Single-chain antibody/activated BID chimeric protein effectively suppresses HER2-positive tumor growth.
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.
Qiu
Xiu-Chun
XC
State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Xi'an, People's Republic of China.
Xu
Yan-Ming
YM
Wang
Fang
F
Fan
Qing-Yu
QY
Wang
Li-Feng
LF
Ma
Bao-An
BA
Jia
Lin-Tao
LT
Zhao
Jing
J
Meng
Yan-Ling
YL
Yao
Li-Bo
LB
Chen
Si-Yi
SY
Yang
An-Gang
AG
D000818:Animals; D000912:Antibodies, Neoplasm / Q000494:pharmacology*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D051023:BH3 Interacting Domain Death Agonist Protein / Q000494:pharmacology*; D019556:COS Cells; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002522:Chlorocebus aethiops; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009369:Neoplasms / Q000276:immunology / Q000473:pathology*; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*; D014161:Transduction, Genetic; D023041:Xenograft Model Antitumor Assays
D000912:Antibodies, Neoplasm; D051033:Apoptosis Inducing Factor; D051023:BH3 Interacting Domain Death Agonist Protein; D045304:Cytochromes c; D010455:Peptides; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins