MPO and neoplasm: Good TANs act as anti-tumorigenic when they acquire the N1 phenotype, which is characterized by killing tumor cells directly by releasing granule contents such as elastase, cathepsin G and myeloperoxidase (MPO), or indirectly by forming neutrophil extracellular traps (NETs) that trap and damage tumor cells and secretion of immunostimulatory cytokines and chemokines such as interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α) and IL-12, or by presenting tumor antigens to T-cells [34].