[Regulatory T Cells and Cancer-Focus on Renal Cell Carcinoma].

Recent advances in cancer immunology have revealed that tumor progression is profoundly influenced by interactions between tumor cells and the host immune system. Although the immune system can recognize and eliminate malignant cells through immune surveillance, tumors can evade immune-mediated destruction by acquiring various immune escape mechanisms. Regulatory T cells (Tregs) represent one of the key immunosuppressive components that facilitate tumor immune evasion. Tregs, typically characterized as CD4+CD25+FoxP3+ T cells, play an essential role in maintaining immune tolerance and preventing excessive immune responses under physiological conditions. However, within the tumor microenvironment (TME), Tregs suppress antitumor immunity through multiple mechanisms, including inhibition of effector T-cell activation, modulation of antigen-presenting cells, secretion of immunosuppressive cytokines, and metabolic regulation. Accumulation of Tregs in tumor tissues has been associated with poor clinical outcomes in various solid tumors. Renal cell carcinoma (RCC) is known as an immunogenic tumor characterized by abundant immune-cell infiltration. Despite the presence of numerous tumor-infiltrating lymphocytes, effective antitumor immunity is often impaired in RCC, partly due to immunosuppressive networks within the TME. In particular, Tregs contribute to the establishment of an immunosuppressive environment that limits the activity of cytotoxic T cells and reduces the efficacy of immune checkpoint inhibitors (ICIs), which have become a cornerstone of therapy for advanced RCC. In this review, we summarize the biological characteristics and immunosuppressive mechanisms of Tregs and discuss their roles in shaping the immune landscape of RCC. Furthermore, we highlight emerging therapeutic strategies targeting Tregs, including depletion, functional inhibition, and blockade of Treg recruitment. A deeper understanding of Treg-mediated immune regulation may facilitate the development of more effective immunotherapeutic approaches for RCC and other malignancies.