Integrins and Caspase 8 in Tumor Progression

描述(申请人提供)：在之前的资助期间，我们证明了caspase 8与体内未连接的整合素联合促进了细胞凋亡，而caspase 8或整合素在神经母细胞瘤中的下调促进了肿瘤转移。在这些研究中，我们证实了细胞凋亡的滚动，我们进行了矛盾的观察，在凋亡抵抗细胞中，caspase8的表达显著促进了整合素介导的体外迁移和体内转移。因此，这项建议的总体目标是了解caspase 8的凋亡与非凋亡功能是如何调节的。作为caspase的起始者，caspase 8在死亡受体、Toll样受体和整合素下游触发细胞凋亡。它在侵袭性神经母细胞瘤和其他神经内分泌肿瘤中经常缺失。这促使临床策略寻求恢复或放大其表达。然而，caspase 8不足以诱导细胞凋亡，但需要顺应的下游caspase级联反应。在凋亡受损的细胞中，我们提供了caspase8表达实际上促进肿瘤转移的证据。这一令人惊讶的结果值得重新考虑，即简单上调caspase 8是普遍有益的；相反，它可能会加剧疾病的进展。虽然caspase 8在免疫和血管内的非凋亡功能是已知的，但使caspase 8发挥这些功能的机制尚不清楚。在这里，我们提供的初步结果表明，在整合素结扎后，细胞迁移增强与caspase8酪氨酸磷酸化和局灶性粘连接触的定位同步发生。这项提案的目标1将描述黏附过程中磷酸化的特定caspase 8酪氨酸残基，并确定那些对迁移至关重要的残基。目的2将评估哪些酪氨酸残基影响caspase8催化和促凋亡活性，包括蛋白质-蛋白质相互作用。最后，AIM 3将测试这些调节酪氨酸残基对体内疾病进展的影响。综上所述，这些研究结果将揭示caspase 8调控的分子机制，这对抗转移治疗的发展至关重要。 公共卫生相关性：众所周知，caspase 8蛋白与细胞程序性死亡有关，它在侵袭性神经内分泌肿瘤中的表达受到抑制。然而，caspase 8也可以促进细胞迁移，我们发现它实际上增强了抗死亡细胞的扩散，这可能解释了为什么它在癌症中频繁上调。这项提议试图了解控制caspase 8在这两个角色之间切换的分子机制。

DESCRIPTION (provided by applicant): During the previous funding period, we demonstrated that caspase 8 association with unligated integrins in vivo promoted apoptosis, and that down-regulation of caspase 8 or integrins in neuroblastoma promoted tumor metastasis. Confirming the roll of apoptosis in these studies, we made the paradoxical observation that, among apoptosis-resistant cells, the expression of caspase 8 significantly enhanced integrin-mediated migration in vitro and metastasis in vivo. The overall goal of this proposal is therefore to understand how caspase 8 apoptotic vs nonapoptotic function is regulated. As an initiator caspase, caspase 8 triggers apoptosis downstream of death receptors, toll-like receptors and integrins. Its expression is frequently lost among aggressive neuroblastoma and other neuroendocrine tumors. This has prompted clinical strategies seeking to restore or amplify its expression. However, caspase 8 is not sufficient for apoptosis, but requires a compliant downstream caspase cascade. Among apoptosis-compromised cells, we provide evidence that caspase 8 expression actually functions to enhance tumor metastasis. This surprising result warrants reconsideration of the concept that simple upregulation of caspase 8 is universally beneficial; rather, it may exacerbate disease progression. While nonapoptotic functions of caspase 8 within the immune and vascular compartments are known, the mechanisms committing caspase 8 to these functions are not. Here, we provide preliminary results showing that enhanced cell migration occurs concurrent with caspase 8 tyrosine phosphorylation and localization in focal adhesion contacts following integrin ligation. AIM 1 of this proposal will characterize the specific caspase 8 tyrosine residues phosphorylated during adhesion, and identify those critical for migration. AIM 2 will evaluate which tyrosine residues influence caspase 8 catalytic and proapoptotic activities, including protein-protein interactions. Finally, AIM 3 will test the impact of these regulatory tyrosine residues on disease progression in vivo. Together, the results of these studies will reveal molecular mechanisms of caspase 8 regulation important for the development of anti-metastatic therapies. PUBLIC HEALTH RELEVANCE: The protein "caspase 8" is well known to be involved in programmed cell death, and its expression is suppressed among aggressive neuroendocrine tumors. However, caspase 8 can also promote cell migration, and we show that it actually enhances the spread of death-resisting cells, which may explain why it is frequently upregulated in carcinoma. This proposal seeks to understand the molecular mechanisms that control caspase 8 switching between these two roles.