Search PubMed⌕ Search

Biomedical subjects

E Roos

Publications and source records attributed to E Roos.

At least 73 records · Page 4Linked to original sources
PubMed1988

Invasiveness in hepatocyte and fibroblast monolayers and metastatic potential of T-cell hybridomas in mice.

Fusion of noninvasive, nonmetastatic BW5147 T-lymphoma cells with normal T-lymphocytes usually resulted in highly invasive and metastatic T-cell hybridomas, apparently due to properties derived from the normal T-cell. Occasionally hybrids arose that were non- or low invasive, probably by loss of relevant genes upon chromosome segregation, since these cells contained much less DNA than highly invasive hybrids. The metastatic potential of 20 representative T-cell hybridomas was tested by tail vein injection in syngeneic mice and cells were found to be either nonmetastatic (NM), low metastatic (LM), or high metastatic (HM). NM hybrids were tumorigenic but did not form metastases and HM hybridomas caused wide-spread metastasis. LM cells formed metastases in a limited number of mice and predominantly in lymphoid tissues. In hepatocyte cultures, NM cell lines were found to be the least invasive, HM cells the most, whereas LM hybrids exhibited intermediate levels. Invasiveness was not only measured in rat hepatocyte cultures but also in rat embryo fibroblast monolayers, and the relative invasive capacity in both model systems correlated well. Pertussis toxin inhibited invasion in both systems to 20-30% of control values. This suggests that the mechanisms of invasion into hepatocyte and fibroblast cultures are at least partially similar and that the fibroblast invasion assay is a relevant model to study aspects of lymphoma metastasis. We conclude that invasive potential is a prerequisite for T-cell hybridomas to colonize tissues from the bloodstream and that a minimum level of invasiveness is necessary for extensive and wide-spread metastasis formation.

Animals↗
PubMed1988

Syngeneic in vivo passage of the murine BW 5147 lymphoma results in the expression of a stable metastatic phenotype.

BW 5147 lymphoma cells are non-invasive tumor cells which do not generate experimental metastases following i.v. inoculation. In contrast, s.c. and intra-splenic (i.s.) growth of BW cells resulted in widespread colonization of liver and spleen. Cells derived from either s.c. tumors or metastatic lesions did generate metastases after i.v. administration. The capacity of these tumor-derived BW cells to disseminate via blood-borne cells was irreversible and stable, indicating that one in vivo passage of BW cells results in the generation of new, metastatic BW variants. Concomitantly, these variants exhibited an inherent invasive potential as manifested by their capacity to infiltrate in vitro monolayers of hepatocytes and fibroblasts. The BW variants expressed new membrane markers such as H-2 antigens, the Lyt 1.2 T-cell differentiation antigen and the MTH antigen (a newly defined membrane antigen expressed predominantly on murine metastatic T-cell lymphomas and mature T lymphocytes). This phenomenon was observed with both cloned and uncloned BW populations, suggesting that an inductive rather than a selective mechanism accounts for the transition of BW cells towards a more malignant phenotype. These observations confirm the concept that local factors at the growth site of a tumor might influence the metastatic behavior of that tumor, possibly via induction of silent differentiation programs.

Animals↗
PubMed1988

Genetic analysis of invasion and metastasis.

Metastasis formation is a multistep process that probably requires a complex interplay of a large and heterogeneous group of genes, including genes involved in cellular resistance to immunorejection and genes controlling the invasive potential of cells. Transfection experiments have shown that oncogenes of the ras gene family as well as oncogenes of the kinase group are able to induce invasive and metastatic properties in non-transformed cells as well as in tumorigenic, but non-metastatic, cells. However, these findings are not in agreement with observations on spontaneous human tumours in which no correlation was found between activation or increased expression of ras genes and the invasive and metastatic properties of these cells. Further studies have indicated that in particular cell types nuclear oncogenes like N-myc and adenovirus derived E1A may influence metastasis formation by trans-regulation of other genes, including class I genes of the major histocompatibility complex and genes coding for proteolytic enzymes. The many efforts to identify additional invasion and metastasis associated genes by transfection of high molecular weight metastatic tumour DNA met with little success. Somatic cell fusion studies, however, indicate that such genes exist and that one or more of them are located on human chromosome 7.

Genetic Techniques↗
PubMed1987

Location of genes involved in invasion and metastasis on human chromosome 7.

We have obtained evidence for the existence of genes controlling invasion and metastasis by somatic cell fusion studies. Noninvasive, nonmetastatic mouse BW5147 T-lymphoma cells were fused with invasive human T-cells. The human cells were either activated normal peripheral blood lymphocytes or leukemic T-lymphoblasts. Both fusions resulted in highly invasive human-mouse T-cell hybrids which metastasized in nude mice. Thus the genes derived from either malignant or nonmalignant but inherently invasive cells enable the T-cell hybridomas to metastasize. By continued in vitro selection for invasive cells employing monolayers of rat embryo fibroblasts followed by subcloning, we were able to isolate invasive hybrids that had lost all human chromosomes except chromosome 7. We present evidence that one or more genes residing on human chromosome 7 are necessary and sufficient for both the establishment and maintenance of invasiveness and metastatic potential of the interspecies T-cell hybrids.

Animals↗
PubMed1987

Inhibition of lymphoma invasion and liver metastasis formation by pertussis toxin.

We have examined whether pertussis toxin, an agent known to inhibit entry of normal lymphocytes into tissues, affects invasion and metastasis formation by malignant lymphoma and T-cell hybridoma cells. The toxin reduced invasion in vitro in hepatocyte cultures to 20% of control values. Inhibition was maximal after pretreatment for 2 h with approximately 100 ng/ml. The effect of pretreatment with 1 to 5 micrograms toxin/ml for 4 h persisted for at least 5 days, despite a more than 100-fold increase in cell number. The proliferation rate was not affected. Liver metastasis formation after tail vein injection of TAM2D2 T-cell hybridoma cells in syngeneic AKR mice, measured as liver weight, was reduced to 10 to 25% of controls after pretreatment of the cells for 4 h with 1 microgram pertussis toxin/ml. Metastasis to kidneys, ovaries, and lymph nodes was not, or less evidently, affected. With MB6A lymphosarcoma cells no effect was seen after treatment with 1 microgram/ml, but a significant reduction of the liver tumor burden to approximately 50% of controls was achieved by treatment with at least 5 micrograms toxin/ml. Spleen metastasis by MB6A cells was not affected. These results provide evidence for a similarity in invasion mechanisms of normal and malignant lymphoid cells, and they suggest that invasiveness is an important factor in the formation of lymphoma metastases, particularly in the liver.

Animals↗
PubMed1987

Induction of tumoricidal activity in isolated rat liver macrophages by liposomes containing recombinant rat gamma-interferon supplemented with lipopolysaccharide or muramyldipeptide.

We examined whether the macrophages in the liver, Kupffer cells, could be activated to a tumoricidal state in a similar way as has been described for other macrophage types. Kupffer cells were isolated by centrifugal elutriation of pronase-treated rat livers. Incubation with highly purified recombinant rat gamma-interferon in combination with small amounts of lipopolysaccharide or muramyldipeptide resulted in highly cytotoxic macrophages, as measured against P815 tumor cells in an 18 h 51Cr-release assay. Incubation of Kupffer cells with the stimulators entrapped within liposomes, caused phagocytosis of the liposomes and subsequent activation to tumor cytotoxicity, provided that both rat gamma-interferon and subthreshold doses of either lipopolysaccharide or muramyldipeptide were encapsulated. The minimum amount of liposomal rat gamma-interferon that induced optimal activation was 0.5 U/ml, while 6 ng/ml of liposomal lipopolysaccharide or muramyldipeptide was required. Cytotoxicity of Kupffer cells activated in this way, persisted for at least 48 h. Since liposomes in circulation are readily cleared by the liver macrophages, these findings may have therapeutic implications.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1987

Invasive and metastatic potential induced by ras-transfection into mouse BW5147 T-lymphoma cells.

Noninvasive, nonmetastatic BW5147 T-lymphoma cells were transfected with the activated human c-Ha-ras oncogene and were examined subsequently for the acquisition of invasive properties in vitro and of metastatic potential in vivo. It was found that several transfectants harboring the ras gene had become invasive in vitro, as assessed in hepatocyte cultures, and metastatic after tail vein injection into syngeneic AKR mice. The induced level of both invasive and metastatic potential appeared to depend on the level of expression of the transfected ras gene. Those transfectants exhibiting an elevated level of ras expression, mostly cells containing a high copy number of the ras gene, showed the highest invasiveness (up to 30-fold increase) and produced widespread metastasis in all mice tested. Transfectants with a low level of ras expression were less invasive and formed metastases in a few mice only, limited to a few organs or even to a single deposit in one organ. Untransfected BW cells, control transfected cells without the ras gene, and ras transfectants that did not express the gene were noninvasive and nonmetastatic. No changes in number of ras gene copies were found between isolated metastases and the transfectants from which they were derived. However, RNA analysis of the cells from the isolated metastases revealed similar, as well as elevated or diminished levels of ras transcription when compared to the corresponding cell lines prior to injection, suggesting that a persistent high expression of the ras gene is not necessarily needed for the independent growth at the secondary site. Our results indicate that the activated human ras oncogene may confer metastatic potential onto lymphoid tumor cells, probably due to the induction of invasiveness.

Animals↗
PubMed1987

Involvement of leukocyte function-associated antigen-1 (LFA-1) in the invasion of hepatocyte cultures by lymphoma and T-cell hybridoma cells.

We studied the interaction of MB6A lymphoma and TAM2D2 T cell hybridoma cells with hepatocyte cultures as an in vitro model for in vivo liver invasion by these tumor cells. A monoclonal antibody against leukocyte function-associated antigen-1 (LFA-1) inhibited adhesion of the tumor cells to the surface of hepatocytes and consequently strongly reduced invasion. This effect was specific since control antibodies, directed against Thy.1 and against T200, of the same isotype, similar affinity, and comparable binding to these cells, did not inhibit adhesion. This suggests that LFA-1 is involved in the formation of liver metastases by lymphoma cells. TAM2D2 T cell hybridoma cells were agglutinated by anti-LFA-1, but not by control antibodies. Reduction of adhesion was not due to this agglutination since monovalent Fab fragments inhibited adhesion as well, inhibition was also seen under conditions where agglutination was minimal, and anti-LFA-1 similarly affected adhesion of MB6A lymphoma cells that were not agglutinated. The two cell types differed in LFA-1 surface density. TAM2D2 cells exhibited 400,000 surface LFA-1 molecules, 10 times more than MB6A cells. Nevertheless, the level of adhesion and the extent of inhibition by the anti-LFA-1 antibody were only slightly larger for the TAM2D2 cells.

Agglutination Tests↗
PubMed1987

Interaction of plasma membrane-associated filaments and H-2 histocompatibility antigens before and after induced patching and capping.

The interaction of H-2 antigens and plasma membrane-associated filaments was studied on dry-cleaved preparations of immunogold-labelled lymphoma cells. In prefixed cells, the plasma membrane-associated network was isotropic without any prevailing direction of the filaments, and the gold-labelled H-2 antigens were preferentially localized over or at a very short distance from membrane-associated filaments. Incubation of unfixed cells with anti-H-2 antibodies followed by fixation and incubation with anti-Ig, did not induce detectable redistribution of H-2 antigens or of the filament network. Notwithstanding this apparent absence of rearrangement of H-2 antigens and filaments, a detergent-resistant linkage to the cytoskeleton was induced. Before immune incubations, virtually all H-2 antigens were solubilized by extraction with Triton X-100, while after incubation with anti-H-2 antibodies about 50% of the H-2 antigens were linked to the Triton X-100-insoluble cytoskeleton. Sequential addition of anti-H-2 and anti-Ig antibodies to unfixed cells induced formation of patches and caps of H-2 antigens. Under these conditions, the majority of the H-2 antigens became linked to the detergent-resistant cytoskeleton. Redistribution into patches and caps was often accompanied by a local rearrangement of the isotropic network into bundles of parallel filaments immediately adjacent to the plasma membrane. Patches were seen to overly both isotropic networks and these parallel filaments. Large sheets of plasma membrane overlying parallel filaments were frequently devoid of gold-labelled H-2 antigens and coated pits, and thus most probably represented areas away from caps. This observation suggests that capping is accompanied by a rearrangement of filaments close to the membrane.

Animals↗
PubMed1986

Cell surface sialic acid and the invasive and metastatic potential of T-cell hybridomas.

T-cell hybridomas prepared by fusion of non-invasive non-metastatic BW5147 T-lymphoma cells and activated normal T-cells were found to be highly invasive in vitro and highly metastatic in vivo upon tail vein injection. By prolonged culturing and subcloning, non-invasive, non-metastatic hybrids were selected with modal DNA/cell contents close to the diploid value of both fusion partners. Since normal activated T-cells were invasive in vitro in hepatocyte cultures, these data suggest that invasiveness of the hybrids is derived from the parental normal T-cells and is one of the properties responsible for the metastatic potential of these cells. Analysis of a large panel of T-cell hybrids with fluorescein isothiocyanate conjugated lectins, specific for terminal galactose and/or N-acetylgalactosamine sugar residues, showed an inverse correlation between expression of lectin receptor sites and invasive and metastatic potential of the hybrids. Soybean agglutinin, as well as peanut agglutinin and Ricinus communis agglutinin, reacted strongly with non- or low-invasive hybrids but only weakly with invasive hybrids. The difference in lectin binding between both types of hybrids appeared to be due to masking of receptor sites by sialic acid. Removal of cell surface sialic acid by neuraminidase treatment unmasked the lectin receptor sites of invasive hybrids to the level of the corresponding sites of non- or low-invasive cells. This increase in active lectin binding sites was simultaneously accompanied by a striking decrease of invasiveness to the level of the low-invasive hybrids. Conversely, the blocking of R. communis agglutinin receptors by sialic acid allowed selection of invasive hybrids from segregating cell populations with the toxic lectin R. communis agglutinin. The results taken together indicate that sialylation of particular cell surface carbohydrate residues on the T-cell hybridomas is associated with the invasive and metastatic potential of these hybrids. The reduction of invasive potential after removal of cell surface sialic acid provides further evidence for a functional role of this sugar residue in invasiveness of the T-cell hybrids.

Animals↗
PubMed1985

Localization of cell surface glycoproteins in membrane domains associated with the underlying filament network.

To visualize the localization of cell surface constituents in relation to the plasma membrane-associated filament network, we developed a method based on a combination of immunogold labeling and dry-cleaving. For labeling we used trinitrophenyl-derivatized ligand, anti-TNP antibodies, and protein A-coated colloidal gold. Dry-cleaving (Mesland, D. A. M., H. Spiele, and E. Roos, 1981, Exp. Cell Res., 132: 169-184) involves cleavage of lightly fixed critical point-dried cells by means of adhesive tape. Since cells cleave close to the cell surface, the remaining layer is thin enough to be examined in transmission electron microscopy. Using this method, we studied concanavalin A-binding constituents on the medium-facing surface of H35 hepatoma cells. The distribution of the gold particles, which was partly dispersed and partly patchy, coincided strikingly with membrane-associated filaments, and label was virtually absent from areas overlying openings in the filament network. In stereo pairs we observed the label to be localized to areas of somewhat enhanced electron density at the plane of the membrane. These areas were interconnected in a pattern congruent with the filament network. Preliminary observations on wheat germ agglutinin receptors on the hepatoma cells as well as concanavalin A receptors on isolated hepatocytes yielded comparable results. It thus appears that surface glycoproteins, although seemingly randomly distributed as observed in thin sections, may actually be localized to particular membrane domains associated with underlying filaments.

Actin Cytoskeleton↗
PubMed1985

Invasiveness of T-cell hybridomas in vitro and their metastatic potential in vivo.

BW5147 lymphoma cells, which are noninvasive and nonmetastatic, were fused with normal T-lymphocytes. The invasiveness of the generated T-cell hybridomas was tested in hepatocyte cultures, and their metastatic potential was tested by tail vein injection. A total of 29 hybridomas generated from alloantigen-activated T-cells were all found to be invasive. One of these cell lines rapidly lost invasiveness in culture. Most hybridomas generated from nonstimulated spleen T-cells were also invasive, but 5 of 27 were not. Six invasive and four noninvasive hybridomas were injected into the tail vein of syngeneic mice. All invasive cell lines caused extensive and widespread tumor growth, particularly in the liver, which was usually severalfold enlarged; the spleen; kidneys; and ovaries. In contrast the noninvasive hybrids, which were tumorigenic upon s.c. injection, did not form any metastases. We conclude that properties derived from normal T-cells, when introduced into noninvasive T-lymphoma cells, cause them to become invasive as well as metastatic. Furthermore for this tumor cell type invasiveness as measured in hepatocyte cultures appears to be closely associated with the ability to colonize organs from the bloodstream.

Animals↗
PubMed1985

Hepatocyte surface molecule involved in the adhesion of TA3 mammary carcinoma cells to rat hepatocyte cultures.

To identify adhesion molecules involved in the formation of liver metastases, we prepared monoclonal antibodies against rat liver plasma membranes, that inhibited the adhesion of mouse metastatic TA3 mammary carcinoma cells to rat hepatocytes in vitro. Two such antibodies (designated OPAR-1 and OPAR-2) were obtained, that inhibited by over 70%. As assessed with gel electrophoresis and immunoblotting, these antibodies bound predominantly to plasma membrane proteins with molecular weights of 125,000 and 100,000. Using immunoelectron microscopy, the OPAR antigen was found to be abundantly present on the sinusoidal surface of hepatocytes, and in addition on contiguous hepatocyte surfaces and Kupffer cells, but was absent from sinusoidal endothelial cells. The tissue distribution and molecular weight indicate that the OPAR antigen is different from other hepatic adhesion molecules. Adhesion of MB6A lymphosarcoma cells was not inhibited by OPAR antibodies, indicating that these cells adhere to hepatocytes via a different surface molecule.

Animals↗
PubMed1984

Generation of invasive and metastatic variants of a non-metastatic T-cell lymphoma by in vivo fusion with normal host cells.

Intravenous inoculation of the AKR mouse-strain-derived BW lymphoma into CBA recipients resulted in a case of liver metastasis; cells derived from this metastatic nodule were termed BW-Li cells. BW-Li cells, upon reinoculation, generated metastases in the spleen, liver, kidney and ovaries in 100% of CBA recipients. Furthermore, BW-Li cells, in contrast to BW cells, were found to infiltrate in vitro monolayers of hepatocytes, thus confirming their inherent invasive potential. Analysis of the alloantigenic phenotype of BW-Li cells revealed that such cells were Thy 1.1+, Thy 1.2+, Lyt 1.2+, Lyt 1.1-, Lyt 2- and H-2Dk+, as compared to BW cells which exhibited the membrane phenotype Thy 1.1+, Thy 1.2-, Lyt 1.2-, Lyt 1.1-, Lyt 2-, H-2Dk-. BW-Li cells also differed functionally from BW cells since these cells secreted IL-2 upon stimulation with Concanavalin A. BW tumor transplantation experiments were repeated in a semi-allogeneic F1 strain combination, i.e. (AKR X CBA)F1, and again a case of massive liver metastasis was observed. Cells derived from these liver metastases (termed BW-O-Li) manifested an invasive and metastatic potential similar to that of BW-Li cells. Furthermore, BW-O-Li cells secreted IL-2 upon stimulation with Con A and manifested the following alloantigenic phenotype: Thy 1.1+, Thy 1.2+, Lyt 1.2+, Lyt 1.1-, Lyt 2-, H-2Dk+ and H-2Kk+. These results indicate that BW-Li and BW-O-Li cells are functional T-cell hybrids which express T-cell markers derived from BW cells and Thy 1.2+ CBA host cells. The acquisition of host-derived T-cell properties may have led to the expression of metastatic and invasive capabilities. From these results we conclude that the acquisition of metastatic properties following somatic cell fusion with normal lymphoreticular cells may represent a mechanism for tumor progression in vivo.

Animals↗
PubMed1984

Nonmetastatic tumor cells acquire metastatic properties following somatic hybridization with normal cells.

Somatic cell hybridization between nonmetastatic tumor cells and normal cells of the lymphoreticular system results in hybrid cells manifesting metastatic properties of defined target organ specificity. Thus, fusion of the nonmetastatic BALB/c originated NSI plasmacytoma with C57BL B lymphocytes resulted in hybridomas, each of which were metastatic. Of 10 hybridomas, 7 generated metastases in the spleen and liver, whereas 3 generated liver metastases. The generation of liver metastases by hybridomas which homed to both spleen and liver, but not by those which homed to the liver only, was controlled by the spleen. The acquisition of metastatic properties via somatic cell fusion seems to represent a general principle, in which the normal partner determines the target organ specificity for the metastatic growth. Thus, fusion of SP2/O myeloma cells with syngeneic B lymphocytes also resulted in a hybrid cell metastasizing to the spleen and liver, yet a somatic hybrid between NSI and a macrophage or dendritic-like cell metastasized to the lung. Cell surface molecules encoded by the genome of the normal partner was demonstrated to control the target organ specificity: antibodies against MHC-encoded antigens of the normal B cell partner prevented the generation of metastases by hybridomas metastasizing to the spleen and liver, but not by those metastasizing to the liver only. This is in accordance with the function of MHC molecules on lymphocytes in controlling their homing to lymphoid organs. Hybridomas of T cell lymphomas also manifested metastatic properties. Analysis of the cell surface Thy-1 antigens of a hybridoma (DCH10), produced via somatic fusion between BW5145 lymphoma and a putative macrophage cell indicated that cells of liver metastases (DCH10-Li) generated by the hybrid cells might have undergone further somatic cell fusion in vivo with host (T?) cells. These cells have acquired new metastatic properties, generating metastases in spleen, liver and kidneys. In fact, even the inoculation of the parental BW lymphoma cells resulted in a case of liver metastasis (BW-Li). Such BW-Li cells, upon reinoculation, also generated metastases in the spleen, liver and kidneys. Analysis of the Thyl phenotype indicated that BW-Li cells may also have undergone somatic cell fusion in vivo with host (T?) cells, resulting in the acquisition of metastatic properties. The pattern of cell-cell interactions (adhesion, infiltration) with liver cell monolayers of BW-Li cells and of DCH10-Li (T-cell lymphomas) was identical, and differed from cells of liver metastases of the myeloma-B cell hybridomas which might be based on responses to liver growth signals.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Adhesion of tumor cells to hepatocytes: different mechanisms for mammary carcinoma compared with lymphosarcoma cells.

Mechanisms of adhesion between tumor cells and hepatocytes, which are likely to play a role in liver metastasis formation, were studied in vitro. TA3 mammary carcinoma and MB6A lymphosarcoma cells were added to rat hepatocytes that had been cultured for 24 hours. Adhesion was quantified by counting adherent cells seen in sections of pelleted, Epon-embedded culture fragments. Adhesion of TA3, but not of MB6A cells, was inhibited by antibodies prepared from an antiserum raised against sinusoidal face-enriched liver plasma membranes. Detergent-solubilized liver components, affinity purified on immobilized inhibitory antibodies, neutralized inhibition, whereas a subfraction separated from this material with the use of immobilized noninhibitory antiliver antibodies had no neutralizing activity. Adhesion of MB6A but not of TA3 cells was inhibited by the calcium ionophore A23187 and the local anesthetic procaine. The calmodulin inhibitor trifluoperazine inhibited adhesion of MB6A cells more strongly than that of TA3 cells. Finally, adhesion of TA3 cells was dependent on external calcium, whereas in the case of MB6A cells calcium could be replaced by magnesium. These observations suggested that adhesion of the two tumor cell types to hepatocytes involved distinct hepatocyte surface molecules and required distinct biochemical machinery.

Animals↗