Radiolabeled small-molecule ligands for prostate-specific membrane antigen: in vivo imaging in experimental models of prostate cancer.
OBJECTIVE
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.


METHODS
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-[(11)C]methyl-L-cysteine ([(11)C]DCMC K(i), 3.1 nmol/L) and N-[N-[(S)-1,3-dicarboxypropyl]carbamoyl]-S-3-[(125)I]iodo-L-tyrosine ([(125)C]DCIT K(i), 1.5 nmol/L) were synthesized using [(11)C]CH(3)I and with [(125)I]NaI/Iodogen, respectively.


RESULTS
At 30 minutes postinjection, [(11)C]DCMC and [(125)I]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 [(11)C]DCMC or [(125)I]DCIT.


CONCLUSIONS
These results show the feasibility of imaging PSMA-positive prostate cancer using low molecular weight agents.
Foss
Catherine A
CA
Johns Hopkins University, Baltimore, Maryland 21287-2182, USA.
Mease
Ronnie C
RC
Fan
Hong
H
Wang
Yuchuan
Y
Ravert
Hayden T
HT
Dannals
Robert F
RF
Olszewski
Rafal T
RT
Heston
Warren D
WD
Kozikowski
Alan P
AP
Pomper
Martin G
MG
D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism*; D001667:Binding, Competitive; D002250:Carbon Radioisotopes; D045744:Cell Line, Tumor; D005260:Female; D043425:Glutamate Carboxypeptidase II / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D008024:Ligands; D008297:Male; D051379:Mice; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D049268:Positron-Emission Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000628:therapy; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000378:metabolism / Q000493:pharmacokinetics; D014018:Tissue Distribution; D014183:Transplantation, Heterologous
D000954:Antigens, Surface; D002250:Carbon Radioisotopes; D007457:Iodine Radioisotopes; D008024:Ligands; D019275:Radiopharmaceuticals; C473848:FOLH1 protein, human; D043425:Glutamate Carboxypeptidase II