Placental protein 4 as a possible tumor marker in ovarian tumors.

Placental protein 4 (PP-4), a recently characterized glycoprotein from human placenta, was studied using a specific double-antibody radioimmunoassay in sera of 130 volunteers, 76 ovarian tumor patients and in ovarian tumor cyst fluid and ascites of 21 patients. Elevated levels (greater than 3 micrograms/l) were found in 45 of 52 ovarian cancer patients (86.5%). PP-4 levels correlated significantly with staging. 31 patients with malignant ovarian tumor were monitored on 2-9 occasions during 5-82 weeks. Rising or falling levels of PP-4 correlated with progression or regression of disease in 25 of 31 instances (80.6%). Elevated levels were found in 10 of 24 benign and borderline ovarian tumors. Elevated PP-4 level does not indicate malignancy in each case. PP-4 can be regarded as tumor-associated antigen and an tumor marker in oncological practice.