CXCR4 and neoplasm: Tumor-derived chemokines (CCL2, CCL5, CCL22, CXCL8, CXCL12) recruit suppressive immune cells including tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Treg) via chemokine receptors (CCR2, CCR4, CCR5, CXCR1/2, CXCR4), reinforcing an immunosuppressive TME.