CCL2 infiltrates tumor tissue by recruiting TAMs, secretes VEGF, TGF - β, TNF - α and other cytokines, promotes tumor cell growth and angiogenesis, and also secretes matrix metalloproteinase MMP2, MMP9, participates in the destruction and reconstruction of extracellular matrix, and promotes tumor cell invasion and metastasis. Here, MMP9 is linked to neoplasm.