Monoclonal antibodies that discriminate between human ovarian carcinomas and benign ovarian tumours

Three hybridoma cell lines producing monoclonal antibodies (MAbs) against ovarian carcinomas were obtained after immunizing mice with an undifferentiated human ovarian cystadenocarcinoma extract. The hybridoma cell supernatants were initially screened for a positive immunohistochemical reaction with ovarian carcinomas concomitant with a negative reactivity with a benign ovarian cystadenoma. The antibodies OV-TL 15 (IgM), OV-TL 30 (IgG1) and OV-TL 31 (IgM) reacted positively with 84, 84 and 74% of the ovarian carcinoma samples (n = 76) respectively. Reactivity with ovarian cysts and cystadenomas (n = 21), with non-ovarian carcinomas (n = 77) and with normal human tissue samples (n = 63) was absent or limited to weak reactivity on incidental samples. All three antibodies were shown by immunoelectron microscopy to react with surface antigens (OA 15, OA 30 and OA 31) of ovarian carcinoma cells. Cross reactivity between OV-TL 15, OV-TL 30, OV-TL 31 and OC 125 monoclonal antibodies was excluded by competitive binding assays on NIH:OVCAR-3 cells. Antigen levels (OA 15 and OA 31) in tumour extracts and cyst fluids were quantified by immunoradiometric assays and compared to the CA 125 antigen levels. High levels of CA 125, OA 15 and OA 31 were found in cyst fluids from ovarian cancers. In benign ovarian cyst fluids, however, the CA 125 content was also high while OA 15 antigen was hardly detectable. The OA 31 antigen was present at relatively low levels. The IRMA data confirmed the immunohistochemical data showing that, in contrast to OC 125, the newly developed MAbs OV-TL 15, OV-TL 30 and OV-TL 31 discriminate between benign ovarian cystadenomas and malignant ovarian cancers.