Tregs are recruited by tumor tissues in the TME through a variety of chemokines, leading to Treg enrichment locally in the tumor (CCL17/22-CCR4, CCL5-CCR5, CCL1-CCR8, CCL28-CCR10 and CXCL9/10/11-CXCR3, etc.)(Figure 4) [102,103,104,105,106,107,108]. The gene discussed is CXCL9; the disease is neoplasm.