Reprogramming regulatory T cell plasticity for cancer immunotherapy

Regulatory T cells (Tregs) maintain immune homeostasis by suppressing excessive immune responses. In the context of cancer, Tregs are abundantly recruited to inhibit immunity against tumoral cells, facilitate immune evasion, and promote tumor progression. While Treg depletion strategies have repeatedly failed in the clinic due to severe autoimmune side effects, lack of specificity, and rapid compensatory recruitment, a critical unmet need remains for safer and more effective approaches. Emerging evidence highlights the remarkable plasticity of Tregs, allowing them to adopt an inflammatory phenotype in response to tumor-associated cytokines. Thus, leveraging this plasticity, rather than attempting broad depletion, may represent a superior anticancer strategy. This plasticity is marked by the expression of transcription factors like T-bet (Th1-like) and RORγt (Th17-like), the production of pro-inflammatory cytokines such as IFN-γ and IL-17, and even the acquisition of differential energetic preferences pertaining to glucose or glutamine. These changes can weaken Treg suppressive functions or paradoxically enhance inflammation in the tumor microenvironment, thereby creating a complex interplay between immune suppression and anti-tumor effector activity. Understanding the molecular cues driving Treg plasticity is therefore critical for designing novel therapies that shift Tregs toward an effector-like state, ultimately enhancing anti-tumor immunity and improving the efficacy of current immunotherapies. This review offers a fresh perspective on how Treg plasticity can be therapeutically harnessed to overcome the persistent limitations of conventional Treg-targeted approaches.