背景：免疫检查点阻断剂(ICBs)对于癌症的疗法是一项革命性的策略，但大多数实体瘤患者对ICBs仍然具有抗药性，部分原因是由于难以逆转高度免疫抑制的肿瘤微环境(TME)。开发肿瘤免疫治疗策略高度依赖于发现肿瘤免疫逃逸分子机制和潜在治疗靶点。Krüppel-like Factor 5(KLF5)是一种内源性致癌基因，能促进肿瘤的形成。然而，KLF5对于抑制癌症免疫反应的细胞外影响尚不清楚。 方法：我们分析了具有KLF5删除/过度表达的肿瘤细胞移植到小鼠模型中的KLF5的免疫抑制作用。我们进行了RNA测序、免疫组织化学、西方印迹、实时荧光定量PCR、ELISA、荧光素酶检测、染色质免疫沉淀(ChIP)和流式细胞术，以证明KLF5对CD8+T细胞浸润和相关分子机制的影响。单细胞RNA测序和空间转录组学分析被应用于进一步解读KLF5表达与浸润免疫细胞的关联。探索KLF5/COX2抑制剂与抗程序性细胞死亡蛋白1(anti-PD1)治疗的联合效力于临床前模型。最后，建立了一个基于KLF5/COX2轴和相关免疫标志物的基因表达签名来预测患者的存活。 结果：KLF5失活以CD8+T细胞为依赖关系减缓了基底样乳腺肿瘤的生长。转录组学分析表明，肿瘤中KLF5缺失增加了T淋巴细胞的数量和活化功能。在机械上，KLF5结合到COX2基因的启动子并促进COX2的转录，随后，KLF5的缺失通过减少COX2表达降低了PGE2从肿瘤细胞中的释放。抑制KLF5/COX2轴使肿瘤内抗肿瘤T细胞的数量和功能增加，以增强抗PD1治疗的抗肿瘤效应。在单细胞和空间分辨率下进行患者数据集分析显示，低KLF5表达与免疫支持型TME相关。 最后，我们生成了一个基于KLF5/COX2关联的免疫得分(KC-IS)来预测患者的生存。 结论：我们的研究结果确定了KLF5介导TME免疫抑制的新机制，针对KLF5/COX2/PGE2轴是一种重要的免疫治疗敏化剂。©作者。

Background: Immune checkpoint blockers (ICBs) are revolutionized therapeutic strategies for cancer, but most patients with solid neoplasms remain resistant to ICBs, partly because of the difficulty in reversing the highly immunosuppressive tumor microenvironment (TME). Exploring the strategies for tumor immunotherapy is highly dependent on the discovery of molecular mechanisms of tumor immune escape and potential therapeutic target. Krüppel-like Factor 5 (KLF5) is a cell-intrinsic oncogene to promote tumorigenesis. However, the cell-extrinsic effects of KLF5 on suppressing the immune response to cancer remain unclear. Methods: We analyzed the immunosuppressive role of KLF5 in mice models transplanted with KLF5-deleted/overexpressing tumor cells. We performed RNA sequencing, immunohistochemistry, western blotting, real time-PCR, ELISA, luciferase assay, chromatin immunoprecipitation (ChIP), and flow cytometry to demonstrate the effects of KLF5 on CD8+ T cell infiltration and related molecular mechanism. Single-cell RNA sequencing and spatial transcriptomics analysis were applied to further decipher the association between KLF5 expression and infiltrating immune cells. The efficacy of KLF5/COX2 inhibitors combined with anti-programmed cell death protein 1 (anti-PD1) therapy were explored in pre-clinical models. Finally, a gene-expression signature depending on KLF5/COX2 axis and associated immune markers was created to predict patient survival. Results: KLF5 inactivation decelerated basal-like breast tumor growth in a CD8+ T-cell-dependent manner. Transcriptomic profiling revealed that KLF5 loss in tumors increases the number and activated function of T lymphocytes. Mechanistically, KLF5 binds to the promoter of the COX2 gene and promotes COX2 transcription; subsequently, KLF5 deficiency decreases prostaglandin E2 (PGE2) release from tumor cells by reducing COX2 expression. Inhibition of the KLF5/COX2 axis increases the number and functionality of intratumoral antitumor T cells to synergize the antitumorigenic effects of anti-PD1 therapy. Analysis of patient datasets at single-cell and spatial resolution shows that low expression of KLF5 is associated with an immune-supportive TME. Finally, we generate a KLF5/COX2-associated immune score (KC-IS) to predict patient survival. Conclusions: Our results identified a novel mechanism responsible for KLF5-mediated immunosuppression in TME, and targeting the KLF5/COX2/PGE2 axis is a critical immunotherapy sensitizer.© The author(s).