放射治疗（RT）是实体瘤的主要治疗方法。它有可能在局部和远端激发针对肿瘤的免疫反应，从而深刻影响临床结果。然而，放疗也可能促进免疫抑制细胞因子和免疫抑制细胞的积累，极大地阻碍抗肿瘤免疫反应的激活，并大大限制放疗的有效性。因此，调节放疗后的免疫抑制以引导免疫环境增强激活可能会增强放疗的治疗潜力。细胞因子是多种细胞反应的有效协调者，在调节这种免疫抑制反应中发挥着关键作用。识别并迅速中和早期释放的免疫抑制细胞因子是增强 RT 免疫调节作用的关键进展。为此，我们在放疗后对免疫抑制细胞因子进行了筛选，并确定巨噬细胞集落刺激因子（MCSF）是一种早期上调且持久的免疫抑制剂。单细胞测序显示MCSF上调的主要来源来源于肿瘤细胞。机制探索表明，p65 蛋白的辐射依赖性磷酸化促进其与 MCSF 基因启动子的结合，从而增强转录。敲低和化学抑制剂实验最终证明，抑制肿瘤细胞来源的 MCSF 可以增强 RT 的免疫激活作用，通过辐射后早期阻断 MCSF 可以达到最佳效果。此外，我们验证了 MCSF 作用于巨噬细胞，诱导大量抑制性细胞因子的分泌。总之，我们提出了一种新方法，通过在照射后早期阻断 MCSF-CSF1R 信号通路来增强放疗的免疫激活效果。版权所有 © 2024 廖志云等人。

Radiotherapy (RT) serves as the primary treatment for solid tumors. Its potential to incite an immune response against tumors both locally and distally profoundly impacts clinical outcomes. However, RT may also promote the accumulation of immunosuppressive cytokines and immunosuppressive cells, greatly impeding the activation of antitumor immune responses and substantially limiting the effectiveness of RT. Therefore, regulating post-RT immunosuppression to steer the immune milieu toward heightened activation potentially enhances RT's therapeutic potential. Cytokines, potent orchestrators of diverse cellular responses, play a pivotal role in regulating this immunosuppressive response. Identifying and promptly neutralizing early released immunosuppressive cytokines are a crucial development in augmenting RT's immunomodulatory effects. To this end, we conducted a screen of immunosuppressive cytokines following RT and identified macrophage colony-stimulating factor (MCSF) as an early up-regulated and persistent immune suppressor. Single-cell sequencing revealed that the main source of up-regulated MCSF derived from tumor cells. Mechanistic exploration revealed that irradiation-dependent phosphorylation of the p65 protein facilitated its binding to the MCSF gene promoter, enhancing transcription. Knockdown and chemical inhibitor experiments conclusively demonstrated that suppressing tumor cell-derived MCSF amplifies RT's immune-activating effects, with optimal results achieved by early MCSF blockade after irradiation. Additionally, we validated that MCSF acted on macrophages, inducing the secretion of a large number of inhibitory cytokines. In summary, we propose a novel approach to enhance the immune activation effects of RT by blocking the MCSF-CSF1R signaling pathway early after irradiation.Copyright © 2024 Zhiyun Liao et al.