Determination of gangliosides in six human primary medulloblastomas

Radio-prevention of micrometastases

In developed countries, the cancer incidence is about 150,000 cases per year and half of people with cancer may die from the extension of the primary tumour in secondary deposits. This disaster costs more than 2 billion euro per year. People with cancer are often treated with surgery and/or radiotherapy of localized primary tumour and chemo-prevention of occult disseminated micrometastases. Since chemotherapy essentially targets cycling tumour cells, quiescent micrometastases which may contain only one cell may escape. We previously reported that human melanoma clones with high metastatic potential and low gangliosides content appeared very radiosensitive to low-dose ionizing radiation both in culture and in immunosuppressed animals. This exquisite radiosensitivity was observed with the highly metastatic single cells which were resting at the time of irradiation. These data are consistent with the dose-response relationship for the radiotherapy of secondary deposits which appears linear with no threshold. Highly metastatic cells at an early stage of growth also appear very sensitive to chemicals and activated immune cells. We propose the medical hypothesis according to which the spread of resting micrometastases should be prevented by a single fraction of total-body irradiation delivered at a dose sufficiently low (below 0.2 Gy) to avoid normal tissue radiotoxicity. Radio-prevention may complement standard treatments for patients with metastases and may be delivered even for patients in whom no distant metastases were detected on tumour diagnosis (M0 stage).

Gangliosides and neutral glycolipids in ependymal, neuronal and primitive neuroectodermal tumors

Neutral glycolipid and ganglioside compositions were determined on 11 ependymal tumors, 12 medulloblastomas, 6 other neuronal tumors of the brain, 4 peripheral neuroblastomas, 1 cerebral primitive neuroectodermal tumor (PNET), and 1 PNET of the thoracic wall. Within the group of tumors that can demonstrate neuronal phenotypes, there was an association between the degree of neuronal differentiation usually demonstrated by these tumors and the proportions of both GD1a and 1b-pathway gangliosides. The amount of globoside also correlated with the amount of 1b pathway gangliosides. Patients with medulloblastomas whose 1b gangliosides made up over 15% of the total gangliosides survived longer that those with lower proportions of 1b gangliosides. The only gangliosides in the choroid plexus papilloma were GM3 and GD1a, but other ependymal tumors had significant amounts of GD1b and its metabolic precursors. Ependymoma and anaplastic ependymoma had similar neutral glycolipid compositions, which were different from subependymoma, which lacked ceramide monohexoside and ceramide dihexoside. These differences in glycolipid compositions suggest that there may be fundamental biological differences between these types of ependymal tumors.

Detection of medulloblastoma and astrocytoma-associated ganglioside GD3 in cerebrospinal fluid

Shedding of gangliosides by tumor cells may enhance tumor development. We recently showed that cells of the human brain tumor, medulloblastoma, shed gangliosides in vitro and have therefore examined ganglioside shedding by pediatric brain tumors into the cerebrospinal fluid (CSF). GD3, a major ganglioside in medulloblastoma and astrocytoma, was the target for detection in the CSF by immunostaining using the monoclonal antibody R24 and enhanced chemiluminescence detection. Mean CSF GD3 levels in patients with medulloblastomas (n = 9) and astrocytomas (n = 10) were significantly higher than those of controls (mean +/- SD 44.7 +/- 8.4 versus 18.2 +/- 1.9 pmol/ml, n = 20, P < 0.0002). Mass spectrometric analysis showed that tumor-derived ganglioside GD3 contained heterogeneous ceramide structures and, interestingly, the ceramide subspecies with shorter fatty acyl chains were selectively shed. The elevated CSF GD3 concentrations in patients with medulloblastoma and astrocytoma support the concept that ganglioside shedding, which may have significant biological consequences, is characteristic of human brain tumors.

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.

Role of gangliosides in tumour progression: a molecular target for cancer therapy?

In a number of patients with tumours of either neuroectodermal or epithelial origin, polysialylated gangliosides (e.g. GD3) are over-expressed. The mechanism of ganglioside over-expression may be different for the two classes of tumour and could represent distinct secondary genetic mutations or epigenetic changes affecting the enzymes (transferases and/or hydrolases) controlling the metabolic interconversions of these gangliosides. Tumour cells of neuroectodermal origin (e.g. melanomas and brain tumours) are known to produce and shed polysialylated gangliosides, whereas paracrine signal(s) from tumour cells of epithelial origin (e.g. carcinomas of cervix, lung, prostate, breast, head and neck, colon and ovary) may stimulate over-expression and shedding from tumour infiltrating mesenchymal cells (e.g. macrophages and/or fibroblasts). This cellular membrane over-expression and shedding of acidic glycosphingolipids into the interstitial spaces and blood of cancer patients may play a central role in increased tumour cell growth, lack of immune cell recognition and neovascularization and could represent a molecular target for cancer therapy.

High-resolution thin-layer chromatography of gangliosides

In this review an updated overview of current improvements on thin-layer chromatography (TLC) of gangliosides over the past decade is provided. Basic general techniques and special advice is given for successful separation of glycosphingolipids. New approaches concerning continuous and multiple development, and several preparative TLC methods are also included. Emphasis is placed on TLC immunostaining and related techniques, i.e. practical applications of carbohydrate-specific antibodies, toxins and bacteria, viruses, lectins and eukaryotic cells. Thus, this review on ganglioside TLC summarizes its power as an analytical tool for a wide range of purposes.

Correlation of ganglioside patterns of primary brain tumors with survival

BACKGROUND

Classification/grading schemes for brain tumors are based mainly on histologic examinations, but these have major limitations, which has led to a search for more objective prognostic markers. Gangliosides have several biologic effects relevant to tumors, and ganglioside compositions of primary brain tumors correlate with diagnosis. This led to the authors' hypothesis that ganglioside patterns of brain tumors might be useful as prognostic indicators.

METHODS

Gangliosides in primary brain tumors of different histologic types from 84 patients were analyzed. Specific ganglioside patterns and several other relevant variables were examined for associations with survival using a Cox proportional hazards model. Kaplan-Meier survival curves were analyzed using the log-rank test.

RESULTS

Patients in whom less than 30% of total tumor gangliosides consisted of 1b pathway gangliosides (GD1b, GT1b, and GQ1b) had significantly higher risk ratios than those with more than 30% 1b gangliosides (P approximately 0.03). The presence of 6'-LM1 (NeuAc alpha 2-->6Gal beta 1-->4Glc-NAc beta 1-->3Gal beta 1-->4Glc beta 1-->1Cer was also associated with a higher risk ratio (P approximately 0.007). Combinations of 1b gangliosides and 6'-LM1 identified three groups of patients regardless of histologic diagnosis. Group A, with less than 30% 1b and the presence of 6'-LM1, had a median survival time of 331 days. Group B, with less than 30% 1b but no 6'-LM1, had a median survival time of more than 698 days. Group C, with more than 30% 1b had a median survival time of more than 776 days.

CONCLUSIONS

The correlation of ganglioside patterns with survival in this initial investigation suggests the potential of 1b gangliosides and 6'-LM1 to be used as prognostic indicators. Continuing research is being conducted to assess this possibility prospectively.

Ganglioside modulation of the PDGF receptor. A model for ganglioside functions

Gangliosides are a family of glycolipids that are present at the cell surface of all mammalian cells. Patterns of gangliosides are different in gliomas than normal brain, and exogenously added gangliosides affect the growth of cultured glioma cells. Gangliosides inhibit the activities of several kinases, including protein kinase C (PKC) and cAMP-kinase. U-1242 MG cells (derived from a human malignant glioma) have receptors for platelet-derived growth factor (PDGF) that become phosphorylated on tyrosine when exposed to PDGF. Exposure of these cells to PDGF also causes an increase in intracellular calcium concentration ([Ca2+]i) and induces a translocation of PKC to the membrane. Preincubation of U-1242 MG cells with several species of gangliosides inhibits the increase in ([Ca2+]i) and PKC translocation in response to PDGF, but GM3 is much less effective than other species tested. This is due to a lack of activation of the receptor tyrosine kinase as monitored by phosphorylation of the receptor on tyrosine residues, but is not due to an inhibition of binding of PDGF to its receptors. The lack of activation of the PDGF receptor tyrosine kinase is due to an inhibition of dimerization of the receptor monomers by gangliosides GM1, GM2, GD1a, GT1b, but not GM3. Therefore, gangliosides may be involved in coordinating the activities of multiple trophic factors simultaneously acting on a cell by regulating the dimerization of their respective receptor monomers.

Gangliosides as diagnostic markers of human astrocytomas and primitive neuroectodermal tumors

BACKGROUND

Limitations of classification schemes for brain tumors based solely on morphology have stimulated searches for molecular markers of nosologic and prognostic value. Gangliosides are logical candidates because there are high concentrations of them in the nervous system, there is evidence of their roles in regulation of growth and differentiation, and data from small series suggest correlations between ganglioside composition and glioma type.

METHODS

Ganglioside compositions were determined for 70 primary human brain tumors: 16 low grade astrocytomas (LG), 12 anaplastic astrocytomas (AA), 34 glioblastoma multiformes (GBM), and 8 primitive neuroectodermal tumors (PNET). This method involved identification and quantitation of specific gangliosides using chemical analysis and immunoanalysis.

RESULTS

Among all tumor types, histologic grade correlated with a progressive loss of 1b gangliosides (P < 0.0001). GQ1b was higher in LGs than in AAs (P < 0.001). Both GT1b and GD1b were higher in AAs than GBMs (P < 0.01 and 0.05, respectively) and lower in PNETs than in GBMs (P < 0.05). GM3 was higher in PNETs than in any astrocytoma group and higher in GBMs than in either AAs or LGs. There was a significant difference in the content of 3'-LM1 among all groups (P < 0.005), between AAs and GBMs (P < 0.05), and between low grade ordinary and juvenile pilocytic astrocyomas (P < 0.01). The lacto-series ganglioside 3'-isoLM1 was present in all groups except PNET.

CONCLUSIONS

These results indicate that patterns of gangliosides could be of considerable value in refining the classification and diagnosis of primary human brain tumors.

Surface antigens of cell subpopulations in prenatal rat brain are expressed in a characteristic non-random pattern on their ethylnitrosourea-induced malignant counterparts

Selective induction of neural tumors in the rat by single-dose exposure of the immature nervous system to ethylnitrosourea (EtNU) is a model for the study of cell lineage-, differentiation stage-, and carcinogen-dependent mechanisms in neuro-oncogenesis. Overall yields and relative frequencies of different types of neural tumors vary with the developmental window chosen for the EtNU-pulse. Precursor cells belonging to different neural lineages and targeted by the carcinogen at distinct developmental stages may thus bear a differential risk of malignant conversion. To specify subpopulations of neural precursors in fetal (prenatal day 18) BDIX-rat brain, four monoclonal antibodies (mAbs) recognizing cell surface differentiation antigens were used: mAb RB13-2 directed against O-acetylated gangliosides and binding to approximately 36% of fetal brain cells (FBC); mAb RB13-6 recognizing a 130 kDa glycoprotein (expressed by approximately 8% of FBC); and mAbs RB21-7 and RB21-15 which bind, respectively, to embryonal neural cell adhesion molecules (N-CAM) and a 24 kDa protein (expressed by approximately 55% and 12% of FBC). Antigen expression profiles were compared with those of 14 primary brain tumors and 16 malignant neural cell lines, all of which had been induced by EtNU on prenatal day 18 in vivo. Monoclonal antibodies RB13-2 and RB21-7 did not bind to any of the tumors or cell lines. In contrast, mAbs RB13-6 and RB21-15 both reacted with 14/14 tumors, and with 16/16 and 10/16 cell lines, respectively. Expression of the latter antigens might thus specify lineage-specific stages of FBC development/differentiation particularly susceptible to EtNU-induced malignant transformation. Two-color fluorescence analyses revealed three subsets of FBC binding mAb RB13-6 (RB13-2+/RB13-6+/RB21-15-; RB13-2-/RB13-6+/RB21-15-; and RB13-2-/RB13-6+/RB21-15+), representing successive stages of differentiation.

Glycosphingolipid component profiles of human gliomas correlate with histological tumour types: analysis of inter-individual and tumour-regional distribution

Three types of glycosphingolipid (GSL) component profiles have been established for human intracranial gliomas. GSL-type I shows only Glac- and lacto-series-sialoglycolipids. Type II consist of Glac- and Gtri-gangliosides, whereas only GSL-type III contains sulphatide and, as a major neutral glycolipid, galactocerebroside, besides gangliosides of the Glac-, Gtri-, and Gtet-families. Whole gliomas of malignancy grading I/II, III and IV, display GSL-Types III, II, and I, respectively. Thus, the GSL component distribution of the samples taken after surgery from three individual gliomas and two biopsies correlate closely with the general diagnosis of these tumours. Arthrobacter ureafaciens sialidase was used for the characterization of gangliosides. GSL-type analysis of multiple regional samples, taken from necropsy and biopsy, were determined by microanalysis of microscopic cryostat section, and shown to be in good agreement with their histology. The results validate the relevance of tumour ganglioside analysis for the characterization and diagnosis of gliomas.

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.

Gangliosides associated with primary brain tumors and their expression in cell lines established from these tumors

Human primary brain tumors differ in their ganglioside composition when compared to adjacent tissues. One ganglioside found in all malignant glioma specimens, but not detected in normal adult brain, is 3'-isoLM1, a ganglioside of the lacto series. This ganglioside was also identified in medulloblastomas with astrocytic differentiation and in brain tissues containing benign proliferating astrocytes. The appearance of 3'-isoLM1 was seen over large regions of brain from glioma but was found mainly in areas either adjacent to the macroscopic tumor or areas corresponding to the tumor in the opposite hemisphere. A high concentration of 3'-isoLM1 was also seen in the corpus callosum, the anatomical structure along which glioma cells may migrate to the opposite brain hemisphere. Ganglioside expressed by cell lines established from primary malignant brain tumors varied widely among cell lines and within a given cell line propagated under different conditions. In in vitro-cultured glioma and medulloblastoma cell lines, gangliosides of the ganglio series dominated and the expression of the lacto series gangliosides, including 3'-isoLM1 was low if at all detectable. However, in vivo growth of solid subcutaneous tumors in nude mice or rats led to a significantly increased expression of the often dominant gangliosides of the lacto series and revealed a decreased expression of ganglio series gangliosides. In conclusion, these findings indicate that environmental factors could strongly influence the expression of gangliosides that may lead to a switch from the ganglio to the lacto series. These results also suggest that ganglioside 3'-isoLM1 is associated with proliferating astrocytes, of both neoplastic and non-neoplastic origin and that this ganglioside may be involved in cell-cell recognition and attachment during development and tumor cell migration.

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)

Ganglioside distribution in murine neural tumors

The ganglioside composition of seven experimental brain tumors was examined in C57BL/6J mice. The tumors were produced from 20-methylcholanthrene (20-MC) implantation into either the cerebrum or cerebellum and were maintained in serial transplants through many generations. The tumors studied were grown subcutaneously as solid tumors, and cells from two of the tumors were also studied in culture. Histologically, all of the tumors were similar and could be broadly classified as highly malignant, poorly differentiated anaplastic astrocytomas. The total ganglioside sialic acid content of the solid tumors was markedly lower than that in adult mouse brain. In addition to N-acetylneuraminic acid (NeuAc), the gangliosides in the solid tumors contained significant amounts of N-glycolylneuraminic acid (NeuGc). The seven solid tumors fell into two general groups with respect to ganglioside composition. Furthermore, the differences in ganglioside composition between the two tumor groups were strongly associated with differences in tumor cell cohesion. The tumors in one group had high levels of GM3 hematosides, low levels of oligosialogangliosides, and grew as firm cohesive tissues. The tumors in the other group, however, had lower levels of GM3 hematosides, noticeable amounts of oligosialogangliosides and grew as soft noncohesive tissues. In culture, clonal cells from one of the tumors in the first group grew as clumps or islands and contained GM3 as the only major ganglioside, whereas clonal cells from a tumor in the second group grew as sheets or monolayers and contained little GM3, but expressed several gangliosides with complex structures. In marked contrast to the gangliosides in the solid tumors, the gangliosides in the cultured tumor cells contained trace amounts of NeuGc. Since NeuGc containing gangliosides are abundant in mouse nonneural tissues, the high content of NeuGc gangliosides in the solid tumors may arise from infiltration of nonneural tissue elements, e.g., macrophages, lymphocytes, and endothelial cells.

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.