目的:通过侵入性程序获得的肿瘤活检中程序性死亡配体1(PD-L1)的免疫组织化学染色通常用于临床实践,以确定最有可能从抗程序性细胞死亡蛋白1(PD-1)治疗中受益的患者。然而,PD-L1表达在肿瘤及其微环境中的各种细胞亚群中观察到,包括肿瘤细胞,树突状细胞,和巨噬细胞。这些不同细胞类型的PD-L1表达对对抗PD-1治疗的反应性的影响尚未完全理解。
方法:我们合成了基于聚合物的溶酶体靶向嵌合体(LYTAC),该嵌合体融合了PD-L1靶向基序和肝细胞特异性去唾液酸糖蛋白受体(ASGPR)识别元件。还使用PD-L1特异性放射性示踪剂89Zr-αPD-L1/Fab进行PD-L1表达的小动物正电子发射断层扫描(PET)成像。
结果:PD-L1LYTAC平台能够通过ASGPR通过溶酶体降解途径特异性降解在肝癌细胞上表达的PD-L1,而不影响宿主细胞上的PD-L1表达。当结合全身PD-L1PET成像时,我们的研究表明,宿主细胞PD-L1,而不是肿瘤细胞PD-L1,在肝癌小鼠模型抗PD-1治疗的抗肿瘤应答中起关键作用.
结论:LYTAC策略,通过PET成像增强,有可能克服敲除小鼠模型的局限性,并为体内靶蛋白的选择性降解提供通用方法。这可以显着帮助研究与活体受试者中特定细胞亚群相关的蛋白质功能的作用和机制。
OBJECTIVE: Immunohistochemical staining of programmed death-ligand 1 (PD-L1) in tumor biopsies acquired through invasive procedures is routinely employed in clinical practice to identify patients who are most likely to benefit from anti-programmed cell death protein 1 (PD-1) therapy. Nevertheless, PD-L1 expression is observed in various cellular subsets within tumors and their microenvironments, including tumor cells, dendritic cells, and macrophages. The impact of PD-L1 expression across these different cell types on the responsiveness to anti-PD-1 treatment is yet to be fully understood.
METHODS: We synthesized polymer-based lysosome-targeting chimeras (LYTACs) that incorporate both PD-L1-targeting motifs and liver cell-specific asialoglycoprotein receptor (ASGPR) recognition elements. Small-animal positron emission tomography (PET) imaging of PD-L1 expression was also conducted using a PD-L1-specific radiotracer 89Zr-αPD-L1/Fab.
RESULTS: The PD-L1 LYTAC platform was capable of specifically degrading PD-L1 expressed on liver cancer cells through the lysosomal degradation pathway via ASGPR without impacting the PD-L1 expression on host cells. When coupled with whole-body PD-L1 PET imaging, our studies revealed that host cell PD-L1, rather than tumor cell PD-L1, is pivotal in the antitumor response to anti-PD-1 therapy in a mouse model of liver cancer.
CONCLUSIONS: The LYTAC strategy, enhanced by PET imaging, has the potential to surmount the limitations of knockout mouse models and to provide a versatile approach for the selective degradation of target proteins in vivo. This could significantly aid in the investigation of the roles and mechanisms of protein functions associated with specific cell subsets in living subjects.