FADD Signaling in Cancer Cells

描述(申请人提供)：Fas相关死亡结构域(FADD)是一种接头蛋白，在肿瘤坏死因子相关的凋亡诱导配体(TRAIL)受体的信号传递中是必需的。TRAIL受体是肿瘤治疗的重要靶点，目前有6种TRAIL受体靶向药物正在进行临床试验，其他几种药物正在临床前开发中，越来越多的证据表明，通过内源性TRAIL信号转导在其他抗癌治疗的作用机制中具有重要作用，包括DNA损伤剂、抗代谢产物和组蛋白去乙酰化酶抑制剂。FADD在TRAIL受体刺激下激活半胱氨酸天冬氨酸酶的分子机制已被人们所熟知，但TRAIL耐药机制仍不甚清楚，这限制了我们优化使用TRAIL受体靶向药物的能力。在之前的资助期间，我们分析了TRAIL耐药和FADD信号的机制，并意外地发现TRAIL受体诱导自噬，FADD抑制剂可以诱导自噬，这意味着FADD负向调节自噬。由于自噬可以影响肿瘤细胞的凋亡反应，我们认为这些活性影响TRAIL受体信号激活凋亡机制从而杀死肿瘤细胞的效率。我们还发现，自噬控制着死亡细胞的特征，特别是一种名为HMGB1的免疫调节因子的释放，这也是以FADD依赖的方式对TRAIL的反应发生的。基于这些发现，这一竞争性更新集中在三个互补的问题上：FADD如何监管自噬？自噬对TRAIL受体信号传导有什么影响？而且，操纵自噬是否提供了一种提高TRAIL受体靶向药物抗肿瘤效果的方法？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。这一目的验证了FADD通过与自噬调节器相互作用负向调节自噬的假说。目的2.确定TRAIL-R靶向药物对自噬信号的影响。这一目的检验了这样的假设，即FADD抑制自噬的能力有助于协调相互竞争的信号，从而在TRAIL R靶向药物治疗期间提供对肿瘤细胞死亡的精细控制。目的3.在体内检测自噬操作是否能提高TRAIL-R靶向药物的疗效。本研究的目的是验证自噬抑制将使TRAIL受体靶向药物(lexatumab，mapatumab)更有效的假设，并使用一组独特的同基因肿瘤细胞，在其中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、自噬在确定抗癌治疗反应中的作用提供新的见解，并为改进TRAIL受体靶向药物在癌症治疗中的使用提供基础。 与公共卫生相关：在过去的几年里，被称为自噬的一种迄今研究不足的细胞过程显然是癌症发展和治疗的重要调节因素。然而，对于我们应该如何尝试自噬来改进癌症治疗，仍然存在相当大的困惑--事实上，我们还不清楚在癌症治疗过程中，我们应该试图抑制自噬还是刺激自噬。这项资助研究了一种名为FADD的蛋白质发出的信号，FADD是激活TRAIL受体后杀死肿瘤细胞所必需的。这一点很重要，因为TRAIL受体是至少6种抗癌药物的靶点，对于通过TRAIL间接发挥作用的其他药物对肿瘤细胞的杀伤也很重要。在之前的资助期间，我们有了几项发现；首先，我们发现FADD(和TRAIL)可以调节自噬。第二，我们发现自噬可以调节包括TRAIL在内的多种药物对肿瘤细胞的杀伤效率。在这项提案中，我们的目标是回答前一项工作中出现的关键问题。我们将研究FADD如何调节自噬，这一活动如何改变TRAIL受体的信号，并测试这些过程的操纵是否改变了人类使用的TRAIL受体靶向药物的治疗效果。这些研究应该提供一种方法来改进针对TRAIL受体的各种抗癌药物的使用，这些药物已经在临床试验中，并为我们在癌症治疗过程中操纵自噬提供了理论基础。

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. PUBLIC HEALTH RELEVANCE: In the last few years it has become clear that a hitherto understudied cellular process called autophagy is an important regulator of cancer development and treatment. However there is considerable confusion about what we should try to do to autophagy to improve cancer therapy- in fact it is not clear whether we should try to inhibit autophagy or stimulate it during treatment of cancer. This grant examines signaling by a protein called FADD, which is required for tumor cell killing after activation of TRAIL receptors. This is important because TRAIL receptors are targeted by at least 6 anti-cancer agents and are also important for tumor cell killing by other drugs that work indirectly through TRAIL. In the previous funding period, we made several discoveries; first we found that FADD (and TRAIL) can regulate autophagy. Second, we found that autophagy can modulate the efficiency of tumor cell killing by various drugs including TRAIL. In this proposal we aim to answer the key questions that arose out of the previous work. We will work out how FADD regulates autophagy, how this activity alters signaling by TRAIL receptors and test whether manipulation of these processes alters the effectiveness of treatment by the TRAIL receptor-targeted drugs that are used in people. These studies should provide a way to improve the use of the various anti-cancer agents that target TRAIL receptors which are already in clinical trials and provide a rationale to allow us to manipulate autophagy during cancer treatment.