Comprehensive analysis of current approaches to inhibit regulatory T cells in cancer

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) have emerged as a dominant T cell population inhibiting anti-tumor effector T cells. Initial strategies used for Treg-depletion (cyclophosphamide, anti-CD25 mAb ...) also targeted activated T cells, as they share many phenotypic markers. Current, ameliorated approaches to inhibit Treg aim to either block their function or their migration to lymph nodes and the tumor microenvironment. Various drugs originally developed for other therapeutic indications (anti-angiogenic molecules, tyrosine kinase inhibitors, etc) have recently been discovered to inhibit Treg. These approaches are expected to be rapidly translated to clinical applications for therapeutic use in combination with immunomodulators.