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  • 1
    Electronic Resource
    Electronic Resource
    Morphological characteristics of tumours formed by Lewis lung carcinoma-derived cloned cell lines with different metastatic potentials: structural differences in their basement membranes formed in vivo (1992)
    Springer
    Virchows Archiv 420 (1992), S. 163-170 
    Details
    ISSN: 1432-2307
    Keywords: Lewis lung carcinoma ; Basement membrane ; Cell attachment ; Metastasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Tumour basement membrane (BM) is an extracellular matrix produced by tumour cells of epithelial origin. We examined the structure and function of the tumour BM of tumour tissues formed by Lewis lung carcinoma-derived cloned cell lines (P29, LM12-3 and LM60-D6 cells) with low, medium and high metastatic potentials, respectively. Immunohistochemical staining of major BM constituents laminin and type IV collagen demonstrated that all the cell lines produced and deposited these materials extracellularly in vivo. However, the continuity of the tumour BM composed of these materials was much greater in the higher metastatic LM12-3 and LM60-D6 tumours than in those with the low metastatic P29 tumour. Electron microscopic examination revealed that in the higher metastatic tumours, especially the LM60-D6 tumour, the tumour BM had a highly organized structure consisting of lamina densa and lamina rara. Parallel bilayers of BM and their fusion were often observed and tumour cells were in direct contact with the BM. In the vicinity of tumour blood vessels, similar interactions between the tumour bM and the vascular BM were observed, and the tumour cells rested on their own BM, the fused BM or the vascular BM. In contrast, in the low metastatic tumour in which the tumour BM was not clearly defined, this close contact between tumour cells and the vascular BM was not observed. In vitro studies showed that the higher metastatic cells adhered more firmly than the LMP cells to a subendothelial matrix. These results suggest that the adhesiveness of tumour cells to the vascular BM in vivo is correlated with their ability to form an integrated BM in vivo, and that this adhesiveness of the tumour cells may be mediated in part by the tumour BM via BM fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02358808
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  • 2
    Electronic Resource
    Electronic Resource
    Hypomethylation of the metastasis-associated S100A4 gene correlates with gene activation in human colon adenocarcinoma cell lines (1997)
    Springer
    Clinical & experimental metastasis 16 (1997), S. 471-479 
    Details
    ISSN: 1573-7276
    Keywords: DNA methylation ; human colon adenocarcinoma ; metastasis ; S100A4 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The DNA methylation status of the metastasis-associated S100A4 gene in S100A4-positive and -negative human colon adenocarcinoma cell lines was examined. Northern and Western blot analyses revealed that HT-29, SW480, SW620, WiDr and Colo201 cells expressed S100A4, whereas SW837, LoVo and DLD-1 cells expressed little S100A4. Using CpG methylation-sensitive and -insensitive restriction enzymes and PCR-based methylation assay, it was found that the S100A4 gene in HT-29, SW480, SW620, WiDr and Colo201 cells, but not in SW837, LoVo and DLD-1 cells, was hypomethylated and that the hypomethylation of the second intron was correlated well with the expression of S100A4. 5-Aza-2'-deoxycytidine, an inhibitor of the eukaryotic DNA methyltransferase, induced the expression of the S100A4 gene in SW837, LoVo and DLD-1 cells, while it showed no effect on the expression of the gene in WiDr cells. These results indicate that hypomethylation of the S100A4 gene results in the expression of the gene in colon adenocarcinoma cells. © Rapid Science Ltd.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006589626307
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  • 3
    Electronic Resource
    Electronic Resource
    Resistance to apoptosis induced by microenvironmental stresses is correlated with metastatic potential in Lewis lung carcinoma (1999)
    Springer
    Clinical & experimental metastasis 17 (1999), S. 409-416 
    Details
    ISSN: 1573-7276
    Keywords: Apoptosis resistance ; Lewis lung carcinoma ; metastasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The apoptosis-resistant phenotype of cloned high-metastatic A11 and low-metastatic P29 cells isolated from Lewis lung carcinoma was compared. The results showed that A11 cells were more resistant to apoptosis induced by microenvironmental stresses such as serum starvation, glucose deprivation and hypoxia than P29 cells as judged by viability, DNA laddering, and chromatin condensation and fragmentation. Both cell lines were insensitive to tumor necrosis factor-α-mediated apoptosis. P29 cells expressed a much higher level of Fas antigen on the cell surface than A11 cells. However, both cell lines were also insensitive to Fas-mediated apoptosis. The apoptosis resistant phenotype of A11 cells was associated with the expression level of caspase-3, but not with those of Bcl-2, Bcl-XL Bax, p27Kip1 and DAP kinase. There was no difference between A11 and P29 cells in the expression of E-cadherin, the adhesiveness to the extracellular matrix components or the expression levels of metastasis-associated genes such as c-Ha-ras, c-jun, p53 and nm23. Furthermore, A11 cells exhibited lower motile and invasive abilities than P29 cells. These results suggest that the apoptosis-resistant phenotype is an important factor for determining the metastatic ability of A11 cells. Supporting this, P29 cells became more apoptosis-resistant after treatment of the cells with dimethylsulfoxide which is reported to enhance the experimental metastatic potential of the cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006632819086
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  • 4
    Electronic Resource
    Electronic Resource
    Modification of the metastatic potential of tumor cells by drugs (1986)
    Springer
    Cancer and metastasis reviews 5 (1986), S. 67-75 
    Details
    ISSN: 1573-7233
    Keywords: metastatic potential ; dimethylsulfoxide ; butyric acid ; 5-azacytidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Treatment of tumor cells that have little if any metastatic potential with certain drugs that have little or no mutagenic activity has been found to result in marked phenotypic alterations of the cells, including development of a metastatic potential. We found that polar compounds and butyric acid, which are known to alter the expressions of normally silent genes, enhanced the lung-colonizing ability of cloned low-metastatic Lewis lung carcinoma cells. This change was accompanied by increases in the activities of degradative enzymes such as glycosidases, cathepsin B, and plasminogen activator; adhesion of the cells to culture dishes, monolayers of endothelial cells, and a subendothelial matrix; and homotypic aggregation. The effects of these drugs in enhancing the lung-colonizing ability of the cells was found to be reversible, suggesting that it was due to epigenetic alterations. Other investigators have shown that treatment of nonmetastatic tumor cells with 5-azacytidine, which causes hypomethylation of DNA and activates normally silent genes, results in the emergence of a small number of clones with a heritable but unstable metastatic phenotype. These findings suggest that epigenetic mechanisms are involved in rapid cellular phenotypic diversification and tumor progression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046423
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  • 5
    Electronic Resource
    Electronic Resource
    Suppression of syntheses of high molecular weight nonmuscle tropomyosins in macrophages (1995)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 31 (1995), S. 273-282 
    Details
    ISSN: 0886-1544
    Keywords: Peritoneal macrophages ; F-actin microfilament ; in situ hybridization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In mouse fibroblasts, at least five TM isoforms are identified and they can be grouped into the high (TM1, TM2, and TM3) and low molecular weight TM isoforms (TM4 and TM5). Suppression of one of the high molecular weight tropomyosin (TM) isoforms in nonmuscle cells is implicated to be one of the causes for disorganization of actin microfilament bundles and subsequent changes in cell motility and cell shape. In this study, we studied the expression of tropomyosin isoforms in macrophages that exhibit high motility and ability to change cell shape. Two-dimensional gel electrophoresis followed by Western blot analysis using polyclonal anti-TM antiserum revealed that the high molecular weight TM isoforms were lacking in both resident and activated mouse peritoneal macrophages. Analyses of newly synthesized TM isoforms, Northern blot analyses using isoform-specific cDNA probes, and immunostaining with monoclonal anti-TM antibody that recognizes only the high molecular weight TM isoforms also demonstrated that the syntheses of the high molecular weight TM isoforms (TM1, TM2, and TM3) were completely suppressed, whereas the low molecular weight TM isoforms (TM4 and TM5) were expressed in macrophages. These results indicate that macrophages intrinsically lack the high molecular weight TM isoforms. In order to obtain information about cellular localization of the low molecular weight TM isoforms in macrophages, they were immunostained with polyclonal anti-TM antiserum that recognizes both the high and low molecular weight TM isoforms. The results showed that the low molecular weight TM isoforms were co-localized with F-actin in punctate and short fibrous structures. In addition, we performed in situ hybridization analysis to examine localizations of the TM mRNAs in fibroblasts and macrophages. The results showed that TM mRNAs were localized throughout the cytoplasm. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970310404
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