Radioimmunolocalization of the monoclonal antibody J28 in early transformation stages in N-nitrosobis(2-hydroxypropyl)amine-induced pancreatic tumors in the Syrian golden hamster

Glycoengineering of alphaGal xenoantigen on recombinant peptide bearing the J28 pancreatic oncofetal glycotope

In human pancreatic adenocarcinoma, alterations of glycosylation processes leads to the expression of tumor-associated carbohydrate antigens, representing potential targets for cancer immunotherapy. Among these pancreatic tumor-associated carbohydrate antigens, the J28 glycotope located within the O-glycosylated mucin-like C-terminal domain of the fetoacinar pancreatic protein (FAPP) and expressed at the surface of human tumoral tissues, can be a good target for anticancer therapeutic vaccines. However, the oncodevelopmental self character of the J28 glycotope associated with the low immunogenicity of tumor-associated carbohydrate antigens may be a major obstacle to effective anti-tumor vaccine therapy. In this study, we have investigated a method to increase the immunogenicity of the recombinant pancreatic oncofetal J28 glycotope by glycoengineering Galalpha1,3Galss1,4GlcNAc-R (alphaGal epitope) which may be recognized by natural anti-alphaGal antibody present in humans. For this purpose, we have developed a stable Chinese hamster ovary cell clone expressing the alphaGal epitope by transfecting the cDNA encoding the alpha1,3galactosyltransferase. These cells have been previously equipped to produce the recombinant O-glycosylated C-terminal domain of FAPP carrying the J28 glycotope. As a consequence, the C-terminal domain of FAPP produced by these cells carries the alphaGal epitope on oligosaccharide structures associated with the J28 glycotope. Furthermore, we show that this recombinant "alpha1,3galactosyl and J28 glycotope" may not only be targeted by human natural anti-alphaGal antibodies but also by the mAbJ28, suggesting that the J28 glycotope remains accessible to the immune system as vaccinating agent. This approach may be used for many identified tumor-associated carbohydrate antigens which can be glycoengineered to carry a alphaGal epitope to increase their immunogenicity and to develop therapeutic vaccines.

Monoclonal antibody 16D10 to the C-terminal domain of the feto-acinar pancreatic protein binds to membrane of human pancreatic tumoral SOJ-6 cells and inhibits the growth of tumor xenografts

Feto-acinar pancreatic protein (FAPP) characterized by mAbJ28 reactivity is a specific component associated with ontogenesis and behaves as an oncodevelopment-associated antigen. We attempted to determine whether pancreatic tumoral SOJ-6 cells are expressed at their surface FAPP antigens and to examine if specific antibodies directed against these FAPP epitopes could decrease the growth of pancreatic tumors in a mice model. For this purpose, we used specific antibodies against either the whole FAPP, the O-glycosylated C-terminal domain, or the N-terminal domain of the protein. Our results indicate that SOJ-6 cells expressed at their surface a 32-kDa peptide corresponding to the C-terminal domain of the FAPP. Furthermore, we show, by using endoproteinase Lys-C or geldanamycin, a drug able to impair the FAPP secretion, that this 32-kDa peptide expressed on the SOJ-6 cell surface comes from the degradation of the FAPP. Finally, an in vivo prospective study using a preventative tumor model in nude mice indicates that targeting this peptide by the use of mAb16D10 inhibits the growth of SOJ-6 xenografts. The specificity of mAb16D10 for pancreatic tumors and the possibility to obtain recombinant structures of mucin-like peptides recognized by mAb16D10 and mAbJ28 are promising tools in immunologic approaches to cure pancreatic cancers.

Antibody constructs for radioimmunodiagnosis and treatment of human pancreatic cancer

Pancreatic cancer (PC) is a common disease that is seldom cured. Current approaches to the treatment of PC are not effective because the non-specific nature of both chemotherapy and external beam radiation results in toxicity to normal tissue. Monoclonal antibodies (MAbs) can be used as selective carriers for delivering radionuclides, toxins, or cytotoxic drugs to malignant cell populations. Therefore, MAb-technology has led to a significant amount of research in targeted therapy. Targeted therapy would generally allow the concentration of cytotoxic agents in tumors and would markedly lessen the toxicity to normal tissues, which limits the dosage and effectiveness of systemically administered drugs. A variety of MAbs are being pre-clinically evaluated for the diagnosis and treatment of PC. Novel recombinant antibody constructs hold a promising future in both the diagnosis and treatment of cancer. By genetic-engineering methods, several high affinity antibody fragments with optimum tumor targeting properties, such as higher functional affinity (divalent and multivalent scFvs) and blood residence time (good tumor localization with high radiolocalization index), have been generated. Animal models have permitted the in vivo assessment of these antibody-based reagents, therapeutic/diagnostic radionuclide, radiolabeling conditions, and efficacy of administration regimes. For PC, immunoscintigraphy using MAbs has taken new strides. The use of MAbs and their fragments for radioimmunoguided surgery and therapy of PC has shown encouraging results at preclinical levels and warrants further attention.

Radioimmunolocalization of human pancreatic carcinoma xenograft by 99mTc-labeled YPC3 monoclonal antibody

Monoclonal antibodies specific to tumor cells may be a useful tool for the diagnosis and treatment of carcinomas. In this study, YPC3 mAb, a specific monoclonal antibody against the human pancreatic carcinoma cell line Capan-2, was labeled directly with 99mTc after being pretreated with 2-mercaptoethanol. The radiolabeling efficiency was found to be high (88%-95%) and the immunoreactivity retained, as assessed by immunohistochemistry and enzyme-linked immunosorbent assay. The biodistribution of 99mTc-YPC3 mAb in nude mice bearing Capan-2 pancreatic carcinoma xenografts was studied and compared with that of labeled mouse immunoglobulin G(99mTc-nmIgG). The xenograft uptake values per gram of tissue 6 h and 24 h after injection of 99mTc-YPC3 mAb were found to be, respectively, 4.72%ID/g and 8.42%ID/g, and the tumor/blood ratios 1.16 and 2.24. At 6 h and 24 h after injection of 99mTc-nmIgG, the uptakes were 2.89%ID/g and 1.80%ID/g, and the tumor/blood ratios 0.84 and 1.02 respectively. External imaging by single-proton emission computed tomography, 24 h after injection of 99mTc-YPC3 mAb, revealed clear scintigraphic visualization of Capan-2 xenografts, whereas injection of 99mTc-nmIgG did not. This study suggests that 99mTc labeling of monoclonal antibody YPC3 might be of practical value in localization diagnosis of human pancreatic carcinoma.