Identification of an ectopic developmental antigen that appears in malignant ascitic fluid.

A tumor-associated antigen that shares antigenicity with a pregnancy-associated protein has been detected in ascitic fluid of patients with advanced ovarian cancer. The protein, prepared from malignant ascitic fluid by the combination of poly(ethylene glycol) 4000 fractionation, DEAE-Sepharose column chromatography and preparative polyacrylamide gel electrophoresis (PAGE), was subsequently separated on sodium dodecyl sulfate-PAGE, as a single band corresponding to an approximate molecular mass of 91 kDa. Immunological analysis showed that this protein was a circulating species of an ectopic developmental antigen that markedly increases in biological fluids in tumor-bearing statuses.