SOLUBLE RECEPTOR FOR UROKINASE PLASMINOGEN-ACTIVATOR IN BOTH FULL-LENGTH AND A CLEAVED FORM IS PRESENT IN HIGH-CONCENTRATION IN CYSTIC FLUID FROM OVARIAN-CANCER

We assayed the levels of soluble urokinase plasminogen activator recep tor (su-PAR) with an ELISA in various body fluids from 77 patients wit h benign or malignant ovarian tumors, histologically classified as fol lows: benign; possibly malignant (borderline); and well, intermediatel y, and poorly differentiated malignant. The concentration of su-PAR in fluid from malignant cysts was extremely high, similar to 10-fold hig her than the concentration in ascitic fluid and similar to 100-fold hi gher than that in blood. Also, the concentration in malignant cysts wa s similar to 10-fold higher than the concentration in benign cysts. Su ch high concentrations of su-PAR were found not only in truly malignan t but also in possibly malignant cysts. Thus, we suggest that the conc entration of su-PAR in cystic fluid can serve as a marker, allowing ea rly diagnosis of malignant ovarian cysts. The concentration of su-PAR in fluid aspirated transvaginally with ultrasonographic guidance can b e used to discriminate possibly and truly malignant cysts from benign cysts without surgery. The high concentrations of su-PAR in ovarian cy stic fluids allowed us to characterize the molecular forms. Cross-link ing of a radiolabeled ligand to the receptor demonstrated that at leas t a fraction of su-PAR was able to bind the ligand. A cleaved form of the receptor constituting domains 2 and 3 was detected with Western bl otting. The cleaved receptor, which is devoid of the ligand-binding do main 1, has not previously been demonstrated in body fluids; it has on ly been demonstrated on cell surfaces, su-PAR domains 2 and 3 were fou nd in cystic fluids from both malignant and benign ovarian tumors.