CA 125: the end of the beginning

CA 125, a high-molecular-weight mucin, was first defined in 1981 by the monoclonal antibody OC125. Until recently, it has defied many attempts to purify it from a variety of sources, although many research groups have successfully raised antibodies that bind to CA 125. Nevertheless, CA 125 has demonstrated its considerable value as a marker in monitoring patients with ovarian cancer. This year, two research groups have succeeded in cloning the high-molecular-weight mucin CA 125. Their findings are summarized and the significance discussed in light of existing data from the human genome.