Oxidative stress and AICD in memory T cell persistence

描述(申请人提供)：CD8 T细胞通过活化、分裂和分化过程对抗原刺激作出反应，以产生大量激活的效应性溶细胞T淋巴细胞(CTL)。许多癌症患者体内有前体CTL，可被激活以对许多“自身”肿瘤相关表位作出反应。在某些情况下，接种这些表位中的一些可以诱导抗肿瘤反应。然而，肿瘤发展为成功逃避宿主免疫系统的各种分子和细胞机制已经被识别。其中一些机制针对的是抗肿瘤效应器CTL，而免疫疗法仅针对激活抗肿瘤免疫反应而不能纠正这些CTL。我们的初步数据显示，在外源性氧化应激条件下，携带T细胞的效应记忆表型优先发生功能障碍，但在抗原遭遇时也会经历更多的激活诱导细胞死亡(AICD)。在接受AICD的CTL中，可以看到超氧化物歧化产物的增加，这可以通过超氧化物歧化酶模拟物MnTBAP的预处理来挽救。根据我们的初步数据，我们假设记忆T细胞亚群之间不同的氧化还原状态调节着对AICD或细胞凋亡的敏感性。利用MART-127-35表位特异的人CTL和来自我们的新型转基因H3T小鼠的T细胞，并在CD4和CD8T细胞上同时携带人类HLA-A2限制性酪氨酸特异功能TCR，我们建议进行以下工作：1)确定T细胞亚群的不同氧化还原状态(Tcm和TEMs)是否通过影响内在信号分子来调节对氧化应激诱导的细胞凋亡和AICD的敏感性；2)确定不同调控氧化应激介导的记忆T细胞亚群的凋亡和AICD的外在因素(Tcm和TEMs)；3)建立体内模型，以评价抗氧化剂处理的T细胞或抗氧化酶转导的T细胞在肿瘤消退、持久性和记忆性方面的作用。我们相信，这项拟议工作的成功完成将有助于确定可用于改善接受癌症采用T细胞疗法的患者的效应型CTL存活和长期记忆发展的靶点。 公共卫生相关性：尽管由癌症疫苗激活的T淋巴细胞实际上有能力攻击和摧毁肿瘤细胞，但它们在控制肿瘤消退方面无效的原因一直令人费解。我们的数据表明，氧化应激和抗原介导的携带CTL的抗原经历/记忆表型的优先死亡可能导致功能不足。由于CTL的持久性是影响任何免疫治疗方案结果的重要因素，我们认为通过识别和靶向将CTL从过早死亡中拯救出来的途径来保护效应淋巴细胞，可以显著提高其抗肿瘤效果。

DESCRIPTION (provided by applicant): CD8+ T cells respond to antigen stimulation through a process of activation, division, and differentiation to generate a large pool of activated effector cytolytic T lymphocytes (CTL). Many cancer patients harbor precursor CTL that can be activated to respond to many "self" tumor-associated epitopes. Vaccination with some of these epitopes can induce anti-tumor responses in some cases. However, various molecular and cellular mechanisms that tumors develop to successfully evade the host immune system have been identified. Some of these mechanisms target anti-tumor effector CTL that cannot be corrected by immunotherapy aimed only at activation of anti-tumor immune responses. Our preliminary data shows that effector memory phenotype bearing T cell becomes preferentially dysfunctional under conditions of exogenous oxidative stress but also undergo increased activation induced cell death (AICD) on antigenic encounter. Increased superoxide production can be seen in CTL undergoing AICD that can be rescued by pretreatment with superoxide dismutase mimetic MnTBAP. Based on our preliminary data we hypothesize that differential redox status between memory T cell subsets regulates the sensitivity towards AICD or apoptosis. Using MART-127-35 epitope specific human CTL and T cells from our novel transgenic h3T mouse that carries HLA-A2 restricted tyrosine specific functional TCR on both CD4+ and CD8+ T cells we propose to carry out the following: 1) To determine if differential redox state of the T cell subsets (TCM vs. TEM) regulates sensitivity to oxidative stress induced apoptosis and AICD by effecting intrinsic signaling molecules.; 2) To determine extrinsic factors that differentially regulate oxidative stress mediated apoptosis and AICD of memory T cell subsets (TCM vs. TEM); and 3) To establish an in vivo model for evaluation of antioxidant treated T cells or antioxidant enzyme transduced T cells in tumor regression, persistence and memory. We believe that successful completion of the proposed work would help identify targets that could be used to improve survival of effector CTL and long-term memory development in patients receiving adoptive T cell therapy for cancer. PUBLIC HEALTH RELEVANCE: Despite T lymphocytes activated by cancer vaccination are virtually competent to attack and destroy neoplastic cells, the reason for their inefficacy in controlling tumor regression has been puzzling. Our data shows that it is both oxidative stress and antigen mediated preferential death of antigen-experienced/memory phenotype bearing CTL that might result in inadequate function. Since persistence of CTL is an important factor that affects the outcome of any immunotherapy protocol we believe that protecting effector lymphocytes by identifying and targeting the pathways to rescue CTL from premature death, their anti-tumor effect could be substantially improved.