Synthesis of oligosaccharide inhibitors of neural cell division

Inhibitors of Glioma Growth that Reveal the Tumour to the Immune System

Treated glioblastoma patients survive from 6 to 14 months. In the first part of this review, we describe glioma origins, cancer stem cells and the genomic alterations that generate dysregulated cell division, with enhanced proliferation and diverse response to radiation and chemotherapy. We review the pathways that mediate tumour cell proliferation, neo-angiogenesis, tumor cell invasion, as well as necrotic and apoptotic cell death. Then, we examine the ability of gliomas to evade and suppress the host immune system, exhibited at the levels of antigen recognition and immune activation, limiting the effective signaling between glioma and host immune cells.The second part of the review presents current therapies and their drawbacks. This is followed by a summary of the work of our laboratory during the past 20 years, on oligosaccharide and glycosphingolipid inhibitors of astroblast and astrocytoma division. Neurostatins, the O-acetylated forms of gangliosides GD1b and GT1b naturally present in mammalian brain, are cytostatic for normal astroblasts, but cytotoxic for rat C6 glioma cells and human astrocytoma grades III and IV, with ID50 values ranging from 200 to 450 nM. The inhibitors do not affect neurons or fibroblasts up to concentrations of 4 μM or higher.At least four different neurostatin-activated, cell-mediated antitumoral processes, lead to tumor destruction: (i) inhibition of tumor neovascularization; (ii) activation of microglia; (iii) activation of natural killer (NK) cells; (iv) activation of cytotoxic lymphocytes (CTL). The enhanced antigenicity of neurostatin-treated glioma cells, could be related to their increased expression of connexin 43. Because neurostatins and their analogues show specific activity and no toxicity for normal cells, a clinical trial would be the logical next step.

Isolation and purification of an epidermal growth factor receptor-related inhibitor of cell growth from cultured rat astrocytes

Astrocytes rarely undergo mitotic cell division in the developed adult. However, following injury to the central nervous system (CNS), astrocytes undergo rapid cell division and reactive astrocytes encapsulate exposed areas of the CNS producing a glial scar. Studies indicate the existence of a family of epidermal growth factor receptor (EGFr) related glycosidic mitogen inhibitors with growth inhibiting properties for astrocytes. Here, for the first time, we describe the isolation of such a factor from cultured rat astrocytes by ion-exchange and immunoaffinity chromatography. The isolated factor is glycosidic in nature, cross reacts with the anti-EGFr monoclonal antibody Clone 29.1, and inhibits the growth of primary astrocytes and N2a neuroblastoma cells in vitro.

Control of glial number: purification from mammalian brain extracts of an inhibitor of astrocyte division

Inhibitors of astrocyte cell division, immunologically related to the sugar moiety of epidermal growth factor receptor and to blood group antigens, have been purified from mammalian brain extracts. Mass spectra, high resolution proton magnetic resonance spectra, and chemical and enzymic analysis of the purified fraction indicated that the compounds isolated were glycosphingolipids, although signals compatible with the presence of aminoacid residues were also observed. Lectin binding indicated the presence of NAc-Neuraminic acid, NAc-glucosamine, fucose, galactose, and glucose. The inhibitor was cytostatic for astrocytes, C6 glioma cells, and endothelial cells, with approximate ID50 of 250 nM. Primary cultures of fibroblasts or 3T3 cells were not affected up to concentrations of 800 nM. Concentrations of the inhibitor of 800 nM or higher, caused non-specific cytotoxicity. The biological and immunological properties of this brain inhibitor were identical to those of the EGF receptor-related inhibitor previously described with the acronym ERI. Because of its source and cytostatic action, the glial inhibitor has been renamed neurostatin. Rabbit antibodies to neurostatin immunostained astrocytes and neurons, both in culture and in tissue sections.

Inhibition of proliferation of normal and transformed neural cells by blood group-related oligosaccharides

A synthetic tetrasaccharide structurally related to blood groups and selectin ligands inhibited division of astrocytes, gliomas, and neuroblastomas at micromolar concentrations. The compound was cytostatic for primary astrocytes in culture, but cytotoxic for fast proliferating cell lines.