Characteristic mucinous ovarian cancer antigen is expressed in malignantly transformed Bloom's syndrome cells

Using a double-antibody panning procedure, we separated a unique cancer antigen cell line (BS-SHI-4M OVC-MU) expressing a mucinous ovarian cancer (OVC) antigen from a malignantly transformed Bloom's syndrome cell line. In order to gain information concerning a mucinous OVC antigen, we tested this unique cell line in the reaction to sera from patients with various OVCs, Krukenberg (KR) tumor, and signet ring cell cancer of the stomach under immunofluorescence and Western blotting protocols and determined the mucinous OVC antigen band at M(r) 84,000. We also undertook an immune electron microscopic study to gain information concerning the antigen-antibody reaction [BS-SHI-4M OVC-MU cells-sera from patients with mucinous OVC and KR tumor] and concerning the antigenic determinant of the membrane using preembedding methods. Occasional protein A-gold particles were observed along the cell membrane of BS-SHI-4M OVC-MU cells, when treated with sera from mucinous OVC and KR tumor patients, but no labeling was observed in the cell membrane when treated with sera from normal patients and those with other cancers. Results of the immune electron microscopic study strongly support the data from the antigen-antibody reaction obtained by immunofluorescence and Western blotting analyses. The BS-SHI-4M OVC-MU cells separated here would be useful for serodiagnosis of mucinous OVC and KR tumors and for follow-up of patients after therapy.