Discovery of PD-L1 Peptide Inhibitors from Ascidian Enzymatic Hydrolysates by Affinity Ultrafiltration Coupled to NanoLC-MS/MS

Anti-PD-1 and anti-PD-L1 antibodies have achieved great clinical success in cancer immunotherapy, and peptide and small molecule inhibitors of PD-1/PD-L1 binding also attract much attention. Ascidians are not only seafood, but are also an important source of bioactive substances, including anti-tumo...

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Main Authors: Qiuyang Huang, Xiaoling Zang, Xinyu Jin, Qian Liu, Xin Zhang, Xinyu Li, Lizhen Zhao, Zhihua Lv
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Marine Drugs
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Online Access:https://www.mdpi.com/1660-3397/23/4/137
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Summary:Anti-PD-1 and anti-PD-L1 antibodies have achieved great clinical success in cancer immunotherapy, and peptide and small molecule inhibitors of PD-1/PD-L1 binding also attract much attention. Ascidians are not only seafood, but are also an important source of bioactive substances, including anti-tumor components. In this study, ascidian enzymatic hydrolysates were found to contain PD-1/PD-L1 inhibitory components. Affinity ultrafiltration (AUF) coupled with the nanoLC-MS/MS method was first applied in screening for PD-L1 peptide inhibitors from ascidian enzymatic hydrolysates. Two anti-PD-L1 ascidian peptides, C5 (LDVVIHTVTYGDR) and S2 (VLRDNIQGITKPAIR), were filtered out from the ascidians <i>Ciona intestinalis</i> and <i>Styela clava</i>, respectively. C5 and S2 showed moderate anti-PD-1/PD-L1 effects with the IC<sub>50</sub> values of 33.9 µM (C5) and 112.8 μM (S2), respectively, by homogenous time-resolved fluorescence (HTRF) binding assay, and the K<sub>D</sub> values of 22.9 µM (C5) and 29.1 µM (S2), respectively, by surface plasmon resonance (SPR) assay. The results of this study suggest that ascidian enzymatic hydrolysates may be a potential source of bioactive peptides with anti-PD-1/PD-L1 activity.
ISSN:1660-3397