Radionuclide Molecular Imaging of EpCAM Expression in Triple-Negative Breast Cancer Using the Scaffold Protein DARPin
Anzhelika Vorobyeva1,2, Ekaterina Bezverkhniaia2,3, Elena Konovalova4
1Department of Immunology, Genetics and Pathology, Uppsala University, 751 85 Uppsala, Sweden.
Abstract:
Efficient treatment of disseminated triple-negative breast cancer (TNBC) remains an unmet clinical need. The epithelial cell adhesion molecule (EpCAM) is often overexpressed on the surface of TNBC cells, which makes EpCAM a potential therapeutic target. Radionuclide molecular imaging of EpCAM expression might permit selection of patients for EpCAM-targeting therapies. In this study, we evaluated a scaffold protein, designed ankyrin repeat protein (DARPin) Ec1, for imaging of EpCAM in TNBC. DARPin Ec1 was labeled with a non-residualizing [125I]I-para-iodobenzoate (PIB) label and a residualizing [99mTc]Tc(CO)3 label. Both imaging probes retained high binding specificity and affinity to EpCAM-expressing MDA-MB-468 TNBC cells after labeling. Internalization studies showed that Ec1 was retained on the surface of MDA-MB-468 cells to a high degree up to 24 h. Biodistribution in Balb/c nu/nu mice bearing MDA-MB-468 xenografts demonstrated specific uptake of both [125I]I-PIB-Ec1 and [99mTc]Tc(CO)3-Ec1 in TNBC tumors. [125I]I-PIB-Ec1 had appreciably lower uptake in normal organs compared with [99mTc]Tc(CO)3-Ec1, which resulted in significantly (p < 0.05) higher tumor-to-organ ratios. The biodistribution data were confirmed by micro-Single-Photon Emission Computed Tomography/Computed Tomography (microSPECT/CT) imaging. In conclusion, an indirectly radioiodinated Ec1 is the preferable probe for imaging of EpCAM in TNBC.
Insights
An indirectly radioiodinated designed ankyrin repeat protein (DARPin) Ec1 probe is superior for imaging epithelial cell adhesion molecule (EpCAM) in triple-negative breast cancer (TNBC) tumors.
Area of Science:
- Oncology
- Molecular Imaging
- Biotechnology
Background:
- Triple-negative breast cancer (TNBC) lacks efficient treatments, creating a clinical need.
- Epithelial cell adhesion molecule (EpCAM) is a potential therapeutic target due to its overexpression on TNBC cells.
- Molecular imaging of EpCAM could guide patient selection for targeted therapies.
Purpose of the Study:
- To evaluate the designed ankyrin repeat protein (DARPin) Ec1 as an imaging probe for EpCAM in TNBC.
- To compare the performance of two radiolabeled Ec1 probes: [125I]I-PIB-Ec1 and [99mTc]Tc(CO)3-Ec1.
Main Methods:
- DARPin Ec1 was labeled with a non-residualizing [125I]I-para-iodobenzoate (PIB) and a residualizing [99mTc]Tc(CO)3 label.
- Binding specificity and affinity to EpCAM-expressing TNBC cells (MDA-MB-468) were assessed.
- In vivo biodistribution and micro-Single-Photon Emission Computed Tomography/Computed Tomography (microSPECT/CT) imaging were performed in mice bearing TNBC xenografts.
Main Results:
- Both radiolabeled Ec1 probes demonstrated high binding specificity and affinity to EpCAM-expressing TNBC cells.
- Ec1 showed high retention on the cell surface up to 24 hours.
- [125I]I-PIB-Ec1 exhibited lower uptake in normal organs and higher tumor-to-organ ratios compared to [99mTc]Tc(CO)3-Ec1.
- MicroSPECT/CT imaging confirmed specific tumor uptake of both probes.
Conclusions:
- An indirectly radioiodinated Ec1 probe is the preferred choice for imaging EpCAM in TNBC.
- This probe facilitates targeted imaging and potential patient selection for EpCAM-targeting therapies.
