Tregs are recruited into tumor tissue by their expressing chemokine receptors such as CC chemokine receptor (CCR) 4, CCR7, CXC-chemokine receptor (CXCR) 4, sphingosin-1-phosphate receptor-1 (S1PR1), and others, which exacerbate the immunosuppressive TME [38–41]. Here, S1PR1 is linked to neoplasm.