title: Selection of tumor-specific internalizing human antibodies from phage libraries.
abstract: Antibody internalization into the cell is required for many targeted therapeutics, such as immunotoxins, immunoliposomes, antibody-drug conjugates and for targeted delivery of genes or viral DNA into cells. To generate directly tumor-specific internalizing antibodies, a non-immune single chain Fv (scFv) phage antibody library was selected on the breast tumor cell line SKBR3. Internalized phage were recovered from within the cell and used for the next round of selection. After three rounds of selection, 40 % of clones analyzed bound SKBR3 and other tumor cells but did not bind normal human cells. Of the internalizing scFv identified, two (F5 and C1) were identified as binding to ErbB2, and one (H7) to the transferrin receptor. Both F5 and H7 scFv were efficiently endocytosed into SKBR3 cells, both as phage antibodies and as native monomeric scFv. Both antibodies were able to induce additional functional effects besides triggering endocytosis: F5 scFv induces downstream signaling through the ErbB2 receptor and H7 prevents transferrin binding to the transferrin receptor and inhibits cell growth. The results demonstrate the feasibility of selecting internalizing receptor-specific antibodies directly from phage libraries by panning on cells. Such antibodies can be used to target a variety of molecules into the cell to achieve a therapeutic effect. Furthermore, in some instances endocytosis serves as a surrogate marker for other therapeutic biologic effects, such as growth inhibition. Thus, a subset of selected antibodies will have a direct therapeutic effect.
authors.affiliation: Departments of Anesthesia and Pharmaceutical Chemistry, University of California, San Francisco, Rm. 3C-38, San Francisco General Hospital, 1001 Potrero Avenue, San Francisco, CA, 94110, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Poul
authors.forename: B
authors.initials: B
authors.lastname: Becerril
authors.forename: U B
authors.initials: UB
authors.lastname: Nielsen
authors.forename: P
authors.initials: P
authors.lastname: Morisson
authors.forename: J D
authors.initials: JD
authors.lastname: Marks
mesh_terms: D000818:Animals; D000912:Antibodies, Neoplasm / Q000235:genetics* / Q000276:immunology* / Q000494:pharmacology; D000915:Antibody Affinity; D000918:Antibody Specificity / Q000276:immunology; D000951:Antigens, Neoplasm / Q000276:immunology*; D001435:Bacteriophages / Q000235:genetics; D001943:Breast Neoplasms / Q000276:immunology* / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D003001:Cloning, Molecular; D006224:Cricetinae; D004705:Endocytosis / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D005347:Fibroblasts; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D019151:Peptide Library; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D011990:Receptors, Transferrin / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014168:Transferrin / Q000037:antagonists & inhibitors / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000912:Antibodies, Neoplasm; D000951:Antigens, Neoplasm; D007135:Immunoglobulin Variable Region; D019151:Peptide Library; D018719:Erb-b2 Receptor Tyrosine Kinases; D011990:Receptors, Transferrin; D014168:Transferrin