The roles of exosomal immune checkpoint proteins in tumors

Targeting immune checkpoints has achieved great therapeutic effects in the treatment of early-stage tumors.However,most patients develop adaptive resistance to this therapy.The latest evidence demonstrates that tumorderived exosomes may play a key role in systemic immune suppression and tumor progression.In this article,we highlight the role of exosomal immune checkpoint proteins in tumor immunity,with an emphasis on programmed death ligand 1(PD-L1) and cytotoxic T lymphocyte-associated antigen 4(CTLA-4),as well as emerging evidence on roles of T cell immunoglobulin-3(TIM-3),arginase 1(ARG1),and estrogen receptor binding fragment-associated antigen 9(EBAG9) expressed by exosomes.