The CA125 gene has been cloned and multiple repeat sequences including the carboxy terminus have been identified. The CA125 molecule comprises three major domains: an extracellular amino terminal domain (Domain 1) a large multiple repeat domain (Domain 2) and a carboxy terminal domain (Domain 3) which includes a transmembrane anchor with a short cytoplasmic domain. An amino terminal extension is present. The structure is dominated by a repeat domain comprising 156 amino acid repeat units, which encompass the epitope binding sites. More than 60 repeat units have been identified. The repeat units encompass the site ofOC125 and M11 binding. Expression of the repeats was demonstrated. Any one of the repeat domains has the potential use as a new gold standard for detecting and monitoring the presence of the CA125 antigen. The repeat domains and other domains also provide a basis for the development of a vaccine.
