Targeting Checkpoint Inhibition in Anti-Tumor Responses

项目概要 该项目的目标是评估阻断 PSGL-1（P-选择素糖蛋白-1）的新型疗法，该疗法 我们确定了 T 细胞上表达的关键抑制性受体 (IR)，并解决了对 T 细胞的影响 免疫细胞在肿瘤微环境（TME）中发挥作用。 PSGL-1 是选择蛋白的保守配体 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 完全糖基化时迁移。 T 细胞是唯一表达 PSGL-非选择素结合形式的细胞 1 作为淋巴结趋化因子 CCL19 和 CCL21 以及 PD-L1 同源物的受体， 远景 (B7-H5)。我们发现 PSGL-1 缺陷型 (Selplg-/-) CD8 T 细胞无法获得 慢性淋巴细胞感染后与野生型（WT）对应物相比，疲劳 脉络膜脑膜炎病毒并显着限制两种黑色素瘤小鼠模型中的肿瘤生长，其中一种是 对抗 PD-1 治疗无反应。我们发现 Selplg-/- 小鼠的 TIL 具有更强的抗肿瘤作用 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 区分衰竭 T 细胞 (TEX) 的 (IR) 在 Selplg-/- T 细胞上下调，包括 PD-1、BTLA、 CD160、LAG3 和 TIM3。值得注意的是，PSGL-1 通过激动剂 mAb 在幼稚 T 细胞 (TN) 和 TEX 上连接 T 细胞受体刺激诱导/增强多种 IR 的表达，强调了整体联系 PSGL-1 与免疫抑制途径的关系，并表明与最近发现的抑制基因模块的联系 调节 IR 的协调转录。我们鉴定出相同激动剂 mAb 的单价 Fab 与 rPSGL-1 融合蛋白治疗一样，T 细胞反应得到显着改善，表明有能力 阻止 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 阻断有可能通过限制 多种 IR 的表达水平，并通过影响其他免疫来改变 TME 中的免疫抑制 细胞。我们建议评估 PSGL-1 阻断对小鼠和人类 T 细胞抗肿瘤反应的影响 使用 rPSGL-1 和 Fab 抗 PSGL-1 作为新型小鼠和人抗 PSGL-1 阻断单克隆抗体的比较。 利用这些工具，我们将分析阻断 PSGL-1 对 IR 表达和 T 细胞功能的影响， TME 中的免疫细胞，以及与抗 PD-1 的潜在协同作用。在这些研究的背景下，我们将 评估 VISTA 作为 TME 中相关 PSGL-1 配体的作用。这些研究将解决以下问题的潜力： 靶向 PSGL-1 以逆转 T 细胞耗竭、诱导抗肿瘤免疫和转化潜力。

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.