SPECIFIC DETECTION OF SIALYL-LEWIS-X DETERMINANT CARRIED ON THE MUCINGLCNAC-BETA-1-]6GALNAC-ALPHA CORE STRUCTURE AS A TUMOR-ASSOCIATED ANTIGEN

Sialyl Lewis X serves as a ligand for selectins and is proposed to be implicated in hematogenous metastasis of cancers. When a cultured huma n breast cancer cell line, MCF-7, which does not express sialyl Lewis X, was transfected with human fucosyltransferase VI cDNA, a strong exp ression of sialyl Lewis X was induced on transfectant cells, The trans fectant cells were found to be also reactive to the antibody NCC-ST-43 9, which was initially raised against human gastric cancer cells and l ater was shown to recognize a tumor-associated carbohydrate antigen in breast, gastric, and colon cancers. This suggested that the antigen r ecognized by NCC-ST-439 is closely related to sialyl Lewis X, Subseque nt studies indicated that NCC-ST-439 specifically reacts to NeuAc alph a 2-->Gal beta 1-->4 (Fuc alpha 1-->3) GlcNAc beta 1-->6GalNAc alpha 1 -->R, the sialyl Lewis X on the mucin GlcNAc beta 1-->6 GalNAc alpha s tructure, The antibody was not reactive to the conventional sialyl Lew is X determinants on straight and/or branched polylactosamine structur es including Ne uAc alpha 2-->3Gal beta 1-->4 (Fuc alpha 1-->3) GlcNAc beta 1-->3 Gal beta 1-->4Glc beta 1-->R and NeuAc alpha 2-3Gal beta 1 -->4(Fuc alpha 1-->3) GlcNAc beta 1-->6Gal beta 1-->4 Glc beta 1-->R. This was in clear contrast to most of the known anti-sialyl Lewis X an tibodies, which do not discriminate internal structures carrying the s ialyl Lewis X determinant. On the other hand, the newly generated mono clonal antibody GSC154-27 had a specificity completely the reverse of the specificity of NCC-ST-439 in that it was strongly reactive to the conventional sialyl Lewis X determinants in straight and branched poly lactosamine structures, while far less reactive to the sialyl Lewis X determinant on the mucin GrlcNAc beta 1-->6GalNAc alpha core structure . A set of these two antibodies would be useful in discriminating the molecular species of sialyl Lewis X expressed by malignant cells and i n studying their functional significance. (C) 1998 Academic Press.