Scientific Report 2003-2004 - Cleveland Clinic Lerner Research ...

THE HESTONLABORATORYSTAFF SCIENTISTC. Thomas Powell, Ph.D.PROJECT SCIENTISTArundhati Ghosh, Ph.D.POSTDOCTORAL FELLOWXinning Wang, Ph.D.RESEARCH FELLOWMasifumi Oyama, M.D.RESEARCH TECHNOLOGISTKelly Harsch, B.S.COLLABORATORSNeil Bander, M.D. 1Carlos Cordon-Cardo, M.D., Ph.D. 2Robert Dreicer, M.D. 3Yuman Fong, M.D. 2Eric Klein, M.D. 4Peter Molloy, Ph.D. 5Joe Neal, Ph.D., 6Dianne Perez, Ph.D. 7Victor Reuter, M.D. 2Barbara Slusher, Ph.D. 81Weill Med. College, CornellUniv., New York, NY2Memorial Sloan-Kettering CancerCtr., New York, NY3Dept. of Hematol./Oncol., CCF4Glickman Urol. Inst., CCF5CSIRO, Sydney, Australia6Georgetown Univ., Washington,DCCSIRO, Sydney, Australia7Dept. of Mol. Cardiol., CCF8Guilford Pharmaceuticals, Baltimore,MDOur laboratory cloned the gene encoding aunique protein that is highly expressed inprostate cancers, which we designatedprotein prostate-specific membrane antigen (PSMA).Surprisingly, PSMA is also highly expressed in theneovasculature of solid tumors, but not expressed inthat of normal tissues. PSMAhas modest homology with thetransferrin receptor, yet it doesnot bind transferrin, nor is itinvolved in cellular irontransport by a transferrin. Wediscovered that PSMA has anenzymatic function as a folatehydrolase. We also discoveredtwo alternative spliced formsof PSMA: PSMA’ is a cytosolicprotein, and the mRNAencoding PSMA’ predominatesin normal prostate cells,whereas PSMA is the predominantform encoded in cancercells and encodes for a type-twoThe Department of Cancer BiologyTHE GEORGE M. O’BRIEN UROLOGY RESEARCH CENTERPSMA May Be Key to Targeted Deliveryof Drugs to Tumorsmembrane protein. In normalcells, given PSMA’s folatehydrolase activity, the humanprostate may be an organ at riskfor developing “localized folatedeficiency.” A cell that is folatedeficient is a cell at high risk to develop cancer, andin the human male, the cells with the highestpropensity for developing cancer are those of theprostate.Because PSMA predominates in prostatecancer and is a type-two membrane protein, we areexploring means to target the extracellular domainfor treatment of prostate cancer. We have foundthat the membrane form of PSMA is expressed inthe tumor-associated neovasculature in all other solidSkip Heston, Ph.D.Director,The George M. O’BrienUrology Research Centertumors. Thus, this form of PSMA becomes a broadspectrumtarget for all tumors. We are developingprodrug strategies based on the folate hydrolase/glutamate carboxypeptidase activity of PSMA.Because PSMA can be induced to internalize, we areusing phage display technology to identify ligands withhigh affinity for PSMA that willinduce internalization to providefor additional therapeutictargeting agents.We have also producedhuman PSMA-expressingtransgenic mice that will serveas a model for targeting thehuman protein in immunocompetentanimals. In mice,the murine homolog of PSMAis expressed in the testes,kidney, and brain. We havegenerated PSMA-knockoutmice to understand thefunctional role of PSMA inthese tissues. In brain, PSMAis considered to be responsiblefor the hydrolysis of N-acetylaspar-tylglutamate(NAAG), a neurotransmitter.PSMA hydrolysis of NAAGreleases the neurotransmitterglutamate. In abnormal situations such asischemia, neurotoxic levels of glutamate areproduced by the hydrolysis of released NAAG,resulting in large areas of neuronal death.Inhibitors of murine PSMA attenuate the damage.Likewise, in the PSMA-knockout animals, thedamage associated with a stroke is significantlyless than in the wild-type animal. Thus, theseknockout animals model the role of this proteinContinued on Page 57Uchida, A.. O’Keefe, D.S., Bacich, D.J., Molloy, P.L., and W.D. Heston (2001) In vivo suicide genetherapy model using a newly discovered prostate-specific membrane antigen promoter/enhancer: apotential alternative approach to androgen deprivation therapy. Urology 58(2 Suppl 1):132-139.Thomas, J., Gupta, M., Grasso, Y., Reddy, C.A., Heston, W.D., Zippe, C., Dreicer, R., Kupelian, P.A.,Brainard, J., Levin, H.S., and E.A. Klein (2002) Preoperative combined nested reverse transcriptasepolymerase chain reaction for prostate-specific antigen and prostate-specific membrane antigen does notcorrelate with pathologic stage or biochemical failure in patients with localized prostate cancer undergoingradical prostatectomy. J. Clin. Oncol. 20:3213-3218.Bacich, D.J., Ramadan, E., O’Keefe, D.S., Bukhari, N., Wegorzewska, I., Ojeifo, O., Olszewski, R.,Wrenn, C.C., Bzdega, T., Wroblewska, B., Heston, W.D., and J.H. Neale (2002) Deletion of the glutamatecarboxypeptidase II gene in mice reveals a second enzyme activity that hydrolyzes N-acetylaspartylglutamate.J. Neurochem. 83:20-29.Cozzi, P.J., Burke, P.B., Bhargav, A., Heston, W.D., Huryk, B., Scardino, P., and Y. Fong (2002)Oncolytic viral gene therapy for prostate cancer using two attenuated, replication-competent, geneticallyengineered herpes simplex viruses. Prostate 53:95-100.Chang, S.S., and W.D. Heston (2002) The clinical role of prostate-specific membrane antigen (PSMA).Urol. Oncol. 7:7-12.56