PPIB and neoplasm: The mechanisms by which TMC play a role in tumor progression are as follows: (1) promotion of angiogenesis by heparin-like molecule, histamine, TNF-α, VEGF, platelet activating factor, IL-8, bFGF and prostaglandin that are secreted from TMC [41,42]; (2) promotion of tumor invasion and metastasis through extracellular matrix degradation by chymase, cathepsin G, carboxypeptidase, gelatinase A and B that are secreted from TMC [43,44]; and (3) immune suppression by secreting inhibitory cytokine IL-10 and maintaining Treg activation that is important in immune tolerance [45].