The function and potential drug targets of tumour-associated Tregs for cancer immunotherapy

Regulatory T cells (Tregs) play an important role in maintaining self-tolerance and immune homeostasis, but they also play a negative role in evoking effective antitumour immune responses. There is ample evidence indicating that the depletion of Tregs or the inhibition of Treg function will enhance antitumour effects. However, it is unclear which surface molecules of Tregs are suitable targets for tumour immunotherapy with minimal toxic side effects, which is a central theme in the field of Treg-targeted immunotherapy. In this review, we focus on the regulatory mechanisms of Tregs, including intrinsic and extrinsic factors within the tumour microenvironment, and we address potential drug targets on Tregs for immunotherapy.