GD3 expression by cultured human tumor cells of neuroectodermal origin

Mechanisms of action of therapeutic antibodies for cancer

The therapeutic utility of antibodies and their derivatives is achieved by various means. The FDA has approved several targeted antibodies that disrupt signaling of various growth factor receptors for the treatment of a number of cancers. Rituximab, and other anti-CD20 monoclonal antibodies are active in B cell malignancies. As more experience has been gained with anti-CD20 monoclonal antibodies, the multifactorial nature of their anti-tumor mechanisms has emerged. Other targeted antibodies function to dampen inhibitory checkpoints. These checkpoint inhibitors have recently achieved dramatic results in several cancers, including melanoma. These and related antibodies continue to be investigated in the clinical and pre-clinical settings. Novel antibody structures that target two or more antigens have also made their way into clinical use. Tumor targeted antibodies can also be conjugated to chemo- or radiotherapeutic agents, or catalytic toxins, as a means to deliver toxic payloads to cancer cells. Here we provide a review of these mechanisms and a discussion of their relevance to current and future clinical applications.

The immune response to disialoganglioside GD3 vaccination in normal dogs: a melanoma surface antigen vaccine

As a result of its metastatic potential, canine malignant melanoma like its human counterpart like its human counter part, has a poor response to conventional treatment protocols. This prompted us to investigate the possibility of enhancing the immune response against the melanoma cell surface antigen, disialoganglioside GD3. Initially a flow cytometric study was designed in which the incidence of GD3 on the cell surface, recognized by the monoclonal antibody Mel-1 (R24), was established in canine melanoma cell lines. Results from the flow cytometry found GD3 to be highly expressed (94.2%) in six out of seven canine melanoma cell lines. Since it was thus potentially a good target, a study in which normal dogs were vaccinated intradermally with a vaccine containing GD3 plus adjuvants was designed. The adjuvant included CpG oligodeoxynucleotide (CpG-ODN) sequences and RIBI-adjuvant, which are known to target toll-like receptors (TLR) of the innate immune system. From a cohort of 10 dogs, 4 were vaccinated 3 times, at 4 weekly intervals with GD3 plus adjuvant, and 4 received only RIBI-adjuvant, and 2 phosphate buffered saline. Caliper measurements were collected to assess skin reaction at the vaccination site and sera assayed for IgM and IgG antibodies against GD3 and cell-mediated cytotoxicity against a melanoma cell line. Results from the study found significant differences (P<0.05) in the vaccine site reactions, IgM/IgG levels and cell-mediated cytotoxicity in the vaccinated versus unvaccinated dogs. The addition of CpG-ODN sequences and increasing GD3 concentration in the vaccine increased the inflammation response at the injection site. GD3 IgG and IgM antibodies in vaccinated dogs showed increasing titers over time and achieved significance at weeks 9 and 12, respectively. Cell-mediated cytotoxicity was only detected in peripheral blood mononuclear cells from vaccinated dogs. In conclusion, by combining the tumor antigen GD3 (a known weak self-antigen) and an adjuvant, tolerance was overcome by an innate and adaptive immune response in this population of normal dogs.

Lipids and glycosphingolipids in caveolae and surrounding plasma membrane of primary rat adipocytes

We have made a comprehensive and quantitative analysis of the lipid composition of caveolae from primary rat fat cells and compared the composition of plasma membrane inside and outside caveolae. We isolated caveolae from purified plasma membranes using ultrasonication in carbonate buffer to disrupt the membrane, or extraction with nonionic detergent, followed by density gradient ultracentrifugation. The carbonate-isolated caveolae fraction was further immunopurified using caveolin antibodies. Carbonate-isolated caveolae were enriched in cholesterol and sphingomyelin, and the concentration was three- and twofold higher, respectively, in caveolae compared to the surrounding plasma membrane. The concentration of glycerophospholipids was similar suggesting that glycerophospholipids constitute a constant core throughout the plasma membrane. The composition of detergent-insoluble fractions of the plasma membrane was very variable between preparations, but strongly enriched in sphingomyelin and depleted of glycerophospholipids compared to carbonate-isolated caveolae; indicating that detergent extraction is not a suitable technique for caveolae preparation. An average adipocyte caveola contained about 22 x 10(3) molecules of cholesterol, 7.5 x 10(3) of sphingomyelin and 23 x 10(3) of glycerophospholipid. The glycosphingolipid GD3 was highly enriched in caveolae, whereas GM3, GM1 and GD1a were present inside as well as outside the caveolae membrane. GD1b, GT1b, GM2, GQ1b, sulfatide and lactosylceramide sulfate were not detected in caveolae.

The glial precursor proteoglycan, NG2, is expressed on tumour neovasculature by vascular pericytes in human malignant brain tumours

Glial precursor cells express NG2 and GD3 in the developing brain. These antigens are both over-expressed during neoplasia, which suggests they may have specific functions in the malignant progression of human brain tumours. This study describes the expression of NG2 and GD3 in 28 paediatric and adult brain tumours. Glioblastoma biopsy spheroids were also implanted into nude rats to assess the regional distribution of the molecules within the tumour. These xenografts showed extensive infiltration and growth that mimicked the growth patterns of human gliomas in situ. NG2 was identified in 20 out of 28 brain tumours, where the expression was confined to the main mass of the tumour, and was reduced towards the tumour periphery. NG2 was mainly associated with blood vessels on both the pericyte and basement membrane components of the tumour vasculature. Ki67 (MIB-1) labelling indicated that NG2 expression was associated with areas of high cellular proliferation. Conversely, all the tumours expressed GD3, which was present both in the tumour main mass and throughout the periphery. Thus, the expression of NG2 may be indicative of tumour progression and might be an amenable target for future therapeutic interventions.

The glioma-associated gangliosides 3'-isoLM1, GD3 and GM2 show selective area expression in human glioblastoma xenografts in nude rat brains

This work describes the in vivo expression and distribution of glioma-associated gangliosides (GD3, GM2, 3'-isoLM1) in a novel human brain tumour nude rat xenograft model. In this model, the tumours, which are established directly from human glioblastoma biopsies, show extensive infiltrative growth within the rat brain. This model therefore provides an opportunity to study ganglioside expression not only within the macroscopic tumour, but also in brain areas with tumour cell infiltration. The ganglioside expression was studied by confocal microscopy of immunostained brain sections using antiganglioside monoclonal antibodies. Xenografts from four human glioblastoma multiformes were established in rats and the brains removed after 3-4 months. Ganglioside GD3 was expressed in the tumour parenchyma while ganglioside 3'-isoLM1 was more abundantly expressed in the periphery of the tumour associated with areas of tumour cell invasion. GM2 expression was only seen in one tumour, where it was located within the main tumour mass. Double staining with a pan antihuman monoclonal antibody (3B4) and the antiganglioside monoclonal antibodies confirmed that the ganglioside expression was associated with tumour cells. This work supports the concept of different biological roles for individual gangliosides and indicates that antibodies or ligands directed against GD3 and 3'-isoLM1 might be complementary when applied in the treatment of human glioblastomas.

Monoclonal anti-GD3 antibodies selectively inhibit the proliferation of human malignant glioma cells in vitro

The frequently occurring alteration of ganglioside expression in tumor cells has been implicated to play a role in the uncontrolled growth of these cells; antibodies to such gangliosides might affect tumor cell growth. We have studied the effect of IgM monoclonal antibodies to two glioma-associated gangliosides, GD3 and GM2, on cell proliferation of four human glioma cell lines and one renal tumor cell line. Of the two anti-ganglioside antibodies tested, only the anti-GD3 antibody resulted in a significant (p<0.005) inhibition of cell proliferation as measured by thymidine incorporation and Brd-U labeling, after 24h incubation. The effect was not dependent on any serum factor and no increased cell death was observed. All cell lines contained higher or similar amounts of GM2 than GD3, and both antigens were shown to be expressed on the cell surface and accessible to antibodies. The selective effect of anti-GD3 antibodies as contrasted to the inactivity of anti-GM2 antibodies suggests a possible role for ganglioside GD3 in tumor cell proliferation.

Immunostaining of ganglioside GD1b, GD3 and GM1 in rat cerebellum: cellular layer and cell type specific associations

We have studied the cellular distribution of gangliosides GD1b, GD3 and GM1 in rat cerebellum by immunostaining, using monoclonal antibodies and confocal microscopy. Antibodies against astroglial, neuronal and synaptic vesicle associated molecules were used for colocalization analyses. In the gray matter, the anti-GD1b antibody stained thin strands in the molecular layer (ML), interpreted as Bergman glia fibers based on colocalized staining with anti-glial fibrillary acidic protein (GFAP). The neuropil in the granule (GL) and Purkinje (PL) cell layers was also anti-GD1b positive. The anti-GD3 antibody stained the ML, the neuropil in the GL and PL and also the granule and Purkinje cell bodies, appearing intracytoplasmically and vesicle associated. Anti-GD1b and anti-GD3 staining in the GL glomeruli were colocalized with anti-synaptophysin staining. The anti-GM1 antibody stained cell bodies in the ML but they could not be characterized in colocalization experiments. The GL and PL were not stained with the anti-GM1 antibody. In the white matter, different staining patterns were seen for the gangliosides, the anti-GM1 staining being the most intense. This study shows cellular layer and cell type specific associations of the investigated gangliosides and localization of GD1b and GD3 at synaptic sites, warranting further studies on their role in synaptic mechanisms.

Reactivity of monoclonal antibodies with ganglioside antigens in human small cell lung cancer tissues

Gangliosides on tumor cells have been suggested as potential target antigens for specific immunotherapy in various types of cancer including small cell lung cancer (SCLC). In this study we have compared the expression of three gangliosides that have been described as tumor-associated antigens, FucGM1, GM2 and GD3 in SCLC tissue specimens collected at autopsy, using a double-layer immunofluorescence staining method and specific monoclonal antibodies (Mabs) directed against these ganliosides. We found expression of FucGM1, GD3 and GM2 in (70% (n=20), 60% (n=15) and 40% (n75% of the tumor cells in all lesions from the same patient (five of eight cases). Our results indicate that FucGM1 is a relevant ganglioside antigen in SCLC, and suggest that specific immunotherapy involving more than one ganglioside antigen in SCLC should at least include FucGM1 and GD3.

A new procedure for determining ganglioside GD3 a potential glial cell activation marker in cerebrospinal fluid

Increased amounts of ganglioside GD3 [II3 (NeuAc)2-LacCer], associated with reactive gliosis, have been documented in a variety of neurodegenerative disorders. GD3 expression has also been reported in microglial cells, not only during development but also in reactive states, where the glial activation is considered to be part of the repair process. It is important to find markers in cerebrospinal fluid that will enable us to identify damage and register changes in pathological processes within the brain. A sensitive and practically applicable method for determination of GD3 ganglioside in cerebrospinal fluid has been developed. The procedure, which includes extraction, purification on silica gel and thin-layer enzyme-linked immunostaining, also allows determination of sulphatide, a marker of demyelinating processes, in the same portion of CSF. The method has been applied to CSF samples from 101 normal individuals aged 2-83 years. The GD3 concentration was found to be significantly correlated to age and reflecting the concentrations within the brain. GD3 ganglioside analysis by means of this method might be useful for studying glial changes during brain maturation as well as in brain disorders.

Characterization of human IgG1 monoclonal antibody against gangliosides expressed on tumor cells

A human IgG1.k monoclonal antibody (MAb) designated GMA1 was developed by fusing pooled lymph node lymphocytes from cancer patients with the human lymphoblastoid cell line, SHFP-1. The GMA1 MAb reacted with several melanoma and neuroblastoma cell lines. Normal tissue derived from human brain and tumor-cell lines derived from colon, ovary, and breast were not reactive. FACS analysis performed using live cells demonstrated that the antibody recognizes a cell-surface antigen. Enzyme immunoassay (EIA) and thin layer chromatography (TLC) immunostaining with purified gangliosides indicated that the antibody has specificity for the major tumor associated gangliosides GD3, GM3, and GD2. GMA1 heavy and light chain genes were isolated by RT-PCR and a recombinant derivative of this human antibody was expressed in Chinese hamster ovary (CHO) cells. High-level antibody synthesis and secretion was achieved using a vector designed to maximize expression. FACS analysis and TLC immunostaining indicated recombinant GMA1 reacted with human tumor cell lines and gangliosides GD3, GM3, GD2 in a manner similar to the antibody produced by the hybridoma cell line, demonstrating that the specificity of the antibody was not altered during molecular cloning.

Ganglioside expression in lung cancer cell lines

Gangliosides are complex glycolipid constituents of cell membranes. They are involved in many biological functions including cell-cell recognition, cell-matrix attachment, cell growth and cell differentiation. Analysis of tumor associated gangliosides may aid in the characterisation of tumour cells and their degree of malignant transformation. We have characterised a total of eight lung cancer cell lines (four small cell and four non-small cell lung cancer) with respect to ganglioside and alpha v integrin receptor expression. Ganglioside GD3 was detected using the monoclonal antibody R24. Ganglioside GM1 was detected using the beta-subunit of cholera toxin. Ganglioside 9-O-acetyl GD3 and the alpha v integrin receptor were measured using commercially available monoclonal antibodies. Our results indicate that small cell lung cancer cell lines express significant levels of GD3 and 9-O-acetyl GD3. Ganglioside GM1 and alpha v integrin receptor were not specific to any histological subtype. The expression of ganglioside GM1 and GD3 was independent of cell-cycle phase. We conclude that GD3 and 9-O-acetyl GD3 expression may be additional markers of the Small Cell Lung Cancer phenotype, but their significance is unknown. Therefore a characteristic ganglioside pattern cannot be defined according to histological subtype. alpha v integrin receptor expression is not unique to cells expressing GD3.

In vivo growth conditions suppress the expression of ganglioside GM2 and favour that of lacto series gangliosides in the human glioma D-54MG cell line

The human glioma D-54MG cell line grown in vitro primarily expresses ganglio series gangliosides, particularly GM2. Subcutaneous injection of these cells into nude mice produced xenografts with an increased content of the human glioma-associated lacto series gangliosides, primarily 3'-isoLM1, an alteration that was dose dependent, with the highest dose (1 x 10(8)) resulting in a phenotype that was most like that of the inoculum. After one passage in vivo, the lacto series dominated and reached a proportional level that was kept throughout the 10 passages. The mRNA levels of the GM2-synthase clearly coincided with GM2 expression and was 20 times higher in cells grown in vitro than in those grown in vivo. These results support the view that ganglioside expression in human gliomas is strongly influenced by environmental factors.

Expression and localization of Lewis(x) glycolipids and GD1a ganglioside in human glioma cells

We analysed the glycolipid composition of glioma cells (N-370 FG cells), which are derived from a culture of transformed human fetal glial cells. The neutral and acidic glycolipid fractions were isolated by column chromatography on DEAE-Sephadex and analysed by high-performance thin-layer chromatography (HPTLC). The neutral glycolipid fraction contained 1.6 micrograms of lipid-bound glucose/galactose per mg protein and consisted of GlcCer (11.4% of total neutral glycolipids), GalCer (21.5%), LacCer (21.4%), Gb4 (21.1%), and three unknown neutral glycolipids (23%). These unknown glycolipids were characterized as Lewis(x) (fucosylneolactonorpentaosyl ceramide; Le(x)), difucosylneolactonorhexaosyl ceramide (dimeric Le(x)), and neolactonorhexaosyl ceramide (nLc6) by an HPTLC-overlay method for glycolipids using specific mouse anti-glycolipid antibodies against glycolipid and/or liquid-secondary ion (LSI) mass spectrometry. The ganglioside fraction contained 0.6 micrograms of lipid-bound sialic acid per mg protein with GD1a as the predominant ganglioside species (83% of the total gangliosides) and GM3, GM2, and GM1 as minor components. Trace amounts of sialyl-Le(x) and the complex type of sialyl-Le(x) derivatives were also present. Immunocytochemical studies revealed that GD1a and GalCer were primarily localized on the surface of cell bodies. Interestingly, Le(x) glycolipids and sialyl-Le(x) were localized not only on the cell bodies but also on short cell processes. Especially, sialyl-Le(x) glycolipid was located on the tip of fine cellular processes. The unique localization of the Le(x) glycolipids suggests that they may be involved in cellular differentiation and initiation of cellular growth in this cell line.

Altered expression of ganglioside phenotypes of human gliomas in vivo and in vitro

A library of epitope-defined antiganglioside monoclonal antibodies has been used to analyze the ganglioside phenotype of human glioma cell lines, rodent xenografts derived from them, and a separate panel of human glioma biopsies by multiple quantitative and qualitative assays. We have shown that the ganglioside phenotypes of cultured cell lines differ from the ganglioside phenotypes in the xenografts grown from the parent lines. The lacto series gangliosides 3'-isoLM1 and 3',6'-isoLD1 are expressed in the majority of primary human central nervous system neoplasms and xenografts derived from glioma cell lines, whereas glioma cell lines themselves express 3'-isoLM1 and 3',6'-isoLD1 in only 2/15 and 0/15 cases, respectively. Examination of the ganglioside profiles of serially passaged xenografts established from the glioma cell line D-54 MG, which does not express the lacto series, revealed the appearance of these gangliosides within one to two passages in vivo. The presence of these defined gangliosides in the majority of human gliomas and their absence in normal brain supports their application in compartmental therapy of primary central nervous system tumors.

Detection of glioma-associated gangliosides GM2, GD2, GD3, 3'-isoLM1 3',6'-isoLD1 in central nervous system tumors in vitro and in vivo using epitope-defined monoclonal antibodies

In this study, MAbs to the 'conventional' gangliosides expressed by human gliomas were generated and used to detect ganglioside species previously unisolated or defined in normal adult CNS tissue. Despite the marked phenotypic and genotypic heterogeneity shown by glioma cell lines (Bigner et al., 1981), the ganglioside phenotype of these cell lines is remarkably consistent qualitatively, if not quantitatively, in the ganglioside species expressed (Table V). The majority of cell lines and tumor samples express GM2, GD2 and GD3; this does not provide a diagnostic advantage (Vick et al., 1992). Nevertheless, as the relative amounts of these gangliosides in tumor as compared with normal adult CNS tissue is considerable, such reagents might be considered in compartmental immunotherapeutic approaches. Since GD2 and GD3 have been determined to mediate tumoricidal activity with human effector cells via specific antiganglioside epitope MAbs (Thurin et al., 1987; Kushner and Cheung, 1991; Barker et al., 1991; Reisfeld, 1993), cell-mediated approaches, as well as targeted immunoglobulin therapies, are also possible. The prospect of a more targeted approach with little or no effect on normal CNS tissue is now possible via the 'oncofetal' epitopes characteristic of 3'-isoLM1 and 3',6'-isoLD1. Several factors recommend the use of these moieties for compartmental immunotherapy; the inability to detect them within the adult CNS; the relatively high frequency of expression of 3'-isoLM1 and 3',6'-isoLD1, especially in human tumor samples (50-100%, depending upon the series and assay); and the existence of specific MAbs reactive with these epitopes. Current technology is being applied to these MAbs to transfer the specific recognition capacity of existing murine MAbs into various human framework structures of any desired immunoglobulin class, and thereby, biologic function. The variety of effector functions, the stability in affinity, labeling capacity, and the exquisite sensitivity of these MAbs for these glioma-distinctive epitopes is an exciting and promising approach for immunotherapy of human CNS tumors.

Expression of gangliosides GD3 and 3'-isoLM1 in autopsy brains from patients with malignant tumors

Three autopsy brains from patients who succumbed to malignant gliomas have been analyzed in various regions with regard to their ganglioside content. The study focused on the gangliosides GD3 and 3'-isoLM1, which in a previous study of biopsies were found to be associated with these tumors. In particular, 3'-isoLM1, was suggested to be a marker for malignant gliomas. The highest concentrations (200-1,000 nmol of sialic acid/g wet weight) of GD3 was found in specimens of macroscopically pure tumor, where the proportion of GD3 was, at the most, 78% (range, 11-78%) of the total ganglioside sialic acid compared with < 10% in normal brain tissue. The proportion of the total ganglioside sialic acid made up by GD3 was also elevated in the periphery of the tumor and in the same region in the opposite hemisphere, where no tumor cells were detected. In four of eight brain metastases of various carcinomas, GD3 was > 10% of the total ganglioside sialic acid (range, 3-37%). The ganglioside 3'-isoLM1, as determined by TLC-enzyme-linked immunosorbent assay using a specific monoclonal antibody (SL-50), was not present at detectable levels in any of the macroscopically homogenous tumor areas. It was, however, found in the periphery of the tumor, in the corpus callosum, and at highest concentrations in the region of the opposite hemisphere corresponding to the tumor. The concentration varied between 0.1 and 6.0 nmol/g wet weight of tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Antitumor effects of a novel monoclonal antibody with high binding affinity to ganglioside GD3

Ganglioside GD3, which is one of the major gangliosides expressed on the cell surface human tumors of neuroectodermal origin, has been studied as a target molecule for passive immunotherapy. We established ten kinds of anti-GD3 monoclonal antibodies (mAb) of the mouse IgG3 subclass by immunization with purified GD3 and melanoma cells. One of the established mAb, KM641, showed major reactivity with GD3 and minor reactivity with GQ1b out of 11 common gangliosides in an enzyme-linked immunosorbent assay. Immunostaining of gangliosides, separated on thin-layer chromatography plates, using KM641 revealed that most of the melanoma cell lines contained immunoreactive GD3 and GD3-lactone at a high level, but only the adrenal gland and the urinary bladder out of 21 human normal tissues had immunoreactive GD3. In immunofluorescence, KM641 bound to a variety of living tumor cell lines especially melanoma cells, including some cell lines to which another anti-GD3 mAb R24, established previously, failed to bind. High-affinity binding of KM641 to a tumor cell line was quantified by Scatchard analysis (Kd = 1.9 x 10(-8) M). KM641 exerted tumor-killing activity in the presence of effector cells or complement against melanoma cells expressing GD3 at a high level. Not only natural killer cells but also polymorphonuclear cells were effective as the effector cells in antibody-dependent cellular cytotoxicity. Intravenous injection of KM641 markedly suppressed the tumor growth of a slightly positive cell line, C24.22 (7.2 x 10(5) binding sites/cell), as well as a very GD3-positive cell line, G361 (1.9 x 10(7) binding sites/cell), inoculated intradermally in nude mice. KM641, characterized by a high binding affinity for GD3, has the potential to be a useful agent for passive immunotherapy of human cancer.

Monoclonal antibodies to malignant human gliomas

Operationally specific monoclonal antibodies (MAbs) reactive with tumor but not normal adult tissues offer great potential for diagnosis and therapy of CNS neoplasms. Two targets for specific MAb localization were chosen for this study: (1) glioma-associated gangliosides GM2 [II3NeuAc-GgOse3Cer], GD2 [II3(NeuAc)2-GgOse3Cer], GD3[II3(NeuAc)2-LacCer], 3'-isoLM1 [IV3NeuAc-LcOse4Cer], and 3',6'-isoLD1 [IV3NeuAc,III6NeuAc-LcOse4Cer] and (2) epidermal growth factor receptor (EGFR) variant molecules. Epitopic specificity of isolated ganglioside hybridomas was determined with FAB-MS defined ganglioside standards. All MAb are IgM. Assay of 14 cytologic specimens and 31 frozen sections of primary CNS neoplasms revealed staining with anti-GD3 (14/14, 31/31), anti-GM2 (9/14, 26/31), and anti-GD2 (6/14, 24/30), respectively. 3'-isoLM1 and 3',6' isoLD1, which exhibit a restricted oncofetal expression pattern and are not detectable in adult human brain, are present in 15/31 primary CNS neoplasms and in 1/8 human glioma xenografts, as detected by MAbs SL-50 and DMAb-14, respectively. EGFR proteins, the second target, have unique amino acid spans resulting from gene deletion in the amplified EGFR gene present in subsets of malignant human gliomas. Antibodies against EGFR deletion-mutant Type III show highly restricted activity with a subset of glioma biopsies (6/35) expressing the mutant EGFR. These reagents should be useful for in vitro and in vivo diagnosis and, potentially, for treatment of malignant brain tumors.

Ganglioside composition and its relation to clinical data in brain tumors

The ganglioside composition of 15 cases of meningioma, 15 cases of astrocytoma, 5 cases of neurinoma, 4 cases of ependymoma, 3 cases of metastatic brain tumor and 1 case each of mixed glioma, oligodendroglioma, medulloblastoma, embryonal carcinoma, and cultured glioma cell line were analyzed by thin-layer chromatography. The GM2, GD3, and GD2 content of the tumors was determined using specific monoclonal antibodies (MAb). Cases were grouped according to the difference in ganglioside pattern and various clinical features. In meningiomas and astrocytomas, GM3 and GD3 were the major gangliosides. The tumor content of the rather simple gangliosides (GM3, GM2, GD3, GD2) increased or was almost equal to that of normal tissue (leptomeninges tissue in the case of meningiomas, and brain tissue in the case of astrocytomas), while the tumor content of complex gangliosides (GM1, GD1a, GT1a, GT1b) decreased as compared with normal tissue. The GM3 content of meningiomas increased in middle-aged patients, who comprised the majority of the patients with these tumors. The GD2 content decreased in middle-aged patients with initial symptoms of meningioma within a year. The GM3 content of astrocytomas decreased in patients who underwent radiotherapy. The amount of GM3 and GD3 increased in small tumors. GM3 may be related to the early proliferative stage. The ganglioside patterns of brain tumors are shown in this study to differ according to clinical features and also to be changeable in their clinical courses.

Generation of one set of monoclonal antibodies specific for b-pathway ganglio-series gangliosides

We established six murine monoclonal antibodies (MAbs) specific for b-pathway ganglio-series gangliosides by immunizing C3H/HeN mice with these purified gangliosides adsorbed to Salmonella minnesota mutant R595. The binding specificities of these MAbs were determined by an enzyme-linked immunosorbent assay and immunostaining on thin-layer chromatogram. These six MAbs, designated GGB19, GMR2, GMR7, GGR12, GMR5, and GGR13 reacted strongly with the gangliosides GD3, O-Ac-GD3, GD2, GD1b, GT1b, and GQ1b, respectively, that were used as immunogens. All these MAbs except GGB19 showed highly restricted binding specificities, reacting only with the immunizing ganglioside. None of other various authentic gangliosides or neutral glycolipids were recognized. On the other hand, MAb GGB19 exhibited a broader specificity, cross-reacting weakly with O-Ac-GD3, GQ1b, and GT1a, but not with other gangliosides or neutral glycolipids. Using these MAbs, we determined the expression of these gangliosides, especially GD1b, GT1b, and GQ1b on mouse, rat, and human leukemia cells. GD1b was expressed on rat leukemia cells, but not on mouse and human leukemia cells tested. Neither GT1b nor GQ1b was detected in these cell lines.

Glycolipids and glycosyltransferases in permanent cell lines established from human medulloblastomas

Medulloblastoma biopsies are heterogenous and might contain normal brain tissue, which limits the usefulness of such tumor material for biochemical analyses. We have, therefore, examined the gangliosides and their metabolism using the medulloblastoma cell lines. Daoy and D341 Med, cultured both in vitro and as xenografts in nude mice. The ganglioside patterns in the Daoy showed a switch from a high GM2, 70% (mol% of total ganglioside sialic acid) and low lactoseries gangliosides (2%) content in monolayer cultures, to a high proportion of lactoseries gangliosides (50%) and virtually no GM2 (1%) in xenografts, but an increased proportion of other a-series gangliosides. The D341 Med showed a similar change regarding the lacto-series gangliosides from 1% in suspension culture to 10% in xenografts. The activity of five glycosyltransferases, GM3, GD3, GM2, GM1 and LA2 synthases, did not parallel the ganglioside patterns and could not account for the noted variations therein. In the Daoy cell line the LA2 synthase as well as the GM2 synthase activity was relatively high in both culture systems, despite the marked difference in the expression of GM2 and the lactoseries gangliosides. These results suggest that environmental factors play a crucial role for the in vivo activity of the glycosyltransferases.

Determination of gangliosides in six human primary medulloblastomas

The ganglioside composition of six human medulloblastomas was analyzed. The characterization was performed by thin-layer chromatography, sialidase hydrolysis, and immunological staining with a panel of characterized antiganglioside monoclonal antibodies. The total ganglioside content ranged from 60 to 1,130 nmol of ganglioside sialic acid/g wet weight. Neuronal gangliosides (gangliotetraose series) were found in varying amounts in all medulloblastomas. Gangliosides of the neolactotetraose series (3'-LM1 and LD1) were present in all specimens, and the lactotetraose series ganglioside 3'-isoLM1 was found in all cases showing astrocytic differentiation. This supports our previous findings that 3'-isoLM1 is a marker for proliferating astroglial cells.

Circulating glycoconjugates in CSF of meningioma patients

This study investigated whether tumor-associated gangliosides or glycoproteins may be markers for meningiomas in CSF. The concentrations of a number of gangliosides and sulphatide were determined with specific monoclonal antibodies and cholera toxin B-subunit in a thin-layer chromatography overlay technique. As compared to a reference group of 10 individuals (mean age 50 +/- 14 years), the CSF samples from 7 meningioma patients (mean age 55 +/- 12 years) were found to contain significantly increased concentrations of ganglioside GD3 [II3(NeuAc)2-LacCer], one of the major gangliosides in meningioma tissue specimens. Sulphatide was significantly increased in 6 of 7 patients. Tumor-associated glycoproteins detected by the lectin Ricinus communis 1 in meningioma tissue specimens, but not in normal human brain tissue, were also found in the CSF of the meningioma patients. An early diagnosis of meningiomas might be achieved by the combined assay in CSF of ganglioside GD3 and glycoproteins with Ricinus communis lectin.