The formation of the oncofetal J28 glycotope involves core-2 beta 6-N-acetylglucosaminyltransferase and alpha 3/4-fucosyltransferase activities

The feto-acinar pancreatic protein or FAPP, the oncofetal glycoisoform of b ile salt-dependent lipase (BSDL), is characterized by the presence of the J 28 glycotope recognized by mAbJ28, This fucosylated epitope is carried out by the O-linked glycans of the C-terminal mucin-like region of BSDL. This g lycotope is expressed by human tumoral pancreatic tissues and by human panc reatic tumoral cell lines such as SOJ-6 and BxPC-3 cells. However, it is no t expressed by the normal human pancreatic tissues and by MiaPaCa-2 and Pan c-1 cells. Due to the presence of many putative sites for O-glycosylation o n FAPP and BSDL, the structure of the J28 glycotope cannot be attained by c lassical physical methods. In the first part of the present study, we have determined which glycosyltransferases were differently expressed in pancrea tic tumoral cell lines compared to normal tissues, focusing in part on fuco syltransferases (Fuc-T) and core-2 beta 6-N-acetylglucosaminyltransferase ( Core2GlcNAc-T). Our data suggested that alpha 2-Fuc-T activity mas decrease d in the four cell lines tested (SOJ-6, BxPC-3, MiaPaCa-2, and Panc-1). The alpha(1-3) and alpha(1-4) fucosylations were decreased in tumor cells that do not express the J28 glycotope whereas alpha 4-Fuc-T and Core2GlcNAc-T a ctivities were significantly increased in SOJ-6 cells which best expressed the J28 glycotope. Therefore, we wished to gain information about glycosylt ransferases involved in the building of this structure by transfecting the cDNA encoding the mucin-like region of BSDL in CHO-K1 also expressing Core2 GlcNAc-T and/or FUT3 and/or FUT7 activities. These CHO-K1 cells have been p reviously transfected with the cDNA encoding Core2GlcNAc-T and/or FUT3 and/ or FUT7, Data indicated that the C-terminal peptide of BSDL (Cter) produced by those cells did not carry out the J28 glycotope unless Core2GlcNAc-T ac tivity is present. Further transfection with FUT3 cDNA, increased the antib ody recognition. Nevertheless, transfection with FUT3 or FUT7 alone did not generate the formation of the J28 glycotope on the C-terminal peptide. Fur thermore, the Cter peptide produced by CHO-K1 cells expressing Core2GlcNAc- T was more reactive to the mAbJ28 after in vitro fucosylation with the reco mbinant soluble form of FUT3. These data suggested that the J28 glycotope e ncompasses structures initiated by Core2GlcNAc-T and further fucosylated by alpha 3/4-Fuc-T such as FUT3, likely on GlcNAc residues.