Affitoxin--a novel recombinant, HER2-specific, anticancer agent for targeted therapy of HER2-positive tumors

J Immunother. 2009 Oct;32(8):817-25. doi: 10.1097/CJI.0b013e3181ad4d5d.

Abstract

Expression of the human epidermal growth factor receptor 2 (HER2) is amplified in 25% to 30% of breast cancers and has been associated with an unfavorable prognosis. Here we report the construction, purification, and characterization of Affitoxin-a novel class of HER2-specific cytotoxic molecules combining HER2-specific Affibody molecule as a targeting moiety and PE38KDEL, which is a truncated version of Pseudomonas exotoxin A, as a cell killing agent. It is highly soluble and does not require additional refolding, oxidation, or reduction steps during its purification. Using surface plasmon resonance technology and competitive binding assays, we have shown that Affitoxin binds specifically to HER2 with nanomolar affinity. We have also observed a high correlation between HER2 expression and retention of Affitoxin bound to the cell surface. Affitoxin binding and internalization is followed by Pseudomonas exotoxin A activity domain-mediated ADP-ribosylation of translation elongation factor 2 and, consequently, inhibition of protein synthesis as shown by protein expression analysis of HER2-positive cells treated with Affitoxin. Measured IC50 value for HER2-negative cells MDA-MB468 (65+/-2.63 pM) was more than 20 times higher than the value for low HER2 level-expressing MCF7 cells (2.56+/-0.1 pM), and almost 3 orders of magnitude higher for its HER2-overexpressing derivative MCF7/HER2 (62.7+/-5.9 fM). These studies suggest that Affitoxin is an attractive PE38-based candidate for treatment of HER2-positive tumors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural

MeSH terms

  • ADP Ribose Transferases / genetics
  • ADP Ribose Transferases / metabolism
  • ADP Ribose Transferases / pharmacology*
  • Antibodies, Bispecific
  • Antibody Affinity
  • Bacterial Toxins / genetics
  • Bacterial Toxins / metabolism
  • Bacterial Toxins / pharmacology*
  • Binding, Competitive
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / therapy*
  • Cell Line, Tumor
  • Drug Delivery Systems
  • Exotoxins / genetics
  • Exotoxins / metabolism
  • Exotoxins / pharmacology*
  • Female
  • Humans
  • Immunotoxins / genetics
  • Immunotoxins / metabolism
  • Immunotoxins / pharmacology*
  • Protein Biosynthesis / drug effects
  • Protein Engineering
  • Receptor, ErbB-2 / genetics
  • Receptor, ErbB-2 / immunology
  • Receptor, ErbB-2 / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Recombinant Fusion Proteins / pharmacology*
  • Surface Plasmon Resonance
  • Virulence Factors / genetics
  • Virulence Factors / metabolism
  • Virulence Factors / pharmacology*

Substances

  • Antibodies, Bispecific
  • Bacterial Toxins
  • Exotoxins
  • Immunotoxins
  • Recombinant Fusion Proteins
  • Virulence Factors
  • ADP Ribose Transferases
  • toxA protein, Pseudomonas aeruginosa
  • ERBB2 protein, human
  • Receptor, ErbB-2