Functional differences between PD-1+ and PD-1- CD4+ effector T cells in healthy donors and patients with glioblastoma multiforme

Immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) have been highly successful in the treatment of cancer. While PD-1 expression has been widely investigated, its role in CD4+ effector T cells in the setting of health and cancer remains unclear, particularly in the setting of glioblastoma multiforme (GBM), the most aggressive and common form of brain cancer. We examined the functional and molecular features of PD-1+CD4+CD25—CD127+Foxp3—effector cells in healthy subjects and in patients with GBM. In healthy subjects, we found that PD-1+CD4+ effector cells are dysfunctional: they do not proliferate but can secrete large quantities of IFNγ. Strikingly, blocking antibodies against PD-1 did not rescue proliferation. RNA-sequencing revealed features of exhaustion in PD-1+ CD4 effectors. In the context of GBM, tumors were enriched in PD-1+ CD4+ effectors that were similarly dysfunctional and unable to proliferate. Furthermore, we found enrichment of PD-1+TIM-3+ CD4+ effectors in tumors, suggesting that co-blockade of PD-1 and TIM-3 in GBM may be therapeutically beneficial. RNA-sequencing of blood and tumors from GBM patients revealed distinct differences between CD4+ effectors from both compartments with enrichment in multiple gene sets from tumor infiltrating PD-1—CD4+ effectors cells. Enrichment of these gene sets in tumor suggests a more metabolically active cell state with signaling through other co-receptors. PD-1 expression on CD4 cells identifies a dysfunctional subset refractory to rescue with PD-1 blocking antibodies, suggesting that the influence of immune checkpoint inhibitors may involve recovery of function in the PD-1—CD4+ T cell compartment. Additionally, co-blockade of PD-1 and TIM-3 in GBM may be therapeutically beneficial.靶向程序性死亡蛋白1（programmed cell death protein 1, PD-1）的免疫检查点抑制剂在癌症治疗中已展现出卓越的临床疗效。尽管PD-1的表达已被广泛研究，但其在健康状态及癌症背景下CD4+效应T细胞中的作用仍不明确，尤其是在多形性胶质母细胞瘤（glioblastoma multiforme, GBM）——这一最具侵袭性且最常见的脑癌类型——的研究场景中。本研究对健康受试者与多形性胶质母细胞瘤患者体内的PD-1+CD4+CD25—CD127+Foxp3—效应细胞的功能与分子特征展开了系统分析。在健康受试者中，我们发现PD-1+CD4+效应细胞存在功能失调现象：此类细胞无法增殖，但可分泌大量干扰素γ（interferon gamma, IFNγ）。值得注意的是，针对PD-1的封闭抗体并未能挽救其增殖能力。RNA测序（RNA-sequencing）结果显示，PD-1+CD4+效应细胞呈现免疫耗竭特征。在多形性胶质母细胞瘤的背景下，肿瘤组织中富集了PD-1+CD4+效应细胞，此类细胞同样存在功能失调且无法增殖。此外，我们发现肿瘤组织中富集了PD-1+T细胞免疫球蛋白黏蛋白3（TIM-3）+CD4+效应细胞，这提示在多形性胶质母细胞瘤中联合阻断PD-1与TIM-3可能具有治疗益处。对多形性胶质母细胞瘤患者血液与肿瘤组织的RNA测序结果显示，两个来源的CD4+效应细胞存在显著差异，肿瘤浸润的PD-1—CD4+效应细胞富集了多个基因集。这些基因集在肿瘤组织中的富集提示，该细胞群处于代谢活性更高的状态，并通过其他共受体进行信号传导。CD4细胞上的PD-1表达可鉴定出一类对PD-1封闭抗体治疗无应答的功能失调细胞亚群，这表明免疫检查点抑制剂的作用机制可能涉及恢复PD-1—CD4+ T细胞亚群的功能。此外，在多形性胶质母细胞瘤中联合阻断PD-1与TIM-3可能具备临床治疗价值。