In particular, Treg cells were reported to lead to immune suppression by inhibiting co-stimulatory signals by CD80 and CD86 through the cytotoxic T-lymphocyte antigen-4 (CTLA-4), secreting inhibitory cytokines, and directly killing effector T cells.362 Treg cells have been shown to be chemoattracted to the TME by chemokines, such as chemokine receptors (CCR4)-CCL17/22 and CXCR3-CCL9/10/11, where they are activated to inhibit anti-tumor immune responses.363 Indeed, a high accumulation of Treg cells in various types of cancer is associated with poor survival.364. This evidence concerns the gene CTLA4 and cancer.