Targeted molecular imaging of prostate cancer using tumor endothelium homing Arg-Arg-Leu peptides

14582 Background: Tumor endothelial cells express a specific and unique cell surface signature. We have previously reported on the discovery of tumor endothelial cell (TDEC) binding peptides that possess the amino acid sequence Arg-Arg-Leu (RRL). We now show specific binding of this synthetic peptide to both surgically resected and experimental human prostate adenocarcinoma tumors thereby allowing for tumor imaging. Methods and Results: Cryosections from human lung, colon, renal, breast and prostate cancers were immunohistochemically processed to reveal the relationship of RRL-peptide staining in relation to Factor VIII labeled tumor vasculature. The RRL-peptide tightly co-localizes onto tumor endothelium within human prostate adenocarcinomas, and did not stain the tumor cells proper. Alexa 680, 800 are two near-infrared dyes that can be conjugated to RRL peptide and which emit at a wavelength unquenched by biologic tissue, thus permitting whole animal imaging. Intravenous administration of RRL-peptide-Al...