CA 125 (Cancer Associated Antigen 125)

Biological activities
CA 125 is a high molecular weight mucin type glycoprotein, originally defined by the Oc 125 monoclonal antibody (Mab) established by Bast et al. Different epitopes, co-expressed with the Oc 125 epitope on the CA 125 antigen, have been used for the development of heterologous assays for determination of the CA 125 antigen.

Clinical applications
Approximately 90% of ovarian cancers are celomic epithelial carcinomas and contain a celomic epithelium-related glycoprotein designated CA 125. CA 125 can be localized in most serous, endometrioid, and clear cell ovarian carcinomas; mucinous tumors express this antigen less frequently. CA 125 is also found in the epithelium of the fallopian tubes, endometrium, and uterine cervix. Elevated CA 125 levels can result from abdominal diseases other than ovarian cancer. Although CA 125 is most consistently elevated in patients with epithelial ovarian cancer, it can be expressed in a number of gynaecologic (eg, endometrium, fallopian tube) and non-gynaecologic (eg, pancreas, breast, colon, lung) cancers. CA 125 levels are frequently elevated with tumor spread beyond the uterus.