Radiation and Dual Checkpoint Blockade Activates Non-Redundant Mechanisms in Cancer. Mus musculus

Response to immune checkpoint inhibitors may be improved through combinations with each other and other therapies, raising questions about non-redundancy and resistance. We report results from parallel studies of melanoma patients and mice treated with anti-CTLA4 and radiation (RT). Although combined treatment improved responses, resistance was common. Computational analyses of immune and transcriptomic profiles (provided here) revealed that resistance in mice was due to upregulation of tumor PD-L1 that drives T cell exhaustion. Accordingly, optimal response requires RT, anti-CTLA4, and anti-PD-L1. Anti-CTLA4 inhibits Tregs, RT diversifies and shapes the TCR repertoire, and anti-PD-L1 reinvigorates exhausted T cells. Together, all three therapies promote the expansion of clonotypes with distinct TCR traits. Similar to mice, patients with melanoma showing high PD-L1 did not respond to RT + anti-CTLA4, demonstrated persistent T cell exhaustion, and rapidly progressed. Thus, the combination of RT, anti-CTLA4, and anti-PD-L1 promotes response through distinct mechanisms. Overall design: Mice with bilateral flank B16-F10 tumors were treated with radiation to one tumor combinated with CTLA4 blockade. From unirradiated tumors that were resistant or relapsed after therapy, cell lines were isolated. After confirming the resistance phenotype by reimplantation, tumors from these resistant cells and control sensitive cells were profiled by microarray.

免疫检查点抑制剂的联合应用（包括彼此联合及与其他疗法联用）或可提升治疗响应率，这也引发了关于非冗余性与耐药性的相关科学问题。本研究报道了针对接受抗CTLA-4（anti-CTLA4）与放射治疗（RT）的黑色素瘤患者及小鼠的平行研究结果。尽管联合治疗改善了治疗响应，但耐药现象仍较为普遍。对本次公开的免疫组学与转录组学图谱进行计算分析后发现，小鼠体内的耐药性源于肿瘤程序性死亡配体1（PD-L1）的上调，该分子可诱导T细胞耗竭。据此，最优治疗响应需联合放射治疗、抗CTLA-4与抗PD-L1治疗。其中，抗CTLA-4可抑制调节性T细胞（Tregs），放射治疗可丰富并塑造T细胞受体（TCR）库，而抗PD-L1则可重振耗竭的T细胞。三者协同可促进具有独特TCR特征的克隆型扩增。与小鼠模型结果一致，高表达PD-L1的黑色素瘤患者对放射治疗联合抗CTLA-4治疗无响应，表现出持续的T细胞耗竭，并快速进展。综上，放射治疗、抗CTLA-4与抗PD-L1的联合方案可通过不同机制提升治疗响应率。总体实验设计：构建双侧皮下侧翼B16-F10黑色素瘤小鼠模型，对其一侧肿瘤施以放射治疗并联合CTLA-4阻断治疗。从治疗后产生耐药或复发的未照射肿瘤中分离细胞系。通过再次移植确认耐药表型后，对这些耐药细胞来源的肿瘤及对照敏感细胞来源的肿瘤进行微阵列（microarray）分析。