Regulatory T cells in the breast cancer tumor microenvironment: new mechanisms, potential therapeutic strategies and future perspectives.

Regulatory T cells (Tregs) are key immunosuppressive components of the tumor microenvironment (TME). Their marked enrichment in breast cancer tissues, compared with normal or benign tissues, promotes tumor immune evasion and represents a major barrier to effective immunotherapy. This review systematically elucidates the multifaceted roles of Tregs in breast cancer progression. We first outline the fundamental characteristics and origins of Tregs within the breast cancer TME. We then examine the molecular mechanisms underlying Treg recruitment, highlighting how tumor cells and stromal components cooperatively establish an immunosuppressive niche. In addition, we analyze the specific pathways through which Tregs promote tumor angiogenesis, facilitate immune escape, and drive metastasis. Finally, we summarize emerging therapeutic strategies targeting Tregs, including biological agents, natural and synthetic compounds, combination therapies, and traditional Chinese medicine formulations, and discuss current challenges and future directions. This review aims to provide a comprehensive framework and novel insights for the development of more effective Treg-targeted immunotherapies for breast cancer.