MMP3 and neoplasm: IL-33 is normally released upon epithelial cell injury or necrosis, and IL-33 in tumor cells induces epithelial to mesenchymal transition by activating the ST2 receptor, which in turn promotes tumorigenesis; IL-33 can further activate the nuclear factor-κB signaling pathway upon activation of ST2 receptor, which promotes matrix metalloproteinase-3 expression and then drives tumorigenesis and metastasis; in addition, IL-33 also inhibits T cell function and promotes tumor tissue angiogenesis and local infiltration [21–24].