EGR2 in T cell tolerance

描述(由申请人提供)：外周免疫耐受的一个关键机制发生在T细胞无能的过程中，特别是在肿瘤的情况下。我们以前已经证明，二酰基甘油激酶(DGK)家族脂蛋白激酶的上调表达参与了RasGRP介导的RAS激活的抑制，并在无能状态下导致T细胞功能障碍。其他研究表明，额外的负性调节信号蛋白上调，这可能有助于维持T细胞功能障碍。最近，通过条件性基因敲除研究、基因表达谱分析和芯片序列实验，我们已经确定转录因子EGR2是这些负调控因子在T细胞无能中表达的中心调节因子。重要的是，新的EGR2驱动的靶点已经出现，它们是细胞表面的标记，这可能使流式细胞仪识别无能细胞。这项建议的主要目的是确定EGR2在肿瘤外周耐受中的作用。在特定目标1中，我们将在活体内确定外周T细胞条件缺失EGR2的效果。将评估T细胞无能的诱导、抗肿瘤免疫的产生和自身免疫进化的潜力。在具体目标2中，将研究EGR2调节的基因子集在T细胞生物学中的相关性。我们将着重于分泌因子CCL1、CRTAM/LAG3/4-1BB的表面表达以及Semaphorin 7A的功能作用。这些标记物的组合是否能够识别肿瘤微环境中的无能细胞将被确定。在特定的目标3中，将评估EGR2及其靶点在浸润性人类黑色素瘤的T细胞中的表达，以走向临床意义。总之，这些研究将大大拓宽和加深我们对体内EGR2和T细胞无能的理解，并有望发现可用于癌症免疫治疗的临床策略。

DESCRIPTION (provided by applicant): One critical mechanism of peripheral immunologic tolerance occurs through the process of T cell anergy, particularly in the tumor context. We previously have shown that upregulated expression of lipid kinases of the diacylglycerol kinase (DGK) family participate in the suppression of RasGRP-mediated Ras activation and contribute to T cell dysfunction in the anergic state. Other studies have implicated upregulation of additional negative regulatory signaling proteins, which may cooperate to maintain T cell dysfunction. Recently, through conditional knockout studies, gene expression profiling and ChIP-Seq experiments, we have identified the transcription factor EGR2 as a central regulator of expression of these negative regulatory factors in T cell anergy. Importantly, new EGR2-driven targets have emerged that are cell surface markers, which may allow flow cytometric identification of anergic cells. The major goal of this proposal is to determine the contribution o EGR2 towards peripheral tolerance to tumors. In Specific Aim 1 we will determine the effects of conditional deletion of EGR2 in peripheral T cells in vivo. Induction of T cell anergy, generation of anti-tumor immunity, and potential for evolving autoimmunity will be assessed. In Specific Aim 2, the relevance of a subset of EGR2- regulated genes in T cell biology will be investigated. We will focus on the secreted factor CCL1; the surface expression of CRTAM/LAG3/4-1BB; and the functional role of Semaphorin 7A. Whether combinations of these markers can identify anergic cells in the tumor microenvironment will be determined. In Specific Aim 3, expression of EGR2 and its targets in T cells infiltrating human melanoma will be evaluated, to move towards clinical relevance. Together, these studies will substantially broaden and deepen our understanding of EGR2 and T cell anergy in vivo, and are expected to uncover strategies that can have clinical application towards immunotherapy of cancer.