Carbohydrates are now known to play a vital role in cell-cell recognition processes. One of the most important carbohydrates for humans is the blood group antigen Sialyl Lewis X (SLeX).
The tetrasaccharide SLeX is displayed on the terminus of glycolipids that are present on the surface of white blood cells. It has been shown1 that SLeX has an important role in inflamation processes. The inital adhesion of white blood cells to a site of injury is mediated by E-selectins which are specific for SLeX. Cell-cell recognition between leukocytes and endothelial cells in blood is believed to occur in part through interactions between lectins and oligosaccharide ligands.
However if too many white blood cells are recruited to one injury site normal cells can also be destroyed leading to conditions such as septic shock and rheumatoid arthritis. Large quantities of SLeX have also been found on the surfaces of certain tumor and cancer cells.
Carbohydrate antigens sialyl Lewis A and sialyl Lewis X and adhesion of human cancer cells to vascular endothelium
Cancer Res. 1993 Jan 15;53(2):354-61.
Takada A, Ohmori K, Yoneda T, Tsuyuoka K, Hasegawa A, Kiso M, Kannagi R.
- The carbohydrate antigen, sialyl Lex, is known to be a ligand for the cell adhesion molecule called ELAM-1 (E-selectin, endothelial cell leukocyte adhesion molecule-1), which is present on cytokine-activated human endothelial cells. Recently, we reported that another carbohydrate antigen, sialyl Lea, can also serve as a ligand for ELAM-1 (A. Takada, K. Ohmori, N. Takahashi, K. Tsuyuoka, K. Yago, K. Zenita, A. Hasegawa, and R. Kannagi, Biochem. Biophys. Res. Commun., 179: 713-719, 1991). Both sialyl Lex and sialyl Lea are expressed in many human malignant cells. In order to assess the contribution of these carbohydrate antigens to the adhesion of human malignant cells to vascular endothelium, we selected a panel of 12 cultured human epithelial cancer cell lines and a panel of 12 human leukemia cell lines which express sialyl Lex and/or sialyl Lea antigens. All 12 epithelial cancer cell lines exhibited a clearly ELAM-1-dependent adhesion to cytokine-activated human umbilical vein endothelial cells, while only 3 of the 12 leukemia cell lines exhibited significant participation of ELAM-1 in the adhesion. With regard to epithelial cancer cells, the adhesion of 6 cancer cell lines, mostly of colon and pancreas origin, was dependent almost exclusively on sialyl Lea. A significant contribution of the sialyl Lex antigen was noted in the adhesion of the other 6 cell lines, including cancers of lung and liver origin. These results imply that the sialyl Lea/ELAM-1 adhesion system, as well as the sialyl Lex/ELAM-1 adhesion system, plays an important role in the adhesion of human cancer cells to human umbilical vein endothelial cells. With regard to leukemia cells, on the other hand, adhesion of the 3 leukemia cell lines that showed ELAM-1-dependent adhesion was mediated by the sialyl Lex antigen, and none of these leukemia cell lines expressed sialyl Lea or exhibited sialyl Lea-dependent adhesion.