Regulatory T cells in solid tumor immunotherapy: effect, mechanism and clinical application.

The tumor-immune response is mobilized to suppress tumorigenesis, while the immune microenvironment and lymph node microenvironment are formed gradually during tumor progression. In fact, tumor surface antigens are not easily recognized by antigen-presenting cells. So it is hard for the immune system to kill the newly formed tumor cells effectively. In a normal immune environment, immune function is always suppressed to maintain the stability of the body, and regulatory T cells play an important role in maintaining immune suppression. However, during tumorigenesis, the suppression of regulatory T cell immune functions is more likely to contribute to tumor cell proliferation and migration leading directly to tumor progression. Therefore, focusing on the role of regulatory T cells in tumor immunity could improve tumor immunotherapy outcomes in the clinic. Regulatory T cells are more mature in hematologic system tumors than in solid tumors. However, there are continuing efforts to apply regulatory T cells for immunotherapy in solid tumors. This review describes the role of regulatory T cells in solid tumor immunotherapy from the perspective of prognosis, immune microenvironment remodeling, and current clinical applications. This summary could help us better understand the mechanisms of regulatory T cells in solid tumor immunotherapy and further expand their clinical application.