理由：免疫抑制性肿瘤微环境（TME）是肿瘤免疫治疗的主要障碍。干扰素基因刺激剂 (STING) 激动剂可触发炎症先天免疫反应，从而可能克服肿瘤免疫抑制。虽然 STING 激动剂可能有望成为潜在的癌症治疗药物，但临床试验中已经出现了肿瘤对 STING 单一疗法的耐药性，且其机制仍不清楚。方法：使用小鼠肿瘤模型测量 STING 激动剂 ADU-S100 (S100) 加上抗 T 细胞免疫球蛋白和粘蛋白结构域 3 抗体 (αTim-3) 的体内抗肿瘤免疫力。使用流式细胞术检测肿瘤特异性 T 细胞激活和 TME 的改变。还使用流式细胞术测量了树突状细胞 (DC) 的成熟和功能，并通过封闭抗体测量了 CD4 T 细胞在联合治疗中的重要性。此外，S100 对 CD4 T 的影响通过体外测定得到验证。最后，在人类肿瘤样本中进一步评估了高表达 Tim-3 的传统树突状细胞 (cDC) 2 对生存或治疗结果的影响。结果：S100 通过激活 cDC1 增强 CD8 T，但未能启动 cDC2。从机制上讲，施用 S100 会导致小鼠和人类 cDC2 (Tim-3 cDC2) 中表达的 Tim-3 上调，从而产生免疫抑制作用。 Tim-3 cDC2 抑制 CD4 T 并减弱 CD4 T 驱动的抗肿瘤反应。 S100与αTim-3联合有效促进cDC2成熟和抗原呈递，释放CD4 T细胞，从而减轻肿瘤负荷，同时延长生存期。此外，人类 TME 中高比例的 Tim-3 cDC2 预示着不良预后，而 Tim-3 cDC2 的丰度可能作为 CD4 T 质量的生物标志物和免疫治疗反应性的重要指标。结论：本研究表明，阻断Tim-3可以通过调节cDC2释放CD4 T细胞来增强STING激动剂ADU-S100的抗肿瘤免疫力。除了提供克服肿瘤免疫抑制的组合策略外，它还揭示了 ADU-S100 单一疗法的内在障碍。© 作者。

Rationale: An immunosuppressive tumor microenvironment (TME) is a major obstacle in tumor immunotherapy. Stimulator of interferon genes (STING) agonists trigger an inflammatory innate immune response to potentially overcome tumor immunosuppression. While STING agonists may hold promise as potential cancer therapy agents, tumor resistance to STING monotherapy has emerged in clinical trials, and the mechanisms remain unclear. Methods: The in vivo anti-tumor immunity of STING agonist ADU-S100 (S100), plus anti-T cell immunoglobulin and mucin-domain containing-3 antibody (αTim-3) were measured using murine tumor models. Tumor-specific T cell activation and alterations in the TME were detected using flow cytometry. The maturation and function of dendritic cells (DC) were also measured using flow cytometry, and the importance of CD4+ T cells in combination therapy was measured by blocking antibodies. Additionally, the effect of S100 on CD4+ T was verified via in vitro assays. Lastly, the impact of conventional dendritic cells (cDC) 2 with a high expression of Tim-3 on survival or therapeutic outcomes was further evaluated in human tumor samples. Results: S100 boosted CD8+ T by activating cDC1 but failed to initiate cDC2. Mechanistically, the administration of S100 results in an upregulation of Tim-3 expressed in cDC2 (Tim-3+cDC2) in both mice and humans, which is immunosuppressive. Tim-3+cDC2 restrained CD4+ T and attenuated the CD4+ T-driven anti-tumor response. Combining S100 with αTim-3 effectively promoted cDC2 maturation and antigen presentation, releasing CD4+ T cells, thus reducing tumor burden while prolonging survival. Furthermore, high percentages of Tim-3+cDC2 in the human TME predicted poor prognosis, whereas the abundance of Tim-3+cDC2 may act as a biomarker for CD4+ T quality and a contributing indicator for responsiveness to immunotherapy. Conclusion: This research demonstrated that blocking Tim-3 could enhance the anti-tumor immunity of STING agonist ADU-S100 by releasing CD4+ T cells through regulating cDC2. It also revealed an intrinsic barrier to ADU-S100 monotherapy, besides providing a combinatorial strategy for overcoming immunosuppression in tumors.© The author(s).