MMP9 and cancer: Some of the molecules described in cancer or sepsis that characterize the polarization of neutrophils are programmed death-ligand 1 (PD-L1) positive on their surface (21), the secretion of regulatory cytokines, i.e., IL-10 (22), polarizing cytokines, i.e., IL-4 (23) or tumor necrosis factor alpha (TNF-α) (24), enzymes able to untie junctions, i.e., matrix metalloproteinase 9 (MMP-9) (25), and growth factors like vascular endothelial growth factor (VEGF) (26) and hepatocyte growth factor (HGF) (27, 28) that directly stimulate angiogenesis.