Targeting CCR2-expressing myeloid cells to overcome immune checkpoint inhibitor resistance in glioma

摘要 靶向癌症免疫系统的治疗方法正在获得牵引力， PD-L1/PD-1轴，即免疫检查点抑制剂，在越来越多的恶性肿瘤中显示出成功。 尽管临床前研究表明PD-1阻断剂在恶性胶质瘤中具有活性，但初步临床试验结果 在胶质母细胞瘤（GBM）患者中的研究表明，大多数患者对PD-1无反应， 阻断单一疗法。这些结果表明，其他免疫抑制途径在恶性肿瘤中起作用。 神经胶质瘤可能会对免疫检查点抑制剂产生耐药性，这突出了联合治疗的必要性。 克服神经胶质瘤诱导的免疫抑制的方法。我们的研究表明肿瘤浸润性 髓样细胞构成耐药神经胶质瘤内的可靶向轴。通过利用遗传工具和临床 我们的目标是提出一种新的组合策略， 这可能与人GBM肿瘤中有效的免疫检查点阻断相关。免疫 肿瘤微环境中的抑制性骨髓源性细胞是导致肿瘤不能被治疗的主要原因。 免疫系统产生有效的抗肿瘤反应。因此，它们构成了一种有希望的细胞类型， 靶点，以增强抗肿瘤免疫疗法。该项目将解决一个重要问题： 抑制神经胶质瘤相关髓源性细胞的肿瘤促进活性， 增强抗GBM免疫疗法的策略？骨髓细胞的迁移和功能是 由趋化因子/趋化因子受体控制，CCL 2/CCR 2系统是利用的主要途径 通过这些细胞进入组织。CCR 2+骨髓细胞存在于人GBM肿瘤中，并且临床前 神经胶质瘤模型，其中它们表现出免疫抑制特性。我们已经确定神经胶质瘤 这些细胞的存在依赖于CCR 2。我们提供了令人信服的结果，CCR 2缺乏促进 免疫检查点抑制剂在α-PD-1不敏感胶质瘤中的疗效，以及抗PD-1活性的增强， 1例敏感性胶质瘤。此外，用新的CCR 2拮抗剂治疗带有神经胶质瘤的小鼠也类似地 克服了胶质瘤对α-PD-1抑制性抗体的抗性。我们假设药理学 CCR 2的拮抗作用将通过抑制免疫应答来增强免疫靶向抗胶质瘤疗法的功效。 抑制性骨髓源性细胞。该假设将通过以下目标来解决：1）确定 PD-1耐药胶质瘤中表达CCR 2的免疫抑制性髓样细胞，2）确定CCR 2的影响 拮抗PD-1抗性胶质瘤中的适应性免疫应答，以及3）确定CCR 2的功效 拮抗剂在人GBM临床前模型中的作用。这些首次研究将提供明确的临床前证据， 使用CCR 2拮抗剂作为免疫检查点抑制剂的连续治疗方式的原理- 耐药GBM。结果将阐明CCR 2影响骨髓细胞功能的机制。 免疫抑制胶质瘤微环境，并有助于抵抗PD-1阻断。

Abstract Therapeutic approaches that target the immune system in cancer are gaining traction, with agents that disrupt the PD-L1/PD-1 axis, i.e. immune checkpoint inhibitors, showing success in a growing list of malignancies. Despite preclinical studies suggesting activity of PD-1 blockade in malignant gliomas, initial clinical trial results in glioblastoma (GBM) patients have demonstrated that the majority of patients do not respond to PD-1 blockade monotherapy. These results suggest other immunosuppressive pathways operative in malignant gliomas may impart resistance to immune checkpoint inhibitors, highlighting a need for combinatorial approaches to overcome glioma-induced immunosuppression. Our studies establish that tumor infiltrative myeloid cells constitute a targetable axis within resistant gliomas. By utilizing genetic tools and clinically available inhibitors of myeloid cell trafficking and function, we aim to advance a novel combinatorial strategy which may hold relevance for effective immune checkpoint blockade in human GBM tumors. Immune suppressive myeloid-derived cells within the tumor microenvironment are a major contributor to the inability of the immune system to mount an effective anti-tumor response. As such, they constitute a promising cell type to target in order to enhance anti-tumor immune-based therapies. This project will address an important question: does inhibiting the tumor promoting activities of glioma-associated myeloid derived cells, provide a viable strategy for enhancing anti-GBM immune-based therapies? The migration and function of myeloid cells are controlled by chemokines/chemokine receptors, with the CCL2/CCR2 system being a major pathway utilized by these cells to access tissues. CCR2+ myeloid cells are present within human GBM tumors, and pre-clinical glioma models, where they exhibit immunosuppressive characteristics. We have determined that the glioma presence of these cells is dependent on CCR2. We provide compelling results that CCR2-deficiency promotes efficacy of immune checkpoint inhibitors in α-PD-1 insensitive gliomas, as well as enhanced activity in anti-PD- 1 sensitive gliomas. Moreover, treatment of glioma-bearing mice with novel CCR2 antagonists also similarly overcomes resistance of glioma to α-PD-1 inhibitory antibodies. We hypothesize that pharmacologic antagonism of CCR2 will augment the efficacy of immune targeted anti-glioma therapies by inhibiting immune suppressive myeloid-derived cells. The hypothesis will be addressed by the Aims 1) Determine the role of CCR2-expressing immune suppressive myeloid cells in PD-1 resistant glioma, 2) Determine impact of CCR2 antagonism on the adaptive immune response in PD-1 resistant glioma, and 3) Determine efficacy of CCR2 antagonists in human GBM pre-clinical models. These first ever studies will provide clear pre-clinical proof of principle for using CCR2 antagonists as an adjunctive therapeutic modality for immune checkpoint inhibitor- resistant GBM. Outcomes will clarify the mechanism(s) by which CCR2 influences myeloid cell function within the immune-suppressed glioma microenvironment and contributes to resistance PD-1 blockade.