title: HER2-mediated internalization of a targeted prodrug cytotoxic conjugate is dependent on the valency of the targeting ligand.
abstract: HER2 is a validated therapeutic target for cancer. There are no natural ligands, but monoclonal antibodies and peptides that bind HER2 act as artificial ligands, selectively affecting HER2-overexpressing tumors. One reported mechanism for this effect is receptor downregulation, but the expected correlation of ligand-dependent HER2 internalization and tumor inhibition remain poorly characterized. Moreover, HER2 ligands have limited therapeutic efficacy and often they require adjuvant treatment with the chemotherapeutic Taxol. Here, we generated a series of HER2 ligands (Anti-HER2/neu peptide ligands, AHNPmonovalent and AHNPbivalent) with different valency and correlated their internalization-promoting ability to biological potency. Since AHNPbivalent (but not AHNPmonovalent) induces rapid receptor internalization, we exploited this feature to deliver cytotoxic conjugates coupling AHNPbivalent and Taxol (Taxol . AHNPbivalent). The prodrug conjugate releases Taxol after receptor-mediated internalization, and cytotoxicity can be used as a marker of internalization. Taxol . AHNPbivalent is significantly more cytotoxic than free Taxol + free AHNPbivalent. Hence, the Taxol x AHNP(bivalent) prodrug binds to HER2, induces receptor internalization and downregulation, and the subsequent release of free Taxol inside the targeted cell results in synergistic toxicity, The effect is selective towards HER2- expressing cells. This work links HER2 receptor internalization and growth arrest, and the chemical conjugation strategy may yield improved and HER2 selective therapeutics.
authors.affiliation: McGill University, Pharmacology and Therapeutics and Oncology/Cancer Center, Lady Davis Research Institute-Jewish General Hospital, Montreal, Quebec, Canada.
authors.forename: Veronique
authors.initials: V
authors.lastname: Guillemard
authors.forename: Hinyu N
authors.initials: HN
authors.lastname: Nedev
authors.forename: Alan
authors.initials: A
authors.lastname: Berezov
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Murali
authors.forename: H Uri
authors.initials: HU
authors.lastname: Saragovi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004705:Endocytosis / Q000187:drug effects*; D000922:Immunotoxins / Q000737:chemistry / Q000494:pharmacology*; D051379:Mice; D008958:Models, Molecular; D015394:Molecular Structure; D041681:NIH 3T3 Cells; D017239:Paclitaxel / Q000737:chemistry / Q000494:pharmacology; D011355:Prodrugs / Q000737:chemistry / Q000494:pharmacology*; D011487:Protein Conformation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D000922:Immunotoxins; D017239:Paclitaxel; D011355:Prodrugs; D018719:Erb-b2 Receptor Tyrosine Kinases; C404542:anti-HER2-neu peptide mimic, 1.5 kDa