title: Conjugation of an anti transferrin receptor IgG3-avidin fusion protein with biotinylated saporin results in significant enhancement of its cytotoxicity against malignant hematopoietic cells.
abstract: We have previously developed an antibody fusion protein composed of a mouse/human chimeric IgG3 specific for the human transferrin receptor genetically fused to avidin (anti-hTfR IgG3-Av) as a universal delivery system for cancer therapy. This fusion protein efficiently delivers biotinylated FITC into cancer cells via TfR-mediated endocytosis. In addition, anti-hTfR IgG3-Av alone exhibits intrinsic cytotoxic activity and interferes with hTfR recycling, leading to the rapid degradation of the TfR and lethal iron deprivation in certain malignant B-cell lines. We now report on the cytotoxic effects of a conjugate composed of anti-hTfR IgG3-Av and biotinylated saporin 6 (b-SO6), a toxin derived from the plant Saponaria officinalis that inhibits protein synthesis. Conjugation of anti-hTfR IgG3-Av with b-SO6 enhances the cytotoxic effect of the fusion protein in sensitive cells and also overcomes the resistance of malignant cells that show low sensitivity to the fusion protein alone. Our results show for the first time that loading anti-hTfR IgG3-Av with a biotinylated toxin enhances the cytotoxicity of the fusion protein alone. These results suggest that anti-hTfR IgG3-Av has great potential as a therapeutic agent for a wide range of applications due to its intrinsic cytotoxic activity plus its ability to deliver biotinylated molecules into cancer cells.
authors.affiliation: Division of Surgical Oncology, Department of Surgery, University of California at Los Angeles, Los Angeles, CA 90095-1782, USA.
authors.forename: Tracy R
authors.initials: TR
authors.lastname: Daniels
authors.forename: Patrick P
authors.initials: PP
authors.lastname: Ng
authors.forename: Tracie
authors.initials: T
authors.lastname: Delgado
authors.forename: Maureen R
authors.initials: MR
authors.lastname: Lynch
authors.forename: Gary
authors.initials: G
authors.lastname: Schiller
authors.forename: Gustavo
authors.initials: G
authors.lastname: Helguera
authors.forename: Manuel L
authors.initials: ML
authors.lastname: Penichet
mesh_terms: D001360:Avidin / Q000378:metabolism*; D019921:Biotinylation; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D064420:Drug-Related Side Effects and Adverse Reactions; D004789:Enzyme Activation / Q000187:drug effects; D019337:Hematologic Neoplasms / Q000201:enzymology / Q000473:pathology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology*; D000090463:Iron Deficiencies; D010940:Plant Proteins / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D011990:Receptors, Transferrin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D054789:Ribosome Inactivating Proteins, Type 1 / Q000378:metabolism*; D000076985:Saporins
chemical_list: D007074:Immunoglobulin G; D010940:Plant Proteins; D011990:Receptors, Transferrin; D011993:Recombinant Fusion Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D001360:Avidin; D000076985:Saporins; D020169:Caspases