The Role of SPARC in Neuroblastoma Angiogenesis

描述（由申请人提供）：小儿肿瘤神经母细胞瘤（NB）具有生物学和临床异质性。NB肿瘤包含神经母细胞/神经节细胞和许旺间质。大量许旺间质的存在有利于预后，并与肿瘤血管性呈负相关。许旺细胞和分化的NB肿瘤细胞产生一系列血管生成抑制剂，包括金属蛋白酶-2 （TIMP-2）和色素上皮衍生因子（PEDF）的组织抑制剂。色谱研究最近发现了另一种源自雪旺细胞的血管生成分泌抑制剂，分泌蛋白酸性和富含半胱氨酸（SPARC）。体外和体内研究表明，SPARC能有效抑制血管生成，并诱导内皮细胞凋亡。我们假设，许旺细胞产生一系列血管生成抑制剂，导致许旺细胞间质丰富的NB肿瘤的低水平血管生成和更良性的临床行为，而SPARC是许旺细胞分泌的抗血管生成活性因子的关键因素。在目前的提案中，将研究SPARC在NB血管生成的调控中所起的作用。第一个具体目的是检查SPARC对NB肿瘤血管和体内生长的影响。我们计划扩大和扩展我们的初步临床前研究，表明SPARC抑制NB血管生成。SPARC将用于皮下NB异种移植动物以及使用ALZET渗透泵的原位NB裸鼠模型。进一步的实验将测试外源表达的SPARC对肿瘤生长的影响。第二个具体目标是生产和表征重组SPARC，以及SPARC结构域和赋予血管生成抑制活性的肽。发现具有抗血管生成活性的重组蛋白和肽将在临床前模型中进一步评估。该资助的第三个具体目的是描述SPARC诱导细胞凋亡的机制，并分析其对内皮细胞功能的影响。这项资助概述的研究将导致对NB血管生成的复杂调控的进一步理解，并提供SPARC在决定NB表型中的作用。这项研究资助的长期目标是产生有效的抗血管生成的sparc衍生分子，这些分子将被证明对治疗高血管性、临床侵袭性NB的儿童有效。

DESCRIPTION (provided by applicant): The pediatric cancer neuroblastoma (NB) is biologically and clinically heterogeneous. NB tumors contain both neuroblastic/ganglionic cells and Schwannian stroma. The presence of abundant Schwannian stroma favorably impacts prognosis and is inversely correlated with tumor vascularity. Schwann cells as well as differentiated NB tumor cells produce a spectrum of angiogenesis inhibitors including tissue inhibitor of metalloproteinase-2 (TIMP-2) and pigment epithelium-derived factor (PEDF). Chromatography studies have recently led to the identification of another Schwann cell-derived secreted inhibitor of angiogenesis, Secreted Protein Acidic and Rich in Cysteine (SPARC). In vitro and in vivo studies show that SPARC potently inhibits angiogenesis, and that SPARC induces endothelial cell apoptosis. We hypothesize that the low level of vascularity and more benign clinical behavior of NB tumors with abundant Schwannian stroma results from the Schwann cell production of a spectrum of angiogenesis inhibitors, and that SPARC is a key contributor to the anti-angiogenic activity of factors secreted by the Schwann cells. In the current proposal, the role SPARC plays in the regulation of NB angiogenesis will be investigated. The first specific aim is to examine the effects of SPARC on NB tumor vascularity and growth in vivo. We plan to expand and extend our preliminary preclinical studies that suggest that SPARC inhibits NB angiogenesis. SPARC will be administered to animals with subcutaneous NB xenografts as well as an orthotopic NB nude mouse model using ALZET osmotic pumps. Additional experiments will be performed testing the effects of exogenously expressed SPARC on tumor growth. The second specific aim is to produce and characterize recombinant SPARC, and SPARC domains and peptides that confer angiogenesis inhibitory activity. Recombinant proteins and peptides found to have anti-angiogenesis activity will be further evaluated in the preclinical models. The third specific aim of this grant is to delineate the mechanisms by which SPARC induces apoptosis and analyze its effects on endothelial cell function. The studies outlined in this grant will lead to a further understanding of the complex regulation of angiogenesis in NB, and provide insight into the role that SPARC plays in determining NB phenotype. The long-term goal of this research grant is to generate potent anti-angiogenic SPARC-derived molecules that will prove to be effective in the treatment of children with highly vascular, clinically aggressive NB.