title: Biological effects of anti-ErbB2 single chain antibodies selected for internalizing function.
abstract: Two internalizing monovalent single chain antibody fragments (scFv), C6.5 and F5, that recognize distinct ErbB2 extracellular domain (ECD) epitopes, and their bivalent forms dbC6.5 and F5(scFv')(2), were compared to the growth-inhibiting anti-ErbB2 antibody Herceptin/trastuzumab, in either its bivalent (Her) or monovalent (4D5Fab') form, for their abilities to induce biological responses in the ErbB2-overexpressing breast cancer cells, SkBr-3. Assays compared internalization by receptor-mediated endocytosis, effects on cell cycling and culture growth, and interference with intracellular MAPK and PI3K signaling pathways. We found no correlation between ErbB2 epitope affinity or valency on degree of antibody-induced endocytosis, since all the scFv were able to internalize better than Her. Unlike Her, neither the monovalent or bivalent forms of the internalizing scFv had any sustained effect on cell growth. Basal levels of MAPK and PI3K signaling in SkBr-3 cells were not inhibited by up to 8 h scFv treatment, while decreased MAPK and PI3K signals were noted within 8 h of Her treatment. In summary, antibody-induced ErbB2-mediated endocytosis is not a surrogate marker for resultant biological response, as it shows no correlation with cell cycle, culture proliferation, or intracellular kinase signal induction by internalizing antibodies. Thus, the enhanced endocytotic property of scFv like C6.6 and F5 in conjunction with their absence of any growth or signaling impact on ErbB2-overexpressing cells favors their choice as ErbB2 targeting moieties for intracellular delivery of novel cancer therapeutics.
authors.affiliation: Department of Medicine, University of California at San Francisco, San Francisco, California 94143, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Neve
authors.forename: U B
authors.initials: UB
authors.lastname: Nielsen
authors.forename: D B
authors.initials: DB
authors.lastname: Kirpotin
authors.forename: M A
authors.initials: MA
authors.lastname: Poul
authors.forename: J D
authors.initials: JD
authors.lastname: Marks
authors.forename: C C
authors.initials: CC
authors.lastname: Benz
mesh_terms: D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D000915:Antibody Affinity; D001943:Breast Neoplasms; D002453:Cell Cycle / Q000187:drug effects / Q000276:immunology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004705:Endocytosis / Q000187:drug effects; D000939:Epitopes / Q000276:immunology; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000378:metabolism / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D011994:Recombinant Proteins / Q000493:pharmacokinetics / Q000494:pharmacology; D000068878:Trastuzumab; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000939:Epitopes; D007128:Immunoglobulin Fragments; D007457:Iodine Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; D000068878:Trastuzumab