FADD Signaling in Cancer Cells

描述（由申请人提供）：Fas相关死亡结构域（FADD）是肿瘤坏死因子相关凋亡诱导配体（TRAIL）受体信号传递所必需的衔接蛋白。TRAIL受体是癌症的重要治疗靶点，目前有6种TRAIL受体靶向药物处于临床试验阶段，还有几种处于临床前开发阶段，越来越多的证据表明，内源性TRAIL信号传导在DNA损伤剂、抗代谢物和组蛋白去乙酰化酶抑制剂等其他抗癌药物的作用机制中也很重要。FADD在TRAIL受体刺激下激活caspases的分子机制已经被很好地理解，然而TRAIL耐药的机制仍然知之甚少，这限制了我们优化使用TRAIL受体靶向药物的能力。在之前的资助期内，我们分析了TRAIL耐药和FADD信号传导的机制，并意外发现TRAIL受体诱导自噬，FADD抑制剂可以诱导自噬，这表明FADD负调控自噬。由于自噬可以影响肿瘤细胞的凋亡反应，我们认为这些活动影响TRAIL受体信号激活凋亡机制的效率，从而杀死肿瘤细胞。我们还发现，自噬控制着垂死细胞的特征，特别是一种名为HMGB1的免疫调节剂的释放，这也以fadd依赖的方式发生，以响应TRAIL。基于这些发现，这一竞争性更新关注三个互补的问题：FADD如何调节自噬？自噬对TRAIL受体信号传导有什么影响？操纵自噬是否为提高TRAIL受体靶向药物的抗肿瘤作用提供了途径？为了回答这些问题，我们有以下目标。目的1。确定FADD在自噬调节中的作用。本研究旨在验证FADD通过与自噬调节因子相互作用负性调节自噬的假设。目标2。确定自噬如何影响TRAIL-R靶向药物的信号传导。本研究旨在验证FADD抑制自噬的能力，该能力可以协调竞争信号，从而在TRAIL r靶向药物治疗期间对肿瘤细胞死亡提供良好的控制。目标3。在体内测试自噬操作是否能提高TRAIL-R靶向药物的有效性。本研究旨在验证自噬抑制将使TRAIL受体靶向药物（lexatumumab, mapatumumab）更有效的假设，并使用一组独特的等基因肿瘤细胞，我们可以确定外源性和内源性TRAIL受体刺激在抗肿瘤反应中的相对作用以及自噬在控制这些反应中的作用。这些研究将为FADD和TRAIL受体信号转导、自噬在决定抗癌治疗反应中的作用提供新的认识，并为改善TRAIL受体靶向药物在癌症患者治疗中的应用提供依据。

DESCRIPTION (provided by applicant): Fas Associated Death Domain (FADD) is an adaptor protein that is required for signaling by the Tumor Necrosis Factor-Related Apoptosis Inducing Ligand (TRAIL) receptors. TRAIL receptors are important therapeutic targets in cancer with six TRAIL receptor-targeted drugs in clinical trials at the current time, several others in pre-clinical development and accumulating evidence suggesting that signaling through endogenous TRAIL is important in the mechanism of action of other anti-cancer treatments including DNA damaging agents, anti-metabolites and histone deacetylase inhibitors. The molecular mechanisms by which FADD activates caspases upon TRAIL receptor stimulation are quite well understood, however mechanisms of TRAIL resistance are still poorly understood and this limits our ability to optimally use the TRAIL receptor-targeted drugs. In the previous funding period we analyzed mechanisms of TRAIL resistance and FADD signaling and made the unexpected discovery that TRAIL receptors induce autophagy and that a FADD inhibitor could induce autophagy implying that FADD negatively regulates autophagy. Because autophagy can affect apoptosis responses in tumor cells, we propose that these activities affect the efficiency by which TRAIL receptor signaling activates the apoptosis machinery and thus kills tumor cells. We have also found that autophagy controls the characteristics of dying cells, particularly the release of an immune regulator called HMGB1 and that this also occurs in a FADD-dependent manner in response to TRAIL. Based on these findings, this competitive renewal focuses on three complementary questions: How does FADD regulate autophagy? What effect does autophagy have on TRAIL receptor signaling? And, does manipulation of autophagy provide a way to improve the anti-tumor effect of TRAIL receptor-targeted drugs? To answer these questions we have the following aims. Aim 1. Determine the role of FADD in regulation of autophagy. This aim tests the hypothesis that FADD negatively regulates autophagy by interaction with autophagy regulators. Aim 2. Determine how autophagy affects signaling by TRAIL-R targeted drugs. This aim tests the hypothesis that FADD's ability to inhibit autophagy serves to coordinate competing signals and thus provide fine control over tumor cell death during treatment with TRAIL R-targeted drugs. Aim 3. Test if autophagy manipulation improves the effectiveness of TRAIL-R targeted drugs in vivo. This aim tests the hypothesis that autophagy inhibition will make TRAIL receptor-targeted drugs (lexatumumab, mapatumumab) more effective and uses a unique set of isogenic tumor cells in which we can determine the relative roles of exogenous and endogenous TRAIL receptor stimuli in the anti-tumor response and the role of autophagy in controlling these responses. These studies should provide new insights into FADD and TRAIL receptor signaling, the role of autophagy in determining the response to anti-cancer therapy and provide a basis for improving the use of TRAIL receptor- targeted drugs in treating people with cancer.