Purification and characterization of a tumor-associated trypsin inhibitor from the urine of a patient with ovarian cancer.

Immunochemical studies on urine from a patient with ovarian cancer revealed the presence of a tumor-associated peptide. This peptide occurred in elevated concentrations in the urine of some patients with gynecologic cancer, in early amniotic fluid, and in some cancer tumor extracts from these patients as described previously (Stenman, U.-H., Huhtala, M.-L., Koistinen, R., and Seppälä, M. (1982) Int. J. Cancer 30, 53-47). The peptide has now been purified from the urine of a patient with ovarian cancer by gel chromatography, ion exchange chromatography, and reverse phase liquid chromatography. The amino acid composition of the peptide is: Lys (4), Arg (3), Asx (8), Thr (4), Ser (3), Glx (6), Pro (3), Gly (5), Ala (1), Val (2), Ile (3), Leu (4), Tyr (3), Phe (1), and Cys (6). These 56 amino acids correspond to Mr = 62000 for the peptide, a value that is in agreement with the molecular weight established by gel chromatography. The molecule contains no carbohydrate. It is microheterogeneous in charge, the isoelectric point of the main component being 5.8. The purity of the peptide was confirmed by determination of the NH2-terminal amino acid sequence. The 21 residues determined were found to be identical with the corresponding ones of human pancreatic trypsin inhibitor. The purified peptide also inhibited bovine trypsin effectively.