CXCR4 and neoplasm: In recent decades, multiple chemokine/chemokine receptor pairs, as CCL2/CCR2, CCL5/CCR5/, CXCL5/CXCR2, and CXCL12/CXCR4, have been reported to indirectly promote tumor progression by increasing the recruitment and suppressive activity of tumor associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) [192,193].