Single-chain antibody/activated BID chimeric protein effectively suppresses HER2-positive tumor growth

Mol Cancer Ther. 2008 Jul;7(7):1890-9. doi: 10.1158/1535-7163.MCT-07-2235.


BH3-interacting domain death agonist (BID) is a crucial element in death signaling pathways and is recognized as an intracellular link connecting the intrinsic mitochondrial apoptotic and extrinsic death receptor-mediated apoptotic pathways. Herein, we describe experiments conducted with a fusion protein, which was generated by fusing a human epidermal growth factor receptor-2 (HER2)-specific single-chain antibody with domain II of Pseudomonas exotoxin A and the truncated active BID (tBID). These experiments extend our previous work on several other immuno-proapoptotic proteins. Specifically, by excluding cells with undetectable HER2, we showed that the secreted immuno-tBID molecule selectively recognized and killed HER2-overexpressing tumor cells in vitro by attacking their mitochondria and inducing their apoptotic death. This apoptosis could only be inhibited partially by caspase pan-inhibitor zVAD and mitochondrial protector TAT-BH4. Subsequently, we transferred the immuno-tbid gene into BALB/c athymic mice bearing HER2-positive tumors together with other immuno-proapoptotic proteins using i.m. injections of liposome-encapsulated vectors. The expression of the immuno-tbid gene suppressed tumor growth and prolonged animal survival significantly. We also shortened the translocation domain of Pseudomonas exotoxin A II to only 10-amino acid sequence, which were crucial for furin cleavage. The new recombinant molecule retained the translocation efficiency and the ability of specific killing HER2-positive tumor cells. Our data showed that, compared with the toxins employed before, the chimeric immuno-tBID molecule can not only specifically recognize HER2-positive tumor cells but also certainly induce apoptosis even in the presence of zVAD and TAT-BH4, thereby suggesting an alternative approach to treating HER2/neu-positive tumors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Neoplasm / pharmacology*
  • Apoptosis Inducing Factor / metabolism
  • BH3 Interacting Domain Death Agonist Protein / pharmacology*
  • COS Cells
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Chlorocebus aethiops
  • Cytochromes c / metabolism
  • Humans
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Neoplasms / immunology
  • Neoplasms / pathology*
  • Peptides / chemistry
  • Protein Structure, Tertiary
  • Receptor, ErbB-2 / metabolism*
  • Recombinant Fusion Proteins / pharmacology*
  • Transduction, Genetic
  • Xenograft Model Antitumor Assays


  • Antibodies, Neoplasm
  • Apoptosis Inducing Factor
  • BH3 Interacting Domain Death Agonist Protein
  • Peptides
  • Recombinant Fusion Proteins
  • Cytochromes c
  • Receptor, ErbB-2