α2→3Sialyltransferase associated with the synthesis of CA 19-9 in colorectal tumors

Abstract

BACKGROUND A novel assay method specific for α2→3sialyltransferase that seems to be responsible for the synthesis of CA 19‐9 antigen was developed and the levels of the enzyme in colorectal tumor tissues were measured and compared with the levels of α1→4fucosyltransferase and the CA 19‐9 antigen. METHODS Lacto‐N‐biose I (Galβ1→3GlcNAcβ, Lewisc [Lec]) and 6‐O‐methyl‐Lec(Galβ1→3[6OMe]GlcNAcβ) were synthesized and covalently attached to bovine serum albumin (BSA). These two substrates were incubated with extracts from colorectal tissues in the presence of cytidine 5′‐monophospho‐N‐acetylneuraminic acid (CMP‐NeuAc) and their resulting products were detected by a sequential use of anti‐BSA monoclonal antibody‐coated beads and 125I‐labelled anti‐sialylated Lec antibody. Levels of α2→3sialyltransferase and α1→4fucosyltransferase activities and CA 19‐9 antigen were measured in the extracts from colorectal tumors and their adjacent normal tissues. RESULTS 6‐O‐Methyl‐Lec‐BSA showed a strong acceptor activity compared with Lec‐BSA and was used as a specific acceptor for α2→3sialyltransferase. Similar elevation patterns of α2→3sialyltransferase activities and CA 19‐9 antigen levels were observed in tumor extracts but no clear correlation was present between the level of α1→4fucosyltransferase activities and CA 19‐9 antigen levels in the same extracts. CONCLUSIONS The accumulation of CA 19‐9 antigen in colorectal tumors might be caused mainly by the activation of α2→3sialyltransferase but not by that of α1→4fucosyltransferase. Cancer 1996;77:1694‐700.