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

With the aim of identifying proteins involved in linking microtubules to other cytoplasmic structures, microtubule-binding proteins were isolated from rat liver extracts by a taxol-dependent procedure. The major non-tubulin component, a 58-kDa protein (designated 58K), was purified to homogeneity by gel filtration chromatography. To aid further characterization of 58K, purified preparations of the protein were used as immunogen for the production of monoclonal antibodies. Five different monoclonals were obtained, and each of these reacted on immunoblots of liver homogenates with a single band that comigrated with 58K. Based on the results of immunochemical, peptide mapping, and microsequencing experiments, 58K was found to be unrelated structurally to similarly sized cytoskeleton-associated proteins, such as tubulin, tau, vimentin, or keratin, and to represent a new protein species. Several in vitro properties of 58K were found to be characteristic of microtubule-associated proteins. For instance, 58K cosedimented quantitatively with microtubules out of liver extracts, stimulated polymerization of tubulin, and bound to microtubules in a saturable manner. In contrast to traditional microtubule-associated proteins, however, 58K was not found to be distributed uniformly along microtubules in cells. Immunofluorescence microscopy of cultured hepatoma cells revealed, instead, that 58K is associated principally with the Golgi apparatus. Moreover, Golgi membranes isolated from rat liver were observed by immunoblotting to contain significant levels of 58K, which, upon subfractionation of the membranes, partitioned as if it were a peripheral membrane protein exposed to the cytoplasmic side of the Golgi. These collective results have been evaluated in terms of earlier evidence that the intracellular position and structural integrity of the Golgi relies on the presence and organization of microtubules. In that context, the observations reported here suggest that the in vivo function of 58K is to provide an anchorage site for microtubules on the outer surface of the Golgi.
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PMID:A novel 58-kDa protein associates with the Golgi apparatus and microtubules. 277 77

Reconstituted Sendai-viral envelopes (RSVE) were fused with hepatoma tissue-culture (HTC) cells, thereby introducing viral membrane glycoproteins into the plasma membrane [Earl, Billett, Hunneyball & Mayer (1987) Biochem. J. 241, 801-807]. Fractionation of homogenized cells on Nycodenz gradients shows that much of the viral 125I-labelled HN and F proteins were rapidly sequestered into a dense fraction distinct from fractions containing plasma membrane, lysosomes and mitochondria. Electron microscopy (results not shown) indicates that the dense fraction contains nuclear residues, multivesicular structures, dense bodies and fibrous structures. Both the dense fraction and a hexosaminidase-enriched fraction contain trichloroacetic acid-insoluble radioactivity, including intact 125I-labelled viral proteins. The viral proteins are progressively transferred from the dense fraction to the hexosaminidase-enriched fraction; the transfer is retarded by 50 micrograms of leupeptin/ml. Trichloroacetic acid-soluble radiolabel is progressively released into the culture medium as the proteins are degraded. Within 5 h after transplantation of viral HN and F proteins into recipient cells, a proportion (approx. 45%) of the 125I-labelled glycoproteins cannot be extracted by sequentially treating cells with digitonin (1 mg/ml), Triton X-100 (1%, w/v) and 0.3 M-KI. HN and F proteins in the non-extractable residue are tightly associated with nuclear-intermediate-filament (vimentin) material, as shown by Western blots and electron microscopy. The viral proteins are progressively transferred out of the nuclear-intermediate-filament residue; the transfer is slowed when cells are cultured with leupeptin. The data are consistent with the notion that transplanted viral HN and F proteins are sequestered to a perinuclear site in tight association with intermediate filaments before transfer into the autophagolysosomal system for degradation.
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PMID:A putative protein-sequestration site involving intermediate filaments for protein degradation by autophagy. Studies with transplanted Sendai-viral envelope proteins in HTC cells. 303 75

Subclones of a human adrenal cortex carcinoma-derived cell line (SW13) are described which by immunofluorescence lack detectable expression of any of the five known classes of intermediate filament (IF) proteins. Further investigation for vimentin and keratins in these subclones by two-dimensional gel analysis and by immunoblotting gave results consistent with the immunofluorescence results. Despite the apparent absence of IFs, SW13 subclones have organized actin and microtubule cytoskeletal networks, maintain an epithelial shape and colony pattern, and grow well in culture. Although a rat hepatoma cell line which similarly appears to have ceased IF expression has been reported, this is the first such report of a human cell line. Although rare, these cases provide evidence that IFs in general are not essential to growth in culture, nor are the keratin-containing IFs in particular necessarily responsible for the 'cobblestone' morphology or colony-type growth pattern characteristic of cultured epithelial cells.
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PMID:Absence of intermediate filaments in a human adrenal cortex carcinoma-derived cell line. 395 86

Antibodies against constitutive proteins of different types of intermediate-sized filaments were used in immunofluorescence microscopy on frozen sections of normal rat liver and various rat liver tumors induced by treatment with nitrosamines. Antibodies to tonofilament prekeratin stained bile duct epithelia and hepatocytes of normal liver and hepatocellular carcinoma cells and ductal cells of cholangiofibromas. These cells were not significantly stained by antibodies to vimentin. By contrast, antibodies to vimentin stained mesenchymal cells of normal liver and cells of early and advanced angiosarcomas and of undifferentiated spindle cell sarcoma. These mesenchymal tumor cells were not stained with antibodies to prekeratin. The presence of intermediate-sized filaments in these tumors, often in large whorl-like aggregates, was also demonstrated by electron microscopy. The results show that immunofluorescence microscopy with antibodies to cytoskeletal proteins is a powerful tool for the classification and differential diagnosis of mesenchymal and epithelial liver tumors. We propose that staining with antibodies to proteins of different types of intermediate filaments can be used to improve the identification of tumors of other organs, including metastases, as well as non-neoplastic proliferative lesions.
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PMID:Liver tumors distinguished by immunofluorescence microscopy with antibodies to proteins of intermediate-sized filaments. 615 36

Murine extra-embryonic endodermal cell lines derived from either teratocarcinomas or mouse embryos contain a cytoskeletal protein (Endo A) of Mr = 55,000. Endo A was immunoprecipitated from [35S]methionine-labeled lysates of three parietal endodermal cell lines, A presumptive visceral endodermal cell line, and a fetal hepatoma cell line, but not from fibroblasts, myoblasts, erythroleukemic cells, neuroblastoma cells, keratinocytes, or embryonal carcinoma cells. Embryonal carcinoma cells induced to differentiate by exposure to retinoic acid synthesized increased amounts of Endo A approximately 48 h after exposure to the inducer. Two-dimensional gel analysis of immunoprecipitated samples confirmed that Endo A is distinct from vimentin and murine keratinocyte proteins recognized by two different keratin antisera. Comparison by two-dimensional gel electrophoresis of immunoprecipitated Endo A labeled with either [35S]methionine or [32P]orthophosphate indicated that the multiple forms of Endo A resolved by isoelectric focusing were due, at least in part, to phosphorylation. Serine was identified as the phosphorylated amino acid. Endo A was the only major antigenic protein found in a parietal endodermal cell line which was recognized by a monoclonal antibody prepared by other investigators against trophoblast cytoskeletons. The results indicate that Endo A, like the previously described Endo B protein, is distinct from other cytoskeletal proteins and will be useful as a marker of the differentiation of murine embryonal carcinoma cells to extra-embryonic endoderm.
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PMID:Developmental expression of murine extra-embryonic endodermal cytoskeletal proteins. 617 20

Monoclonal antibodies were generated against the intermediate filament proteins of different human cells. The reactivity of these antibodies with the different classes of intermediate filament proteins was determined by indirect immunofluorescence on cultured cells, immunologic indentification on SDS polyacrylamide gels ("wester blot" experiments), and immunoperoxidase assays on intact tissues. The following four antibodies are described: (a) an antivimentin antibody generated against human fibroblast cytoskeleton; (b), (c) two antibodies that recognize a 54-kdalton protein in human hepatocellular carcinoma cells; and (d) an antikeratin antibody made to stratum corneum that recognizes proteins of molecular weight 66 kdaltons and 57 kdaltons. The antivimentin antibody reacts with vimentin (58 kdaltons), glial fibrillary acidic protein (GFAP), and keratins from stratum corneum, but does not recognize hepatoma intermediate filaments. In immunofluorescence assays, the antibody reacts with mesenchymal cells and cultured epithelial cells that express vimentin. This antibody decorates the media of blood vessels in tissue sections. One antihepatoma filament antibody reacts only with the 54 kdalton protein of these cells and, in immunofluorescence and immunoperoxidase assays, only recognizes epithelial cells. It reacts with almost all nonsquamous epithelium. The other antihepatoma filament antibody is much less selective, reacting with vimentin, GFAP, and keratin from stratum corneum. This antibody decorates intermediate filaments of both mesenchymal and epithelial cells. The antikeratin antibody recognizes 66-kdalton and 57-kdalton proteins in extracts of stratum corneum and also identifies proteins of similar molecular weights in all cells tested. However, by immunofluorescence, this antibody decorates only the intermediate filaments of epidermoid carcinoma cells. When assayed on tissue sections, the antibody reacts with squamous epithelium and some, but not all, nonsquamous epithelium. Therefore this antistratum corneum antibody and the anti-54-kdalton antibody identify unique epitopes present in the various cytokeratin molecules of epithelial cells. None of the hybridoma antibodies react with neurofilament proteins. The different patterns of reactivity of these antibodies suggest that many of the immunologically distinct intermediate filament proteins contain common antigenic determinants.
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PMID:Monoclonal antibodies to intermediate filament proteins of human cells: unique and cross-reacting antibodies. 618 72

The intermediate filament proteins of rhabdoid tumors of the kidney were investigated with a panel of monoclonal antibodies to different intermediate filament proteins. Rhabdoid tumor cells are decorated by an antivimentin antibody and by an antibody made against a 54-kilodalton (kd) cytokeratin from human hepatoma cells. The rhabdoid tumor cells fail to react with an antibody generated against keratin from stratum corneum or with an anti-200-kd neurofilament protein antibody. Cytoskeleton preparations of rhabdoid tumor cells grown in vitro demonstrate the presence of vimentin (58 kd) and the 54-kd cytokeratin. Thus, these cells contain two different intermediate filament proteins characteristic of epithelial and mesenchymal cells. We also demonstrate that rhabdoid tumor cells can form tumors in athymic (nude) mice and that the intracytoplasmic globules are present in the nude mouse lesions.
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PMID:Rhabdoid tumors of the kidney contain mesenchymal specific and epithelial specific intermediate filament proteins. 619 60

It has been shown by means of the immunoblot technique in combination with monoclonal antibodies and peptide mapping that hepatocytes, hepatoma 27 cells, and rat colon enterocytes exhibit a common prekeratin protein with a molecular weight of 49 kD (PK49). This protein and vimentin, a protein contained by intermediate filaments of mesenchymal cells, share at least one antigenic determinant. The generally accepted procedure for prekeratin purification leads to a more or less pronounced degradation of PK49. The degree of degradation is dependent on the type of the tissue extracted. High heterogenicity of prekeratin polypeptides described elsewhere might be due partly to such a degradation process. In addition to PK49, hepatoma 27 cells, absorbing, goblet and proliferating cells of the colon demonstrated three more prekeratin proteins: two major (PK55 and PK40) and one minor (PK53). Monoclonal antibodies not reacting with PK49 do not recognize PK55, PK53 and PK40. PK55, PK49 and PK40 of hepatoma 27 are identical to the appropriate proteins of the colonic epithelium as judged by peptide mapping. Thus, the cells of the hepatocyte origin are able to synthesize the same prekeratins as the colonic epithelium.
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PMID:[Hepatoma 27 cells and the epithelium of the large intestine in rats contain the identical set of prekeratin proteins]. 620 7

Two rat ascites hepatoma lines, AH130, originating from a azodye-induced liver carcinoma, and AH130F(N), spontaneously derived from the AH130 line during serial i.p. transplantation were analyzed for their intermediate filament protein expression by one and two-dimensional gel electrophoresis, in vitro translation of their mRNAs and immunolocalization using antisera against distinct subunits and compared with intermediate filament expression of normal hepatocytes. Normal rat hepatocytes synthesize mainly two keratin subunits at 55 and 47 kDa. The AH130 hepatoma line maintains the expression of these proteins, however, in addition also synthesizes a 40-kDa keratin subunit and large amounts of vimentin. In contrast, the AH130F(N) hepatoma line has lost the ability to express keratin subunits; its intermediate-sized filament compound is apparently built up only by vimentin. Even by means of the sensitive immunoblotting technique using antisera against the normal hepatocyte keratin subunits, no keratin synthesis can be demonstrated in this line. The marked differences in the metastatic capacity of the two hepatoma lines make them promising tools to investigate a possible involvement of intermediate-sized filament expression in the process of tumor spreading.
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PMID:Differential expression of intermediate filament proteins in two rat ascites hepatoma lines of common origin. 620 51

Cytoskeletal residues obtained after extraction of rat liver and cultured rat hepatoma cells (line MH1C1) were used to isolate cytokeratin subunit complexes by solubilization in low salt buffer containing 4 M-urea. Alternatively, the complexes were prepared by solubilization of total cytoskeletal proteins in 9.5 M-urea or 6 M-guanidinium hydrochloride (Gu . HCl), followed by separation using reversed phase high pressure liquid chromatography and dialysis first against either 9.5 M-urea or 6 M-Gu . HCl and then against buffers containing either 4 M-urea or 2 M-Gu . HCl, respectively. The complexes contained only two cytokeratin polypeptides in a 1 : 1 ratio as demonstrated by electrophoresis and isoelectric focusing, i.e. components A (Mr 55,000; isoelectric point in 9.5 M-urea, pH 6.4) and D (Mr 49,000; isoelectric point, pH 5.38) which were separated from each other at urea concentrations higher than 7 M. The complex had a sedimentation coefficient S25,w of 4.96 S in 2 M-Gu . HCl. Sedimentation equilibrium analysis gave an average Mr value of 207,000 which was interpreted as a tetramer containing two chains each of A and D. This complex was also directly demonstrated by gel electrophoresis under non-dissociating conditions. Using dimethyl suberimidate to cross-link the complex in solution of 4 M-urea or 2 M-Gu . HCl, we identified covalently linked heterodimers of A and D, and a tetrameric unit containing equal amounts of A and D which was the largest cross-link product obtained. This complex was similar to the tetrameric complex of rat and human vimentin formed under the same conditions. The constituents of the cross-linked products were identified by two-dimensional ("diagonal") gel electrophoresis, involving the cleavage of the bis(amidine) cross-links after the initial separation in the first dimension. Identical cross-link products were recognized when cytokeratin filaments were used. By electron microscopy the complexes appeared as threads of 2 to 3 nm diameter with a mean length of approximately 48 nm. On dialysis to low salt buffer, the complexes formed 2 to 3 nm protofilaments, intertwisted 3 to 4 nm protofilaments and typical 7 to 11 nm intermediate-sized filaments. Complexes formed from equivalent cytokeratins of other species such as man and cow, as well as heterologous recombinations such as human component A mixed with bovine component D and vice versa, showed the same characteristics.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Heterotypic tetramer (A2D2) complexes of non-epidermal keratins isolated from cytoskeletons of rat hepatocytes and hepatoma cells. 620 69


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