title: New chimeric anti-pancarcinoma monoclonal antibody with superior cytotoxicity-mediating potency.
abstract: The monoclonal antibodies (MAbs) 323/A3 and 17-1A both recognize a 40-kDa carcinoma-associated epithelial glycoprotein (EGP40). MAb 17-1A has been used in many therapeutic trials as an immunotherapeutic agent to combat advanced colorectal cancer, and about 5-10% overall responses have been observed. It has been shown that MAb 323/A3 has a higher affinity than 17-1A, which might be an advantageous feature for a therapeutic agent. In our immunohistological studies different reaction patterns of these two MAbs were observed, suggesting that MAb 323/A3 reacts more intensely with carcinoma cells than MAb 17-1A. This also suggests that MAb 323/A3 might be a more effective immunotherapeutic tool. Because chimerization may reduce the immunogenicity of the murine MAb 323/A3 and increase the interaction with human effector mechanisms, we developed a chimeric form of murine MAb 323/A3. MAb 323/A3 heavy and light chain variable genes were cloned and grafted onto human C gamma 1 and C kappa domains, respectively. A chimeric antibody-producing cell line was established by transfection of the chimeric constructs into a nonproducing myeloma cell. The chimeric and murine 323/A3 MAbs were evaluated for efficacy of inducing complement-mediated cytotoxicity (CMC) and mediating antibody-dependent cellular cytotoxicity against LS 180 cells derived from human colon carcinoma. Both forms were found to mediate similar levels of CMC in the presence of human complement; however, higher levels of lysis of target cells were observed with human peripheral blood lymphocytes when the chimeric 323/A3 was used. Chimeric 323/A3 mediated higher maximal cytotoxicity than chimeric 17-1A in both CMC and antibody-dependent cellular cytotoxicity assays and was equally active as chimeric 17-1A at 100- to 1000-fold lower concentrations. The superior reactivity of chimeric 323/A3 with EGP40 on carcinoma cells and its higher cytotoxicity-mediating capacity, compared to chimeric 17-1A, are important characteristics, which support further clinical studies with chimeric MAb 323/A3 in immunotherapy of carcinomas.
authors.affiliation: Department of Pathology, State University Leiden, The Netherlands.
authors.forename: M P
authors.initials: MP
authors.lastname: Velders
authors.forename: S V
authors.initials: SV
authors.lastname: Litvinov
authors.forename: S O
authors.initials: SO
authors.lastname: Warnaar
authors.forename: A
authors.initials: A
authors.lastname: Gorter
authors.forename: G J
authors.initials: GJ
authors.lastname: Fleuren
authors.forename: V R
authors.initials: VR
authors.lastname: Zurawski
authors.forename: L R
authors.initials: LR
authors.lastname: Coney
mesh_terms: D000230:Adenocarcinoma; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000633:toxicity*; D000951:Antigens, Neoplasm / Q000276:immunology*; D015815:Cell Adhesion Molecules; D002470:Cell Survival / Q000187:drug effects*; D003110:Colonic Neoplasms; D015342:DNA Probes; D000071858:Epithelial Cell Adhesion Molecule; D005803:Genes, Immunoglobulin; D006801:Humans; D006825:Hybridomas; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007147:Immunoglobulin Light Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics; D051379:Mice; D009101:Multiple Myeloma; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000633:toxicity; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D015342:DNA Probes; D000071858:Epithelial Cell Adhesion Molecule; D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007135:Immunoglobulin Variable Region; D011993:Recombinant Fusion Proteins; C050928:carcinoma-associated antigen 17-1A