Molecular imaging of glioblastoma multiforme using anti-insulin-like growth factor-binding protein-7 single-domain antibodies.
BACKGROUND
Insulin-like growth factor-binding protein 7 (IGFBP7) is an abundant, selective and accessible biomarker of glioblastoma multiforme (GBM) tumour vessels. In this study, an anti-IGFBP7 single-domain antibody (sdAb) was developed to target GBM vessels for molecular imaging applications.


METHODS
Human GBM was modelled in mice by intracranial implantation of U87MG.EGFRvIII cells. An anti-IGFBP7 sdAb, isolated from an immune llama library by panning, was assessed in vitro for its binding affinity using surface plasmon resonance and by ex vivo immunobinding on mouse and human GBM tissue. Tumour targeting by Cy5.5-labelled anti-IGFBP7 sdAb as well as by anti-IGFBP7 sdAb conjugated to PEGylated Fe₃O₄ nanoparticles (NPs)-Cy5.5 were assessed in U87MG.EGFRvIII tumour-bearing mice in vivo using optical imaging and in brain sections using fluorescent microscopy.


RESULTS
Surface plasmon resonance analyses revealed a medium affinity (K(D)=40-50 nM) binding of the anti-IGFBP7 sdAb to the purified antigen. The anti-IGFBP7 sdAb also selectively bound to both mouse and human GBM vessels, but not normal brain vessels in tissue sections. In vivo, intravenously injected anti-IGFBP7 sdAb-Cy5.5 bound to GBM vessels creating high imaging signal in the intracranial tumour. Similarly, the anti-IGFBP7 sdAb-functionalised PEGylated Fe₃O₄ NP-Cy5.5 demonstrated enhanced tumour signal compared with non-targeted NPs. Fluorescent microscopy confirmed the presence of anti-IGFBP7 sdAb and anti-IGFBP7 sdAb-PEGylated Fe₃O₄ NPs selectively in GBM vessels.


CONCLUSIONS
Anti-IGFBP7 sdAbs are novel GBM vessel-targeting moieties suitable for molecular imaging.
Iqbal
U
U
Institute for Biological Sciences, National Research Council of Canada, 1200 Montreal Road, Ottawa, Ontario, Canada K1A 0R6.
Albaghdadi
H
H
Luo
Y
Y
Arbabi
M
M
Desvaux
C
C
Veres
T
T
Stanimirovic
D
D
Abulrob
A
A
D000818:Animals; D000906:Antibodies; D001921:Brain / Q000276:immunology / Q000473:pathology; D001932:Brain Neoplasms / Q000276:immunology / Q000473:pathology* / Q000648:ultrastructure; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics / Q000276:immunology; D005784:Gene Amplification; D005909:Glioblastoma / Q000276:immunology / Q000473:pathology* / Q000648:ultrastructure; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D007150:Immunohistochemistry; D018969:Insulin-Like Growth Factor Binding Proteins / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008856:Microscopy, Fluorescence; D016133:Polymerase Chain Reaction; D014018:Tissue Distribution
D000906:Antibodies; D017931:DNA Primers; D018076:DNA, Complementary; D007074:Immunoglobulin G; D018969:Insulin-Like Growth Factor Binding Proteins; C102529:insulin-like growth factor binding protein-related protein 1