[Carcinoembryonic antigen gene family and its clinical application]

Carcinoembryonic antigen (CEA) gene was cloned in 1987. Thereafter, the structures of non-specific cross-reacting antigen (NCA) and biliary glycoprotein I (BGPI) have also been clarified. These three antigens contain immunoglobulin-like domains in their basic structures and it could be possible that CEA gene was originated from this basic structure by internal gene multiplication. Each CEA and NCA has hydrophobic domain in the C-terminus consisting of 26 amino acids which is eliminated when it binds with membrane and is reconstituted by combining with phosphatidylinositol glycan, whereas BGPI contains transmembrane and cytoplasmic domains. It is of interest that CEA and NCA have been found to function as adhesion molecules. The structure and possible function of another CEA gene family, PS beta G, were also introduced in this short review.