Expression of core 2 beta-1,6-N-acetylglucosaminyltransferase in a human pancreatic cancer cell line results in altered expression of MUC1 tumor-associated epitopes

Abstract

Many tumor-associated epitopes possess carbohydrate as a key component, and thus changes in the activity of glycosyltransferases could play a role in generating these epitopes. In this report we describe the stable transfection of a human pancreatic adenocarcinoma cell line, Panc1-MUC1, with the cDNA for mucin core 2 GlcNAc-transferase (C2GnT), which creates the core 2 beta-1,6 branch in mucin-type glycans. These cells lack endogenous C2GnT activity but express a recombinant human MUC1 cDNA. C2GnT-transfected clones expressing different levels of C2GnT were characterized using monoclonal antibodies CC49, CSLEX-1, and SM-3, which recognize tumor-associated epitopes. Increased C2GnT expression led to greatly diminished expression of the CC49 epitope, which we identified as NeuAcalpha2,6(Galbeta1,3)GalNAcalpha-Ser/Thr in the Panc1-MUC1 cells. This was accompanied by the emergence of the CSLEX-1 epitope, sialyl Lewis x (NeuAcalpha2,3Galbeta1,4(Fucalpha1,3)GlcNAc-R), an important selectin ligand. Despite this, however, the C2GnT transfectants could not bind to selectins. Increased C2GnT expression also led to masking of the SM-3 peptide epitope, which persisted after the removal of sialic acid, further suggesting greater complexity of the core 2-associated O-glycans on MUC1. The results of this study suggest that C2GnT could play a regulatory role in the expression of certain tumor-associated epitopes.