Integrins and Caspase 8 in Neuroblastoma Progression

描述(由申请人提供)：本提案的总体目标是了解神经母细胞瘤恶性表型的调节机制。神经母细胞瘤(NB)是儿科最常见的实体瘤，占所有儿童癌症的7-10%。NB进展为侵袭性的播散性疾病，称为IV期NB，其特征是肿瘤广泛扩散，并在包括骨髓在内的特权部位定居。目前的治疗效果有限，与晚期疾病相关的死亡率很高(约70%)。最恶性的NB(IV期)的一个特征是caspase8的表达完全丧失。我们在这里表明，caspase8的这种缺失与对一种被称为整合素介导的死亡的凋亡形式的抵抗有关，在这种形式中，细胞凋亡是由未连接的细胞表面整合素触发的。Caspase8的缺失与整合素功能的其他改变有关，包括恶性NB对ECM的黏附减少和迁移/侵袭增加。重要的是，正如我们在初步结果中所显示的那样，caspase8表达的生理水平的稳定重建在体外逆转了IV期NB的每一个属性。此外，初步研究表明，caspase8的重新表达可阻断体内IV期NB的转移。因此，我们建议研究半胱氨酸天冬氨酸氨基转移酶8调节晚期神经母细胞瘤恶性特征的分子机制。在最初的目标中，我们将进行分子图谱研究，以确定未连接的整合素如何招募和激活caspase8，促进体外培养的NB肿瘤细胞的凋亡。在Aim 2中概述的研究将集中于caspase 8增加ECM黏附和影响NB细胞迁移的机制。最后，在第三个目标中，我们将检查这些事件对NB进展和体内传播的影响。对这些分子机制的理解对于未来针对NB恶性特性的治疗方法的设计至关重要。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to understand the mechanisms regulating the malignant phenotype of neuroblastoma. Neuroblastoma (NB) is the most common pediatric solid tumor, accounting for 7-10 percent of all childhood cancer. NB progresses to an aggressive, disseminated disease, termed stage IV NB, characterized by widespread dissemination of the tumor, and colonization of privileged sites, including bone marrow. Current treatments have limited success, and mortality associated with late stage disease is high (approximately 70%). One hallmark of the most malignant form of NB (stage IV) is the complete loss of caspase 8 expression. We show here that this loss of caspase 8 is associated with resistance to a form of apoptosis termed "Integrin-mediated Death," in which apoptosis is triggered by unligated cell-surface integrins. Loss of caspase 8 is associated with other alterations in integrin function, including decreased adhesion of malignant NB to ECM and increased migration/invasion. Importantly, as we show in the Preliminary Results, stable reconstitution of physiological levels of caspase 8 expression reverses each of these properties of stage IV NB in vitro. Moreover, initial studies suggest that caspase 8 re-expression blocks the metastasis of stage IV NB in vivo. We therefore propose to examine the molecular mechanisms by which caspase 8 may regulate these malignant characteristics of advanced NB. In the initial Aim, we will perform molecular mapping studies to determine how unligated integrins can recruit and activate caspase 8, promoting apoptosis among NB tumor cells in vitro. Studies outlined in Aim 2 will focus on the mechanisms by which caspase 8 increase ECM adhesion and influence the migration of NB cells. Finally, in the third Aim we will examine the impact of these events on NB progression and dissemination in vivo. An understanding of these molecular mechanisms will be crucial for the design of future therapies that target the malignant properties of NB.