Molecular characteristics of the CA 125 antigen produced by human endometrial epithelial cells: comparison between eutopic and heterotopic epithelial cells

OBJECTIVE: To characterize the CA 125 antigen purified from the conditioned media using an in vitro system that we have established for the culture of epithelial cells from human uterine endometrium. STUDY DESIGN: CA 125 was purified separately from the conditioned media of eutopic and heterotopic epithelial cells by gel chromatography and OC 125 immunoaffinity column chromatography. RESULTS: Western blot analysis of conditioned media from eutopic epithelial cells revealed a single polydisperse band of 200 kd, whereas two major CA 125 isoforms of 200 and 110 kd, as well as two minor forms of 100 and 70 kd, were observed in heterotopic epithelial cells. The 110 kd CA 125 was more prominent than the 200 kd antigen in heterotopic epithelial cells. CONCLUSION: These results strongly suggest that CA 125 antigens purified by immunoaffinity chromatography have different molecular mass in eutopic and heterotopic epithelial cells even though the OC 125 binding site may remain intact.