Local immune checkpoint blockade therapy by an adenovirus encoding a novel PD-L1 inhibitory peptide inhibits the growth of colon carcinoma in immunocompetent mice.
Transl Oncol 2022;
16:101337. [PMID:
34990908 PMCID:
PMC8741604 DOI:
10.1016/j.tranon.2021.101337]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 12/18/2021] [Accepted: 12/21/2021] [Indexed: 11/05/2022] Open
Abstract
A novel inhibitory peptide interfering with the PD-L1/PD-1 immune checkpoint pathway, dubbed PD-L1ip3, was designed.
The affinity of PD-L1ip3 for PD-L1 was only a few times weaker than that of its natural ligand, PD-1.
Direct treatment with PD-L1ip3 enhanced the ability of CD8+ T cells primed with cancer antigens to kill cancer cells in culture.
A combination treatment including transduction into cancer cells of a gene encoding PD-L1ip3 coupled with direct administration of PD-L1ip3 in peptide form significantly attenuated the growth of murine colon carcinoma in mice.
A novel peptide that interferes with the PD-1/PD-L1 immune checkpoint pathway, termed PD-L1 inhibitory peptide 3 (PD-L1ip3), was computationally designed, experimentally validated for its specific binding to PD-L1, and evaluated for its antitumor effects in cell culture and in a mouse colon carcinoma syngeneic murine model. In several cell culture studies, direct treatment with PD-L1ip3, but not a similar peptide with a scrambled sequence, substantially increased death of CT26 colon carcinoma cells when co-cultured with murine CD8+ T cells primed by CT26 cell antigens. In a syngeneic mouse tumor model, the growth of CT26 tumor cells transduced with the PD-L1ip3 gene by an adenovirus vector was significantly slower than that of un-transduced CT26 cells in immunocompetent mice. This tumor growth attenuation was further enhanced by the coadministration of the peptide form of PD-L1ip3 (10 mg/kg/day). The current study suggests that this peptide can stimulate host antitumor immunity via blockade of the PD-1/PD-L1 pathway, thereby increasing CD8+ T cell-induced death of colon carcinoma cells. The tumor site-specific inhibition of PD-L1 by an adenovirus carrying the PD-L1ip3 gene, together with direct peptide treatment, may be used as a local immune checkpoint blockade therapy to inhibit colon carcinoma growth.
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