Evaluation of prostate-specific membrane antigen as an imaging reporter.
Genetic reporters provide a noninvasive method to monitor and evaluate a population of cells. The ideal properties of a gene reporter-probe system include biocompatibility, lack of immunogenicity, low background expression or signal, and high sensitivity of detection. The prostate-specific membrane antigen (PSMA) is an attractive candidate for a genetic reporter as it is a human transmembrane protein with a selective expression pattern, and there are several PSMA imaging agents available for clinical and preclinical applications. We evaluated the use of PSMA as a genetic imaging reporter by comparison to 2 clinically established reporters, the mutant herpes simplex virus type I thymidine kinase and the human sodium-iodide symporter.


METHODS
Adenoviruses expressing each reporter were constructed and validated in vitro for expression and function. To compare PSMA with existing imaging reporters, a bilateral Matrigel suspension model was established with nude mice bearing cells equally infected with each reporter or control adenovirus. Dynamic PET was performed, and time-activity curves were generated for each reporter-probe pair.


RESULTS
A comparison of peak target-to-background ratios revealed that PSMA offered the highest ratio relative to the control Matrigel suspension as well as muscle. Further, as proof of concept, PSMA was applied as an imaging reporter to monitor adenoviral liver transduction with both nuclear and optical imaging probes.


CONCLUSIONS
These preliminary studies support further development of PSMA as a noninvasive genetic reporter.
Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Mark A
MA
Castanares
Amarnath
A
Mukherjee
Wasim H
WH
Chowdhury
Minzhi
M
Liu
Ying
Y
Chen
Ronnie C
RC
Mease
Yuchuan
Y
Wang
Ronald
R
Rodriguez
Shawn E
SE
Lupold
Martin G
MG
Pomper
D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D003094:Collagen / Q000737:chemistry; D004338:Drug Combinations; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D015316:Genetic Therapy; D043425:Glutamate Carboxypeptidase II / Q000378:metabolism*; D006801:Humans; D007797:Laminin / Q000737:chemistry; D008024:Ligands; D008099:Liver / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D055095:Optics and Photonics; D049268:Positron-Emission Tomography; D011509:Proteoglycans / Q000737:chemistry; D027981:Symporters / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D000099209:Sodium-Iodide Symporters
D000954:Antigens, Surface; D014408:Biomarkers, Tumor; D003094:Collagen; D004338:Drug Combinations; D043425:Glutamate Carboxypeptidase II; D007797:Laminin; D008024:Ligands; D011509:Proteoglycans; D027981:Symporters; D013937:Thymidine Kinase; D000099209:Sodium-Iodide Symporters; C059485:matrigel; C473848:FOLH1 protein, human
DCFPyL; PSMA; molecular-genetic imaging; optical imaging; positron emission tomography