The biology of the 17-1A antigen (Ep-CAM)

The glycoprotein recognized by the monoclonal antibody (mAb) 17-1A is prese nt on most carcinomas, which makes it an attractive target for immunotherap y, Indeed, adjuvant treatment with mAb 17-1A did successfully reduce the 5 years mortality among colorectal cancer patients with minimal residual dise ase. Currently the antibody is approved for clinical use in Germany, and is on its way to approval in a number of other countries. New immunotherapeut ic strategies targeting the 17-1A antigen are in development or even in ear ly-phase clinical trials. Therefore, a better understanding of the biology of the 17-1A antigen may result in improved strategies for the treatment an d diagnosis of human carcinomas. In this review the properties of the 17-1A antigen are discussed concerning tumor biology and the function of the mol ecule. This 40-kDa glycoprotein functions as an Epithelial Cell Adhesion Mo lecule, therefore the name Ep-CAM was suggested. Ep-CAM mediates Ca2+-indep endent homotypic cell-cell adhesions. Formation of Ep-CAM-mediated adhesion s has a negative regulatory effect on adhesions mediated by classic cadheri ns, which may have strong effects on the differentiation and growth of epit helial cells. Indeed, in vivo expression of Ep-CAM is related to increased epithelial proliferation and negatively correlates with cell differentiatio n. A regulatory function of Ep-CAM in the morphogenesis of epithelial tissu e has been demonstrated for a number of tissues, in particular pancreas and mammary gland. The function of Ep-CAM should be taken into consideration w hen developing new therapeutic approaches targeting this molecule.