Fig. 1
From: The roles of exosomal immune checkpoint proteins in tumors
Exosomes carrying immune checkpoint proteins can inhibit immune cell function and promote tumor progression. Exo-TIM-3 derived from NSCLC cells positively correlates with larger tumor size and worse distant metastasis. Exo-CTLA-4 secreted by glioblastoma cells suppress the activation of immune cells including CD4+ T cells, CD8+ T cells, NK cells and macrophages. Glioblastoma-derived Exo-PD-L1 and epithelial OvCa-derived Exo-ARG1 both inhibit the proliferation of CD4+ T cells and CD8+ T cells. Exo-PD-L1 secreted by HNSCC cells or metastatic melanoma cells suppresses the function of CD8+ T cells. Besides, Exo-PD-L1 from ESCC cells inhibits the proliferation of B cells and induces an increase in PD-1high Breg cells. The cytotoxicity of CTLs could be inhibited by breast cancer-derived Exo-PD-L1 and prostate cancer-derived Exo-EBAG9. ↑ Promotion; ↓ Inhibition; Exo-TIM-3 Exosomes containing T cell immunoglobulin-3; NSCLC Non-small-cell lung cancer; Exo-CTLA-4 Exosomes containing cytotoxic T lymphocyte-associated antigen 4; NK cells Natural killer cells; Exo-PD-L1 Exosomes containing programmed death ligand 1; OvCa Ovarian cancer; Exo-ARG1 Exosomes containing arginase 1; HNSCC Head and neck squamous cell carcinoma; ESCC Esophageal squamous cell carcinoma; CTLs Cytotoxic T lymphocytes; Exo-EBAG9, Exosomes containing estrogen receptor binding fragment-associated antigen 9