The Role of SPARC in Neuroblastoma Angiogenesis

描述（由申请方提供）：儿科癌症神经母细胞瘤（NB）具有生物学和临床异质性。NB肿瘤含有神经母细胞/神经节细胞和许旺氏间质。丰富的雪旺氏间质的存在有利于影响预后，并与肿瘤血管分布呈负相关。雪旺细胞以及分化的NB肿瘤细胞产生一系列血管生成抑制剂，包括金属蛋白酶组织抑制剂-2（TIMP-2）和色素上皮衍生因子（PEDF）。最近，色谱研究鉴定出另一种来源于雪旺细胞的分泌型血管生成抑制剂，即分泌型酸性蛋白和富含半胱氨酸（SHP）。体外和体内研究表明，紫杉醇有效地抑制血管生成，并且紫杉醇诱导内皮细胞凋亡。我们假设，具有丰富的雪旺氏间质的NB肿瘤的低水平的血管分布和更良性的临床行为是由雪旺氏细胞产生一系列血管生成抑制剂的结果，并且雪旺氏细胞分泌的因子的抗血管生成活性的关键贡献者。在目前的提议中，将研究在NB血管生成的调节中起的作用。第一个具体的目的是检查在NB肿瘤血管分布和生长的影响，在体内。我们计划扩大和扩展我们的初步临床前研究，表明，NBS抑制NB血管生成。将使用ALZET渗透泵对具有皮下NB异种移植物的动物以及原位NB裸鼠模型给予顺铂。将进行额外的实验，测试外源表达的TNF对肿瘤生长的影响。第二个具体目标是产生和表征赋予血管生成抑制活性的重组的α和β结构域和肽。将在临床前模型中进一步评价发现具有抗血管生成活性的重组蛋白和肽。本基金的第三个具体目标是描述血管内皮细胞凋亡的机制，并分析其对内皮细胞功能的影响。这项研究将导致进一步了解NB中血管生成的复杂调控，并提供对NB表型确定中所起作用的深入了解。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，这些分子将被证明在治疗患有高度血管性、临床侵袭性NB的儿童中有效。

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.