, Volume 41, Issue 5, pp 1093-1101
Date: 11 Mar 2010

A cell permeable peptide analog as a potential-specific PET imaging probe for prostate cancer detection

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Abstract

Non-invasive detection of prostate cancer or metastases still remains a challenge in the field of molecular imaging. In our recent work of screening arginine- or lysine-rich peptides for intracellular delivery of a therapeutic agent into prostate cancer cells, an arginine-rich cell permeable peptide (NH2GR11) was found with an unexpectedly preferential uptake in prostate cancer cell lines. The goal of this work was to develop this peptide as a positron emission tomography (PET) imaging probe for specific detection of distant prostate cancer metastases. The optimal length of arginine-rich peptides was evaluated by the cell uptake efficiency of three fluorescein isothiocyanate (FITC)-tagged oligoarginines (NHGR9, NHGR11, and NHGR13) in four human prostate cell lines (LNCaP, PZ-HPV-7, DU145, and PC3). Of the three oligoarginines, NH2GR11 showed the highest cell uptake and internalization efficiency with its subcellular localization in cytosol. The biodistribution of FITC-NHGR9, FITC-NHGR11, and FITC-NHGR13 performed in control nude mice displayed the unique preferential accumulation of FITC-NHGR11 in the prostate tissue. Further in vivo evaluation of FITC-NHGR11 in PC3 tumor-bearing nude mice revealed elevated uptake of this peptide in tumors as compared to other organs. In vivo pharmacokinetics evaluated with 64Cu-labeled NH2GR11 showed that the peptide was rapidly cleared from the blood (t 1/2 = 10.7 min) and its elimination half-life was 17.2 h. The PET imaging specificity of 64Cu-labled NH2GR11 was demonstrated for the detection of prostate cancer in a comparative imaging experiment using two different human cancer xenograft models.