[A new monoclonal antibody (SH-9) recognizes the low molecular mass of ovarian cancer antigen CA125]

The SHIN-3 cell line producing CA125 was established from an ovarian cancer patient. Using the SHIN-3 cell line, we found that the low-molecular-mass antigen (about 50 KDa) might be the main antigenic determinant in CA125-immunoreactive species. A new monoclonal antibody to this low-molecular-mass was raised to examine a new cancer associated antigen by a hybridoma technique. Using enzyme linked immuno sorbent assay, ten clones were selected from among 398 clones. Two clones were IgG1 and eight were IgM. By immunostaining (ABC assay), a new antibody (named SH-9) reacted with normal pulmonary bronchus and uterine cervical glands. No positivity, however, was observed in endometriosis (adenomyosis). In tumorous lesions of ovary, SH-9 antibody reacted specifically with mucinous cystadenoma-benign, borderline or malignant. However, no positivity was found in serous cystadenocarcinoma. In any other carcinomas, only lung cancer (adenocarcinoma, squamous cell carcinoma) showed a clear positivity. Immuno blotting analysis showed that SH-9 antibody recognized a low molecular mass. Therefore, SH-9 is seen to be an extremely unique antibody when compared with OC125 biochemically and histochemically.