Targeting Checkpoint Inhibition in Anti-Tumor Responses

项目摘要 该项目的目标是评估阻断PSGL-1（P-选择素糖蛋白-1）的新疗法， 我们确定了一种在T细胞上表达的关键抑制性受体（IR），并讨论了其对T细胞的影响。 免疫细胞在肿瘤微环境（TME）中的功能。PSGL-1是选择素的保守配体， 粘附分子家族，P、E和L，在大多数造血细胞上表达并调节白细胞 完全糖基化时的迁移。T细胞是唯一表达PSGL的非选择素结合形式的细胞。 1，其作为淋巴结趋化因子CCL 19和CCL 21以及PD-L1同源物的受体， VISTA（B7-H5）。我们发现PSGL-1缺陷型（Selplg-/-）CD 8 T细胞不能获得免疫应答的标志。 与野生型（WT）对应物相比， 脉络丛脑膜炎病毒和显着限制肿瘤生长的两个小鼠模型的黑色素瘤，一个是 对抗PD-1治疗无反应。我们发现来自Selplg-/-小鼠的TIL具有更强的抗肿瘤活性， 功能，包括细胞毒性和细胞因子的产生。此外，多种抑制性受体的表达 (IRs)在Selplg-/- T细胞上，包括PD-1，BTLA， CD 160、LAG 3和TIM 3。值得注意的是，PSGL-1连接幼稚T细胞（TN）和TEX的激动剂单克隆抗体的背景下， T细胞受体刺激诱导/增强了多种IR的表达，强调了一个完整的联系， PSGL-1的免疫抑制途径，并建议最近确定的抑制基因模块的链接 调节IR的协调转录。我们发现，相同激动剂mAb的单价Fab 与用rPSGL-1融合蛋白处理一样，显著改善了T细胞应答，表明了 块PSGL-1功能。值得注意的是，阻断PSGL-1不会导致广泛的炎症或毒性。我们 假设PSGL-1阻断剂具有通过限制T细胞增殖而增强抗肿瘤T细胞应答潜力， 多个IR的表达水平，并通过影响其他免疫抑制因子来改变TME中的免疫抑制。 细胞我们建议评估PSGL-1阻断对小鼠和人T细胞抗肿瘤反应的影响 使用rPSGL-1和Fab抗PSGL-1作为新的小鼠和人抗PSGL-1阻断mAb的比较物。 利用这些工具，我们将分析阻断PSGL-1对T细胞IR表达和功能的影响， TME中的免疫细胞，以及与抗PD-1的潜在协同作用。在这些研究中，我们将 评估VISTA作为TME中相关PSGL-1配体的作用。这些研究将探讨 靶向PSGL-1逆转T细胞耗竭、诱导抗肿瘤免疫和翻译潜能。

PROJECT SUMMARY The goal of this project is to evaluate novel therapeutics that block PSGL-1 (P-selectin glycoprotein-1), which we identified as a key inhibitory receptor (IR) that is expressed on T cells, and address the impact(s) on immune cell functions in the tumor microenvironment (TME). PSGL-1 is a conserved ligand for the selectin family of adhesion molecules, P, E, and L, that is expressed on most hematopoietic cells and regulates leukocyte migration when fully glycosylated. T cells are the only cells that express the non-selectin binding form of PSGL- 1 that serves as a receptor for the lymph node chemokines, CCL19 and CCL21, and the PD-L1 homologue, VISTA (B7-H5). We showed that PSGL-1-deficient (Selplg-/-) CD8 T cells fail to acquire the hallmarks of exhaustion compared to their wild-type (WT) counterparts after infection with chronic lymphocytic choriomeningitis virus and significantly limit tumor growth in two murine models of melanoma, one that is nonresponsive to anti-PD-1 treatment. We identified that TILs from Selplg-/- mice have greater anti-tumor function, including cytotoxicity and cytokine production. Moreover, expression of multiple inhibitory receptors (IRs) that distinguish exhausted T cells (TEX) were downregulated on Selplg-/- T cells, including PD-1, BTLA, CD160, LAG3, and TIM3. Notably, PSGL-1 ligation on naïve T cells (TN) and TEX by an agonist mAb in the context of T cell receptor stimulation induced/augmented expression of multiple IRs, underscoring an integral connection of PSGL-1 to immune inhibitory pathways and suggesting a link to the recently identified inhibitory gene module that regulates the coordinated transcription of IRs. We identified that a monovalent Fab of the same agonist mAb dramatically improved T cell responses as did treatment with a rPSGL-1 fusion protein, indicating a capacity to block PSGL-1 function. Notably, blocking PSGL-1 did not lead to widespread inflammation or toxicity. We hypothesize that PSGL-1 blockade has the potential to augment anti-tumor T cell responses by limiting expression levels of multiple IRs, and alter immunosuppression in the TME by impacting other immune cells. We propose to evaluate the effects of PSGL-1 blockade on mouse and human T cell anti-tumor responses using rPSGL-1 and Fab anti-PSGL-1 as comparators to novel mouse and human anti-PSGL-1 blocking mAbs. With these tools, we will analyze the impacts of blocking PSGL-1 on IR expression and functions of T cells and immune cells in the TME, as well as potential synergy with anti-PD-1. In the context of these studies, we will assess the role of VISTA as the relevant PSGL-1 ligand in the TME. These studies will address the potential of targeting PSGL-1 for reversal of T cell exhaustion, induction of anti-tumor immunity, and translational potential.