Rescuing CTL from Activation Induced Death

描述（由申请人提供）：我们最近发现，在体外负载肽的基于DC的CTL产生方案中产生的大部分Mart-1表位特异性初级CTL在同源抗原的第一次二次遭遇后经历AICD。这些CTL中的AICD不是由通常的外部死亡受体（FAS，TNFR等）触发的。介导的信号传导，并且不是半胱天冬酶依赖性的。我们的研究表明，这些CTL可以通过c-jun N末端激酶（JNK）抑制剂SP 600125从AICD中拯救出来。在拯救过程中，SP 600125干扰它们合成IFNg的能力，但不阻断它们的细胞溶解功能。我们最近发现，这些CTL中的AICD是由线粒体凋亡机制的激活介导的，该机制的特征在于释放基于线粒体的凋亡诱导因子（AIF）而不释放任何细胞色素c。然后AIF易位到细胞核上，并引起大规模（约50 kbp）的单链DNA断裂。JNK抑制剂SP 600125阻断AIF释放。我们已经检测到，一个短的磷酸化片段的Bim，可通过JNK抑制剂SP 600125，产生在这些CTL在AICD。我们还发现JNK存在于线粒体上，并与几种基于线粒体的Bcl-2家族蛋白和线粒体孔蛋白电压依赖性阴离子通道（VDAC）相互作用。这些观察结果促使我们假设，自身但黑素瘤表位特异性CTL中的AICD主要是由线粒体JNK-BH 3-only促凋亡蛋白- VDAC轴的激活触发的基于细胞凋亡的效应蛋白如AIF的释放引起的，并且SP 600125通过阻断JNK激活从AICD中拯救了这些CTL中的一些。因此，对肿瘤表位的长寿命CTL应答可能通过干扰这种JNK驱动的凋亡途径来协调。因此，具体的目的是：1）定义“自身”但黑色素瘤表位特异性CTL和流感MP中AICD和AICD拯救的潜在规则（非自身和危险抗原）特异性CTL; 2）在黑色素瘤表位特异性初级CTL中研究参与AICD的基于JNK-Bim/JNK-VDAC相互作用作为AIF释放触发剂的潜在作用的机制; 3）在Rag 1-/-小鼠的异种移植模型中，在体内扩展我们在黑素瘤表位特异性CTL中的AICD和从AICD的拯救的发现。该工作将用在体外CTL产生方案中产生的相应抗原特异性CTL进行，然后在Rag 1-/-小鼠的异种移植模型中在体外和体内不同实验条件下评估它们对AICD的敏感性。AICD的机制和AICD的救援将通过药理学，遗传学（干扰RNA为基础的沉默JNK，Bim）和生化方法进行探索。这些研究将提供对针对相关肿瘤相关抗原产生的CTL如何能够保持更长时间存活的迫切需要的理解，因此将促进更有效的肿瘤免疫疗法的设计。

DESCRIPTION (provided by applicant): We have recently found that a large fraction of Mart-1 epitope specific primary CTLs, generated in an in vitro peptide-loaded DC-based CTL generation protocol, undergoes AICD after the very first secondary encounter of the cognate antigen. The AICD in these CTLs is not triggered by the usual external death receptor (FAS, TNFR, etc.)- mediated signaling and is not caspase dependent. Our studies indicated that these CTLs could be rescued from AICD by the c-jun N terminal kinase (JNK) inhibitor, SP600125. In the process of rescuing, SP600125 interfered with their capacity to synthesize IFNg but did not block their cytolytic function. We have recently found that the AICD in these CTLs is mediated by the activation of a mitochondrial apoptotic machinery characterized by the release of the mitochondria-based apoptosis inducing factor (AIF) without any cytochrome c release. AIF then translocates onto the nuclei and causes large scale (around 50 kbp) single stranded DNA breaks. The JNK inhibitor SP600125 blocks the AIF release. We have detected that a short phosphorylated fragment of Bim, inhibitable by the JNK inhibitor SP600125, is generated in these CTLs during AICD. We have also found that JNK to be present on mitochondria and to interact with several mitochondria-based Bcl-2 family proteins and with the mitichondrial porin voltage dependent anion channel (VDAC). These observations have prompted us to hypothesize that AICD in self-but-melanoma epitope-specific CTLs mostly results from the release of the mitochondria-based apoptotic effector proteins such as AIF triggered by the activation of the mitochondrial JNK-BH3-only proapoptotic protein- VDAC axis and that SP600125 rescues some of these CTLs from AICD by blocking JNK activation. Thus, a long-lived CTL response to tumor epitopes might be orchestrated by interfering with this JNK-driven apoptotic pathway". Hence, the specific aims are :1) To define the rule(s) underlying AICD and rescue from AICD in "self" but melanoma epitope specific CTLs and influenza MP (a non-self and dangerous antigen)-specific CTLs; 2) To study the mechanism underlying the mitochondria-based apoptotic machinery involved in AICD in the melanoma epitope specific primary CTLs with emphasis on elucidating a potential role of JNK-Bim/Bax-VDAC interaction as the trigger for AIF release; 3) To extend our findings of AICD and rescue from AICD in the melanoma epitope specific CTLs in a xenograft model in Rag1-/- mice, in vivo. The work will be carried out with the respective antigen specific CTLs generated in an in vitro CTL generation protocol followed by assessing their sensitivity to AICD under different experimental conditions in vitro and in vivo in a xenograft model in Rag1-/- mice. The mechanism of AICD and rescue from AICD will be explored through pharmacologic, genetic (interfering RNA-based silencing of JNK, Bim), and biochemical approaches. These studies will provide much needed understanding of how CTLs generated against a relevant tumor associated antigen can be kept alive longer and will therefore facilitate the design of more effective tumor immunotherapy.