The immunosuppressive microenvironment in solid tumors is thought to form a barrier to the entry and efficacy of cell‐based therapies such as chimeric antigen receptor (CAR) T cells. Combining CAR T cell therapy with checkpoint inhibitors has been demonstrated to oppose immune escape mechanisms in solid tumors and augment antitumor efficacy. We evaluated PD‐1/PD‐L1 signaling capacity and the impact of an inhibitor of this checkpoint axis in an in vitro system for cancer cell challenge, the coculture of L1CAM‐specific CAR T cells with neuroblastoma cell lines. Fluorescence‐activated cell sorting‐based analyses and luciferase reporter assays were used to assess PD‐1/PD‐L1 expression on CAR T and tumor cells as well as CAR T cell ability to kill neuroblastoma cells. Coculturing neuroblastoma cell lines with L1CAM‐CAR T cells upregulated PD‐L1 expression on neuroblastoma cells, confirming adaptive immune resistance. Exposure to neuroblastoma cells also upregulated the expression of the PD‐1/PD‐L1 axis in CAR T cells. The checkpoint inhibitor, nivolumab, enhanced L1CAM‐CAR T cell‐directed killing. However, nivolumab‐enhanced L1CAM‐CAR T cell killing did not strictly correlate with PD‐L1 expression on neuroblastoma cells. In fact, checkpoint inhibitor success relied on strong PD‐1/PD‐L1 axis expression in the CAR T cells, which in turn depended on costimulatory domains within the CAR construct, and more importantly, on the subset of T cells selected for CAR T cell generation. Thus, T cell subset selection for CAR T cell generation and CAR T cell prescreening for PD‐1/PD‐L1 expression could help determine when combination therapy with checkpoint inhibitors could improve treatment efficacy.

中文翻译：

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中枢记忆表型与CAR T细胞联合使用可成功促进检查点抑制。

实体瘤中的免疫抑制性微环境被认为对诸如嵌合抗原受体（CAR）T细胞等基于细胞的疗法的进入和疗效形成了障碍。已证明将CAR T细胞疗法与检查点抑制剂相结合可对抗实体瘤中的免疫逃逸机制并增强抗肿瘤功效。我们评估了PD-1 / PD-1L1信号传导能力以及该检查点轴抑制剂在体外系统中对癌细胞攻击，L1CAM特异性CAR T细胞与神经母细胞瘤细胞系的共培养的影响。基于荧光激活细胞分选的分析和萤光素酶报告基因分析可评估CAR T和肿瘤细胞上PD-1 / PD-L1的表达以及CAR T细胞杀死神经母细胞瘤细胞的能力。将神经母细胞瘤细胞系与L1CAM-CAR T细胞共培养可上调神经母细胞瘤细胞上PD-L1的表达，从而确认适应性免疫抵抗。暴露于神经母细胞瘤细胞也会上调CAR T细胞中PD-1 / PD-L1轴的表达。检查点抑制剂nivolumab增强了L1CAM‐CAR T细胞定向杀伤。但是，尼古鲁单抗增强的L1CAM-CAR T细胞杀伤与神经母细胞瘤细胞上PD-L1表达并不严格相关。实际上，检查点抑制剂的成功依赖于CAR T细胞中强大的PD-1 / PD-L1轴表达，这又取决于CAR构建体中的共刺激结构域，更重要的是取决于为CAR T选择的T细胞子集细胞生成。从而，