The effects of PD-1 on tumor-mediated “emergency” myelopoiesis and fate commitment of myeloid cells: Implications for anti-tumor immunity

PD-1阻断剂在抗癌治疗方面取得了显著的成功。机制(S) PD-1对抗肿瘤功能的影响仍知之甚少。我们产生了一种抗体，可以识别 PD-1pY248是PD-1抑制信号所必需的。在三种小鼠肿瘤模型中，我们发现了PD-1 肿瘤微环境(TME)中CD4+和CD8+T细胞的表达和磷酸化 尤其是在髓系细胞中。这些发现促使我们研究PD-1在髓系细胞中的作用 肿瘤免疫中的分化和功能。造血细胞产量的快速变化发生在 对免疫应激的反应被称为“紧急”骨髓生成。在持续的低水平刺激期间 由肿瘤衍生因子、普通髓系祖细胞和粒细胞/巨噬细胞介导 前体细胞(GMP)经历温和但持续的扩张，分化受阻导致产量 未成熟的髓系来源的抑制细胞(MDSC)。我们分析了荷瘤的骨髓室 并确定在癌症驱动的紧急骨髓生成过程中扩张的髓系细胞表达PD- 1和PD-L1。用PD-1封闭抗体处理PD-1 KO小鼠或WT小鼠，检测PD-1 缺失或阻断可防止未成熟的髓系祖细胞聚集，并被刺激 Ly6chi效应器单核细胞、巨噬细胞和树突状细胞的分化和输出。要确定 无论这些结果是由PD-1消融的髓系固有影响还是PD-1的影响所介导的。 1neg T细胞在髓系细胞上，我们建立了条件靶向Pdcd1基因(PD-1f/f)的小鼠，并 选择性清除髓系细胞或T细胞中的PD-1。与T细胞特异性、髓系细胞特异性PD-1相比 消融更有效地减少了肿瘤的生长。癌症驱动的急诊骨髓生成是不同的 受影响。髓系特异性和T细胞特异性PD-1消融均可导致cMP的扩张和积聚 但只有髓系特异性PD-1消融术才能阻止GMP的积聚并改变髓系细胞的命运 从MDSCs到分化的效应单核细胞、巨噬细胞、DC。我们的发现揭示了之前 PD-1：PD-L1通路的作用不明，并支持髓系细胞命运转换的新假说 承诺可能是PD-1拮抗剂介导其抗肿瘤作用的关键机制。去调查 为此，我们将追求以下具体目标来确定： 1.PD-1信号如何介导髓系祖细胞的谱系命运决定 急诊骨髓再生。 2.PD-1靶向对髓系细胞代谢和表观遗传程序的影响。 3.PD-1如何通过调节先天和肿瘤之间的串扰来影响抗肿瘤免疫- 相关T细胞。

PD-1 blocking agents have achieved significant success as anti-cancer therapeutics. The mechanism(s) of how PD-1 compromises anti-tumor function remain poorly understood. We generated an antibody that recognizes PD-1pY248 that is required for PD-1 inhibitory signaling. In three mouse tumor models, we identified PD-1 expression and phosphorylation in CD4+ and CD8+ T cells of the tumor microenvironment (TME) but more prominently in myeloid cells. These findings prompted us to examine the role of PD-1 in myeloid cell differentiation and function in cancer immunity. The rapid change in hematopoietic cell output that occurs in response to immunologic stress is known as “emergency” myelopoiesis”. During continuous low-level stimulation mediated by cancer-derived factors, common myeloid progenitors (CMP) and granulocyte/macrophage progenitors (GMP), undergo modest but continuous expansion with hindered differentiation leading to the output of immature myeloid-derived suppressor cells (MDSC). We analyzed the myeloid compartment of tumor-bearing mice and determined that myeloid cells that expand during cancer-driven emergency myelopoiesis express PD- 1 and PD-L1. Using PD-1 KO mice or WT mice treated with PD-1 blocking antibody we determined that PD-1 deletion or blockade prevented the accumulation of immature myeloid progenitor cells and stimulated differentiation and output of Ly6Chi effector monocytes, macrophages and dendritic cells (DC). To determine whether these outcomes were mediated by a myeloid-intrinsic impact of PD-1 ablation or by the effects of PD- 1neg T cells on myeloid cells, we generated mice with conditional targeting of the Pdcd1 gene (PD-1f/f) and selectively eliminated PD-1 in myeloid cells or T cells. Compared to T cell-specific, myeloid cell-specific PD-1 ablation more effectively decreased tumor growth. Cancer-driven emergency myelopoiesis was differentially affected. Both myeloid-specific and T cell-specific PD-1 ablation resulted in expansion and accumulation of CMP but only myeloid-specific PD-1 ablation prevented the accumulation of GMP and switched the myeloid cell fate from MDSCs to differentiated effector monocytes, macrophages, DC. Our findings reveal a previously unidentified role of the PD-1: PD-L1 pathway and support the novel hypothesis that switch of myeloid cell fate commitment might be a key mechanism by which PD-1 blockade mediates its anti-tumor function. To investigate this, we will pursue the following specific aims to determine: 1. How PD-1 signaling mediates lineage fate determination of myeloid progenitor cells in response to emergency myelopoiesis. 2. How PD-1 targeting impacts the metabolic and epigenetic program of myeloid cells. 3. How PD-1 affects anti-tumor immunity by regulating the crosstalk between innate and tumor- associated T cells.