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Published on: January 7, 2019
Evaluation of an 111In-radiolabeled peptide as a targeting and imaging agent for ErbB-2 receptor expressing breast
Senthil R Kumar1, Thomas P Quinn, Susan L Deutscher
1Department of Biochemistry, University of Missouri-Columbia, Columbia, Missouri 65212, USA.
Purpose:
The cellular targeting and tumor imaging properties of a novel ErbB-2-avid peptide, discovered from bacteriophage display, were evaluated in human breast carcinoma cells and in breast carcinoma-xenografted mice.
Experimental Design:
The affinity of the ErbB-2 targeting peptide KCCYSL and its alanine substituted counterparts for the extracellular domain (ECD) of purified recombinant ErbB-2 (ErbB-2-ECD) was assessed by fluorescence titration. Binding of the KCCYSL peptide to breast and prostate carcinoma cells was analyzed by confocal microscopy. A DOTA(GSG)-KCCYSL peptide conjugate was radiolabeled with 111In, and stability, target binding, and internalization were analyzed in vitro. In vivo biodistribution and single-photon emission computed tomography imaging studies were done with the radiolabeled peptide in MDA-MB-435 human breast tumor-bearing severe combined immunodeficient mice.
Results:
KCCYSL peptide exhibited high affinity (295 +/- 56 nmol/L) to ErbB-2-ECD. Substitution of alanine for lysine, tryptophan, and cysteine reduced the peptide affinity approximately 1- to 2.4-fold, whereas replacing leucine completely abolished binding. Both biotin-KCCYSL and 111In-DOTA(GSG)-KCCYSL were capable of binding ErbB-2-expressing human breast carcinoma cells in vitro. Approximately 11% of the total bound radioactivity was internalized in the carcinoma cells. Competitive binding studies indicated that the radiolabeled peptide exhibited an IC(50) value of 42.5 +/- 2.76 nmol/L for the breast carcinoma cells. 111In-DOTA(GSG)-KCCYSL was stable in serum and exhibited rapid tumor uptake (2.12 +/- 0.32 %ID/g) at 15 min postinjection and extended retention coupled with rapid whole body disappearance, as observed by biodistribution and single-photon emission computed tomography imaging studies, respectively.
Conclusions:
The DOTA(GSG)-KCCYSL peptide has the potential to be used as a tumor-imaging agent and a vehicle for specific delivery of radionuclide or cytotoxic agents for tumors overexpressing ErbB-2.
Insights
A novel peptide, KCCYSL, effectively targets ErbB-2 positive breast cancer cells and shows potential for tumor imaging. This peptide demonstrates rapid tumor uptake and retention, suggesting its utility in targeted cancer therapies.
Area of Science:
- Oncology
- Molecular Biology
- Biotechnology
Background:
- ErbB-2 (Human Epidermal growth factor Receptor 2) is a key target in breast cancer therapy.
- Novel peptides are needed for targeted delivery and imaging of ErbB-2-expressing tumors.
Purpose of the Study:
- To evaluate the cellular targeting and tumor imaging properties of a novel ErbB-2-avid peptide, KCCYSL.
- To assess the peptide's potential as a diagnostic or therapeutic agent for ErbB-2-positive cancers.
Main Methods:
- Peptide affinity for ErbB-2 extracellular domain (ECD) was measured using fluorescence titration.
- Binding and internalization in breast carcinoma cells were analyzed via confocal microscopy.
- Radiolabeled peptide (111In-DOTA(GSG)-KCCYSL) biodistribution and SPECT imaging were performed in tumor-bearing mice.
Main Results:
- KCCYSL peptide demonstrated high affinity for ErbB-2-ECD.
- The radiolabeled peptide specifically bound to and was internalized by ErbB-2-expressing breast cancer cells in vitro.
- In vivo studies showed rapid tumor uptake and retention of the radiolabeled peptide.
Conclusions:
- The DOTA(GSG)-KCCYSL peptide exhibits promising tumor targeting and imaging capabilities for ErbB-2-overexpressing cancers.
- This peptide serves as a potential vehicle for targeted delivery of radionuclides or cytotoxic agents.
