Biology and function of tumor-associated trypsin inhibitor, TATI.

Tumor-associated trypsin inhibitor (TATI) is a 6,000 Daltons peptide, which is synthesized by several tumors and cell lines. TATI is identical to pancreatic secretory trypsin inhibitor (PSTI). This peptide is also produced by the mucosa of the gastrointestinal tract, where it is thought to protect the mucosal cells from proteolytic breakdown. Elevated serum and urine levels of TATI occur in connection with many types of cancer, especially mucinous ovarian cancer. Elevated levels may also occur in nonmalignant diseases, e.g. in pancreatitis, severe infections and tissue destruction. Thus TATI may behave as an acute phase reactant. Tumors producing TATI often express tumor-associated trypsinogen. Elevation of TATI in cancer and pancreatic disease is therefore associated with expression of trypsin, but such a connection has not been demonstrated in inflammatory disease. TATI can inhibit trypsin-mediated degradation of extracellular matrix by tumor cells. Therefore its role may be to control the activation of tumor-associated trypsinogen. TATI has also been shown to possess growth factor activity in vitro, but it is not known whether this is a physiological function.