Inflammatory proteases from neutrophils (proteinase 3, elastase, and cathepsin G) [65] and mast cells within the tumor microenvironment (chymase, tryptase, and granzyme B) [21] can process full-length IL-33 into shorter mature forms (18–21 kDa), with a 10- to 30-fold higher amount of activity [66,67]. Here, PRTN3 is linked to neoplasm.