members of the immune checkpoint family

PD-1 and its ligand PD-L1 play critical roles in maintaining the balance between autoimmunity and tolerance. The interaction of PD-1/PD-L1 is also involved in tumor evasion inside the tumor microenvironment

caused by reduced T cell activation

proliferation

cytotoxic secretion

and survival. Previous research has shown that the expression level of PD-1/PD-L1 may be regulated by ubiquitin-mediated proteasome degradation

which is an important mode of post-translational modification (PTM). PD-1/PD-L1 ubiquitin modification research in tumor immunotherapy is the subject of the present review

which aims to assess the most recent developments in this area. We offer a short explanation of PD-1/PD-L1 as well as some basic background information on the UPS system and discuss many routes that target E3s and DUBs

respectively

in the regulation of PD-1/PD-L1 in tumor immunotherapy. In addition

we offer numerous innovative prospective research areas for the future

as well as novel immunotherapy concepts and ideas. Taken together

the information compiled herein should serve as a comprehensive repository of information about tumor immunotherapy that is currently available

and it should be useful in the design of future studies

as well as the development of potential targets and strategies for future tumor immunotherapy.