Glycosphingolipid Effects on Brain Tumor Angiogenesis

描述(申请人提供)：这项研究的目的是确定神经鞘糖脂在脑肿瘤生长和血管生成(即血管生成)中的作用。神经节苷脂是一种含唾液酸的糖脂，富含在质膜中，从肿瘤细胞释放到细胞外基质中。神经节苷脂可能通过对肿瘤细胞和肿瘤相关宿主细胞，如内皮细胞和巨噬细胞的多方面作用而影响脑肿瘤血管生成。本实验室的初步发现表明，在实验性小鼠脑瘤中，简单的单唾液酸神经节苷脂GM3具有抗血管生成作用，而更复杂的神经节苷脂(GM2、GM1、GDLA和GT1b)具有促血管生成作用。我们认为改变肿瘤神经节苷脂的组成会影响肿瘤的生长和血管。我们将通过操纵GalNAc转移酶(GalNAc-T)和唾液酸基转移酶2(SAT-2)的基因来检验这一假设，这两种酶是合成复杂神经节苷脂所必需的。这些基因将在三种成熟的实验性脑肿瘤，即小鼠EPEN和CT-2A肿瘤以及人脑胶质瘤U87的稳定转染体中上调或下调。这些肿瘤是建议研究的良好模型，因为它们在神经节苷脂成分、血管和生长速度上有所不同。对照未转染或载体转染的肿瘤将与其稳定的转染体进行比较，并将作为体内生长的实体瘤和体外生长的细胞系进行研究。通过分析微血管密度、肿瘤生长速度、血管内皮生长因子(VEGF)的表达和巨噬细胞的浸润来评估体内肿瘤血管生成的程度。神经节苷脂影响血管生成的机制将通过培养的内皮细胞和血管生成的Matrigel Plug模型来检验。这项拟议的研究将更好地确定神经节苷脂和肿瘤血管生成之间的关系，并可能导致治疗脑肿瘤的新的实验策略。

DESCRIPTION (provided by applicant): The objective of this research is to define the role of glycosphingolipids in brain tumor growth and vascularity (i.e., angiogenesis). Gangliosides are sialic acid-containing glycolipids that are enriched in plasma membranes and are shed from tumor cells into the extracellular matrix. Gangliosides may influence brain tumor angiogenesis through multiple effects on the tumor cells and tumor associated host cells, e.g., endothelial cells and macrophages. Preliminary findings from this laboratory suggest that the simple monosialoganglioside GM3 is antiangiogenic and that more complex gangliosides (GM2, GM1, GDla and GTlb) are proangiogenic in experimental mouse brain tumors. We propose that altering tumor ganglioside composition will influence tumor growth and vascularity. We will test this hypothesis by manipulating the genes for GalNAc transferase (GalNac-T) and sialyltransferase 2 (SAT-2), two essential enzymes required for the synthesis of complex gangliosides. These genes will be up-regulated or down-regulated in stable transfectants of three well-established experimental brain tumors, i.e., the mouse EPEN and CT-2A tumors and the human glioma U87. These tumors are good models for the proposed studies because they differ in ganglioside composition, vascularity, and growth rate. Control untransfected or vector transfected tumors will be compared with their stable transfectants and will be studied as solid tumors grown in vivo and as cell lines grown in vitro. The degree of tumor angiogenesis in vivo will be assessed from analysis of microvessel density, tumor growth rate, vascular endothelial growth factor (VEGF) expression, and macrophage infiltration. The mechanisms by which gangliosides influence angiogenesis will be examined using cultured endothelial cells and the Matrigel plug model of angiogenesis. The proposed research will better define the relationship between gangliosides and tumor angiogenesis and can lead to new experimental strategies for managing brain tumors.