Inflammation and cancer metastasis are associated with extravasation of leukocytes or tumor cells from blood into tissue. Such movement is believed to follow a coordinated and sequential molecular cascade initiated, in part, by the three members of the selectin family of carbohydrate-binding proteins: E-selectin (CD62E), L-selectin (CD62L) and P-selectin (CD62P). E-selectin is particularly noteworthy in disease by virtue of its expression on activated endothelium and on bone-skin microvascular linings and for its role in cell rolling, cell signaling and chemotaxis. E-selectin, along with L-or P-selectin, mediates cell tethering and rolling interactions through the recognition of sialofucosylated Lewis carbohydrates expressed on structurally diverse protein-lipid ligands on circulating leukocytes or tumor cells. Major advances in understanding the role of E-selectin in inflammation and cancer have been advanced by experiments assaying E-selectin-mediated rolling of leukocytes and tumor cells under hydrodynamic shear flow, by clinical models of E-selectindependent inflammation, by mice deficient in E-selectin and by mice deficient in glycosyltransferases that regulate the binding activity of E-selectin ligands. Here, the authors elaborate on how E-selectin and its ligands may facilitate leukocyte or tumor cell recruitment in inflammatory and metastatic settings. Antagonists that target cellular interactions with E-selectin and other members of the selectin family, including neutralizing monoclonal antibodies, competitive ligand inhibitors or metabolic carbohydrate mimetics, exemplify a growing arsenal of potentially effective therapeutics in controlling inflammation and the metastatic behavior of cancer.

Prostate cancer (PCa) cell tethering and rolling on microvascular endothelium has been proposed to promote the extravasation of PCa cells. We have shown that these adhesive events are mediated through binding interactions between endothelial (E)-selectin and Lewis carbohydrates on PCa cells. Prior data indicate that E-selectin-mediated rolling of bone-metastatic PCa MDA PCa 2b (MDA) cells is dependent on sialyl Lewis X (sLeX)-bearing glycoproteins. To explore the molecular basis of sLeX synthesis and E-selectin ligand (ESL) activity on PCa cells, we compared and contrasted the expression level of glycosyltransferases, characteristically involved in sLeX and ESL synthesis, in ESL+ MDA cells among other ESL− metastatic PCa cell lines. We also created and examined ESLhi and ESLlo variants of MDA cells to provide a direct comparison of glycosyltransferase expression level. We found that normal prostate tissue and all metastatic PCa cell lines expressed glycosyltransferases required for sialo-lactosamine synthesis, including N-acetylglucosaminyl-, galactosyl-, and sialyltransferases. However, compared with expression in normal prostate tissue, ESL+ MDA cells expressed a 31- and 10-fold higher level of α1,3 fucosyltransferases (FT) 3 and 6, respectively. Moreover, FT3 and FT6 were expressed at 2 to 354-fold lower levels in ESL− PCa cell lines. Consistent with these findings, ESLhi MDA cells expressed a 131- and 51-fold higher level of FT3 and FT6, respectively, compared with expression in ESLlo MDA cells. We also noted that α1,3 FT7 was expressed at a 5-fold greater level in ESLhi MDA cells. Furthermore, ESLlo MDA cells did not display sLeX on glycoproteins bearing sLeX, notably P-selectin glycoprotein ligand-1 (PSGL-1). These results implicate the importance of α1,3 FT3, FT6 and/or FT7 in sLeX and ESL synthesis on metastatic PCa cells.