MMP9 and neoplasm: In contrast, the pro-tumor TANs have higher levels of Arginase 1 (Arg1), CD206, Ym1, IL-6, CCL17, CXCR4, neutrophil elastase (NE), matrix metalloproteinase 9 (MMP9), vascular endothelial growth factor (VEGF), and the neuropeptide prokineticin 2 (PROK2, also known as Bv8) [4, 20, 26, 27].