title: A bispecific monoclonal antibody directed against both the membrane-bound complement regulator CD55 and the renal tumor-associated antigen G250 enhances C3 deposition and tumor cell lysis by complement.
abstract: Tumor cells may inhibit the induction of a complement-mediated inflammatory response through overexpression of membrane-bound regulators of complement activation. Therefore, it is of interest to determine the most efficient approach to block these membrane-bound complement regulators on tumor cells. In the present study, we first generated a bispecific mAb directed against both CD55, using the functional blocking mAb MBC1, and the highly expressed HLA class I molecule as a model for a tumor-associated Ag, using the mAb W6/32. Tumor cells opsonized with bispecific mAb W6/32*MBC1, then exposed to complement and subsequently stained for C3 deposition, were assessed by flow cytometric analysis. We found that opsonization with W6/32*MBC1 resulted in a 92% enhancement of C3 deposition on renal tumor cells as compared with opsonization with W6/32 alone and a 17% enhancement of the C3 deposition as compared with incubation with a mixture of both parental mAb. Based on these results, we developed a bispecific mAb recognizing both CD55 and the relatively low expressed renal tumor-associated Ag G250. Increasing concentrations of the bispecific mAb G250*MBC1 resulted in a 25 to 400% increase in C3 deposition on renal tumor cells as compared with C3 deposition in the presence of the parental mAb G250 alone. G250*MBC1 enhanced C3 deposition by 21% in comparison with a mixture of both parentals. Furthermore, opsonization of tumor cells with G250*MBC1 rendered these cells more sensitive to complement-mediated lysis. In conclusion, the bispecific mAb G250*MBC1 induces deposition of C3 and tumor cell lysis more efficiently than G250 alone.
authors.affiliation: Department of Pathology, Leiden University Hospital, The Netherlands. vblok@path_1.medfac.leidenuniv.nl
authors.forename: V T
authors.initials: VT
authors.lastname: Blok
authors.forename: M R
authors.initials: MR
authors.lastname: Daha
authors.forename: O
authors.initials: O
authors.lastname: Tijsma
authors.forename: C L
authors.initials: CL
authors.lastname: Harris
authors.forename: B P
authors.initials: BP
authors.lastname: Morgan
authors.forename: G J
authors.initials: GJ
authors.lastname: Fleuren
authors.forename: A
authors.initials: A
authors.lastname: Gorter
mesh_terms: D018033:Antibodies, Bispecific / Q000494:pharmacology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000951:Antigens, Neoplasm / Q000276:immunology*; D018958:CD55 Antigens / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D002999:Clone Cells; D003167:Complement Activation / Q000276:immunology; D003176:Complement C3 / Q000276:immunology / Q000378:metabolism*; D003169:Complement Inactivator Proteins / Q000276:immunology*; D003165:Complement System Proteins / Q000502:physiology*; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007680:Kidney Neoplasms / Q000276:immunology; D014407:Tumor Cells, Cultured
chemical_list: D018033:Antibodies, Bispecific; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D018958:CD55 Antigens; D003176:Complement C3; D003169:Complement Inactivator Proteins; C106533:G250 monoclonal antibody; D003165:Complement System Proteins