Fourth, Monocytes release monocyte chemoattractant protein-1 to stimulate and mediate tumor-associated monocyte infiltration in solid tumors and then produce various chemokines, such as TGF-α, TNF-α, IL-1, and IL-6 which promote tumorigenesis, angiogenesis, and distant metastasis of malignant tumors [33]. This evidence concerns the gene CCL2 and neoplasm.