免疫检查点抑制剂(ICI)针对程序性细胞死亡1(PD-1)/程序性细胞死亡配体1(PD-L1)的治疗显示出有前途的临床效益。然而，相对较低的反应率突显了需要开发替代策略以针对PD-1/PD-L1免疫检查点。我们的研究聚焦于骨化前蛋白A1(ANXA1)-衍生肽A11降解PD-L1的作用和机制以及A11对多癌种肿瘤免疫逃避的影响。通过生物素拉升耦合质谱分析鉴定了A11与PD-L1的结合。筛选了一个人源去泛素酶cDNA文库，发现了作为PD-L1去泛素酶的USP7。分析了A11与USP7竞争性降解PD-L1的作用和机制。通过抑制肿瘤免疫逃避来研究A11提高T细胞介导的肿瘤细胞杀伤活性和抗肿瘤效果的能力。在小鼠身上研究了A11和PD-L1 mAb(单克隆抗体)通过抑制肿瘤免疫逃避的协同抗肿瘤效应。用免疫组织化学评估了癌细胞组织中USP7和PD-L1的表达和临床意义。在乳腺癌、非小细胞肺癌和皮肤黑色素瘤组织中，USP7和PD-L1的表达水平显著高于相应正常组织，且在癌组织中呈正相关，两种蛋白质预测PD-1 mAb免疫治疗的疗效和患者预后的能力均优于单个蛋白质。我们的结果揭示了A11在癌细胞中与USP7竞争性结合和降解PD-L1,A11表现出明显的抗肿瘤效应，并通过抑制肿瘤免疫逃避与PD-1 mAb呈协同抗肿瘤活性，A11可以作为多种癌症ICIs治疗的替代策略。©作者(或其雇主)2023。根据CC BY-NC许可再使用。不得商业再利用。由BMJ出版。

Immune checkpoint inhibitors (ICIs) therapy targeting programmed cell death 1 (PD-1)/programmed cell death ligand 1 (PD-L1) shows promising clinical benefits. However, the relatively low response rate highlights the need to develop an alternative strategy to target PD-1/PD-L1 immune checkpoint. Our study focuses on the role and mechanism of annexin A1 (ANXA1)-derived peptide A11 degrading PD-L1 and the effect of A11 on tumor immune evasion in multiple cancers.Binding of A11 to PD-L1 was identified by biotin pull-down coupled with mass spectrometry analysis. USP7 as PD-L1's deubiquitinase was found by screening a human deubiquitinase cDNA library. The role and mechanism of A11 competing with USP7 to degrade PD-L1 were analyzed. The capability to enhance the T cell-mediated tumor cell killing activity and antitumor effect of A11 via suppressing tumor immune evasion were investigated. The synergistic antitumor effect of A11 and PD-L1 mAb (monoclonal antibody) via suppressing tumor immune evasion were also studied in mice. The expression and clinical significance of USP7 and PD-L1 in cancer tissues were evaluated by immunohistochemistry.A11 decreases PD-L1 protein stability and levels by ubiquitin proteasome pathway in breast cancer, lung cancer and melanoma cells. Mechanistically, A11 competes with PD-L1's deubiquitinase USP7 for binding PD-L1, and then degrades PD-L1 by inhibiting USP7-mediated PD-L1 deubiquitination. Functionally, A11 promotes T cell ability of killing cancer cells in vitro, inhibits tumor immune evasion in mice via increasing the population and activation of CD8+ T cells in tumor microenvironment, and A11 and PD-1 mAb possess synergistic antitumor effect in mice. Moreover, expression levels of both USP7 and PD-L1 are significantly higher in breast cancer, non-small cell lung cancer and skin melanoma tissues than those in their corresponding normal tissues and are positively correlated in cancer tissues, and both proteins for predicting efficacy of PD-1 mAb immunotherapy and patient prognosis are superior to individual protein.Our results reveal that A11 competes with USP7 to bind and degrade PD-L1 in cancer cells, A11 exhibits obvious antitumor effects and synergistic antitumor activity with PD-1 mAb via inhibiting tumor immune evasion and A11 can serve as an alternative strategy for ICIs therapy in multiple cancers.© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.