Abstract | PURPOSE: 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:
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Authors | Senthil R Kumar, Thomas P Quinn, Susan L Deutscher |
Journal | Clinical cancer research : an official journal of the American Association for Cancer Research
(Clin Cancer Res)
Vol. 13
Issue 20
Pg. 6070-9
(Oct 15 2007)
ISSN: 1078-0432 [Print] United States |
PMID | 17947470
(Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, Non-P.H.S.)
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Chemical References |
- Contrast Media
- Indium Radioisotopes
- Peptides
- Recombinant Proteins
- Receptor, ErbB-2
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Topics |
- Animals
- Breast Neoplasms
(diagnostic imaging, metabolism)
- Cell Line, Tumor
- Contrast Media
(pharmacology)
- Diagnostic Imaging
(methods)
- Gene Expression Regulation, Neoplastic
- Humans
- Indium Radioisotopes
(pharmacology)
- Inhibitory Concentration 50
- Mice
- Mice, SCID
- Microscopy, Confocal
- Peptides
(chemistry)
- Receptor, ErbB-2
(metabolism)
- Recombinant Proteins
(chemistry)
- Tomography, Emission-Computed, Single-Photon
(methods)
- Tomography, X-Ray Computed
(methods)
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