Immune complexes in ovarian cancer

Ovarian cancer-associated antibodies recovered from ascites: their use for the isolation of ovarian cancer-associated antigen to produce monoclonal antibodies

Immune complexes (ICs) were recovered from the ascites of a patient with stage IV endometrioid ovarian cancer by sequential precipitation with 33% saturated ammonium sulfate and 2.5% polyethylene glycol 6000 (PEG 6000), followed by affinity chromatography on protein A-Sepharose CL-4B. The IgG-containing ICs were dissociated using 8 M urea, separated by ion-exchange chromatography on Sephadex QAE-50, and subsequently analyzed for purity by immunoelectrophoresis (IEP) and radial immunodiffusion (RID). Recovered antibody was tested for reactivity by immunohistologic techniques against paraffin-embedded tumor tissue and acetone-fixed cell suspensions of epithelial tumors. The antibody which demonstrated ovarian cancer-associated activity was absorbed with antigen extracts of breast, colon, and lung cancers as well as keratin to reduce cross-reactivity. The absorbed endometrioid ovarian cancer-associated antibody (OCAAb) was used to produce an immunoadsorbent column for the recovery of tumor-associated antigens. A mouse monoclonal antibody designated FEN-1 was produced using this antigen-containing fraction, and preliminary screening has demonstrated ovarian tumor-associated reactivity. The use of autologous ICs as reagents for preparing tumor antigen-rich immunogens may provide a valuable tool in the search for tumor-associated antigens.

Immune complexes in ovarian carcinoma

Immunodiagnostic screening may improve the survival of ovarian carcinoma by earlier detection and follow-up during treatment. Presently, several ovarian cancer-associated antigens are being utilized to monitor treatment response; a specific and precise test for screening is not currently available. The present study was designed to investigate the presence and clinical significance of circulating immune complexes (IC) in patients with ovarian carcinoma using a polyethylene glycol (PEG) assay. If this assay were to prove clinically useful in patients with ovarian carcinoma, its potential as a screening test would then be evaluated. Serum was obtained from 38 patients with advanced ovarian carcinoma preoperatively, postoperatively, and prior to the administration of a combination chemotherapy regimen containing cisplatin. Five patients had values greater than or equal to 0.10. This test identified only 12.5% of the patients with active disease. Serial sampling failed to reveal any correlation with disease status. Our experience does not support the usefulness of IC levels in studying or treating patients with ovarian carcinoma.

Activity of antibodies recovered from immune complexes of ovarian cancer patients

Ascites fluids from ovarian cancer patients contain immune complexes (IC). Attempts were made to characterize those antigens to which the patient is reacting using antibody recovered from these complexes. Polyethylene glycol (PEG) precipitation and protein A Sepharose 4B affinity chromatography were used to isolate IC. Dissociation of the IC was achieved by G-150 gel filtration in 0.1 M acetic acid, 0.15 M NaCl. Activity of antibody preparations was measured using a binding assay with 125I-labeled staphylococcal protein A. Confluent monolayers of various cell lines (including human ovarian and cervical carcinoma lines, human lymphoblastoid cell lines, human and chick embryo fibroblasts) were used. Six of nine antibody preparations isolated from ovarian cancer patient IC contained at least some reactivity against all cell types. Specificity was further defined using cell adsorption assays and polyacrylamide gel electrophoresis. These results indicate what appears to be autoreactivity directed against a normal component(s) of many cells. No evidence for an ovarian cancer-restricted response was shown. Immunoprecipitation analyses showed several polypeptide bands on autoradiograms (49K, 46K, 33K, 25K), which deviated distinctly from the pattern obtained for whole cell extracts.