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.