Journal
EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING
Volume 40, Issue 11, Pages 1718-1729Publisher
SPRINGER
DOI: 10.1007/s00259-013-2471-2
Keywords
Nanobody; VHH; HER2; Breast cancer; Optical imaging
Funding
- Center for Translational Molecular Medicine (MAMMOTH project)
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Purpose Molecular optical imaging using monoclonal antibodies is slow with low tumour to background ratio. We used anti-HER2 VHHs conjugated to IRDye 800CW to investigate their potential as probes for rapid optical molecular imaging of HER2-positive tumours by the determination of tumour accumulation and tumour to background levels. Three anti-HER2 VHHs (11A4, 18C3, 22G12) were selected with phage display and produced in Escherichia coli. Binding affinities of these probes to SKBR3 cells were determined before and after site-specific conjugation to IRDye 800CW. To determine the potential of VHH-IR as imaging probes, serial optical imaging studies were carried out using human SKBR3 and human MDA-MB-231 xenograft breast cancer models. Performance of the anti-HER2 VHH-IR was compared to that of trastuzumab-IR and a non-HER2-specific VHH-IR. Image-guided surgery was performed during which SKBR3 tumour was removed under the guidance of the VHH-IR signal. Site-specific conjugation of IRDye 800CW to three anti-HER2 VHHs preserved high affinity binding with the following dissociation constants (K-D): 11A4 1.9 +/- 0.03, 18C3 14.3 +/- 1.8 and 22G12 3.2 +/- 0.5 nM. Based upon different criteria such as binding, production yield and tumour accumulation, 11A4 was selected for further studies. Comparison of 11A4-IR with trastuzumab-IR showed similar to 20 times faster tumour accumulation of the anti-HER2 VHH, with a much higher contrast between tumour and background tissue (11A4-IR 2.5 +/- 0.3, trastuzumab-IR 1.4 +/- 0.4, 4 h post-injection). 11A4-IR was demonstrated to be a useful tool in image-guided surgery. VHH-IR led to a much faster tumour accumulation with high tumour to background ratios as compared to trastuzumab-IR allowing same-day imaging for clinical investigation as well as image-guided surgery.
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