CA 125

Carcinoma antigen 125 (CA 125) is a high molecular weight tumor antigen that is the basis for a widely used serum assay for the monitoring of patients with ovarian epithelial cancer (1). It is a heavily glycosylated mucin expressed on the surface of ovarian tumor cells and on human MUC16, a cell surface bound mucin that is also shed by proteolytic cleavage (2, 3). Furthermore, MUC16 is a potent inhibitor of natural killer cell mediated anti-tumor cytotoxic responses (3). Binding of CA125 to membrane-bound mesothelin mediates heterotypic cell adhesion, which may contribute to the metastasis of ovarian cancer to the peritoneum by initiating cell attachment to the mesothelial epithelium (1).