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Published on: May 16, 2020
64Cu-labeled affibody molecules for imaging of HER2 expressing tumors
Zhen Cheng1, Omayra Padilla De Jesus, Daniel J Kramer
1Molecular Imaging Program at Stanford, Departments of Radiology and Bioengineering, Bio-X Program, Stanford University, California, CA 94305-5344, USA. zcheng@stanford.edu
Introduction:
The development of molecular probes based on novel engineered protein constructs is under active investigation due to the great potential of this generalizable strategy for imaging a variety of tumor targets.
Discussion:
In this report, human epidermal growth factor receptor type 2 (HER2)-binding Affibody molecules were radiolabeled with (64)Cu and their imaging ability was further evaluated in tumor mice models to understand the promise and limitations of such probes. The anti-HER2 Affibody molecules in monomeric (Z(HER2:477)) and dimeric [(Z(HER2:477))(2)] forms were site specifically modified with the maleimide-functionalized chelator, 1,4,7,10-tetraazacyclododecane-1,4,7-tris(acetic acid)-10-acetate mono (N-ethylmaleimide amide) (Mal-DOTA). The resulting DOTA-Affibody conjugates were radiolabeled with (64)Cu and evaluated in nude mice bearing subcutaneous SKOV3 tumors. Biodistribution experiments showed that tumor uptake values of (64)Cu-DOTA-Z(HER2:477) and (64)Cu-DOTA-(Z(HER2:477))(2) were 6.12 +/- 1.44% and 1.46 +/- 0.50% ID/g, respectively, in nude mice (n = 3 each) at 4 h postinjection. Moreover, (64)Cu-labeled monomer exhibited significantly higher tumor/blood ratio than that of radiolabeled dimeric counterpart at all time points examined in this study. MicroPET imaging of (64)Cu-DOTA-Z(HER2:477) in SKOV3 tumor mice clearly showed good and specific tumor localization. This study demonstrates that (64)Cu-labeled Z(HER2:477) is a promising targeted molecular probe for imaging HER2 receptor expression in living mice. Further work is needed to improve the excretion properties, hence dosimetry and imaging efficacy, of the radiometal-based probe.
Insights
This study developed a novel molecular probe using copper-64 labeled Affibody molecules to image HER2-expressing tumors in mice. The monomeric probe showed promising tumor localization and specific targeting, indicating its potential for future cancer imaging applications.
Area of Science:
- Molecular imaging
- Bioconjugation chemistry
- Radiopharmaceutical development
Background:
- Engineered protein constructs offer a versatile strategy for developing molecular probes for diverse tumor targets.
- Targeted molecular imaging is crucial for accurate cancer diagnosis and treatment monitoring.
Purpose of the Study:
- To develop and evaluate copper-64 labeled anti-HER2 Affibody molecules as molecular probes for imaging HER2 receptor expression.
- To assess the in vivo performance of monomeric and dimeric Affibody-based probes in tumor-bearing mice models.
Main Methods:
- Site-specific modification of anti-HER2 Affibody molecules (monomeric Z(HER2:477) and dimeric [Z(HER2:477)](2)) with a maleimide-functionalized chelator (Mal-DOTA).
- Radiolabeling of DOTA-Affibody conjugates with copper-64 ((64)Cu).
- Evaluation of radiolabeled probes in nude mice bearing SKOV3 tumors using biodistribution studies and MicroPET imaging.
Main Results:
- (64)Cu-labeled monomeric Z(HER2:477) demonstrated significant tumor uptake (6.12 +/- 1.44% ID/g at 4 h postinjection) in SKOV3 tumor-bearing mice.
- The monomeric probe exhibited higher tumor/blood ratios compared to the dimeric counterpart across all measured time points.
- MicroPET imaging confirmed specific and good tumor localization of (64)Cu-DOTA-Z(HER2:477).
Conclusions:
- Copper-64 labeled Z(HER2:477) Affibody molecule is a promising targeted molecular probe for in vivo imaging of HER2 receptor expression.
- Further optimization is required to enhance excretion properties, dosimetry, and overall imaging efficacy of the radiometal-based probe.
