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Biomedical subjects

A Raz

Publications and source records attributed to A Raz.

At least 163 records · Page 9Linked to original sources
PubMed1987

Endogenous galactoside-binding lectins: a new class of functional tumor cell surface molecules related to metastasis.

The formation of secondary tumors by circulating cancer cells (blood-borne metastasis) correlates with an increased tendency of the cells to form emboli by aggregation with other tumor cells or with host cells. Although it is evident that cell-cell recognition and adhesion are mediated by cell surface components, the identity of these molecules is only now being unraveled. Over the last decade an increasing number of studies have demonstrated the presence of endogenous carbohydrate-binding proteins on the surface of various normal cells, and it has been proposed that such lectin-like molecules might be involved in intercellular adhesion. We have shown that various tumor cell lines contain endogenous galactose-specific lectins. Lectin activity was detected at the cell surface by the binding of asialofetuin. This glycoprotein also enhanced the aggregation of the tumor cells. After purification by affinity chromatography on immobilized asialofetuin the lectin activity was associated with two proteins of Mr 14,500 and 34,000. By using polyclonal and monoclonal antilectin antibodies in conjunction with various immunologic techniques we have demonstrated that the endogenous lectins are present on the surface of different tumor cells. Quantitation of cell surface lectins by flow cytometric analyses of antilectin antibody binding revealed that among related tumor cells those exhibiting a higher metastatic potential expressed more lectin on their surface. The binding of monoclonal antilectin antibodies to metastatic cells decreased asialofetuin-induced homotypic aggregation in vitro and suppressed the ability of the cells to form lung metastases after intravenous injection in the tail vein of syngeneic mice. These results strongly implicate the tumor cell surface lectins in cell adhesion and metastasis. We propose that such lectins can increase the ability of tumor cells that enter the blood stream to form aggregates with other tumor cells, or to adhere to host cells or the extracellular matrix and thereby increase their metastatic potential. Other contributing components to tumor cell-host cell interactions are cell surface carbohydrate-binding proteins that have been detected on lymphocytes, platelets, macrophages, hepatocytes, and endothelial cells. These lectin-like molecules might recognize and bind carbohydrates expressed on the surface of tumor cells and enhance emboli formation and organ colonization.

Animals↗
PubMed1987

Cloning and expression of cDNA for two endogenous UV-2237 fibrosarcoma lectin genes.

cDNA libraries from the murine UV-2237-IP3 fibrosarcoma cell line were prepared in the expression vector lambda gt11. Using specific antibodies, cDNA clones coding for the 14.5-kDa and the 34.0-kDa endogenous galactoside-specific lectins were isolated. In vitro translation and immunoprecipitation of mRNAs hybrid-selected by the cloned sequences from whole cell RNA provided confirmation for the clones. RNA and DNA blot analyses revealed that the two lectin proteins represent products of two different genes. We found differential levels of the specific mRNAs when low- and high-metastatic counterparts of the UV-2237 tumor system were compared, and these genes were not expressed in detectable amounts in normal mouse liver.

Animals↗
PubMed1986

Cell configuration and adhesive properties of metastasizing and non-metastasizing BSp73 rat adenocarcinoma cells.

The pattern of cell substrate interaction, the cell surface composition and the organization of cytoskeletal elements was studied in tumour cell variants of the BSp73 rat adenocarcinoma displaying different metastatic capabilities and cell configuration. The non-metastasizing AS variant cells adhered to the substrate and spread via vinculin-containing focal contacts. These cells also synthesized, secreted and assembled fibronectin at the pericellular area. The metastasizing ASML variant cells adhered to the substrate at a slower rate via thick cytoplasmic protrusions, but were removed from the substrate by trypsin-EDTA slower than the non-metastasizing AS variant cells. The ASML cells also synthesized very low levels of both vinculin and fibronectin, displayed a diffuse pattern of actin and tubulin organization, and were unable to spread on the substrate. Spreading could not be induced in the ASML cells by seeding the cells on an extracellular matrix derived from bovine corneal endothelial cells or on concanavalin A (conA)-coated substrates, or by the addition of db-cAMP to the medium. The metastasizing cells expressed a unique and abundant cell surface glycoprotein of Mr 170 000 which was also shed into the growth medium. The relationships among the adhesive properties, the organization of cell surface components and of the cytoskeleton in the tumour cell variants, and the expression of their metastatic phenotype is discussed.

Actins↗
PubMed1986

Implications of endogenous tumor cell surface lectins as mediators of cellular interactions and lung colonization.

A monoclonal antibody (mAb) designated 5D7 that is directed against endogenous, galactoside-specific lectin and binds to the surface of various tumor cells was used to examine the involvement of cell surface lectin molecules in cellular interactions in vitro and in vivo. The mAb 5D7 was found to inhibit asialofetuin-induced homotypic aggregation of B16 melanoma and UV-2237 fibrosarcoma cell variants by up to 80%. The rate at which these cells, as well as the virally transformed fibroblasts (SVPy-3T3), adhere to tissue culture dishes was reduced in the presence of mAb 5D7 to less than 50% of the control. The anti-lectin mAb had no effect on the adhesion rate of untransformed 3T3 fibroblasts. Treatment of B16 and UV-2237 cells with mAb 5D7 in vitro before their injection into the tail vein of syngeneic mice resulted in a decrease of up to 90% in the appearance of tumor lung colonies. These findings imply that tumor cell surface lectins might play a role in mediation of cell-to-cell and cell-to-substratum adhesion in vitro as well as in similar interactions in vivo that are relevant for metastasis.

Animals↗
PubMed1986

Differential expression of endogenous lectins on the surface of nontumorigenic, tumorigenic, and metastatic cells.

A monoclonal antibody that was found to recognize endogenous galactoside-specific lectins of various tumor cells by immunoblot analysis was used for quantitative analyses of cell surface lectin on nontumorigenic, tumorigenic, and metastatic cells of diverse histological types and origin. Indirect immunofluorescent staining of viable cells followed by analysis with a fluorescence-activated cell sorter revealed marked differences in the amount of surface lectins between untransformed and malignant cells. While lectin was either absent or present in a very low density on the surface of normal cells, neoplastic cells were invariably stained by the antilectin antibodies. Furthermore, among related tumor cell variants of the K-1735 melanoma and UV-2237 fibrosarcoma tumor systems, cells exhibiting a higher lung-colonizing potential also expressed higher levels of cell surface lectin. These results suggest that the presence of a lectin on the cell surface may be related to neoplastic transformation and progression toward metastasis.

Animals↗
PubMed1986

Differential expression of intermediate filament proteins in metastatic and nonmetastatic variants of the BSp73 tumor.

The pattern of intermediate filament protein expression was studied in tumor cell variants of the BSp73 spontaneous rat adenocarcinoma of the pancreas exhibiting distinct morphology and metastatic phenotype. The non-metastasizing AS cells which adhere and spread on a solid substrate express only the vimentin type mesenchymal intermediate filament protein. The ASML metastatic cell variant which adheres but does not spread on the substrate expresses a complex pattern of cytokeratins characteristic of the adenocarcinoma of the pancreas and a low level of vimentin. The differences in the expression of the intermediate filament proteins between the variants were also reflected at the level of the corresponding mRNAs as revealed by RNA blot analysis with complementary DNA clones specific to vimentin and the acidic as well as the basic cytokeratin subfamily. When the two cell variants were cultured for 72 h in suspension culture on nonadhesive substrata the AS cells responded with a marked reduction in their vimentin synthesis. The ASML variant cells which are characterized by a round configuration in both monolayer and suspension culture continue to synthesize the same intermediate filament proteins under both culture conditions. The relationships among environmental conditions that affect cell shape and contacts, the shifts in the expression of intermediate filaments, and the metastatic property of tumor cells are discussed.

Adenocarcinoma↗
PubMed1985

The establishment and characterization of a new BALB/c angiosarcoma tumor system.

A BALB-3T3/A31 untransformed cloned cell line and 3 selected variants derived from this parental cell line, expressing 3 increasingly malignant phenotypes, have been established and characterized in vivo and in culture. This new tumor series, identified as angiosarcoma, consists of an anchorage-independent non-tumorigenic cell clone and 2 sublines exhibiting tumorigenic and metastatic properties. Morphological examination revealed that the 3 transformed cell variants differed from the normal parental cells and were not contact-inhibited. Karyotype and rate of cell proliferation in culture were similar for all the cell variants. Cytoskeletal visualization by immunofluorescence staining revealed that the tumorigenic and metastatic cell lines expressed an altered organization of actin cables and a smaller number of vinculin-containing focal contacts. Lactoperoxidase iodination of cell surface proteins showed the appearance of an Mr 86,000 protein in the tumorigenic and metastatic cell variants. Analysis of cell-surface glycoproteins demonstrated an increased sialylation of Mr 66,000 and Mr 62,000 glycoproteins in the transformed, tumorigenic and metastatic cell lines. This angiosarcoma tumor model system allows investigation of cellular characteristics which might be relevant to specific stages in tumor progression.

Actins↗
PubMed1985

Expression of ki-ras oncogene in tumor cell variants exhibiting different metastatic capabilities.

The expression of oncogenes in well-characterized B16 melanoma and UV-2237 fibrosarcoma cell variants that exhibit distinct metastatic properties was explored. The search for the expression of 11 different oncogenes revealed that the major oncogene in those two tumor systems is the Kirsten-ras (ki-ras). The results indicate that the amounts of specific ki-ras mRNA and the p21 protein are similar in both low- and high-metastatic counterparts. These results suggest that in these systems there is no apparent direct correlation between the amount and expression of the major cellular oncogene so far identified and the metastatic potential of these tumor cells.

Animals↗
PubMed1985

Inhibition of tumor cell colony formation in culture by a monoclonal antibody to endogenous lectins.

The presence of endogenous, galactoside-specific lectin molecules on the surface of various neoplastic cells has been demonstrated recently using monoclonal antibody (mAb) 5D7 [Raz et al., EMBO (Eur. Mol. Biol. Organ.) J., 3: 2979, 1984]. The effect of this mAb on the growth of several transformed and tumor cell lines of murine and human origin was investigated using in vitro techniques. A dose-dependent reduction (30 to 100%) in colony formation on a solid substrate or in a semisolid medium was observed when the cells were cultured in the presence of 15 to 100 micrograms of mAb 5D7 per ml of medium. Inhibition of anchorage-independent growth was more pronounced (2- to 3-fold) than inhibition of anchorage-dependent growth for most of the cells. The growth-inhibitory effects of mAb 5D7 were not the result of a cytolytic activity, for neither DNA nor protein synthesis was suppressed in semiconfluent cell cultures after 3 days of exposure to the antibody. Other mAbs that recognize cell surface components, such as chondroitin sulfate or fibronectin, failed to inhibit colony formation. These results suggest that endogenous tumor cell-surface lectin molecules may be involved in intercellular interactions or interactions between the cells and exogenous ligands; these interactions are important for growth regulation.

Animals↗
PubMed1985

Relationship between the organization and synthesis of vimentin and the metastatic capability of B16 melanoma cells.

The organization and synthesis of the vimentin-containing cytoskeletal network as well as the metastatic capability of B16-F1 melanoma cells were investigated in cells treated with cycloheximide (CH). The addition of CH to cells for 4-8 h resulted in a marked reversible alteration in the organization of the vimentin-containing network in B16-F1 melanoma cells as well as in a variety of epithelial and fibroblast cell lines. Treatment of cells with CH led to a reduction in the synthesis of vimentin, tubulin, and actin followed by a decrease in the concentrations of mRNAs coding for these proteins. However, out of these three cytoskeletal elements, only the organization of the intermediate filaments was disrupted by CH. Cells treated previously with CH and injected i.v. into syngeneic mice had diminished capacity to form lung metastases as compared to control untreated cells. This effect was reversible, and the metastatic capability recovered to the control level after the drug was removed from the growth medium for 16 h. The possibility that the organization and the synthesis of the cytoskeletal components are related and that the metastatic capability of B16 melanoma is influenced by the organization of the cytoskeletal networks are discussed.

Animals↗
PubMed1984

Monoclonal antibodies to endogenous galactose-specific tumor cell lectins.

A monoclonal antibody, 5D7, was obtained after immunization of syngeneic mice with B16 melanoma cell extracts enriched for endogenous lectin activity and screening for inhibition of lectin-mediated hemagglutination. Binding of this antibody to affinity-purified B16 melanoma galactoside-specific lectin was revealed by solid-phase radioimmunoassay and binding to the surface of viable B16 cells was demonstrated by indirect immunofluorescence. Inhibition of lectin activity and cell surface labeling by 5D7 antibody were also found with several types of cultured human and murine cells including melanoma, sarcoma and carcinoma. This monoclonal antibody should be useful for evaluating the role of tumor cell surface lectins in intercellular interactions and metastasis.

Animals↗
PubMed1984

Prostaglandin biosynthesis in rabbit kidney: mepacrine inhibits renomedullary cyclooxygenase.

Mepacrine was found to exert a dose-dependent inhibition of prostaglandin E2 synthesis in rabbit kidney medulla slices and in medullary microsomes. Mepacrine at 0.5 mM produced 90% inhibition of microsomal prostaglandin E2 biosynthesis from added arachidonic acid. This effect results from inhibition of medullary cyclooxygenase; the activities of the prostaglandin G2 hydroperoxidase and the prostaglandin H2 isomerases are unaffected. In experiments with medulla slices prelabelled with [14C]arachidonate, the effect of mepacrine on the inhibition of [14C]prostaglandin generation was significantly higher (2.5 to 3.5-fold) than its inhibition of [14C]arachidonate release. Hence, although mepacrine reduces prostaglandin production by decreasing the lipolytic release of arachidonate from medullary lipids, its inhibitory effect on prostaglandin cyclooxygenase activity is substantial and appears to contribute significantly to its overall inhibition of prostaglandin generation in kidney medulla. Mepacrine is thus not only a non-selective antilipolytic agent but also a potent cyclooxygenase inhibitor.

Animals↗
PubMed1984

Cell-substrate interaction. A method for evaluating the possible correlation between metastatic phenotype and cell surface energy.

The interfacial energy of the non-attached to substrate cell surface was analysed in tumor cell variants of the K-1735 melanoma and UV-2237 fibrosarcoma series, which exhibit distinct metastatic phenotypes. The highly metastatic cell variants exhibited a two-fold increase in the ability to form rapid cell substrate interactions, as compared with their low-metastatic counterparts. These results further highlight the possible role of cell adhesiveness in the process of metastasis.

Animals↗
PubMed1984

Motility and adhesive properties of high- and low-metastatic murine neoplastic cells.

Randomly chosen clones of the murine K-1735 melanoma tumor were used by Raz and Geiger to address the question of whether variations in actin organization in these cells may be related to their lung colonization capability in syngeneic hosts (Cancer Res., 42: 5183-5190, 1982). In 14 of 15 clones tested, we found that the degree of actin organization was inversely correlated to their metastatic capability. We have further shown that remarkable variations exist in the adhesive properties and locomotor activity of four K-1735 melanoma cell variants that exhibit distinct metastatic properties. The low-metastatic cell variants displayed large focal adhesion plaques, tightly packed actin bundles, elaborate extracellular networks of fibronectin, and restricted motility. In contrast, the high-metastatic variants were poorly attached with only few distinct actin bundles, were unable to reorganize extracellular fibronectin into cables, and exhibited high motile activity. Electron microscopic examination of local s.c. tumors of the high- and low-metastatic lines indicated that the former formed loose tumor masses with very few intercellular connections, while the low-metastatic line developed into a considerably more compact tumor with numerous intercellular contacts, in line with the in vitro findings. It is proposed that the differences in cellular properties manifested by these cell lines may be related to their metastatic properties. Specifically, the highly metastatic cells of this tumor system may easily detach from the primary tumor mass, form weak and transient connections with surrounding connective tissue, and actively migrate through it. Furthermore, these results point to the close interrelationships between different mechanochemical features in cells, including specific cell adhesiveness, cytoskeletal organization, locomotion, and rearrangement of extracellular fibronectin. The possible nature of these interrelationships is discussed.

Actins↗
PubMed1983

Mepacrine blockade of arachidonate-induced washed platelet aggregation: relationship to mepacrine inhibition of platelet cyclooxygenase.

Mepacrine, in addition to its established antilipolytic activity, was also found to inhibit the conversion of 14C-arachidonic acid to 14C-thromboxane B2 in human washed platelets. In the concentration range of 3.33-33 microM, meparcrine exerted a dose dependent inhibition of arachidonate conversion to thromboxane B2 in parallel to inhibition of arachidonate-induced platelet aggregation. Mepacrine inhibition of thromboxane formation was not accompanied by a concomitant increase in other cyclooxygenase products. Furthermore, mepacrine did not affect platelet transformation of added prostaglandin H2 to thromboxane A2 and other products. These results indicate that mepacrine inhibits the cyclooxygenase enzyme and not thromboxane synthase. In washed platelets, mepacrine inhibition of arachidonic acid conversion to thromboxane A2 appears to be a major factor in the overall inhibitory effect of the compound on the combined process of arachidonate release from cellular phospholipids and its conversion to proaggregatory products.

Arachidonic Acid↗
PubMed1983

Bradykinin-stimulated differential incorporation of arachidonic acid into lipids of kidney cortex and medulla.

We investigated bradykinin-induced changes in the turnover of arachidonate in renal lipids of the perfused rabbit kidney. Upon hormone stimulation, this cellular system undergoes only transient dynamic changes in arachidonic acid metabolism; no loss of bradykinin effect on arachidonate release and prostaglandin generation is shown upon repeated hormone administrations during 8-9 hr of perfusion. Ureter-obstructed rabbit kidneys were perfused for 5-6 hr and then saline or bradykinin in saline was administered, followed after 10 sec by pulse labelling with [14C]arachidonate. The pattern of distribution of [14C]arachidonate in lipid fractions of the cortex showed that bradykinin caused a 2 to 2.5-fold increase in the relative incorporation of arachidonic acid into phosphatidylinositol (PI), phosphatidic acid (PA), diglyceride (DG) and triglyceride (TG) fractions and a concomitant decrease in its incorporation into phosphatidylcholine (PC) and phosphatidylethanolamine (PE). In contrast, in the medulla hormone administration caused a marked increase of arachidonate incorporation into PI and PC, and a decrease in incorporation into PE, PA, DG and TG. This differential arachidonate labelling of cortical vs medullary lipids following bradykinin stimulation suggests that the hormone activates different lipolytic processes in cortex and medulla, and promotes hydrolysis of arachidonic acid from different phospholipid pools.

Animals↗