抗PD-1/PD-L1单克隆抗体展现出显著的临床效益，并为多种肿瘤的治疗带来革命性的进展，但低反应率和免疫相关的不良事件限制了它们的应用，促使小分子药物的发展以提高PD-1/PD-L1阻断治疗的效果。波尼霉素（BON）是一种新的属于博来霉素（BLM）家族的小分子，体外和体内都表现出强效的抗癌活性，并且肺毒性可忽略不计，因此可以成为BLM的替代品。然而，对于BLM相关化合物的抗癌机制的了解极为有限，尚不清楚它们是否以与其他抗肿瘤药物类似的方式影响PD-L1水平。在本研究中，我们发现BON显著降低NCI-H460和HT-1080细胞中的PD-L1蛋白水平。同时，BON还能减少NCI-H460细胞的肿瘤异种移植模型中PD-L1蛋白水平。然而，在BON暴露后，mRNA水平没有受到影响。此外，BON诱导的PD-L1减少是蛋白酶体依赖的。通过使用特定的抑制剂和RNA干扰技术，我们确认BON引起的PD-L1蛋白降低是通过AMPK激活的内质网相关降解途径介导的，这类似于二甲双胍的作用。最后但并非最不重要的，BON在体外和体内对吉非替尼具有协同作用。总之，这是第一个报告表明BON通过AMPK介导的内质网相关降解途径降低PD-L1蛋白水平。这些发现将有助于BON的临床转化，并有助于揭示BLM相关化合物的分子机制。版权所有©2023 Elsevier B.V.保留所有权利。

Anti-PD-1/PD-L1 monoclonal antibodies have displayed remarkable clinical benefits and revolutionized the treatment of multiple tumor types, but the low response rates and immune-related adverse events limit their application, which promoting the development of small molecule agents to improve the efficacy of PD-1/PD-L1 blockade therapy. Boningmycin (BON), a new small molecule belonging to bleomycin (BLM) family, exhibits potent anticancer activity in vitro and in vivo, as well as negligible lung toxicity, thereby can be an alternative of BLM. However, understandings about the anticancer mechanism of BLM-related compounds are extremely rare, it remains unclear if they affect PD-L1 level in a manner similar to that of other antitumor drugs. In this study, we discover that BON significantly reduces PD-L1 protein level in NCI-H460 and HT-1080 cells. Meanwhile, BON decreases the protein level of PD-L1 in a tumor xenograft model of NCI-H460 cells. Nevertheless, the mRNA level is not influenced after BON exposure. Furthermore, BON-induced PD-L1 reduction is proteasome- dependent. By using specific inhibitors and RNA interference technology, we confirm that the decline of PD-L1 protein by BON is mediated by AMPK-activated endoplasmic reticulum-associated degradation pathway, which is like to the action of metformin. Last but not the least, BON has synergism on gefitinib in vitro and in vivo. In conclusion, it is the first report demonstrating that BON decreases PD-L1 protein level through AMPK-mediated endoplasmic reticulum-associated degradation pathway. These findings will benefit the clinical transformation of BON and aid in the elucidation of molecular mechanism of BLM-related compounds.Copyright © 2023 Elsevier B.V. All rights reserved.