FADD Signaling in Cancer Cells

描述（由申请方提供）：Fas相关死亡结构域（FADD）是一种衔接蛋白，是肿瘤坏死因子相关凋亡诱导配体（TRAIL）受体发出信号所必需的。TRAIL受体是癌症中的重要治疗靶点，目前有六种TRAIL受体靶向药物处于临床试验中，其他几种处于临床前开发中，并且积累的证据表明，通过内源性TRAIL的信号传导在其他抗癌治疗的作用机制中是重要的，包括DNA损伤剂，抗代谢物和组蛋白脱乙酰酶抑制剂。FADD在TRAIL受体刺激后激活半胱天冬酶的分子机制已经非常清楚，但是对TRAIL抗性的机制仍然知之甚少，这限制了我们最佳使用TRAIL受体靶向药物的能力。在之前的资助期间，我们分析了TRAIL抗性和FADD信号传导的机制，并意外地发现TRAIL受体诱导自噬，并且FADD抑制剂可以诱导自噬，这意味着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受体信号转导激活凋亡机制的效率，从而杀死肿瘤细胞。我们还发现，自噬控制垂死细胞的特征，特别是一种名为HMGB 1的免疫调节剂的释放，并且这也以FADD依赖的方式响应TRAIL。基于这些发现，这种竞争性更新集中在三个互补的问题：FADD如何调节自噬？自噬对TRAIL受体信号传导有什么影响？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。目标1.确定FADD在自噬调节中的作用。该目的检验FADD通过与自噬调节因子相互作用来负调节自噬的假设。目标二。确定自噬如何影响TRAIL-R靶向药物的信号传导。该目的测试了FADD抑制自噬的能力用于协调竞争信号并因此在用TRAIL R靶向药物治疗期间提供对肿瘤细胞死亡的精细控制的假设。目标3：测试自噬操作是否改善体内TRAIL-R靶向药物的有效性。该目的测试了自噬抑制将使TRAIL受体靶向药物（lexatumumab，mapatumumab）更有效的假设，并使用了一组独特的同基因肿瘤细胞，其中我们可以确定外源性和内源性TRAIL受体刺激物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。这些研究应该为FADD和TRAIL受体信号传导提供新的见解，自噬在确定抗癌治疗反应中的作用，并为改善TRAIL受体靶向药物在治疗癌症患者中的使用提供基础。

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.