title: Superior activity of fusion protein scFvRit:sFasL over cotreatment with rituximab and Fas agonists.
abstract: The clinical efficacy of the CD20-specific chimeric monoclonal antibody rituximab is significantly hampered by intrinsic or acquired resistance to therapy. Rituximab activates antibody-dependent cellular cytotoxicity/complement-dependent cytotoxicity-dependent lysis but also induces apoptosis by cross-linking of its target antigen CD20. Recent reports indicate that this apoptotic activity of rituximab can be synergized by cotreatment with Fas agonists. Here, we report on a strategy designed to exploit and optimize the synergy between rituximab and Fas signaling by genetically fusing a rituximab-derived antibody fragment to soluble Fas ligand (sFasL). The resultant fusion protein, designated scFvRit:sFasL, potently induced CD20-restricted apoptosis in a panel of malignant B-cell lines (10 of 11) and primary patient-derived malignant B cells (two of two non-Hodgkin lymphoma and five of six B cell chronic lymphocytic leukemia). ScFvRit:sFasL efficiently activated CD20 and Fas apoptotic signaling, resulting in a far superior proapoptotic activity compared with cotreatment with rituximab and Fas agonists. ScFvRit:sFasL lacked activity toward normal human B cells and also lacked systemic toxicity in nude mice with no elevation of aspartate aminotransferase and alanine aminotransferase levels or liver caspase-3 activity. In conclusion, scFvRit:sFasL efficiently activates CD20 and Fas-apoptotic signaling and may be useful for the elimination of malignant B cells.
authors.affiliation: Groningen University Institute for Drug Exploration, Department of Pathology and Laboratory Medicine, University Medical Center Groningen, Groningen, the Netherlands.
authors.forename: Edwin
authors.initials: E
authors.lastname: Bremer
authors.forename: Bram
authors.initials: B
authors.lastname: ten Cate
authors.forename: Douwe F
authors.initials: DF
authors.lastname: Samplonius
authors.forename: Nicole
authors.initials: N
authors.lastname: Mueller
authors.forename: Harald
authors.initials: H
authors.lastname: Wajant
authors.forename: Alja J
authors.initials: AJ
authors.lastname: Stel
authors.forename: Martine
authors.initials: M
authors.lastname: Chamuleau
authors.forename: Arjan A
authors.initials: AA
authors.lastname: van de Loosdrecht
authors.forename: Julia
authors.initials: J
authors.lastname: Stieglmaier
authors.forename: Georg H
authors.initials: GH
authors.lastname: Fey
authors.forename: Wijnand
authors.initials: W
authors.lastname: Helfrich
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage*; D058846:Antibodies, Monoclonal, Murine-Derived; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001402:B-Lymphocytes / Q000187:drug effects; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D053222:Fas Ligand Protein / Q000819:agonists*; D005260:Female; D015316:Genetic Therapy / Q000009:adverse effects / Q000379:methods; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000628:therapy*; D008228:Lymphoma, Non-Hodgkin / Q000235:genetics / Q000628:therapy*; D008297:Male; D011993:Recombinant Fusion Proteins / Q000009:adverse effects / Q000235:genetics* / Q000627:therapeutic use*; D000069283:Rituximab; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D057127:Single-Chain Antibodies; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D011993:Recombinant Fusion Proteins; D057127:Single-Chain Antibodies; C526446:scFvRit-sFasL protein, human; D000069283:Rituximab