MPO and neoplasm: Recently, accumulating evidence has started to support the idea that tumour-associated neutrophils (TANs) play a role in tumour progression via the formation of neutrophil extracellular traps (NETs), which are composed of extracellular chromatin decorated with citrulline histone H3 (citH3) together with antimicrobial protein granules and enzymes, such as neutrophil elastase (NE) and myeloperoxidase (MPO), in the TIME [9, 10].