Abstract
Programmed death ligand 1 (PD-L1) is a typical immune surface protein that binds to programmed cell death 1 (PD-1) on T cells through its extracellular domain. Subsequently, T cell activity is inhibited, and tumor immune tolerance is enhanced. Anti-PD-1/PD-L1 immune checkpoint therapy blocks the combination of PD-1/PD-L1 and rejuvenates depleted T cells, thereby inhibiting tumor growth. Exosomes are biologically active lipid bilayer nanovesicles secreted by various cell types, which mediate signal communication between cells. Studies have shown that PD-L1 can not only be expressed on the surface of tumor cells, immune cells, and other cells in the tumor microenvironment, but also be released from tumor cells and exist in an extracellular form. In particular, exosome PD-L1 plays an unfavorable role in tumor immunosuppression. The immunomodulatory effect of exosome PD-L1 and its potential in fluid diagnosis have attracted our attention. This review aims to summarize the available evidence regarding the biological characteristics of exosome PD-L1 in tumor immunity, with a particular focus on the mechanisms in different cancers and clinical prospects. In addition, we also summarized the current possible and effective detection methods for exosome PD-L1 and proposed that exosome PD-L1 has the potential to become a target for overcoming anti-PD-1/PD-L1 antibody treatment resistance.
Highlights
Programmed cell death-1 (PD-1), known as CD279, is expressed in a variety of immune cells, including peripheral activated T cells, B cells, and monocytes (Nishimura et al, 1996; Keir et al, 2008)
Tumor-derived exosomes Programmed death ligand 1 (PD-L1) play a key role in tumor immune escape of tumors
Many studies have confirmed that PD-L1 on tumor cells mediates immunosuppressive effects
Summary
Programmed cell death-1 (PD-1), known as CD279, is expressed in a variety of immune cells, including peripheral activated T cells, B cells, and monocytes (Nishimura et al, 1996; Keir et al, 2008). The two known ligands of PD-1 are Programmed death-ligand 1 PD-L1 (B7-H1) and PDL2 (B7-DC) (Blank et al, 2004). Exosomal PD-L1 on Tumor Immunity on T cells through its extracellular domain (Dong et al, 1999). PD-L1 inhibits the activity of T cells and enhances the immune tolerance of tumor cells, thereby preventing the immune response, which may damage the tumor, and leading to the immune escape of the tumor. PD-L1 is considered to be a critical factor involved in tumor immune escape
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