Expression Of Gangliosides Research Articles

Interaction of glycosphingolipids GD3 and GD2 with growth factor receptors maintains breast cancer stem cell phenotype.

Many studies have suggested that disialogangliosides, GD2 and GD3, are involved in the development of various tumor types. However, the functional relationships between ganglioside expression and cancer development or aggressiveness are not fully described. GD3 is upregulated in approximately half of all invasive ductal breast carcinoma cases, and enhanced expression of GD3 synthase (GD3S, alpha-N-acetylneuraminide alpha-2,8-sialyltransferase) in estrogen receptor-negative breast tumors, was shown to correlate with reduced overall patient survival. We previously found that GD2 and GD3, together with their common upstream glycosyltransferases, GD3S and GD2/GM2 synthase, maintain a stem cell phenotype in breast cancer stem cells (CSCs). In the current study, we demonstrate that GD3S alone can sustain CSC properties and also promote malignant cancer properties. Using MALDI-MS and flow cytometry, we found that breast cancer cell lines, of various subtypes with or without ectopic GD3S-expression, exhibited distinct GD2/GD3 expression profiles. Furthermore, we found that GD3 was associated with EGFR and activated EGFR signaling in both breast CSCs and breast cancer cell lines. In addition, GD3S knockdown enhanced cytotoxicity of the EGFR-inhibitor gefitinib in resistant MDA-MB468 cells, both in vitro and in vivo. Based on this evidence, we propose that GD3S contributes to gefitinib-resistance in EGFR-positive breast cancer cells and may be an effective therapeutic target in drug-resistant breast cancers.

Aberrant ganglioside composition in glioblastoma multiforme and peritumoral tissue: A mass spectrometry characterization

Tumor cells are characterized by aberrant glycosylation of the cell surface glycoconjugates. Gangliosides are sialylated glycosphingolipids highly abundant in neural tissue and considered as tumor markers and therapeutic targets. In this study, a detailed characterization of native ganglioside mixtures from glioblastoma multiforme, corresponding peritumoral tissue and healthy human brain was performed using mass spectrometry and high performance thin layer chromatography in order to elucidate their roles as tumor-associated antigens. Distinctive changes in ganglioside expression were determined in glioblastoma compared to healthy brain tissue showing 5 times lower total ganglioside content and higher abundance of simple gangliosides. Glioblastoma gangliosides were characterized by highly diverse ceramide composition with fatty acyl chains varying from 16 to 24 carbon atoms, while in normal and peritumoral tissue mostly C18 chains were found. The most abundant ganglioside in glioblastoma was GD3 (d18:1/18:0), followed by GD3 (d18:1/24:0) that was exclusively detected in glioblastoma tissue. Peritumoral tissue expressed higher abundance of GD3- and nLM1/GM1-species while lower GT1-species vs. normal brain. O-Ac-GD1, known as neurostatin, was detected in normal and peritumoral tissue, but not in glioblastoma. O-Ac-GD3 species were found exclusively in glioblastoma; MS structural characterization of the isomeric form possessing the O-acetylation at the inner sialic acid residue confirmed our previous finding that this isomer is glioma-associated. This, to our knowledge, the most detailed characterization of ganglioside composition in glioblastoma and peritumoral tissue, especially addressing the ceramide variability and O-acetylation of tumor-associated gangliosides, could contribute to recognition of new molecular targets for glioblastoma treatment and sub-classification.

Restoring GM1 ganglioside expression ameliorates axonal outgrowth inhibition and cognitive impairments induced by blast traumatic brain injury

Blast induced traumatic brain injury (B-TBI) may cause various degrees of cognitive and behavioral disturbances but the exact brain pathophysiology involved is poorly understood. It was previously suggested that ganglioside alteration on the axon surface as well as axonal regenerating inhibitors (ARIs) such as myelin associated glycoprotein (MAG) were involved in axonal outgrowth inhibition (AOI), leading to brain damage. GM1 ganglioside content in the brain was significantly reduced while GD1 ganglioside was not affected. The axonal regeneration was also reduced as seen by the phosphorylated NF-H expression. Moreover, B-TBI induced a significant elevation in MAG expression in the brains of the injured mice. The blast injured mice exhibited a significant decline in spatial memory as seen by the Y-maze test. In addition, the injured mice showed pronounced damage to the visual memory (as evaluated by the Novel object recognition test). A single low dose of GM1 (2 mg/kg; IP), shortly after the injury, prevented both the cognitive and the cellular changes in the brains of the injured mice. These results enlighten part of the complicated mechanism that underlies the damage induced by B-TBI and may also suggest a potential new treatment strategy for brain injuries.

Combined deficiencies of endosomal ganglioside neuraminidases 3 and 4 in mice cause lysosomal GM3 gangliosidosis

The sialylated glycosphingolipids gangliosides are essential to myelination, axon integrity, transmission of nervous impulses and memory consolidation. Ganglioside expression patterns in the brain are cell-specific, dynamic and maintained by highly coordinated processes of biosynthesis, trafficking, processing and catabolism.

Comparison of the glycosphingolipids of human-induced pluripotent stem cells and human embryonic stem cells.

High expectations are held for human-induced pluripotent stem cells (hiPSC) since they are established from autologous tissues thus overcoming the risk of allogeneic immune rejection when used in regenerative medicine. However, little is known regarding the cell-surface carbohydrate antigen profile of hiPSC compared with human embryonic stem cells (hESC). Here, glycosphingolipids were isolated from an adipocyte-derived hiPSC line, and hiPSC and hESC glycosphingolipids were compared by concurrent characterization by binding assays with carbohydrate-recognizing ligands and mass spectrometry. A high similarity between the nonacid glycosphingolipids of hiPSC and hESC was found. The nonacid glycosphingolipids P1 pentaosylceramide, x2 pentaosylceramide and H type 1 heptaosylceramide, not previously described in human pluripotent stem cells (hPSC), were characterized in both hiPSC and hESC. The composition of acid glycosphingolipids differed, with increased levels of GM3 ganglioside, and reduced levels of GD1a/GD1b in hiPSC when compared with hESC. In addition, the hESC glycosphingolipids sulf-globopentaosylceramide and sialyl-globotetraosylceramide were lacking in hiPSC. Neural stem cells differentiating from hiPSC had a reduced expression of sialyl-lactotetra, whereas expression of the GD1a ganglioside was significantly increased. Thus, while sialyl-lactotetra is a marker of undifferentiated hPSC, GD1a is a novel marker of neural differentiation.

Preparation of CD4+ T Cells for Analysis of GD3 and GD2 Ganglioside Membrane Expression by Microscopy.

The methods described herein for activation of naïve CD4+ T cells in suspension and their adherence in coverslips for confocal microscopy analysis allow the spatial localization and visualization of gangliosides involved in CD4+ T cell activation, that complement expression profiling experiments such as flow cytometry, western blotting or real-time PCR. The quantification of ganglioside expression through flow cytometry and their cellular localization through microscopy can be obtained by the use of anti-ganglioside antibodies with high affinity and specificity. Nonetheless, an adequate handling of cells in suspension involves the treatment of culture plates to promote the necessary adherence required for fluorescence or confocal microscopy acquisition. In this work, we describe a protocol for determining GD3 and GD2 ganglioside expression and colocalization with the TCR during naïve CD4+ T cell activation. Also, real-time PCR experiments using <40,000 cells are described for the determination of the GD3 and GM2/GD2 synthase genes, demonstrating that gene analysis experiments can be performed with a low number of cells and without the need of additional low input RNA kits.

Expression of B4GALNT1, an essential glycosyltransferase for the synthesis of complex gangliosides, suppresses BACE1 degradation and modulates APP processing

Alzheimer’s disease (AD) is the most prevalent form of dementia characterized by the extracellular accumulation of amyloid β (Aβ) peptides, which are produced by proteolytic cleavages of amyloid precursor protein (APP). Gangliosides are involved in AD pathophysiology including Aβ deposition and APP processing, yet the detailed mechanisms are not fully understood. Here we examined how changes in the carbohydrate moiety of gangliosides alter APP processing in human melanoma cells, neuroectoderm-derived cells. We showed that forced expression of GD2, GM2 or GM1 (by introducing B4GALNT1 cDNA into cells not expressing this glycosyltransferase) results in increases of α- and β-site cleavages of APP with a prominent increase in β-cleavage. We also showed that β-site APP cleaving enzyme 1 (BACE1) protein is highly protected from the degradation in cells expressing these gangliosides, thereby increasing the expression of this protein. Unexpectedly, adding gangliosides exogenously altered neither BACE1 levels nor β-site cleavage. The stabilisation of BACE1 protein led to the increase of this protein in lipid rafts, where BACE1 processes APP. Based on the current results, we propose a hitherto undisclosed link between ganglioside expression and AD; the expression of B4GALNT1 positively regulates the β-site cleavage by mainly inhibiting the lysosomal degradation of BACE1 protein.

Mice lacking sialyltransferase ST3Gal-II develop late-onset obesity and insulin resistance.

Sialyltransferases are a family of 20 gene products in mice and humans that transfer sialic acid from its activated precursor, CMP-sialic acid, to the terminus of glycoprotein and glycolipid acceptors. ST3Gal-II (coded by the St3gal2 gene) transfers sialic acid preferentially to the three positions of galactose on the Galβ1-3GalNAc terminus of gangliosides GM1 and GD1b to synthesize GD1a and GT1b, respectively. Mice with a targeted disruption of St3gal2 unexpectedly displayed late-onset obesity and insulin resistance. At 3 months of age, St3gal2-null mice were the same weight as their wild type (WT) counterparts, but by 13 months on standard chow they were visibly obese, 22% heavier and with 37% greater fat/lean ratio than WT mice. St3gal2-null mice became hyperglycemic and displayed impaired glucose tolerance by 9 months of age. They had sharply reduced insulin responsiveness despite equivalent pancreatic islet morphology. Analyses of insulin receptor (IR) tyrosine kinase substrate IRS-1 and downstream target Akt revealed decreased insulin-induced phosphorylation in adipose tissue but not liver or skeletal muscle of St3gal2-null mice. Thin-layer chromatography and mass spectrometry revealed altered ganglioside profiles in the adipose tissue of St3gal2-null mice compared to WT littermates. Metabolically, St3gal2-null mice display a reduced respiratory exchange ratio compared to WT mice, indicating a preference for lipid oxidation as an energy source. Despite their altered metabolism, St3gal2-null mice were hyperactive. We conclude that altered ganglioside expression in adipose tissue results in diminished IR sensitivity and late-onset obesity.

Epigenetic regulation of ganglioside expression in neural stem cells and neuronal cells.

The structural diversity and localization of cell surface glycosphingolipids (GSLs), including gangliosides, in glycolipid-enriched microdomains (GEMs, also known as lipid rafts) render them ideally suited to play important roles in mediating intercellular recognition, interactions, adhesion, receptor function, and signaling. Gangliosides, sialic acid-containing GSLs, are most abundant in the nerve tissues. The quantity and expression pattern of gangliosides in brain change drastically throughout development and these changes are mainly regulated through stage-specific expression of glycosyltransferase genes. We previously demonstrated for the first time that efficient histone acetylation of the glycosyltransferase genes in mouse brain contributes to the developmental alteration of ganglioside expression. We further demonstrated that acetylation of histones H3 and H4 on the N-acetylgalactosaminyltransferase I (GalNAcT, GA2/GM2/GD2/GT2-synthase; B4galnt1) gene promoter resulted in recruitment of trans-activation factors. In addition, we showed that epigenetic activation of the GalNAcT gene was detected and accompanied by an apparent induction of neuronal differentiation of neural stem cells (NSCs) responding to an exogenous supplement of ganglioside GM1. Most recently, we found that nuclear GM1 binds with acetylated histones on the promoters of the GalNAcT as well as on the NeuroD1 genes in differentiated neurons. Here, we will introduce epigenetic regulation of ganglioside synthase genes in neural development and neuronal differentiation of NSCs.

Altered gene expression of glycosyltransferases and sialyltransferases and total amount of glycosphingolipids following herpes simplex virus infection

There is a case report of a patient with overlapping Guillain–Barré syndrome and Bickerstaff brainstem encephalitis after infection with herpes simplex virus type 1 (HSV-1), who carried high titers of serum anti-GQ1b IgG antibodies. Several studies have linked viral infection to the modulation of ganglioside expression such as human T-lymphotropic virus to GD2 and simian virus 40 to GM3. Also, enhancement of the expression of GM2 on the cell membrane after cytomegalovirus infection has been reported. The objective of this study was to unveil the relationship between HSV-1 infection and the alteration of cellular ganglioside expression in neuronal and glial cell lines. In addition to these cell lines, several human tumor cell lines including astrocytoma cells, neuroblastoma cells, T-cell leukemia cells and kidney cells derived from normal human and monkey were infected with HSV-1 as well as HSV-2. To measure changes in ganglioside-related gene expressions and gangliosides levels in cells, quantitative PCR and glycosphingolipid-glycomic analysis were performed. Changes in gene expression of glycosyltransferases and sialyltransferases were observed in HSV-1- and HSV-2-infected cells, although with different trends. 39 glycosphingolipid-glycans were quantitatively analyzed. HSV-1 and HSV-2 infections resulted in changes in the total amount of gangliosides depending on the cell lines used and type of virus. Qualitative changes caused by each infection of HSV-1 and HSV-2 were almost negligible.

ST6GALNAC5 Expression Decreases the Interactions between Breast Cancer Cells and the Human Blood-Brain Barrier.

The ST6GALNAC5 gene that encodes an α2,6-sialyltransferase involved in the biosynthesis of α-series gangliosides, was previously identified as one of the genes that mediate breast cancer metastasis to the brain. We have shown that the expression of ST6GALNAC5 in MDA-MB-231 breast cancer cells resulted in the expression of GD1α ganglioside at the cell surface. By using a human blood-brain barrier in vitro model recently developed, consisting in CD34+ derived endothelial cells co-cultivated with pericytes, we show that ST6GALNAC5 expression decreased the interactions between the breast cancer cells and the human blood-brain barrier.

English

Sialic acid O-acetylation is a developmentally regulated modification of gangliosides implicated in ontogeny and tumor progression. Their existence has been underestimated in the past because of their alkali-labile nature and their transient expression. New data indicates, however, that O-acetylated gangliosides perform important function in tumor malignancy. Best studied O-acetyl-GD3 blocks the pro-apoptotic activity of GD3 and promotes survival of cancer cells. In acute lymphoblastic leukaemia cells, O-acetyl-GD3 expression level also correlates with survival and drug resistance. The recent identification of the enigmatic O-acetyltransferase opens new experimental approaches for designing novel effective therapeutics targeting drug-resistant cancer cells in acute lymphoblastic leukaemia. In addition, O-acetylated gangliosides expressed at the tumor cell surface are accessible for specific monoclonal antibodies to inhibit cell growth, to induce apoptosis, and to inhibit tumor metastasis formation. Thus, passive immunotherapy using murine or murine/human chimeric monoclonal anti-O-acetylated ganglioside antibodies are currently being investigated. Particularly, targeting of O-acetyl-GD2 could reduce the acute toxicities currently associated with anti-GD2 therapeutic antibodies. This review summarizes the molecular mechanisms involved in the biosynthesis and the expression of O-acetylated gangliosides and presents the new experimental approaches that allow the characterization of their importance in tumor progression. The different strategies used by different teams to develop specific monoclonal antibodies against these poorly immunogenic glycolipids for therapeutic application are also discussed.

Frequent co-expression of EGFR and NeuGcGM3 ganglioside in cancer: it's potential therapeutic implications.

Interaction between epidermal growth factor receptor (EGFR) signaling with GM3 ganglioside expression has been previously described. However, little is known about EGFR and NeuGcGM3 co-expression in cancer patients and their therapeutic implications. In this paper, we evaluate the co-expression of EGFR and NeuGcGM3 ganglioside in tumors from 92 patients and in two spontaneous lung metastasis models of mice (Lewis lung carcinoma (3LL-D122) in C57BL/6 and mammary carcinoma (4T1) in BALB/c). As results, co-expression of EGFR and NeuGcGM3 ganglioside was frequently observed in 63 of 92 patients (68 %), independently of histological subtype. Moreover, EGFR is co-expressed with NeuGcGM3 ganglioside in the metastasis of 3LL-D122 and 4T1 murine models. Such dual expression appears to be therapeutically relevant, since combined therapy with mAbs against these two molecules synergistically increase the survival of mice treated. Overall, our results suggest that NeuGcGM3 and EGFR may coordinately contribute to the tumor cell biology and that therapeutic combinations against these two targets might be a valid strategy to explore.

Glycosylation Changes Triggered by the Differentiation of Monocytic THP-1 Cell Line into Macrophages

The human acute monocytic leukemia cell line THP-1 is widely used as an in vitro phagocytic cell model because it exhibits several immune properties similar to native monocyte-derived macrophages. In this study, we investigated the alteration of N- and O-linked glycans as well as glycosphingolipids, during THP-1 differentiation, combining mass spectrometry, flow cytometry, and quantitative real-time PCR. Mass spectrometry revealed that macrophage differentiation led to a marked upregulation of expression of GM3 ganglioside as well as an increase in complex-type structures, particularly triantennary glycans, occurring at the expense of high-mannose N-glycans. Moreover, we observed a slight decrease in the proportion of multifucosylated N-glycans and α2,6-sialylation. The uncovered changes in glycosylation correlated with variations of gene expression of relevant glycosyltransferases and glycosidases including sialyltransferases, β-N-acetylglucosaminyltransferases, fucosyltransferases, and neuraminidase. Furthermore, using flow cytometry and antibodies directed against glycan structures, we confirmed that the alteration of glycosylation occurs at the cell surface of THP-1 macrophage-like cells. Altogether, we established that macrophagic maturation of THP-1 induces dramatic modifications of the surface glycosylation pattern that may result in differential interaction of monocytic and macrophagic THP-1 with immune or bacterial lectins.

Involvement of oxidative stress and impaired lysosomal degradation in amiodarone‐induced schwannopathy

Amiodarone hydrochloride (AMD), an anti-arrhythmic agent, has been shown to cause peripheral neuropathy; however, its pathogenesis remains unknown. We examined the toxic effects of AMD on an immortalized adult rat Schwann cell line, IFRS1, and cocultures of IFRS1 cells and adult rat dorsal root ganglion neurons or nerve growth factor-primed PC12 cells. Treatment with AMD (1, 5, and 10μm) induced time- and dose-dependent cell death, accumulation of phospholipids and neutral lipids, upregulation of the expression of gangliosides, and oxidative stress (increased nuclear factor E2-related factor in nuclear extracts and reduced GSH/GSSG ratios) in IFRS1 cells. It also induced the upregulation of LC3-II and p62 expression, with phosphorylation of p62, suggesting that deficient autolysosomal degradation is involved in AMD-induced IFRS1 cell death. Furthermore, treatment of the cocultures with AMD induced detachment of IFRS1 cells from neurite networks in a time- and dose-dependent manner. These findings suggest that AMD-induced lysosomal storage accompanied by enhanced oxidative stress and impaired lysosomal degradation in Schwann cells might be a cause of demyelination in the peripheral nervous system.

Enhanced expression of unique gangliosides with GM2-determinant in human uterine cervical carcinoma-derived cell lines

Monoclonal antibody YHD-06 generated by immunization with GM2 reacted with gangliosides with GM2-determinant, i.e., GM2, GalNAc-GM1b and GalNAc-GD1a, among which GalNAc-GD1a was characterized as an antigen of autoimmune peripheral neuropathies including Guillain-Barré syndrome. When glycolipids were examined by TLC-immunostaining with YHD-06 in seven human cervical carcinoma-derived cell lines, GM2 was found in all cell lines, amounting to 15.5% to 57.5% of total gangliosides. Whereas GalNAc-GD1a was present in three cell lines, amounting to 5.4-17.5% of total gangliosides, and GalNAc-GM1b in four cell lines in amounts of less than 2%. The elevated amounts of gangliosides with GM2 determinant were closely correlated with the relative intensities of gene expression of GalNAc transferase, this being characteristic of cervical carcinoma-derived cells. However, in tissues from patients with several histological types of cervical carcinomas, GM3 was ubiquitously expressed in amounts of more than 66% of total gangliosides, GM2 was expressed in only five of 15 tissues, and both GalNAc-GM1b and GalNAc-GD1a were not even detected in trace amounts. Since GM1 was detected in all tissues in amounts of less than 0.06μg/mg dried tissue, all cervical carcinoma tissues were revealed to exhibit GM2 synthesis, indicating that enhanced synthesis of gangliosides with GM2 determinant is a characteristic of cultivated cells in vitro. Similarly, although I(3)SO3-GalCer was not present in the squamous cell carcinoma (SCC) tissues, SCC-derived cells selectively expressed II(3)SO3-LacCer. Since enhanced synthesis of GM2 has been reported in SV-40 virus-transfected fibroblasts, papilloma virus might be involved in the expression of GM2 in cervical carcinoma-derived cells.

Ganglioside as a Therapy Target in Various Types of Cancer.

Since their discovery in 1940, it has been well established that gangliosides are associated with a number of biological pathways and cellular processes such as growth, differentiation and toxin uptake. Gangliosides are glycosphingolipids containing neuraminic acid which are expressed on the plasma membrane of cells particularly in the nervous system. Heterogeneity and structural variation in the carbohydrate chains of gangliosides contributes to unique features of each of these molecules. Thirty five years ago it was discovered that aberrant glycosylation occurs in a variety of human cancers, including aberrant glycosylation of gangliosides. Ganglioside expression in terms of quality and quantity varies in different cancers and different roles may be played. Gangliosides, by affecting the immune system, including esxpression of cytokines and adhesion molecules, may inhibit anti-tumor mechanisms, as well as having direct impact on angiogenesis, cell movement and metastasis. It should be noted that different kinds of gangliosides do not all act by the same mechanisms.

Interactions between Campylobacter jejuni and AB5 toxins in the gut

Campylobacter jejuni is a ubiquitous commensal in chickens, but a major cause of human diarrheal disease worldwide. To avoid immune detection by its host, most C. jejuni isolates express human ganglioside‐mimicking lipooligosaccharide (LOS) structures and it has been shown that host recognition of these antigens as non‐self results in the development of Guillain‐Barré syndrome. In addition to immune evasion, expression of ganglioside mimics in C. jejuni has been associated with improved host cell invasion and resistance to human serum. Although only positive benefits for ganglioside mimic expression have been described for C. jejuni, the organism has the ability to quickly switch off the mimicry through a phase‐variable galactosyltransferase, CgtB, involved in LOS biosynthesis. Vibrio cholerae secretes the bacteriophage‐encoded cholera toxin (CT) which binds to GM1 ganglioside structures on human cells as well as to C. jejuni GM1 ganglioside‐mimics. Enterotoxigenic Escherichia coli secretes heat‐labile enterotoxin I (LT), which also binds to these structures. Since C. jejuni, V. cholerae and E. coli can co‐infect the same niche, we examined the effects of these AB5 toxins on C. jejuni biology in order to determine if this relationship could represent a new mechanism for interpathogen competition in the intestine. We demonstrate that CT and LT specifically bind only to C. jejuni strains expressing GM1 mimics. Interestingly, our experiments show that addition of CT or LT to C. jejuni strains expressing GM1‐mimicking LOS partially clears cell growth on agar. LOS from bacteria remaining inside these zones of clearance was isolated and compared to LOS from untreated bacteria. SDS‐PAGE and silver staining of the LOS showed the loss of a band from the exposed cells compared to untreated cells, and Western blot analysis revealed reduced binding of LOS to CT. Sequencing cgtB in these two groups demonstrated that this enzyme is “on” or “off” in the unexposed group, while cgtB in the CT‐ and LT‐treated cells showed a frameshift mutation, causing premature truncation of the galactosyltransferase. Examination of an engineered E. coli strain expressing GM1 mimics shows that CT is capable of binding to the mimicking cells without inducing growth clearance, pointing toward a Campylobacter‐specific mechanism of action. These results suggest that CT and LT have a negative influence on C. jejuni and could contribute to competition between these pathogens. Further studies describing the interactions between these zoonotic pathogens, the resident gut microbiome and poultry will be described.Support or Funding InformationCMS is an Alberta Innovates Technology Futures iCORE Strategic Chair in Bacterial Glycomics.

Cytotoxic activity against human neuroblastoma and melanoma cells mediated by IgM antibodies derived from peripheral blood of healthy donors.

A small percentage of healthy donors identified in the Western population carry antibodies in their peripheral blood which convey cytotoxic activity against certain human melanoma and neuroblastoma cell lines. We measured the cytotoxic activity of sera and plasmas from healthy donors on the human neuroblastoma cell line Kelly and various melanoma cell lines. Antibodies of IgM isotype, presumably belonging to the class of naturally occurring antibodies, exerted cytotoxic activity in a complement-dependent fashion. Apart from complement-dependent tumor cell lysis, we observed C3 opsonization in all tumor cell lines upon treatment with cytotoxic plasmas. Cell lines tested primarily expressed membrane complement regulatory proteins (mCRP) CD46, CD55 and CD59 to various extents. Blocking of mCRPs by monoclonal antibodies enhanced cell lysis and opsonization, though some melanoma cells remained resistant to complement attack. Epitopes recognized by cytotoxic antibodies were represented by gangliosides such as GD2 and GD3, as evidenced by cellular sialidase pretreatment and enhanced expression of distinct gangliosides. It remains to be clarified why only a small fraction of healthy persons carry these antitumor cytotoxic antibodies.

Progenitor/Stem Cell Markers in Brain Adjacent to Glioblastoma: GD3 Ganglioside and NG2 Proteoglycan Expression.

Characterization of tissue surrounding glioblastoma (GBM) is a focus for translational research because tumor recurrence invariably occurs in this area. We investigated the expression of the progenitor/stem cell markers GD3 ganglioside and NG2 proteoglycan in GBM, peritumor tissue (brain adjacent to tumor, BAT) and cancer stem-like cells (CSCs) isolated from GBM (GCSCs) and BAT (PCSCs). GD3 and NG2 immunohistochemistry was performed in paired GBM and BAT specimens from 40 patients. Double-immunofluorescence was carried out to characterize NG2-positive cells of vessel walls. GD3 and NG2 expression was investigated in GCSCs and PCSCs whose tumorigenicity was also evaluated in Scid/bg mice. GD3 and NG2 expression was higher in tumor tissue than in BAT. NG2 decreased as the distance from tumor margin increased, regardless of the tumor cell presence, whereas GD3 correlated with neoplastic infiltration. In BAT, NG2 was coexpressed with a-smooth muscle actin (a-SMA) in pericytes and with nestin in the endothelium. Higher levels of NG2 mRNA and protein were found in GCSCs while GD3 synthase was expressed at similar levels in the 2 CSC populations. PCSCs had lower tumorigenicity than GCSCs. These data suggest the possible involvement of GD3 and NG2 in pre/pro-tumorigenic events occurring in the complex microenvironment of the tissue surrounding GBM.