The CC chemokine receptor 4 (CCR4) is a crucial chemokine receptor that mediates Tregs infiltrating into the tumor microenvironment through binding to its ligands CCL17 or CCL22.378 Gao et al. demonstrated that CCR4+ Tregs was the predominant Tregs in HBV+ HCC, and displayed enhanced immunosuppressive ability. The gene discussed is CCR4; the disease is neoplasm.