THE ROLE OF SPARC IN GLIOMA INVASION

描述（由申请人提供）：胶质瘤患者的不良预后主要是由于这些肿瘤的高度侵袭性。富含半胱氨酸的酸性分泌蛋白在胶质瘤中高表达。我们已经证明，在体外和体内，促进胶质瘤的侵袭，同时减缓胶质瘤的增殖具有不同的效果。改变这些表型的能力使其成为治疗胶质瘤的主要治疗靶点。然而，目前尚不清楚这两种机制是否可以独立靶向，从而允许抑制其在入侵中的作用，但允许其生长抑制作用。此外，侵袭性表型是复杂的，需要肿瘤细胞运动性的变化以及细胞外基质（ECM）的降解来为浸润细胞提供空间。联合国在这两项职能中的作用可能也需要分别加以定位。此外，目前还不知道脑内神经元是否在细胞内起作用，或者脑内内源性神经元对这一过程的贡献（如果有的话）是什么。我们提出，ECM的降解，肿瘤细胞的运动性，肿瘤细胞增殖，通过不同的机制调节。以下具体目的旨在表征这些独立途径。在具体目标1中，我们将描述细胞外的机制，通过它来调节体外侵袭。这一目标将侧重于通过增加相邻ECM的降解来促进入侵的能力。特别是，我们将研究其与ECM蛋白玻连蛋白，与调节ECM降解（MMP-2，MT 1-MMP，PA 1 -1）和α v整联蛋白的SPARC上调酶的相互作用。在具体目标2中，我们将描述细胞外的机制，通过它来调节体内侵袭。我们将在体内进行平行实验，以确定内源性β-淀粉样蛋白是否在SPARC诱导的侵袭中起作用，以及诱导的侵袭是否可以通过干扰整合素和/或MMP活性来抑制。在特定目标3中，我们将确定肿瘤细胞中的cytokine的丢失是否足以抑制肿瘤侵袭并增加体内肿瘤生长和增殖。我们将使用由p53-/- / Sparc +/+与p53-/- / Sparc -/-转化的星形胶质细胞组成的新型肿瘤模型来确定p53-/- / Sparc +/+肿瘤的丢失是否将高度侵袭性的p53-/- / Sparc +/+肿瘤转化为非侵袭性的高度增殖性肿瘤。在具体目标4中，我们将确定是否通过β 1整合素依赖或非依赖的细胞内信号转导介导的运动，但不增殖。我们还将确定是否Escherichia coli的调节表型的结果在细胞与细胞外定位的差异。

DESCRIPTION (provided by applicant): The poor prognosis of glioma patients is largely due to the highly invasive nature of these tumors. Secreted protein acidic and rich in cysteine (SPARC) is highly expressed in gliomas. We have demonstrated that SPARC has disparate effects in vitro and in vivo, promoting glioma invasion while slowing glioma proliferation. The ability to alter these phenotypes makes it a prime therapeutic target for the treatment of gliornas. However, it is not known whether these two mechanisms can be targeted independently, thereby allowing the inhibition of its role in invasion but permitting its growth-suppressive effect. In addition the invasive phenotype is complex, requiring both changes in tumor cell motility as well as degradation of the extracellular matrix (ECM) to provide space for infiltrating cells. SPARC's role in both of these functions may also need to be targeted separately. Furthermore, it is not known if SPARC functions within the cell, or what contribution, if any, brain endogenous SPARC may contribute to the process. We propose that SPARC modulates ECM degradation, tumor cell motility, and tumor cell proliferation via separate mechanisms. The following Specific Aims are directed at characterizing these independent pathways. In Specific Aim 1, we will characterize the extracellular mechanisms by which SPARC modulates invasion in vitro. This aim will focus on SPARC's ability to promote invasion by increasing the degradation of the adjacent ECM. In particular, we will examine its interactions with the ECM protein vitronectin, with the SPARC-upregulated enzymes that modulate ECM degradation (MMP-2, MT1-MMP, PAl-1), and the alpha v integrins. In Specific Aim 2, we will characterize the extracellular mechanisms by which SPARC modulates invasion in vivo. We will perform parallel experiments in vivo to determine whether endogenous SPARC plays a role in SPARC-induced invasion and whether the induced invasion can be inhibited by interfering with integrin and/or MMP activity. In Specific Aim 3, we will determine whether the loss of SPARC in tumor cells is sufficient to inhibit tumor invasion and increase tumor growth and proliferation in vivo. We will use a novel tumor model consisting of p53-/- / Sparc +/+ versus p53-/- / Sparc -/-transformed astrocytes to determine whether the loss of SPARC converts the highly invasive p53-/- / Sparc +/+ tumors into noninvasive, highly proliferative tumors. In Specific Aim 4, we will determine whether SPARC mediates motility, but not proliferation, via beta1 integrin-dependent or -independent intracellular signaling. We will also determine whether SPARC's regulation of the phenotypes results from differences in cellular versus extracellular localization.