EP-CAM - A HOMOPHILIC CELL-CELL ADHESION MOLECULE WITH EGF-LIKE DOMAINS

Ep-CAM is a recently identified Ca2+-independent, hemophilic cell-cell adhesion molecule of epithelial cells. This transmembrane glycoprotein has a molecular weight of only 40 kD, which is unusually small for an adhesion protein. The extracellular domain of Ep-CAM contains two EGF-like domains followed by a cysteine-poor region- structural features that set Ep-CAM apart-from, the four main groups of cell adhesion molecules - cadherins, integrins, selectins and adhesion molecules of the immunoglobulin superfamily. Ep-CAM is abundantly expressed in simple, transitional and some pseudostratified epithelia, but not in squamous epithelia, where the de novo expression of this molecule is often associated with proliferative/neoplastic changes. Ep-CAM is not expressed in cell types of nonepithelial origin. The exact biological role of the Ep-CAM molecule is still unknown, but the evidence so far suggests involvement in regulation of cell-cell interactions, segregation of cell types, tissue pattern formation, and support of tissue architecture.