Pibaxizine

The fetoacinar pancreatic protein (FAP), characterized by the mAb J28, is an oncofetal form of bile salt dependent lipase (BSDL), the expression of which is related to pancreatic differentiation and neoplastic processes. Because the J28 epitope, recognized by mAb J28, is suggested to be dependent upon carbohydrates, we have attempted to gain information about the structure of this epitope. Indeed, treatment of FAP with sodium periodate abolished the reactivity of the protein to mAb J28, which demonstrates the implication of oligosaccharides in the structure of the J28 epitope. FAP offers both O-linked and N-linked carbohydrate structures, of which, as we have determined, one is involved. Peptides obtained after cyanogen bromide cleavage were desialylated then separated by affinity chromatography on an immobilized peanut agglutinin agarose column. The peptide retained on this column carried out the reactivity with the mAb J28. Although some differences in amino acid analysis were observed, the N-terminal sequence of this peptide correlates with that of the C-terminal part of the enzyme. Carbohydrate analysis of the peptide bearing the J28 epitope revealed fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, and N-acetylneuraminic acid. The competition observed between mAb J28 and Ulex europaeus I lectin for binding to the J28 epitope suggested that fucose residue alpha (1-2) linked to a galactose residue was implicated in the structure of the J28 epitope. Alternatively, the loss of the mAb J28 reactivity upon treatment of FAP either with bovine kidney or bovine epididymis fucosidase was observed indicating that fucose residues linked at the alpha (1-2) and alpha (1-6) positions may be involved in the establishment of the structure of the J28 epitope. These observations suggest that mAb J28 recognized a particular fucosylated O-linked oligosaccharide structure located at the mucin-like extended C-terminal part of FAP.

We describe the in vivo localization of radiolabeled mAb J28, a murine monoclonal antibody characterizing the oncodevelopmental human fetoacinar pancreatic (FAP) protein, at different stages of chemical induction of pancreatic tumors in the Syrian golden hamster. Before doing localization studies in this model, we looked at the cross-reactivity of mAb J28. Semiquantitative dot-blot analysis demonstrated that the antigen recognized in hamster pancreas has an oncodevelopmental expression pattern, while a molecular mass identical to that of human FAP was deduced from sodium dodecyl sulfate/polyacrylamide gel electrophoresis/nitrocellulose immunoblot. 125I-labeled mAb J28 was administered through micro-osmotic pumps to hamsters treated with N-nitrosobis(2-hydroxypropyl)amine (BHP). This was done at three intervals that roughly correspond to the latent period, pretumoral stages, and terminal cancerogenesis in two independent groups of hamsters. Both studies allowed similar results: (a) mAb J28 accumulated almost specifically in the pancreas; (b) maximal accumulation was associated with pleomorphic alterations of the acinar cell tissue at pretumoral stages; (c) no accumulation was found in the case of adenocarcinoma of the pancreas. It is concluded that FAP behaves as a marker of preneoplastic lesions, and therefore that radioimmunoimaging with mAb J28 might help with early diagnosis of pancreatic cancer.