Leeds Institute of Medical Research at St James's, University of Leeds, Leeds, UK.
Cancer Research UK National Biomarker Centre, The University of Manchester, Manchester, UK.
J Immunother Cancer. 2024 Nov 17;12(11):e009522. doi: 10.1136/jitc-2024-009522.
Brain metastases (BrM) affect up to 60% of patients with metastatic melanoma and are associated with poor prognosis. While combined immune checkpoint blockade of programmed death-1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) demonstrates intracranial efficacy in a proportion of patients with melanoma, the responses are rarely durable, particularly in patients with symptomatic BrM. The brain is an immune-specialized organ and immune responses are regulated differently to the periphery. Using our previously established two-site model of melanoma BrM with concomitant intracranial and extracranial tumors, in which clinically observed efficacy of the combined PD-1/CTLA-4 (PC) blockade can be reproduced, we here explored the role of natural killer (NK) cells in BrM, using functional studies, immunophenotyping and molecular profiling. We demonstrate that NK cells are required for the intracranial efficacy of PC blockade. While both perforin and interferon gamma were necessary for the PC blockade-dependent control of intracranial tumor growth, NK cells isolated from intracranial tumors demonstrated only a limited cancer cell killing ability, and PC blockade did not alter the abundance of NK cells within tumors. However, the depletion of NK cells in PC blockade-treated mice led to tumor molecular profiles reminiscent of those observed in intracranial tumors that failed to respond to therapy. Furthermore, the depletion of NK cells resulted in a strikingly reduced abundance of CD8+ T cells within intracranial tumors, while the abundance of other immune cell populations including CD4+ T cells, macrophages and microglia remained unaltered. Adoptive T cell transfer experiments demonstrated that PC blockade-induced trafficking of CD8+ T cells to intracranial tumors was chemokine-dependent. In line with this, PC blockade enhanced intratumoral expression of several T cell-attracting chemokines and we observed high expression levels of cognate chemokine receptors on BrM-infiltrating CD8+ T cells in mice, as well as in human BrM. Importantly, the depletion of NK cells strikingly reduced the intratumoral expression levels of T cell attracting chemokines and vascular T cell entry receptors that were upregulated following PC blockade. Our data demonstrate that NK cells underpin the efficacy of PC blockade in BrM by orchestrating the "responder" molecular profile in tumors, and by controlling the intratumoral abundance of CD8+ T cells through regulation of multiple key molecular mediators of T cell trafficking.
脑转移瘤（BrM）影响多达 60%的转移性黑色素瘤患者，且预后不良。尽管程序性死亡受体-1（PD-1）和细胞毒性 T 淋巴细胞相关蛋白 4（CTLA-4）的联合免疫检查点阻断在一部分黑色素瘤患者中显示出颅内疗效，但这些反应很少持久，特别是在有症状的 BrM 患者中。大脑是一个免疫特化的器官，免疫反应的调节与外周不同。我们使用之前建立的伴有颅内和颅外肿瘤的黑色素瘤 BrM 双部位模型，在此模型中可以重现临床观察到的 PD-1/CTLA-4（PC）阻断联合治疗的疗效，我们在此探索 NK 细胞在 BrM 中的作用，采用功能研究、免疫表型分析和分子谱分析。我们证明 NK 细胞是 PC 阻断颅内疗效所必需的。虽然穿孔素和干扰素γ对于 PC 阻断依赖性颅内肿瘤生长的控制都是必要的，但从颅内肿瘤中分离的 NK 细胞仅显示出有限的癌细胞杀伤能力，PC 阻断并未改变肿瘤内 NK 细胞的丰度。然而，在接受 PC 阻断治疗的小鼠中耗尽 NK 细胞会导致肿瘤分子谱类似于那些对治疗无反应的颅内肿瘤。此外，NK 细胞的耗竭导致颅内肿瘤内 CD8+T 细胞的丰度显著降低，而包括 CD4+T 细胞、巨噬细胞和小胶质细胞在内的其他免疫细胞群体的丰度保持不变。过继性 T 细胞转移实验表明，PC 阻断诱导 CD8+T 细胞向颅内肿瘤的转移依赖于趋化因子。与此一致的是，PC 阻断增强了颅内肿瘤中几种吸引 T 细胞的趋化因子的表达，我们观察到在小鼠和人类 BrM 中浸润性 CD8+T 细胞上表达高水平的同源趋化因子受体。重要的是，NK 细胞的耗竭显著降低了 PC 阻断后上调的吸引 T 细胞的趋化因子和血管 T 细胞进入受体的肿瘤内表达水平。我们的数据表明，NK 细胞通过协调肿瘤中的“应答者”分子谱，并通过调节 T 细胞迁移的多个关键分子介质来控制 CD8+T 细胞在肿瘤内的丰度，从而为 BrM 中的 PC 阻断疗效提供支持。
