MMP9 and breast carcinoma: Neutrophils exposed to breast cancer cell-derived supernatant displayed heightened levels of interleukin-1β (IL-1β), CC-chemokine ligand-2-4 (CCL2, CCL3, and CCL4), inducible nitric oxide synthase (iNOS), and matrix metallopeptidase-9 (MMP9) [99].