title: HER2-affitoxin: a potent therapeutic agent for the treatment of HER2-overexpressing tumors.
abstract: OBJECTIVE
  Cancers overexpressing the HER2/neu gene are usually more aggressive and are associated with poor prognosis. Although trastuzumab has significantly improved the outcome, many tumors do not respond or acquire resistance to current therapies. To provide an alternative HER2-targeted therapy, we have developed and characterized a novel recombinant protein combining an HER2-specific Affibody and modified Pseudomonas aeruginosa exotoxin A (PE 38), which, after binding to HER2, is internalized and delivered to the cytosol of the tumor cell, where it blocks protein synthesis by ADP ribosylation of eEF-2.
  
  
  METHODS
  The effect of the Affitoxin on cell viability was assessed using CellTiter-Glo (Promega). To assess HER2-specific efficacy, athymic nude mice bearing BT-474 breast cancer, SK-OV-3 ovarian cancer, and NCI-N87 gastric carcinoma xenografts were treated with the Affitoxin (HER2- or Tag-specific), which was injected every third day. Affitoxin immunogenicity in female BALB/c mice was investigated using standard antibody production and splenocyte proliferation assays.
  
  
  RESULTS
  In vitro experiments proved that HER2-Affitoxin is a potent agent that eliminates HER2-overexpressing cells at low picomolar concentrations. Therapeutic efficacy studies showed complete eradication of relatively large BT-474 tumors and significant effects on SK-OV-3 and NCI-N87 tumors. HER2-Affitoxin cleared quickly from circulation (T(1/2) < 10 minutes) and was well tolerated by mice at doses of 0.5 mg/kg and below. Immunogenicity studies indicated that HER2-Affitoxin induced antibody development after the third injected dose.
  
  
  CONCLUSIONS
  Our findings showed that HER2-Affitoxin is an effective anticancer agent and a potential candidate for clinical studies.
authors.affiliation: Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute (NCI), Section on Analytical and Functional Biophotonics, Program on Pediatric Imaging and Tissue Sciences, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA.
authors.forename: Rafal
authors.initials: R
authors.lastname: Zielinski
authors.forename: Ilya
authors.initials: I
authors.lastname: Lyakhov
authors.forename: Moinuddin
authors.initials: M
authors.lastname: Hassan
authors.forename: Monika
authors.initials: M
authors.lastname: Kuban
authors.forename: Kimberly
authors.initials: K
authors.lastname: Shafer-Weaver
authors.forename: Amir
authors.initials: A
authors.lastname: Gandjbakhche
authors.forename: Jacek
authors.initials: J
authors.lastname: Capala
mesh_terms: D036002:ADP Ribose Transferases / Q000008:administration & dosage*; D000818:Animals; D001427:Bacterial Toxins / Q000008:administration & dosage*; D045744:Cell Line, Tumor; D005098:Exotoxins / Q000008:administration & dosage*; D000922:Immunotoxins / Q000627:therapeutic use*; D051379:Mice; D008819:Mice, Nude; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000627:therapeutic use; D037521:Virulence Factors / Q000008:administration & dosage*; D023041:Xenograft Model Antitumor Assays; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D000922:Immunotoxins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C568088:HER2 affitoxin