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）是最常见的儿童实体肿瘤，占所有儿童癌症的7- 10%。NB发展为侵袭性弥散性疾病，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殊部位定植。目前的治疗成功有限，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caspase 8表达的完全丧失。我们在这里表明，caspase 8的缺失与对一种称为“整合素介导的死亡”的细胞凋亡形式的抗性有关，在这种凋亡形式中，细胞凋亡是由未连接的细胞表面整合素触发的。caspase 8的缺失与整合素功能的其他改变有关，包括恶性NB对ECM的粘附减少和迁移/侵袭增加。重要的是，正如我们在初步结果中所显示的那样，在体外，caspase 8生理水平表达的稳定重建逆转了IV期NB的这些特性。此外，初步研究表明，体内再表达caspase 8可阻断IV期NB的转移。因此，我们建议研究caspase 8可能调节晚期NB这些恶性特征的分子机制。在最初的Aim中，我们将进行分子定位研究，以确定未连接的整合素如何在体外招募和激活caspase 8，促进NB肿瘤细胞的凋亡。Aim 2中概述的研究将重点关注caspase 8增加ECM粘附和影响NB细胞迁移的机制。最后，在第三个目标中，我们将研究这些事件对NB在体内进展和传播的影响。了解这些分子机制对于设计针对NB恶性特性的未来治疗方法至关重要。

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.