Targeting regulatory T cells in anti-PD-1/PD-L1 cancer immunotherapy

The programmed death (PD)-1/PD-ligand (PD-L) pathway and regulatory T cells (Tregs) are essential for the maintenance of immune tolerance. Their activation in the tumour microenvironment contributes to the evasion of the transformed cells from the immune surveillance and the suppression of an antitumour immune response. Therefore, PD-1/PD-L1 and Tregs are important targets for cancer immunotherapy. Our review focuses on the current role of the PD-1/PD-L1 axis in Treg development and function in the tumour microenvironment. We also discuss combination therapy with PD-1/PD-L1 inhibitors and Treg-modulating agents affecting the adenosinergic pathway, TGF-beta signalling, immune checkpoints and other approaches to downregulation of Tregs.

Automated summary

The programmed death (PD)-1/PD-ligand (PD-L) pathway and regulatory T cells (Tregs) are crucial for maintaining immune tolerance and their activation in the tumour microenvironment plays a significant role in immune evasion and suppression of antitumour immune response. Therefore, PD-1/PD-L1 and Tregs are important targets for cancer immunotherapy. This review focuses on the current understanding of the role of the PD-1/PD-L1 axis in Treg development and function in the tumour microenvironment, as well as discusses combination therapies targeting PD-1/PD-L1 and Treg-modulating agents.