Table 1.

Examples of exosomal PD-L1 in tumor immune evasion.

Cancer type	Role of exosomal PD-L1 in cancer	Potential mechanism	References
Metastatic melanoma	Exosomal PD-L1 facilitates the progression of melanoma in vitro and in vivo, and stratifies clinical responders to pembrolizumab and non-responders	Suppresses the function of CD8+ T cells to mediate immunosuppression	(8)
PC, CRC	Exosomal PD-L1 promotes tumor growth across different cancer types through suppression of the immune system	Suppresses T cell activity in the draining lymph node, and suppresses systemic anti-tumor immunity	(13)
Breast cancer	Exosomal PD-L1 suppresses killing of breast cancer cells by T cells and promote tumor growth	Inhibits CD3/CD28-induced ERK phosphorylation and NF-κB-mediated activation of T cells to attenuate anti-tumor immunity and suppresses T cell activity	(9)
Glioblastoma	EVs containing PD-L1 DNA could provide a surrogate marker of tumor volume and possibly help in real-time monitoring of cancer progression	Blocks TCR-mediated T cell activation to mediate immune evasion	(10)
HNSCC	The level of exosomal PD-L1 correlates with disease activity in patients with HNSCC, UICC stage, and lymph node status	Downregulates expression CD69 in effector T cells to suppress T cell-mediated killing	(11)
NSCLC	Exosomal PD-L1 promotes tumor growth in vitro and in vivo	Exosomal PD-L1 induces apoptosis and inhibits IFN-γ production in CD8+ T cells, and inhibits T cell activity	(15)
GC	Exosomal PD-L1 is associated with poor prognosis of patients with GC	Decreases expression of CD69 and PD-1 on T cell surface	(14)

PC, prostate cancer; EVs, extracellular vehicles; CRC, colorectal cancer; HNSCC, head and neck squamous cell carcinoma; UICC, Union for International Cancer Control; NSCLC, non-small cell lung cancer; GC, gastric cancer.