title: Generation of Peptide mimics of the epitope recognized by trastuzumab on the oncogenic protein Her-2/neu.
abstract: Immunizations with the oncogenic protein Her-2/neu elicit Abs exerting diverse biological effects--depending on epitope specificity, tumor growth may be inhibited or enhanced. Trastuzumab (herceptin) is a growth-inhibitory humanized monoclonal anti-Her-2/neu Ab, currently used for passive immunotherapy in the treatment of breast cancer. However, Ab therapies are expensive and have to be repeatedly administered for long periods of time. In contrast, active immunizations produce ongoing immune responses. Therefore, the study aims to generate peptide mimics of the epitope recognized by trastuzumab for vaccine formulation, ensuring the subsequent induction of tumor growth inhibitory Abs. We used the phage display technique to generate epitope mimics, mimotopes, complementing the screening Ab trastuzumab. Five candidate mimotopes were isolated from a constrained 10 mer library. These peptides were specifically recognized by trastuzumab, and showed distinctive mimicry with Her-2/neu in two experimental setups. Subsequently, immunogenicity of a selected mimotope was examined in BALB/c mice. Immunizations with a synthetic mimotope conjugated to tetanus toxoid resulted in Abs recognizing Her-2/neu in a blotted cell lysate as well as on the SK-BR-3 cell surface. Analogous to trastuzumab, the induced Abs caused internalization of the receptor from the cell surface to endosomal vesicles. These results indicate that the selected mimotopes are suitable for formulation of a breast cancer vaccine because the resulting Abs show similar biological features as trastuzumab.
authors.affiliation: BioLife Science, and Department of Pathophysiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria.
authors.forename: Angelika B
authors.initials: AB
authors.lastname: Riemer
authors.forename: Markus
authors.initials: M
authors.lastname: Klinger
authors.forename: Stefan
authors.initials: S
authors.lastname: Wagner
authors.forename: Astrid
authors.initials: A
authors.lastname: Bernhaus
authors.forename: Luca
authors.initials: L
authors.lastname: Mazzucchelli
authors.forename: Hubert
authors.initials: H
authors.lastname: Pehamberger
authors.forename: Otto
authors.initials: O
authors.lastname: Scheiner
authors.forename: Christoph C
authors.initials: CC
authors.lastname: Zielinski
authors.forename: Erika
authors.initials: E
authors.lastname: Jensen-Jarolim
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D061067:Antibodies, Monoclonal, Humanized; D001943:Breast Neoplasms / Q000276:immunology*; D019496:Cancer Vaccines / Q000276:immunology*; D045744:Cell Line, Tumor; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005455:Fluorescent Antibody Technique; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology*; D000068878:Trastuzumab; D014611:Vaccination
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D019496:Cancer Vaccines; D000939:Epitopes; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab