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

Abstract

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.

• Authors: Xiu-Chun Qiu, Yan-Ming Xu, Fang Wang, Qing-Yu Fan, Li-Feng Wang, Bao-An Ma, Lin-Tao Jia, Jing Zhao, Yan-Ling Meng, Li-Bo Yao, Si-Yi Chen, An-Gang Yang
• Journal: Molecular cancer therapeutics (Mol Cancer Ther) Vol. 7 Issue 7 Pg. 1890-9 (Jul 2008) ISSN: 1535-7163 [Print] United States
• PMID: 18644999 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

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

Topics

• 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, pathology)
• Peptides (chemistry)
• Protein Structure, Tertiary
• Receptor, ErbB-2 (metabolism)
• Recombinant Fusion Proteins (pharmacology)
• Transduction, Genetic
• Xenograft Model Antitumor Assays