A monoclonal antibody specific for non-reducing terminal Gal?1-4Gal residues

Characterization of galactosyl glycerolipids in the HT29 human colon carcinoma cell line

Glycoglycerolipids constitute a family of glycolipids with apparently very restricted expression in human tissues. They have previously been detected only in the testis and the nervous system. In the present study, two glycoglycerolipids were isolated from the HT29 human colon carcinoma cell line. The glycoglycerolipids were structurally characterized as a monogalactosylglycerolipid (1-O-alkyl-2-O-acyl-3-O-(beta-galactosyl)-sn-glycerol) and a digalactosylglycerolipid (1-O-alkyl-2-O-acyl-3-O-(beta-galactosyl(1-4)alpha-galactosyl)-sn-glycerol) using NMR and mass spectrometry. This digalactosylglycerolipid has not previously been structurally characterized. When HT29 cells were allowed to differentiate into more enterocyte-like cells by culture in glucose-free medium, expression of both of these glycoglycerolipids was greatly diminished. The presence of glycoglycerolipids in a human colon carcinoma cell line indicates that expression of this family of glycolipids may not be as restricted as previously thought. Instead this class of glycolipids may serve as differentiation antigens in various normal tissues and in tumor development. The Galalpha1-4Gal epitope was previously identified as a receptor for bacterial adhesins and toxins. The finding that this epitope is also linked to a glycerolipid moiety opens up new possible roles for this carbohydrate receptor in intracellular signaling.

Glycosphingolipid-enriched signaling domain in mouse neuroblastoma Neuro2a cells. Mechanism of ganglioside-dependent neuritogenesis

Differentiation and neuritogenesis of mouse neuroblastoma Neuro2a cells are induced by exogenous ganglioside but are not induced by nerve growth factor because its receptor is absent in these cells. In view of the emerging concept of the "glycosphingolipid-enriched domain" (GEM), we studied the mechanism of the ganglioside effect, focusing on the structure and function of such a domain. GEM in Neuro2a cells, separated as a low density membrane fraction, contains essentially all glycosphingolipids and sphingomyelin, together with five signal transducer molecules (c-Src, Lyn, Csk, Rho A, Ha-Ras). (3)H-Labeled Il(3)NeuAc-LacCer (GM3), Gb4Cer (globoside), and Il(3)NeuAc-Gg4Cer (GM1) added exogenously to cells were incorporated and concentrated in the low density GEM fraction. In contrast, more than 50% of glycerophospholipids and 30% of cholesterol were found in the high density fraction. (3)H-Labeled phosphatidylcholine added exogenously to cells was incorporated exclusively in the high density fraction. c-Src, the predominant signal transducer in the microdomain, was coimmunoprecipitated with anti-GM3 antibody DH2 or with anti-Csk; reciprocally, Csk was coimmunoprecipitated with anti-c-Src, indicating a close association of GM3, c-Src, and Csk. Brief stimulation of an isolated GEM fraction by the exogenous addition of GM3, but not lactosylceramide, caused enhanced c-Src phosphorylation with a concomitant decrease of Csk level in GEM. A decreased Csk/c-Src ratio in GEM may cause activation of c-Src because Csk is a negative regulator of c-Src. The effect of exogenous GM3 on c-Src activity was also observed in intact Neuro2a cells. Activation of c-Src was followed by rapid and prolonged (60 min) enhancement of mitogen-activated protein kinase activity leading to neuritogenesis. Thus, the ganglioside induction of neuritogenesis in Neuro2a cells is mediated by GEM structure and function.

Signal transduction through glyco(sphingo)lipids. Introduction and recent studies on glyco(sphingo)lipid-enriched microdomains

The presence of microdomains enriched in clustered glycosphingolipids (GSLs) at the surface of plasma membranes and liposome membranes, and their functional role in signal transduction, have been suggested by a series of observations, as follows: (1) GSL clusters (patches) are observed by electron microscopy; (2) microvesicles enriched in GSLs and other sphingolipids can be isolated as detergent-insoluble particles by sucrose density gradient ultracentrifugation: (3) such vesicles isolated from B16 melanoma cells contain > 90% of cellular GM3, > 90% of c-Src and Ras, approximately 50% of Rho, and approximately 20 percent of Fak, despite the fact that this vesicle fraction contains only 0.5% of total cellular protein (this fraction is termed "detergent-insoluble GSL-enriched microdomain" (DIGEM)); (4) GM3 in DIGEM can be coimmunoprecipitated with c-Src and Rho, indicating a close association of GM3 with these transducer molecules; (5) stimulation of GM3 in B16 melanoma cells by anti-GM3 antibody or by Gg3 results in change of signal transduction. Thus, GSLs, together with various transducer molecules present at DIGEM, may directly induce signal transduction rather than modulate or modify signal transduction created through receptors of growth factors or hormones as previously observed.

GM3-enriched microdomain involved in cell adhesion and signal transduction through carbohydrate-carbohydrate interaction in mouse melanoma B16 cells

Mouse melanoma B16 cells are characterized by the predominant presence of ganglioside GM3 and adhere to lactosylceramide- or Gg3-coated plates through interaction of GM3 with lactosylceramide or Gg3, whereby not only adhesion but also spreading and enhancement of cell motility occur (Kojima, N., Hakomori, S. (1991) J. Biol. Chem. 266, 17552-17558). We now report that the adhesion process is based essentially on a glycosphingolipid-enriched microdomain (GEM) at the B16 cell surface, since >90% of GM3 present in the original cells is found in GEM, and GEM is also enriched in several signal transducer molecules, e.g. c-Src, Ras, Rho, and focal adhesion kinase (FAK). GEM was isolated as a low density membranous fraction by homogenization of B16 cells in lysis buffer under two different conditions (i.e. buffer containing 1% Triton X-100, or hypertonic sodium carbonate without detergent), followed by sucrose density gradient centrifugation. A close association of GM3 with c-Src, Rho, and FAK was indicated by co-immunoprecipitation of GM3 present in GEM by anti-GM3 monoclonal antibody DH2, followed by Western blotting with antibodies directed to these transducer molecules. The following data indicate that GEM is a structural and functional unit for initiation of GM3-dependent cell adhesion coupled with signal transduction. 1) Tyrosine phosphorylation in FAK was greatly enhanced in B16 cells adhered to Gg3-coated plates but was minimal in cells adhered to GM3-coated, GlcCer-coated, or noncoated plates. 2) GTP loading on Ras and Rho increased significantly when cells were adhered to Gg3-coated plates, compared with GM3-coated, GlcCer-coated, or noncoated plates. Since Ras and Rho are closely associated with GM3 in GEM, cell adhesion/stimulation through GM3 in GEM may induce activation of Ras and Rho through enhanced GTP binding.

A close association of GM3 with c-Src and Rho in GM3-enriched microdomains at the B16 melanoma cell surface membrane: a preliminary note

B16 melanoma is characterized by high content of GM3 ganglioside, which has been recognized as a melanoma-associated antigen defined by specific monoclonal antibodies. We report now that GM3 is present predominantly (>90%) in the 1% Triton X-100-insoluble, low-density microvesicular fraction ("detergent-insoluble glycosphingolipid-enriched microdomain"; DIGEM) separated on sucrose density-gradient centrifugation. Associated with DIGEM, many signal transducer molecules such as c-Src, FAK, and the low-molecular-weight G-proteins Rho A and H-Ras were also found. Rho A and FAK were found in part, and PLC-beta2 and G alphas were found exclusively, in the high-density fraction. Immunoprecipitation of GM3 present in DIGEM by anti-GM3 antibody DH2, followed by Western blotting, revealed co-precipitation of Rho A and c-Src with GM3. These findings suggest (i) a specific organization of GM3 in close association with Rho A and c-Src within DIGEM at the melanoma cell surface; and (ii) such organizational units may be directly involved in signal transduction, in which glycosphingolipids receive signals which are subsequently transduced by associated transducer molecules.

Monoclonal antibodies directed to the synthetic carbohydrate antigen Ley

Tetrasaccharide Fuc alpha 1-2Gal beta 1-4(Fuc alpha 1-3)GlcNAc is known as carbohydrate determinant of cancer- and AIDS-associated antigen Lewisy (Ley). Synthetic antigen to generate mouse monoclonal antibodies (MAbs) directed to Ley was prepared and constructed as a spacer-armed tetrasaccharide coupled with lipophilized polymer, Ley-PAA-PE, where PAA is a 30-kD polyacrylamide and PE is phosphatidylethanolamine. An efficient immune response was provided by using Ley-PAA-PE adsorbed on Salmonella minnesota. Positive hybridomas were screened by enzyme-linked immunosorbent assay (ELISA) using Ley-PAA as a coating agent. An inhibitory version of the same test system showed absolute specificity of two MAbs: only hapten Ley and Ley-PAA were strong inhibitors, in contrast to Leb, tri- and disaccharidic fragments of the mentioned tetrasaccharides, as well as their PAA-conjugates. MAbs obtained against synthetic antigen specifically stained the Ley (+) cell line A431.

Localization and identification of T-(Gal beta 1-3GalNAc alpha 1-O-R) and T-like antigens in experimental rat bladder cancer

A mouse monoclonal antibody and a rabbit polyclonal antibody against the T-antigen (Gal beta 1-3GalNAc alpha 1-O-R) were used to study the distribution of T-antigens in an experimental rat bladder cancer model. Neoplasia was induced in 28 rats by intravesical installation of N-nitroso-N-methylurea (NMU) dissolved in acetate buffer. Fifteen rats were installed with acetate buffer, and served as controls. Urothelial samples were taken from all animals, the atypia was graded and detailed data on the location of the antibody binding structures were obtained by immunohistochemical methods. In addition, Western Blots of glycoproteins and thin-layer-chromatography (TLC) immunostainings of glycolipids extracted from normal and malignant tissue were performed to characterize the molecules presenting T-antigens. Examination of the histologic distribution of T-antigens showed that both the monoclonal and the polyclonal reagents reacted with atypical cells in proportion to the grade of atypia, but showed no reaction in invasive cells. These results confirm previously obtained data on the T-antigen using peanut (arachis hypogaea) agglutinin (PNA), and support the structure identity as being the classical O-linked mucin type T-antigen. Western blots of tumor glycoproteins showed that the monoclonal and the polyclonal antibody reacted with epitopes different from that of PNA, but all the probes correlated with atypia. In addition PNA, as the only anti-T reagent, bound to glycolipid. By using well characterized and highly specific immunological reagents the present study shows that the T-antigen is a highly selective marker of urothelial atypia.

Lewis antigen expression in benign and malignant tissues from RBC Le(a-b-) cancer patients

Eight red blood cell (RBC) Le(a-b-) individuals were selected from a series of patients with bladder or colon cancer. Defined by the presence or absence of alpha 1-4-L-fucosyltransferase activity in saliva, four of these patients were characterized as non-genuine Lewis negative [RBC Le(a-b-) with alpha 1-4-L-fucosyltransferase activity in saliva], and four as genuine Lewis negative [RBC Le(a-b-) with no alpha 1-4-L-fucosyltransferase activity in saliva]. Stainings of paraffin embedded formalin fixed tissue sections for Lea and Leb antigens were performed by means of an indirect immunohistochemical method on all malignant and benign tissue previously removed from these eight patients. Leb antigens were always expressed independently of both the Lewis and the secretor status of the individual. Lea antigens, on the other hand, showed a different staining pattern. Although primarily expressed in non-genuine Le(a-b-) individuals, Lea antigens were expressed in genuine Le(a-b-) individuals as well--to a limited extent, but still detectable. Thus, these findings seem to show that the Lewis antigen expression is tissue dependent, and it is not possible to predict tissue Lewis antigen expression by merely examining erythrocytes or saliva.

Glycosphingolipids of human urothelial cell lines with different grades of transformation

Neutral glycolipids and gangliosides from seven human urothelial cell lines, differing in grades of transformation (TGr), were characterized by fast atom bombardment mass spectrometry, exoglycosidase treatment and an immunostaining procedure. The major neutral glycolipids identified in all cell lines studied included CMH, CDH, CTH, globoside and paragloboside, the gangliosides were GM3, GM2, sialosylparagloboside and GD1a. The following observations were made: 1. GM2 was the major ganglioside in the TGrII cell lines (non-tumorigenic, non-invasive), but a minor component in the TGrIII cell lines (tumorigenic, invasive). 2. All components showed C16:0 and C24:0 as major fatty acids, but in the TGrIII cell lines the fatty acid composition of CMH and some of the gangliosides were more complex showing unsaturated and hydroxy-fatty acids as well.

Monoclonal antibodies produced by immunization with neoglycoproteins containing Gal alpha 1-4Gal beta 1-4Glc beta-O and Gal alpha 1-4Gal beta 1-4GlcNAc beta-O residues: useful immunochemical and cytochemical reagents for blood group P antigens and a differentiation marker in Burkitt lymphoma and other B-cell malignancies

Several monoclonal antibodies (MAbs) directed to blood group P1 (Gal alpha 1-4Gal beta 1-4GlcNAc beta-O) and Pk (Gal alpha 1-4Gal beta 1-4Glc beta-O) determinants were produced with high efficiency by using synthetic neoglycoproteins as immunogens. The specificity of IgM and IgG1 MAbs was characterized by binding to defined oligosaccharides and glycoconjugates. Antibodies that bound equally well to P1 and Pk determinants and to Gal alpha 1-4Gal beta 1-O-derivatives were obtained, together with others that showed selective recognition of the entire trisaccharide chain. Selected antibodies were shown to be useful as reagents for detection of the blood group P antigens in glycolipid extracts of erythrocytes and on the surface of erythrocytes of different P phenotypes, demonstrated both by radioimmune assays and hemagglutination. Six IgM MAbs directed to the Pk determinant bound selectively to Burkitt lymphoma cells and 2 of these antibodies (424/3D9 and 424/6A2) could be used as auxiliary reagents in immunofluorescence for diagnosis and classification of B-cell lymphomas and leukemias using flow cytometric analysis. Eight normal individuals and 37 patients with lymphoma or leukemia were studied. Tumor cells of 2/2 patients with "Burkitt-like" lymphoma, 1 patient with centroblastic lymphoma and 2 patients with acute leukemia were strongly stained for the Pk antigen. The staining patterns for differentiation markers classified the tumor cells to a developmental stage closely related to the Burkitt cell type.

Intestinal-type glycosphingolipids in urine from patients with enterocutaneous urinary diversions

Ureteroenterocutaneous stoma is a surgical procedure for urinary diversion by which an intestinal segment is used as a conduit or reservoir for the urine. The intestinal mucosa continues to produce a mucous gel containing desquamated epithelial cells. This mucous gel is easily obtainable from the urine. Glycosphingolipids were isolated from such gels and analyzed with immunological methods using a thin-layer chromatography overlay assay and mass spectrometry. The glycosphingolipids obtained mainly belong to the lacto-type I series comprising ABH, Lea, and Leb determinants. These observations support the intestinal origin of the glycosphingolipids. A regional distribution of the ABH and Lewis antigens, which is in accordance with previous immunohistochemical findings, was observed.

High-performance liquid affinity chromatographic separation of mouse monoclonal antibodies with protein A silica

Protein A, a bacterial cell wall protein found in Staphylococcus aureus, has been widely used for the analysis of immunoglobulins. By attaching protein A to a microparticulate silica support, a rapid and efficient chromatographic sorbent has been created for the separation of monoclonal antibodies. Examples are given of rapid separations (within 10 min) of murine monoclonal antibodies, belonging to various IgG subclasses and including IgG1. The monoclonal antibodies were isolated with a high purity and with 60-90% recovery of activity. The high-performance liquid affinity chromatography technique based on protein A provides a useful method for monitoring monoclonal antibodies in crude samples, such as ascites and cell culture supernatants.

Lewis blood group antigens in urine sediments from patients with urinary bladder carcinoma

Urine sediments from 20 patients with urinary bladder carcinoma, and from 11 healthy individuals were investigated for their content of Lea and Leb active glycolipids. The investigation was restricted to blood group phenotype Le (a-b+). All individuals exhibited both Lea- and Leb-active glycolipids. In healthy individuals the ratio Lea/Leb was less than 1 in 10 out of 11 cases, whereas in patients with bladder cancer the ratio Lea/Leb was greater than 1 in 11 out of 20 cases. No correlation between the Lea/Leb ratio on the one hand and tumour grade or stage on the other hand could be shown. The results indicate one possible explanation for the loss of ABH antigens in bladder cancer and also demonstrate the potential of detailed biochemical investigations on exfoliated material in urine.