Epithelial cell adhesion molecule (EPCAM) is a type I membrane protein expressed in a variety of human epithelial tissues, cancers, and progenitor and stem cells. It consists of an extracellular domain with epidermal growth factor (EGF)-like and thyroglobulin repeat-like domains, a single transmembrane domain, and a short 26-amino acid intracellular domain called EpICD (Balzar et al. 1999). In normal cells EPCAM is predominantly present at the surfaces of intercellular spaces where epithelial cells form very tight junctions. The extracellular domain of EPCAM interacts with a second EPCAM molecule resulting in homotypic cell-cell adhesion (Litvinov et al. 1994, 1997). Formation of EPCAM-mediated adhesions has a negative regulatory effect on adhesions mediated by classic cadherins, which may have strong effects on the differentiation and growth of epithelial cells (Balzar et al. 1999).