MMP9 and neoplasm: TAMs promote tumor progression by producing/expressing a variety of immunosuppressive molecules (e.g.,CCL13 [53], CCL18 [54], matrix metalloproteinase 9 [MMP9], osteonectin [51], TGF-β [55], programmed death-ligand 1 [PD-L1] [56], human leucocyte antigen-G [HLA-G] [45], TGF-β, and IL-10 [57]), and stimulating angiogenesis by producing vascular endothelial growth factor (VEGF) [51] (Fig. 3).