Expression of the high-affinity selectin glycan ligand C2-O-sLeX by colon carcinoma cells.

The selectin family of adhesion proteins directs leukocytes in the blood to lymphoid organs and sites of inflammation, and is also thought to be involved in the dissemination of carcinomas expressing sialylated Lewis glycan structures, such as sialyl-Lewis X (sLeX). The expression of core 2 beta1,6 N-acetylglucosaminyltransferase (C2GnT) by leukocytes allows for the biosynthesis of core 2 O-glycans that when terminated by sLeX can serve as high-affinity selectin glycan ligands. In particular, the sLeX-modified core 2 O-glycan structure C2-O-sLeX has been directly demonstrated to confer significantly higher affinity selectin binding than sLeX. We have recently described the reactivity of the mAb CHO-131, which is dependent on the enzymes alpha2,3-sialyltransferase, alpha1,3-fucosyltransferase, and C2GnT, and specifically recognizes the glycan structure C2-O-sLeX. Here we examined a defined pair of colon carcinoma cell lines that are distinct in their capacity to bind E-selectin, as demonstrated by shear flow assays involving whole blood and shear stresses that occur in the microvasculature. CHO-131 demonstrated reactivity with such cancer cells, but only with the cell line that avidly attached to E-selectin. Hence, we demonstrate for the first time the detection of C2-O-sLeX on colon carcinoma cells, which, as with leukocytes, may be directly relevant to the expression of high affinity glycan ligands for the selectins.