Phage display-identified PD-L1-binding peptides reinvigorate T-cell activity and inhibit tumor progression
Smriti Gurung1, Fatima Khan1, Gowri Rangaswamy Gunassekaran1
1Department of Biochemistry and Cell Biology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu, 41944, Republic of Korea; BK21 Plus KNU Biomedical Convergence Program, Department of Biomedical Science, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu, 41944, Republic of Korea; CMRI, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu, 41944, Republic of Korea.
Abstract:
Blockade of programmed cell death ligand-1 (PD-L1) restores T-cell activity and enhances anti-tumor immunity. Screening a phage-displayed peptide library for peptides that selectively bind to PD-L1-overexpressing cells identified two peptides, CLQKTPKQC and CVRARTR (PD-L1Pep-1 and PD-L1Pep-2, respectively) that appeared to block PD-L1. PD-L1Pep-1 and PD-L1Pep-2 preferentially bound to high PD-L1-expressing cells over low PD-L1-expressing cells; binding was further enhanced by interferon-γ, an inducer of PD-L1 expression. Binding affinities of PD-L1Pep-1 and PD-L1Pep-2 were approximately 373 and 281 nM, respectively. Cellular binding of the PD-L1-binding peptides was reduced by silencing PD-L1 gene expression or competition with anti-PD-L1 antibody. PD-L1Pep-1 and PD-L1Pep-2 induced the internalization and downregulated cell surface levels of PD-L1. The PD-L1-binding peptides restored cytokine secretion and T-cell proliferation to cells inhibited by co-culture with tumor cells or culture on PD-L1-coated plates. Intravenously injected PD-L1Pep-1 and PD-L1Pep-2 efficiently homed to tumor tissues, inhibited tumor growth, and increased CD8+/FoxP3+ ratio in mice. The PD-L1-binding peptides in combination with doxorubicin or PD-L1-targeted liposomal doxorubicin inhibited tumor growth and increased CD8+/FoxP3+ ratio more efficiently than doxorubicin alone and untargeted liposomal doxorubicin, respectively. These results suggest that PD-L1Pep-1 and PD-L1Pep-2 block PD-L1 and reinvigorate T-cell activity, inhibiting tumor growth by enhancing anti-tumor immunity.
Insights
Two novel peptides, PD-L1Pep-1 and PD-L1Pep-2, were identified that block programmed cell death ligand-1 (PD-L1), restoring T-cell activity and enhancing anti-tumor immunity to inhibit tumor growth.
Area of Science:
- Immunology
- Cancer Biology
- Drug Discovery
Background:
- Programmed cell death ligand-1 (PD-L1) blockade enhances anti-tumor immunity by restoring T-cell activity.
- Identifying novel agents that target PD-L1 is crucial for cancer immunotherapy.
Purpose of the Study:
- To screen for and characterize peptides that selectively bind to and block PD-L1.
- To evaluate the therapeutic potential of these PD-L1-binding peptides in preclinical cancer models.
Main Methods:
- Phage display library screening to identify PD-L1-binding peptides.
- In vitro assays to assess peptide binding affinity, specificity, and mechanism of action (e.g., PD-L1 internalization).
- In vivo studies in mice to evaluate tumor homing, tumor growth inhibition, and immune cell modulation (CD8+/FoxP3+ ratio).
- Combination therapy studies with chemotherapy agents.
Main Results:
- Two peptides, PD-L1Pep-1 and PD-L1Pep-2, were identified with specific binding to PD-L1-expressing cells.
- These peptides induced PD-L1 internalization, restored T-cell cytokine secretion and proliferation, and inhibited tumor growth in mice.
- Intravenously administered peptides effectively homed to tumors and increased the CD8+/FoxP3+ ratio.
- Combination therapy with PD-L1Pep-1/2 and doxorubicin showed enhanced tumor inhibition.
Conclusions:
- PD-L1Pep-1 and PD-L1Pep-2 effectively block PD-L1 function, reinvigorating T-cell-mediated anti-tumor immunity.
- These peptides represent promising therapeutic candidates for cancer treatment, potentially enhancing existing therapies.
