A New CA125‐like Antigen (CA602) Recognized by Two Monoclonal Antibodies against a Newly Established Ovarian Clear Cell Carcinoma Cell Line (RMG‐II)

Abstract

A cell line designated RMG‐II was established from the ascites of a patient with ovarian clear cell carcinoma. The chromosomal analysis revealed aneuploidy with a hypertetraploid modal numher and 8 marker chromosomes. Radioimmunoassay and immunocytochemical staining showed that RMG‐II cells produced some tumor markers such as CA125 and TPA. Two monoclonal antibodies, designated MA602‐1 and MA602‐6, were generated by immunization of mice with an extract prepared from the culture supernatant of RMG‐II cells. The epitopes recognized by these two monoclonal antibodies were proved to differ from the CA125 epitope, but to exist on the molecule bearing CA125. We developed a double‐determinant sandwich enzyme imnnmoassay using these two monoclonal anti‐bodies, and the antigen defined by this assay was termed CA602. CA602 was frequently found in the sera of ovarian cancer patients; the positive rates were 92%, 38%, 60%, and 80% for serous, mucinous, clear cell, and endometrioid ovarian carcinomas, respectively, when the cut‐off value was set at 60 U/ml (=mean + 3SD of healthy females). CA602 levels in serum were also high in endometriosis patients and in early pregnancy, as is the case for CA125, and the correlation coefficient between CA602 and CA125 was high (r=0.88). Our preliminary evidence suggests that this CA602 assay system has higher sensitivity than the CA125 one.

Human monoclonal antibody for ovarian clear cell carcinoma-2, a human monoclonal antibody with antitumor activity against ovarian cancer cells that recognizes CA125-like antigen

“…However, the two antibodies show a strong correlation ( r = 0.88) (7) . CA602 is also frequently detected in the serum of ovarian cancer patients, with the positive rate being 76% (7) . These features of CA602 are similar to those of CA125.…”

“…Although the epitope targeted by these antibodies is present in the CA125 molecule, the binding site differs from that recognized by the monoclonal antibody OC125, which was established using ovarian serous cystadenocarcinoma cells (8) . However, the two antibodies show a strong correlation ( r = 0.88) (7) . CA602 is also frequently detected in the serum of ovarian cancer patients, with the positive rate being 76% (7) .…”

“…Thus, these tumor markers are different epitopes on the same protein (6) . CA602 is a core protein‐related antigen recognized by monoclonal antibodies (MA602‐1 and MA602‐6) that we established using an ovarian clear cell adenocarcinoma cell line designated as RMG‐II (7) . Although the epitope targeted by these antibodies is present in the CA125 molecule, the binding site differs from that recognized by the monoclonal antibody OC125, which was established using ovarian serous cystadenocarcinoma cells (8) .…”

Germ line and somatic mutations of BRAF V599E in ovarian carcinoma

“…Three conventional human ovarian serous cystadenocarcinoma [SHIN‐3 (12) , HOC‐21 (13) , and HTOA (14) ], two mucinous cystadenocarcinoma [MN‐1 (12) and OMC‐3 (15) ], four clear‐cell adenocarcinoma [RMG‐I (16) , RMG‐II (17) , HUOCA‐II (18) , and HAC‐2 (19) ], and one endometrioid adenocarcinoma [HMOA (20) ] cell lines originating from Japanese ovarian cancer patients were also included in the mutation analysis. These cell lines were kindly provided from the Japanese institutes where each cell line was established.…”

Specificity of a Tumor Marker (CA54/61) and Its Individual Epitopes Recognized by Monoclonal Antibodies, MA54 and MA61, in Human Tumor Patients

“…10%-50%; ( + +), 5&90%; ( + + +),Competitive antibody (llg/mt)Competitive antibody (llglmt) Competition assays of HRP-labeled MA54 (left) or HRP-labeled MA61 (right) with MA54, MA61, and B72.3 antibodies. As a negative control, 602-6 antibody, which recognizes a polypeptide part of CA602 antigen(19), was also tested. Procedure details were described in Materials and Methods.…”