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Radiolabeled Small-Molecule Ligands for Prostate-Specific Membrane Antigen: In vivo Imaging in Experimental Models of Prostate Cancer

2005; American Association for Cancer Research; Volume: 11; Issue: 11 Linguagem: Inglês

10.1158/1078-0432.ccr-04-2690

1557-3265

Catherine A. Foss, Ronnie C. Mease, Hong Fan, Yuchuan Wang, Hayden T. Ravert, Robert F. Dannals, Rafal T. Olszewski, Warren D.W. Heston, Alan P. Kozikowski, Martin G. Pomper,

Monoclonal and Polyclonal Antibodies Research

Abstract Purpose: Prostate-specific membrane antigen (PSMA) is a cell surface protein that is overexpressed in prostate cancer, including hormone-refractory and metastatic disease. Our goal in this study was to develop a series of PSMA-based imaging agents for clinical use. Experimental Design: We have synthesized and evaluated the in vivo biodistribution of two radiolabeled urea derivatives that have high affinity for PSMA in severe combined immunodeficient mice harboring MCF-7 (breast, PSMA-negative), PC-3 (prostate, PSMA-negative), and LNCaP (prostate, PSMA-positive) xenografts. Radiopharmaceutical binding selectivity and tumor uptake were also evaluated in vivo using dedicated small animal positron emission tomography, single photon emission computed tomography, and gamma scintigraphic imaging devices. N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-[11C]methyl-l-cysteine ([11C]DCMC Ki, 3.1 nmol/L) and N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-3-[125I]iodo-l-tyrosine ([125C]DCIT Ki, 1.5 nmol/L) were synthesized using [11C]CH3I and with [125I]NaI/Iodogen, respectively. Results: At 30 minutes postinjection, [11C]DCMC and [125I]DCIT showed tumor/muscle ratios of 10.8 and 4.7, respectively, with clear delineation of LNCaP-derived tumors on imaging. MCF-7- and PC-3-derived tumors showed significantly less uptake of [11C]DCMC or [125I]DCIT. Conclusion: These results show the feasibility of imaging PSMA-positive prostate cancer using low molecular weight agents.