Metabolic Regulation of Tregs in Cancer: Opportunities for Immunotherapy

The promising outcomes observed in cancer immunotherapy are evidence that the immune system provides a powerful arsenal for the restriction of tumor outgrowth; however, the immunosuppressive tumor microenvironment (TME) is known to impair antitumor immunity and impede the efficacy of cancer immunotherapies. Regulatory T cells (Tregs), which prevent overt immune responses and autoimmunity, accumulate aberrantly in some types of tumor to suppress antitumor immunity and support the establishment of an immunosuppressive microenvironment. Ablation of Tregs has been shown to not only unleash antitumor immunity and interrupt formation of an immunosuppressive TME, but also lead to severe autoimmune disorders. Therefore, it is essential to develop approaches to specifically target intratumoral Tregs. Herein, we summarize the immunomodulatory functions of Tregs in the TME and discuss how metabolic regulation of Tregs can facilitate intratumoral Treg accumulation.