Determining mechanisms of resistance to αPD-1/PD-L1 immune-checkpoint immunotherapy is key to developing new treatment strategies. Cancer-associated fibroblasts (CAF) have many tumor-promoting functions and promote immune evasion through multiple mechanisms, but as yet, no CAF-specific inhibitors are clinically available. Here we generated CAF-rich murine tumor models (TC1, MC38, and 4T1) to investigate how CAFs influence the immune microenvironment and affect response to different immunotherapy modalities [anticancer vaccination, TC1 (HPV E7 DNA vaccine), αPD-1, and MC38] and found that CAFs broadly suppressed response by specifically excluding CD8+ T cells from tumors (not CD4+ T cells or macrophages); CD8+ T-cell exclusion was similarly present in CAF-rich human tumors. RNA sequencing of CD8+ T cells from CAF-rich murine tumors and immunochemistry analysis of human tumors identified significant upregulation of CTLA-4 in the absence of other exhaustion markers; inhibiting CTLA-4 with a nondepleting antibody overcame the CD8+ T-cell exclusion effect without affecting Tregs. We then examined the potential for CAF targeting, focusing on the ROS-producing enzyme NOX4, which is upregulated by CAF in many human cancers, and compared this with TGFβ1 inhibition, a key regulator of the CAF phenotype. siRNA knockdown or pharmacologic inhibition [GKT137831 (Setanaxib)] of NOX4 "normalized" CAF to a quiescent phenotype and promoted intratumoral CD8+ T-cell infiltration, overcoming the exclusion effect; TGFβ1 inhibition could prevent, but not reverse, CAF differentiation. Finally, NOX4 inhibition restored immunotherapy response in CAF-rich tumors. These findings demonstrate that CAF-mediated immunotherapy resistance can be effectively overcome through NOX4 inhibition and could improve outcome in a broad range of cancers. SIGNIFICANCE: NOX4 is critical for maintaining the immune-suppressive CAF phenotype in tumors. Pharmacologic inhibition of NOX4 potentiates immunotherapy by overcoming CAF-mediated CD8+ T-cell exclusion. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/9/1846/F1.large.jpg.See related commentary by Hayward, p. 1799.

中文翻译：

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NOX4 抑制通过克服癌症相关成纤维细胞介导的 CD8 T 细胞排斥肿瘤来增强免疫治疗。


确定 αPD-1/PD-L1 免疫检查点免疫疗法的耐药机制是开发新治疗策略的关键。癌症相关成纤维细胞（CAF）具有多种促肿瘤功能，并通过多种机制促进免疫逃避，但目前临床上尚无CAF特异性抑制剂。在这里，我们生成了富含 CAF 的小鼠肿瘤模型（TC1、MC38 和 4T1），以研究 CAF 如何影响免疫微环境并影响对不同免疫治疗方式的反应 [抗癌疫苗、TC1（HPV E7 DNA 疫苗）、αPD-1 和 MC38] ] 并发现 CAF 通过特异性排除肿瘤中的 CD8+ T 细胞（不是 CD4+ T 细胞或巨噬细胞）来广泛抑制反应； CD8+ T 细胞排斥同样存在于富含 CAF 的人类肿瘤中。对富含 CAF 的小鼠肿瘤中的 CD8+ T 细胞进行 RNA 测序，并对人类肿瘤进行免疫化学分析，发现在没有其他耗竭标志物的情况下 CTLA-4 显着上调；用非消耗性抗体抑制 CTLA-4 克服了 CD8+ T 细胞排斥效应，而不影响 Tregs。然后，我们检查了 CAF 靶向的潜力，重点关注产生 ROS 的酶 NOX4（该酶在许多人类癌症中被 CAF 上调），并将其与 TGFβ1 抑制（CAF 表型的关键调节因子）进行了比较。 NOX4 的 siRNA 敲低或药物抑制 [GKT137831 (Setanaxib)] 将 CAF“正常化”至静止表型，并促进瘤内 CD8+ T 细胞浸润，克服排斥效应； TGFβ1 抑制可以阻止但不能逆转 CAF 分化。最后，NOX4 抑制恢复了富含 CAF 的肿瘤的免疫治疗反应。 这些发现表明，通过抑制 NOX4 可以有效克服 CAF 介导的免疫治疗耐药性，并可以改善多种癌症的治疗结果。意义：NOX4 对于维持肿瘤中免疫抑制 CAF 表型至关重要。 NOX4 的药理抑制可通过克服 CAF 介导的 CD8+ T 细胞排斥来增强免疫治疗。图解摘要：http://cancerres.aacrjournals.org/content/canres/80/9/1846/F1.large.jpg。参见 Hayward 的相关评论，第 14 页。 1799.