KLK4 and neoplasm: Among them are the kinin-kallikrein system [32,33], nitric oxide NO [34,35], reactive oxygen and nitrogen species, including H2O2, O2–•, ONOO–, formed in various reactions both by tumor cells and tumor infiltrating leukocytes [36,37], carbon monoxide CO, which is a product of the reaction of hemoxygenase [38], prostaglandins [39], matrix metalloproteinases [40,41], protein factors, including vascular endothelial growth factor (VEGF), transforming growth factor TGF-β, tumor necrosis factor TNF-α [42,43,44].