Data Sheet 1_Rational modulation of immune mechanisms synergizes the anti-tumor effects of targeted radiation therapy in pre-clinical models.pdf

Immunotherapy has revolutionized cancer treatment, offering new hope for many patients. However, while some individuals show remarkable responses, the overall success rate remains limited. This has spurred interest in combination therapies, particularly with established treatments like radiation therapy (RT), to improve outcomes. RT is a cornerstone of cancer therapy and known to influence the immune landscape, yet a systematic characterization of its effects on tumor-infiltrating leukocytes (TILs) and a rationale-based therapy is still lacking. In this study, we employed a diverse set of pre-clinical syngeneic murine tumor models with varying immune profiles to investigate the immunological impact of tumor targeted RT. We observed that immunologically ‘hot’ tumors showed stronger tumor growth inhibition (TGI) after RT compared to ‘cold’ tumors. Additionally, RT induced both pro- and anti-inflammatory shifts within the tumor immune microenvironment. Importantly, RT led to an intra-tumoral increase in proliferating CD8+ T cells, while the population of proliferating macrophages was notably reduced. To identify immune-modulatory pathways that shape the response to RT across different tumor immune contexts, we tested RT in HPK1 (Hematopoietic Progenitor Kinase 1) and STING (Stimulator of Interferon Genes) deficient mice. These experiments revealed that STING deficiency compromises TGI in tumors with a high baseline population of myeloid cells expressing an interferon response signature. Moreover, we identified a synergistic effect on survival in tumor-bearing mice when combining HPK1 deficiency with RT. Thus, RT promotes expansion of cytotoxic T cells while limiting macrophage proliferation, with therapeutic outcomes strongly influenced by STING and HPK1 pathways. Collectively, these results highlight the complex interplay between RT, tumor immune microenvironment and response to therapy, offering potential avenues for novel therapeutic combinations.

免疫疗法（Immunotherapy）彻底革新了癌症治疗格局，为众多患者带来了新的生存希望。然而，尽管部分患者可获得显著疗效，但整体治疗成功率仍较为有限。这一现状推动了联合疗法的研究热潮，尤其是与放疗（Radiation Therapy, RT）这类成熟治疗手段的联合，以期改善治疗结局。放疗是癌症治疗的核心支柱之一，且已被证实可调控肿瘤免疫微环境，但目前仍缺乏针对其在肿瘤浸润淋巴细胞（Tumor-Infiltrating Leukocytes, TILs）上的作用开展系统性表征的研究，同时基于科学依据的联合疗法也尚未得到充分开发。本研究采用了一组具有不同免疫表型的多样化临床前同基因小鼠肿瘤模型，以探究靶向肿瘤的放疗对肿瘤免疫的影响。我们观察到，与免疫“冷”肿瘤相比，免疫“热”肿瘤在接受放疗后展现出更显著的肿瘤生长抑制（Tumor Growth Inhibition, TGI）效果。此外，放疗可在肿瘤免疫微环境中同时诱导促炎与抗炎的免疫表型转变。值得注意的是，放疗可使肿瘤内增殖性CD8+ T细胞数量增加，而增殖性巨噬细胞的群体规模则显著减少。为了明确在不同肿瘤免疫背景下调控放疗应答的免疫调控通路，我们在造血祖细胞激酶1（Hematopoietic Progenitor Kinase 1, HPK1）与干扰素基因刺激因子（Stimulator of Interferon Genes, STING）基因缺陷小鼠中开展了放疗实验。这些实验结果表明，在基线状态下髓系细胞高表达干扰素应答特征的肿瘤中，STING基因缺陷会削弱放疗的肿瘤生长抑制效果。此外，我们还发现，将HPK1基因缺陷与放疗联合使用时，可对荷瘤小鼠的生存产生协同增益效应。综上，放疗可促进细胞毒性T细胞的扩增，同时抑制巨噬细胞的增殖，其治疗结局受STING与HPK1通路的显著调控。综合来看，本研究结果揭示了放疗、肿瘤免疫微环境与治疗应答之间的复杂相互作用，为开发新型联合治疗方案提供了潜在方向。