The use of tissue-specific receptor ligands is a promising approach for cancer diagnostics and therapy.
Lorglumide, a highly effective competitive ligand for the cholecystokinine-A receptor (CCKRA) was conjugated to a fluorescent dye and a magnetic resonance imaging (MRI) contrast agent to obtain a bifunctional marker for tissue with high CCKRA expression. An intermediate conjugate containing only lorglumide and a fluorescent dye was also produced. By performing CCKRA mRNA expression analysis on carcinoma cell lines we found that CCKRA is highly expressed in PC3 prostate carcinoma cells compared to U373 glioma and U2OS osteosarcoma cells. Uptake, specificity and detection sensitivity of both lorglumide conjugates was evaluated by confocal laser scanning microscopy, fluorescence activated cell sorting (FACS) and magnetic resonance relaxometry. While the conjugate containing only lorglumide and rhodamine isothiocyanate as fluorescent dye showed clearly higher uptake than the bifunctional conjugate in FACS analysis, both conjugates clearly showed preferential staining of the PC3 prostate carcinoma cells. Magnetic resonance relaxometry experiments with the bifunctional conjugate containing the MRI contrast agent gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid confirmed the higher PC3-affinity of the lorglumide ligand. Confocal laser scanning microscopy images of PC3/U2OS mixed cell cultures incubated with the bifunctional conjugate also clearly showed PC3 preference and cytoplasmic dot-like staining concurring with uptake by receptor binding and subsequent receptor internalization. Considering these results, CCKRA ligands like lorglumide could play a role in the future design of prostate-cancer-specific markers.
Written by:
Sturzu A, Sheikh S, Klose U, Echner H, Kalbacher H, Deeg M, Nägele T, Horger M, Schwentner C, Ernemann U, Heckl S. Are you the author?
Department of Neuroradiology, University of Tübingen, Germany; Peptide Synthesis Laboratory, Interfaculty Institute of Biochemistry, University of Tübingen, Germany.
Reference: Eur J Pharm Sci. 2012 Apr 11;45(5):575-80. Epub 2011 Dec 30.
PubMed Abstract
PMID: 22226647
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