Tumour-associated trypsin inhibitor and tumour-associated trypsin.

Tumour-associated trypsin inhibitor (TATI) is a 6 kDa peptide, which is synthesized at low concentrations by several tumours and cell lines. Very high concentrations of TATI occur in mucinous ovarian tumours. Elevated levels of TATI occur in serum and urine in connection with most types of cancer at advanced stages. In mucinous ovarian cancer up to 85% of all cases have elevated serum levels. Because high levels also occur in early mucinous ovarian cancer TATI appears to be the marker of choice for this tumour. Elevated levels may also occur in nonmalignant disease, especially in patients with severe infections, tissue destruction and pancreatitis. Production of TATI in tumours is associated with expression of two new tumour-associated trypsin(ogen) (TAT) isoenzymes, TAT-1 and -2, TAT-2 being the major form. These enzymes are immunologically similar to trypsinogen-1 and -2, respectively. They activate prourokinase and may therefore trigger the tumour-associated protease cascade contributing to the invasiveness of malignant tumours.