Dissecting the role of hypoxia in T cell differentiation in cancer

项目摘要/摘要 肿瘤的免疫治疗，尤其是使用单抗介导的阻断 像PD-1这样的“检查点”分子已经改变了实体瘤患者的治疗模式，比如 黑色素瘤。然而，由于几种抗药性，只有少数患者从这些疗法中受益。 机制集中在肿瘤微环境(TME)，即细胞毒性T细胞的作用部位。T 细胞必须与渗透的物理屏障、免疫抑制细胞类型、协同-1基因的表达作斗争 靶细胞上的抑制配体，以及癌细胞产生的恶劣代谢环境。除了T 细胞-外源性免疫抑制，肿瘤内的T细胞有明显的分化轨迹，导致 获得另一种功能失调的命运，称为精疲力竭。耗尽的T细胞是终末的 分化，在刺激下功能低下，增殖能力差，这是一个关键组成部分 免疫记忆。我们和其他人已经证明，精疲力竭的T细胞有严重的代谢缺陷， 而TME内的代谢应激，最明显的是低氧暴露，加强了向 疲惫不堪。与此相一致，我们和其他人已经表明，黑色素瘤患者具有更多的氧化、缺氧 肿瘤更有可能在抗PD1的情况下进展。因此，缺氧性TME和固有功能缺陷 耗尽的T细胞是相连的。然而，低氧和由此产生的氧化应激如何改变T细胞分化 目前仍不清楚。我们的假设是，低氧暴露通过驱动异常，促进T细胞耗竭 染色质二价性和转录缺失，因此低氧缓解治疗将改变T细胞 分化和支持T细胞功能增强。目标1：低氧如何驱动表观遗传变化 偏向T细胞分化和功能？低氧驱动几种细胞适应，包括转录 通过缺氧诱导因子-1α重新编程，诱导活性氧物种(ROS)，以及代谢转变。我们将A)使用在 体外系统识别低氧导致组蛋白甲基化和二价体改变的机制 小鼠T细胞；以及B)确定低氧对T细胞表观基因组的贡献并探索潜力 小鼠肿瘤模型中的缓解策略。目的2：低氧疗法如何改变肿瘤内T 黑色素瘤患者的细胞分化？我们和其他人已经表明，靶向肿瘤细胞代谢或 在小鼠模型和黑色素瘤患者中，血管生成都可以增加肿瘤内的氧分压。在……里面 为了实现这一目标，我们将利用两项由研究者发起的使用二甲双胍或二甲双胍治疗黑色素瘤的临床试验。 阿西替尼联合抗PD-1，深入探讨转录、表观遗传、代谢和功能 与减少缺氧相关的结果与抗PD-1一致。我们希望这些研究能够解决 表观遗传学、免疫学和癌症免疫治疗领域的知识差距，揭示肿瘤是如何 低氧可以影响T细胞的分化和对抗PD-1的反应，目的是识别新的靶点 缓解缺氧导致的T细胞耗竭，克服癌症免疫治疗的障碍。

PROJECT SUMMARY/ABSTRACT Immunotherapeutic treatments for cancer, especially the use of monoclonal antibody mediated blockade of `checkpoint' molecules like PD-1, has changed the treatment paradigm for patients with solid tumors like melanoma. However, only a subset of patients benefit from these therapies, due to several resistance mechanisms concentrated within the tumor microenvironment (TME), the site of action of cytotoxic T cells. T cells must contend with physical barriers to infiltration, immunosuppressive cell types, the expression of co- inhibitory ligands on target cells, and a harsh metabolic environment produced by cancer cells. In addition to T cell-extrinsic immunosuppression, T cells within tumors have a distinct differentiation trajectory, resulting in acquisition of an alternative, dysfunctional fate termed exhaustion. Exhausted T cells are terminally differentiated, hypofunctional upon stimulation, and possess poor capacity to proliferate, a crucial component of immune memory. We and others have shown that exhausted T cells have severe metabolic deficiencies, and that metabolic stress within the TME, most notably hypoxia exposure, potentiates differentiation towards exhaustion. In line with this, we and others have shown that melanoma patients with more oxidative, hypoxic tumors are more likely to progress on anti-PD1. Thus, the hypoxic TME and the intrinsic functional deficiency of exhausted T cells are linked. However, how hypoxia and resultant oxidative stress alter T cell differentiation remain unclear. Our hypothesis is that hypoxia exposure promotes T cell exhaustion, by driving aberrant chromatin bivalency and loss of transcription, such that hypoxia mitigation treatments will alter T cell differentiation and support increased T cell function. AIM 1: How does hypoxia drive epigenetic changes that bias T cell differentiation and function? Hypoxia drives several cellular adaptations, including transcriptional reprogramming via HIF-1α, induction of reactive oxygen species (ROS), and metabolic shifts. We will A) use in vitro systems to identify mechanisms of hypoxia contributing to altered histone methylation and bivalency in murine T cells; and B) determine contributions of hypoxia to the T cell epigenome and explore potential mitigation strategies in murine tumor models. AIM 2: How do hypoxia reducing regimens alter intratumoral T cell differentiation in melanoma patients? We and other have shown that targeting tumor cell metabolism or angiogenesis can increase the oxygen tension within tumors in both mouse models and melanoma patients. In this Aim, we will take advantage of two investigator-initiated clinical trials in melanoma utilizing metformin or axitinib in combination with anti-PD-1, and deeply explore transcriptional, epigenetic, metabolic, and functional outcomes associated with reduction of hypoxia coincident with anti-PD-1. We expect these studies to address knowledge gaps in the fields of epigenetics, immunology, and cancer immunotherapy, uncovering how tumor hypoxia can bias T cell differentiation and response to anti-PD-1, with the goal of identifying novel targets that mitigate hypoxia driven T cell exhaustion and overcome barriers to immunotherapy for cancer.