies surrounded by filamentous structures. Autophagic vacuoles and lysosomes were frequently observed, and the organization of the Golgi apparatus was disrupted in these cells. After the removal of the proteasome inhibitors, the IF network and organization of the Golgi apparatus were restored. The IF inclusions could be induced by inhibition of the proteasome function. IF inclusions induced fragmentation of the Golgi apparatus and might inhibit the function of this important station of membrane traffic. The IF inclusions disappeared by restoring proteasome function, and autophagy and lysosomal degradation might be, at least in part, associated with the elimination of inclusion bodies.
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PMID:Proteasome inhibition induces inclusion bodies associated with intermediate filaments and fragmentation of the Golgi apparatus. 1287 59


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