Exploring the potential of TET inhibition in cancer immunotherapy

抽象的。癌症免疫治疗的目标是利用免疫系统摧毁癌症中的肿瘤。 病人。有两种方法在临床上取得了成功。(I)“检查站封锁”疗法利用封锁 抑制性细胞表面受体抗体或其配体(CTLA4、PD-1/PD-L1)清除肿瘤内 调节性T细胞(Tregs)或克服低反应状态，称为“衰竭”或“功能障碍”， 在浸润性实体瘤的CD8T细胞中发展。然而，只有一小部分患者达到完全 缓解，一个潜在的问题，可以通过使用多种抗体组合来对抗多重抑制 感受器。(Ii)表达识别肿瘤抗原的嵌合抗原受体(CARS)的T细胞 对B-CLL(B细胞慢性淋巴细胞白血病)等造血癌非常有效，但 对实体瘤不是很有效，显然是因为它们变得像正常的CD8一样“筋疲力尽” T细胞对标准肽/MHC配体的反应。 在这里，我们提出了一种新的策略，以提高CAR T细胞攻击实体瘤的有效性。一些人 几年前，我们发现TET(10-11易位)酶是一种使用分子的双加氧酶 氧、α-酮戊二酸(αKG)和还原铁(Fe2)氧化5-甲基胞嘧啶(5mC)的甲基 DNA到5-羟甲基胞嘧啶(5HmC)和额外的氧化甲基胞嘧啶，这些都是 DNA去甲基化。我们已经在小鼠模型中表明，Tet缺乏会导致细胞谱系扭曲 多种细胞类型的特异性和增强的信号依赖性细胞增殖；损害T细胞的功能 通过降低Foxp3表达的稳定性来调节(Treg)细胞；并提高脾组织中CD4的能力 CD8肿瘤浸润性T细胞(TIL)促进肿瘤消退。此外，TET2缺陷小鼠CD8 T 细胞表现出细胞固有的扩张和偏向中央记忆表型，两者都是内稳态的 作为对病毒感染的反应；髓系细胞中TET2缺乏通过以下方式导致免疫抑制减少 肿瘤相关巨噬细胞和髓系抑制细胞，导致更有效的肿瘤 肿瘤浸润性T细胞的消退；当TET2缺乏时，CAR T细胞促进完全缓解 给一位慢性淋巴细胞白血病患者用药。 在这里，我们将检验Tet功能丧失在肿瘤浸润性CD8 T细胞(CD8 TIL)中得到改善的假设 肿瘤排斥反应。在目标1中，我们将研究Tet蛋白在CD8 TIL的扩增和功能中的作用。 代谢物L-2-羟基戊二酸(L-2HG)是一种有效的Tet酶和其他α、KG-和Fe2-的抑制剂。 依赖的双加氧酶。L-2HG水平通常由L酶在细胞内维持在很低的水平- 2HG脱氢酶(L2HGDH)。在目标2中，我们将评估L2HGDH耗竭或L-2HG预处理的影响。 汽车瓷砖上的印花税。在目标3中，我们将描绘CD8 TIL中涉及Tet酶的转录网络。

Abstract. The goal of cancer immunotherapy is to harness the immune system to destroy tumors in cancer patients. Two approaches have been successful in the clinic. (i) “Checkpoint blockade” therapies utilize blocking antibodies to inhibitory cell surface receptors or their ligands (CTLA4, PD-1/PD-L1) to deplete intratumoral regulatory T cells (Tregs) or to overcome a hyporesponsive state, termed “exhaustion” or “dysfunction”, that develops in CD8+ T cells that infiltrate solid tumors. However, only a subset of patients achieve complete remission, a problem that can potentially be countered by using combinations of antibodies to multiple inhibitory receptors. (ii) T cells expressing chimeric antigen receptors (CARs) that recognize tumor antigens are remarkably effective against hematopoietic cancers such as B-CLL (B cell chronic lymphocytic leukemia), but are not as effective against solid tumors, apparently because they become “exhausted” much like normal CD8 T cells responsive to standard peptide/MHC ligands. Here we propose a new strategy for increasing the effectiveness of CAR T cells attacking solid tumors. Some years ago, we discovered that TET (Ten-Eleven Translocation) enzymes are dioxygenases that use molecular oxygen, α-ketoglutarate (αKG) and reduced iron (Fe2+) to oxidize the methyl group of 5-methylcytosine (5mC) in DNA to 5-hydroxymethylcytosine (5hmC) and additional oxidized methylcytosines that are all intermediates in DNA demethylation. We have shown in mouse models that TET deficiency results in skewed cell lineage specification and enhanced signal-dependent cell proliferation in many cell types; impairs the function of T regulatory (Treg) cells by decreasing the stability of Foxp3 expression; and improves the ability of splenic CD4+ and CD8+ tumor-infiltrating T cells (TILs) to promote tumor regression. Moreover, Tet2-deficient mouse CD8+ T cells displayed cell-intrinsic expansion and skewing towards a central memory phenotype, both homeostatically and in response to viral infection; Tet2 deficiency in myeloid cells resulted in decreased immunosuppression by tumor-associated macrophages and myeloid-derived suppressive cells, resulting in more effective tumor regression by tumor-infiltrating T cells; and TET2-deficient CAR T cells promoted complete remission when administered to a patient with chronic lymphocytic leukemia. Here we will test the hypothesis that TET loss-of-function in tumor-infiltrating CD8+ T cells (CD8 TILs) improves tumor rejection. In Aim 1, we will examine the role of TET proteins in the expansion and function of CD8+ TILs. The metabolite L-2-hydroxyglutarate (L-2HG) is a potent inhibitor of TET enzymes and other αKG- and Fe2+- dependent dioxygenases. L-2HG levels are normally maintained at very low levels in cells by the enzyme L- 2HG dehydrogenase (L2HGDH). In Aim 2, we will assess the effects of L2HGDH depletion or L-2HG pretreat- ment on CAR TILs. In Aim 3, we will delineate the transcriptional networks involving TET enzymes in CD8+ TILs.