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Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy
Published on: September 11, 2015
Feasibility of imaging of epidermal growth factor receptor expression with ZEGFR:2377 affibody molecule labeled with
Ken G Andersson1, Maryam Oroujeni2, Javad Garousi2
1Division of Protein Technology, KTH Royal Institute of Technology, SE-10691 Stockholm, Sweden.
Abstract:
The epidermal growth factor receptor (EGFR) is overexpressed in a number of malignant tumors and is a molecular target for several specific anticancer antibodies and tyrosine kinase inhibitors. The overexpression of EGFR is a predictive biomarker for response to several therapy regimens. Radionuclide molecular imaging might enable detection of EGFR overexpression by a non-invasive procedure and could be used repeatedly. Affibody molecules are engineered scaffold proteins, which could be selected to have a high affinity and selectivity to predetermined targets. The anti-EGFR ZEGFR:2377 affibody molecule is a potential imaging probe for EGFR detection. The use of the generator-produced radionuclide 99mTc should facilitate clinical translation of an imaging probe due to its low price, availability and favorable dosimetry of the radionuclide. In the present study, we evaluated feasibility of ZEGFR:2377 labeling with 99mTc using a peptide-based cysteine-containing chelator expressed at the C-terminus of ZEGFR:2377. The label was stable in vitro under cysteine challenge. In addition, 99mTc-ZEGFR:2377 was capable of specific binding to EGFR-expressing cells with high affinity (274 pM). Studies in BALB/C nu/nu mice bearing A431 xenografts demonstrated that 99mTc-ZEGFR:2377 accumulates in tumors in an EGFR-specific manner. The tumor uptake values were 3.6±1 and 2.5±0.4% ID/g at 3 and 24 h after injection, respectively. The corresponding tumor-to-blood ratios were 1.8±0.4 and 8±3. The xenografts were clearly visualized at both time-points. This study demonstrated the potential of 99mTc-labeled ZEGFR:2377 for imaging of EGFR in vivo.
Insights
This study developed a new imaging probe, 99mTc-labeled ZEGFR:2377, for detecting epidermal growth factor receptor (EGFR) overexpression in tumors. The probe showed specific tumor accumulation and clear visualization in preclinical models, indicating its potential for non-invasive cancer diagnosis.
Area of Science:
- Oncology
- Molecular Imaging
- Radiochemistry
Background:
- Epidermal growth factor receptor (EGFR) is a key target in many cancers.
- Non-invasive imaging of EGFR overexpression can guide cancer therapy.
- Affibody molecules offer high affinity and selectivity for molecular imaging targets.
Purpose of the Study:
- To evaluate the feasibility of labeling the anti-EGFR Affibody molecule ZEGFR:2377 with technetium-99m (99mTc).
- To assess the in vitro stability and in vivo targeting of 99mTc-ZEGFR:2377 for EGFR-expressing tumors.
- To determine the potential of 99mTc-ZEGFR:2377 as a non-invasive imaging agent for EGFR.
Main Methods:
- ZEGFR:2377 was labeled with 99mTc using a cysteine-containing chelator.
- In vitro stability was tested under cysteine challenge.
- Binding affinity to EGFR-expressing cells was measured.
- In vivo studies were conducted in A431 xenografts in BALB/C nu/nu mice.
Main Results:
- Stable 99mTc-ZEGFR:2377 labeling was achieved.
- The probe exhibited high affinity (274 pM) for EGFR-expressing cells.
- Significant tumor accumulation of 99mTc-ZEGFR:2377 was observed in EGFR-specific manner.
- Tumor uptake reached 3.6±1% ID/g at 3 hours and 2.5±0.4% ID/g at 24 hours.
- Xenografts were clearly visualized with good tumor-to-blood ratios.
Conclusions:
- 99mTc-labeled ZEGFR:2377 is a stable and specific imaging probe for EGFR.
- The probe demonstrates promising potential for non-invasive in vivo imaging of EGFR overexpression in tumors.
- This Affibody-based radiotracer could facilitate personalized cancer therapy guided by EGFR expression levels.
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