¹¹¹In-Bn-DTPA-nimotuzumab with/without modification with nuclear translocation sequence (NLS) peptides: an Auger electron-emitting radioimmunotherapeutic agent for EGFR-positive and trastuzumab (Herceptin)-resistant breast cancer.
Increased expression of epidermal growth factor receptors (EGFR) in breast cancer (BC) is often associated with trastuzumab (Herceptin)-resistant forms of the disease and represents an attractive target for novel therapies. Nimotuzumab is a humanized IgG(1) monoclonal antibody that is in clinical trials for treatment of EGFR-overexpressing malignancies. We show here that nimotuzumab derivatized with benzylisothiocyanate diethylenetriaminepentaacetic acid for labelling with the subcellular range Auger electron-emitter, (111)In and modified with nuclear translocation sequence (NLS) peptides ((111)In-NLS-Bn-DTPA-nimotuzumab) was bound, internalized and transported to the nucleus of EGFR-positive BC cells. Emission of Auger electrons in close proximity to the nucleus caused multiple DNA double-strand breaks which diminished the clonogenic survival (CS) of MDA-MB-468 cells that have high EGFR density (2.4 × 10(6) receptors/cell) to less than 3 %. (111)In-Bn-DTPA-nimotuzumab without NLS peptide modification was sevenfold less effective for killing MDA-MB-468 cells. (111)In-Bn-DTPA-nimotuzumab with/without NLS peptide modification were equivalently cytotoxic to MDA-MB-231 and TrR1 BC cells that have moderate EGFR density (5.4 × 10(5) or 4.2 × 10(5) receptors/cell, respectively) reducing their CS by twofold. MDA-MB-231 cells have intrinsic trastuzumab resistance due to low HER2 density, whereas TrR1 cells have acquired resistance despite HER2 overexpression. Biodistribution and microSPECT/CT imaging revealed that (111)In-NLS-Bn-DTPA-nimotuzumab exhibited more rapid elimination from the blood and lower tumour uptake than (111)In-Bn-DTPA-nimotuzumab. Tumour uptake of the radioimmunoconjugates in mice with MDA-MB-468 xenografts was high (8-16 % injected dose/g) and was blocked by administration of an excess of unlabelled nimotuzumab, demonstrating EGFR specificity. We conclude that (111)In-Bn-DTPA-nimotuzumab with/without NLS peptide modification are promising Auger electron-emitting radioimmunotherapeutic agents for EGFR-positive BC, but (111)In-Bn-DTPA-nimotuzumab may be preferred due to its higher tumour uptake in vivo.
Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON, Canada.
Aisha
A
Fasih
Humphrey
H
Fonge
Zhongli
Z
Cai
Jeffrey V
JV
Leyton
Ilia
I
Tikhomirov
Susan J
SJ
Done
Raymond M
RM
Reilly
D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000378:metabolism / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000528:radiation effects; D019008:Drug Resistance, Neoplasm; D066246:ErbB Receptors / Q000276:immunology / Q000378:metabolism*; D005260:Female; D006801:Humans; D018796:Immunoconjugates / Q000627:therapeutic use; D007074:Immunoglobulin G / Q000627:therapeutic use*; D007205:Indium Radioisotopes / Q000627:therapeutic use*; D051379:Mice; D019913:Nuclear Localization Signals; D004369:Pentetic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D016499:Radioimmunotherapy; D014018:Tissue Distribution; D000068878:Trastuzumab
D061067:Antibodies, Monoclonal, Humanized; C069971:DTPA-IgG complex; D018796:Immunoconjugates; D007074:Immunoglobulin G; D007205:Indium Radioisotopes; D019913:Nuclear Localization Signals; C501466:nimotuzumab; D004369:Pentetic Acid; D066246:ErbB Receptors; D000068878:Trastuzumab