title: Exceptionally potent anti-tumor bystander activity of an scFv:sTRAIL fusion protein with specificity for EGP2 toward target antigen-negative tumor cells.
abstract: Previously, we reported on the target cell-restricted fratricide apoptotic activity of scFvC54:sTRAIL, a fusion protein comprising human-soluble tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) genetically linked to the antibody fragment scFvC54 specific for the cell surface target antigen EGP2. In the present study, we report that the selective binding of scFvC54:sTRAIL to EGP2-positive target cells conveys an exceptionally potent pro-apoptotic effect toward neighboring tumor cells that are devoid of EGP2 expression (bystander cells). The anti-tumor bystander activity of scFvC54:sTRAIL was detectable at target-to-bystander cell ratios as low as 1:100. Treatment in the presence of EGP2-blocking or TRAIL-neutralizing antibody strongly inhibited apoptosis in both target and bystander tumor cells. In the absence of target cells, bystander cell apoptosis induction was abrogated. The bystander apoptosis activity of scFvC54:sTRAIL did not require internalization, enzymatic conversion, diffusion, or communication (gap junctional intracellular communication) between target and bystander cells. Furthermore, scFvC54:sTRAIL showed no detectable signs of innocent bystander activity toward freshly isolated blood cells. Further development of this new principle is warranted for approaches where cancer cells can escape from antibody-based therapy due to partial loss of target antigen expression.
authors.affiliation: Groningen University Institute for Drug Exploration (GUIDE), Laboratory for Tumor Immunology, Section Medical Biology, Department of Pathology and Laboratory Medicine, University Hospital Groningen, Hanzeplein 1, Groningen 9713 GZ, The Netherlands.
authors.forename: Edwin
authors.initials: E
authors.lastname: Bremer
authors.forename: Douwe
authors.initials: D
authors.lastname: Samplonius
authors.forename: Bart-Jan
authors.initials: BJ
authors.lastname: Kroesen
authors.forename: Linda
authors.initials: L
authors.lastname: van Genne
authors.forename: Lou
authors.initials: L
authors.lastname: de Leij
authors.forename: Wijnand
authors.initials: W
authors.lastname: Helfrich
mesh_terms: D000951:Antigens, Neoplasm / Q000187:drug effects* / Q000235:genetics; D000954:Antigens, Surface / Q000032:analysis / Q000187:drug effects* / Q000276:immunology; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D024201:Bystander Effect; D053181:Caspase 8; D020169:Caspases / Q000032:analysis / Q000378:metabolism; D045744:Cell Line, Tumor; D000071858:Epithelial Cell Adhesion Molecule; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy* / Q000276:immunology; D011065:Poly(ADP-ribose) Polymerases / Q000032:analysis / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000494:pharmacology* / Q000627:therapeutic use; D057127:Single-Chain Antibodies; D014162:Transfection
chemical_list: D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D000970:Antineoplastic Agents; C499379:EPCAM protein, human; D000071858:Epithelial Cell Adhesion Molecule; D011993:Recombinant Fusion Proteins; D057127:Single-Chain Antibodies; C499789:scFvC54-sTRAIL fusion protein; D011065:Poly(ADP-ribose) Polymerases; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases