ELAM-1 (endothelial-leukocyte adhesion molecule-1, E-selectin) is a
cell adhesion molecule which is specifically expressed on
cytokine-activated endothelial cells. It is known to bind a
carbohydrate antigen sialyl Le(x) (sialyl SSEA-1) present on leukocytes, and the
sialyl Le(x)/ELAM-1 adhesion system is suggested to play a physiologically important role in leukocyte recruitment in the process of
inflammation. Some
leukemia cells also express the
sialyl Le(x)
antigen, and in such a case, the
sialyl Le(x)/ELAM-1 adhesion system will be involved in the organ infiltration of
leukemia cells. On the other hand, in the adhesion of human
cancer cells to endothelial cells, another
carbohydrate antigen,
sialyl Le(a), serves as the
ligand for
ELAM-1, as well as
sialyl Le(x). These two
carbohydrate determinants,
sialyl Le(a) and
sialyl Le(a), on
cancer cells will be involved in the hematogenous
metastasis of
cancer cells. The physiological function of these two
carbohydrate determinants at the surface of normal epithelial cells is most probably to mediate stage-specific cell-to-cell recognition and adhesion during the course of organogenesis in developing embryos, and the abnormal cell-adhesion behaviors of
cancer cells are the results of aberrant expression of
cell adhesion molecules which would play physiologically important roles under normal condition.