Interaction between Tissue Factor, Junctional Adhesion Molecule-A, and Integrin B1 to drive self-renewal in glioblastoma

项目摘要 胶质母细胞瘤（GBM）是成人大脑中最常见的癌症，几乎在所有情况下都是致命的。一个关键 GBM患者预后不良的一个因素是一种称为癌症干细胞的细胞亚群 （CSC），其对常规使用的遗传毒性/细胞毒性疗法具有高度抗性，并最终表现为 复发性肿瘤因此，抑制在治疗中存活的CSC的肿瘤复发将改善GBM 患者结局。我们的初步和最近发表的工作表明，CSC的生存依赖于组织 凝血因子（TF），一种保守的跨膜分泌蛋白，参与血液凝固。TF激活蛋白酶- 活化受体2（PAR 2），GBM细胞上的G蛋白偶联受体，促进CSC维持 和扩增，如通过分析CSC的标记物表达、自我更新能力和体内生长所指示的。 TF抑制大大减少了CSC亚群，在某些情况下甚至导致肿瘤完全根除 in vivo. TF-PAR 2信号传导对CSC的保护和增殖作用似乎是通过激活 多种类型的致癌受体酪氨酸激酶（RTK），如EGFR，虽然其机制， TF-PAR 2-RTK刺激CSC尚不清楚。我们的初步数据还表明，TF与 连接粘附分子-A（JAM-A）的表达，JAM-A是一种通过稳定 整合素β1。CSC依赖于这种细胞间粘附，我们的数据表明，JAM-A是CSC所必需的 GBM中的行为。由于TF也可以通过整合素β1信号，我们的总体假设是，TF 上调JAM-A表达，稳定整合素β1，增强TF作用于整合素β1的能力 并促进GBM的自我更新。这具有治疗相关性，因为TF的促CSC作用是 独立于其止血作用，阻断JAM-A可能会降低TF的促肿瘤作用， 而不会导致直接靶向TF所导致的出血。在具体目标1中，我们将检验假设 TF通过PAR 2-RTK信号驱动JAM-A表达。我们将确定TF-PAR 2的组成部分 复合物是TF-PAR 2促肿瘤活性所必需的，并将测试TF触发JAM-A的能力 表达，同时抑制RTK信号传导的每个主要下游途径。在第二阶段，我们将 确定JAM-A是否需要丝氨酸蛋白酶抑制剂B3，一种我们已经证明与JAM-A结合的丝氨酸蛋白酶抑制剂， 支持CSC的活动在特定目标3中，我们将使用分子敲除来确定JAM-A是否是一种特异性靶基因。 有效治疗靶点针对侵袭性、高表达TF的GBM。该项目的完成将提前 我们对CSC亚群如何在GBM中维持的理解，很可能适用于广泛的 并将在治疗许多恶性肿瘤方面展示一种引人注目的新治疗靶点， 包括GBM。

PROJECT SUMMARY Glioblastoma (GBM) is the most common cancer arising in the adult brain, and is lethal in nearly all cases. A key contributing factor to poor outcomes for GBM patients is a subpopulation of cells, known as cancer stem cells (CSCs), that are highly resistant to routinely used genotoxic/cytotoxic therapies, and ultimately manifest as recurrent tumor. Inhibiting tumor recurrence from CSCs that survive therapy would therefore improve GBM patient outcomes. Our preliminary and recently published work show that CSC survival is dependent on Tissue Factor (TF), a conserved transmembrane and secreted protein involved in blood clotting. TF activates protease- activated receptor 2 (PAR2), a G-protein-coupled receptor on GBM cells, which promotes CSC maintenance and expansion, as indicated by analysis of marker expression, self-renewal capacity, and in vivo growth of CSCs. TF suppression greatly reduces CSC subpopulations, in some cases even leading to complete tumor eradication in vivo. Protective and proliferative effects of TF-PAR2 signaling on CSCs appears to be through activation of multiple classes of oncogenic receptor tyrosine kinases (RTKs) like EGFR, although the mechanism by which TF-PAR2-RTKs stimulate CSCs is unclear. Our preliminary data also show that TF positively correlates with expression of Junctional Adhesion Molecule-A (JAM-A), a protein that promotes cell-cell adhesion by stabilizing integrin β1. CSCs depend on such cell-cell adhesion, and our data show that JAM-A is necessary for CSC behavior in GBM. Because TF can also signal through integrin β1, our overarching hypothesis is that TF upregulates JAM-A expression, which stabilizes integrin β1 and enhances the ability of TF to act on integrin β1 and promote self-renewal in GBM. This has therapeutic relevance, because the pro-CSC effects of TF are independent of its role in hemostasis, and blocking JAM-A could potentially reduce the pro-tumor effects of TF, without causing bleeding that would result from targeting TF directly. In Specific Aim 1, we will test the hypothesis that TF drives JAM-A expression through PAR2-RTK signaling. We will identify components of the TF-PAR2 complex that are essential for TF-PAR2 pro-tumor activities, and will test the ability of TF to trigger JAM-A expression while inhibiting each major downstream pathway of RTK signaling. In Specific Aim 2, we will determine whether JAM-A requires serpin B3, a serine-protease inhibitor that we have shown binds to JAM-A, for its pro-CSC activities. In Specific Aim 3, we will use molecular knockouts to determine whether JAM-A is an effective therapeutic target against aggressive, high TF-expressing GBM. Completion of this project will advance our understanding of how CSC subpopulations are maintained in GBM, could well be applicable to a wide range of cancers, and would demonstrate a compelling new therapeutic target in treating numerous malignancies, including GBM.