In addition to their effects on immune responses, MDSCs promote tumor development by secreting vascular endothelial growth factor (VEGF) [10] and matrix metalloproteinase-9 (MMP9) [11] to support tumor angiogenesis and expressing CXCR2 to promote the formation of pre-metastatic niche [12]. This evidence concerns the gene CXCR2 and neoplasm.