TUMOR-IMPOSED GLUCOSE RESTRICTIONS ON T CELLS DAMPEN IMMUNITY

描述（由申请人提供）：在产生免疫应答过程中，肿瘤抗原特异性T细胞会被激活并产生多种介导肿瘤清除的效应分子。然而，在癌症期间，T细胞的功能和反应性往往会逐渐下降，没有正常功能的T细胞，肿瘤将继续生长。这种T细胞功能障碍或衰竭被认为是由于持续暴露于抗原，因此重复的刺激使T细胞进入更深层次的无反应状态，在这种状态下，增殖、细胞因子产生、细胞毒性能力等功能丧失，最终丧失生存能力。目前正在开发的许多癌症治疗方法都试图瞄准T细胞中的途径，将它们从功能失调状态中拉回来，并增强效应功能。虽然使用这种方法的治疗方法很有希望，但T细胞在癌症期间耗尽和/或功能失调的潜在基础尚未完全了解，并且为了有效地设计新的抗癌治疗方法，必须克服对这一过程的清晰理解。这个建议解决了这个问题。这是基于我们的新发现，在T细胞代谢转录后调节效应功能，这一过程是由其他细胞在特定微环境中竞争营养物质控制的。我们发现甘油醛-3-磷酸脱氢酶（GAPDH）通过参与或脱离糖酵解途径，调节T细胞转录后细胞因子的产生。我们发现，激活的T细胞可以使用氧化磷酸化（OXPHOS）或糖酵解来支持增殖和存活，但是当T细胞在这些ATP生成程序之间切换时，就像营养可用性的变化、共刺激或生长因子信号的变化一样，GAPDH从糖酵解代谢酶的功能转换为控制免疫调节因子表达的RNA结合蛋白的功能。因此，虽然OXPHOS可以支持T细胞存活和增殖，但只有糖酵解才能促进完全的效应状态。这些发现表明，葡萄糖（Glc）的可用性直接决定了T细胞在收到激活信号后是否能产生细胞因子。鉴于许多肿瘤也参与糖酵解（Warburg效应），我们假设肿瘤浸润性T细胞在癌症期间经历功能丧失可能是肿瘤施加的Glc限制的结果。为了验证这一点，我们使用了体外方法和体内肉瘤模型，我们的初步数据支持肿瘤对T细胞施加Glc限制，抑制T细胞参与糖酵解和产生效应细胞因子的能力。我们的实验将确定肿瘤微环境是否对肿瘤浸润性T细胞有营养限制，以及T细胞是否无法参与

DESCRIPTION (provided by applicant): During a productive immune response na¿ve tumor antigen-specific T cells will become activated and produce a variety of effector molecules that mediate tumor clearance. However, T cells often experience a progressive decline in function and responsiveness during cancer, and without properly functioning T cells, tumors will continue to grow. This T cell dysfunction, or exhaustion, is thought to result from continuous exposure to antigen, such that repetitive stimulation drives T cells into deeper states of unresponsiveness where functions such as proliferation, cytokine production, cytotoxic ability, and finally survival are lost. Many cancer treatments currently under development attempt to target pathways in T cells that will pull them back from their dysfunctional state and boost effector functions. While therapies using this approach hold promise, the underlying basis of why T cells become exhausted and/or dysfunctional during cancer is not completely understood and a clear understanding of this process is a critical barrier that must be overcome in order to effectively design new anti-cancer treatments. This proposal addresses this issue. It is based on our novel finding that in T cells metabolism posttranscriptionally regulates effector function and that this process is controlled by competition from other cells for nutrients in a given microenvironment. We found that the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH), by engaging or disengaging the glycolysis pathway, regulates the posttranscriptional production of cytokines by T cells. We showed that activated T cells can use either oxidative phosphorylation (OXPHOS) or glycolysis to support proliferation and survival, but when T cells switch between these ATP generating programs, as can occur with changes in nutrient availability, or co-stimulatory or growth factor signals, GAPDH switches from its function as a metabolic enzyme in glycolysis to its function as an RNA binding protein controlling expression of immunomodulatory factors. Thus while OXPHOS can support T cell survival and proliferation, only glycolysis can facilitate full effector status. These findings showed that glucose (Glc) availability directly determines whether a T cell can produce cytokines after the receipt of activation signals. Given that many tumors also engage glycolysis (Warburg effect) we hypothesize that tumor-infiltrating T cells that experience a loss of function during cancer may do so as a result of tumor-imposed Glc restrictions. To test this we have used in vitro approaches and an in vivo sarcoma model and our preliminary data support that tumors impose Glc restrictions on T cells that dampens the T cell's ability to engage glycolysis and produce effector cytokines. Our experiments will establish whether the tumor microenvironment is nutrient-restrictive for tumor-infiltrating T cells, and whether the inability of T cells to engage glycolysis renders them unable to produce cytokines (via posttranscriptional mechanisms) and control tumor growth. We hope that by completing our aims we will provide crucial knowledge toward developing new treatments to reverse immune dysfunction in cancer through the manipulation of metabolic pathways.