@article{f24609e087234323aade936fa42e20e9,
title = "Use of methotrexate-based peptide substrates to characterize the substrate specificity of Prostate-Specific Membrane Antigen (PSMA)",
abstract = "Prostate-Specific Membrane Antigen (PSMA) is a glutamate carboxypeptidase II that is highly expressed by both normal and malignant prostate epithelial cells and by the neovasculature of many tumor types but is not expressed by endothelial cells in normal tissue. PSMA possesses the hydrolytic properties of an N-acetylated α-linked acidic dipeptidase (NAALADase) and also functions as a pteroyl poly-γ-glutamyl carboxypeptidase (i.e., folate hydrolase). Therefore, PSMA can be targeted for activation of peptide-based prodrugs within the extracellular fluid of prostate cancers. In this study, methotrexate-based peptide analogs were evaluated to identify PSMA selective substrates that are also stable to nonspecific hydrolysis in human and mouse plasma. These methotrexate analogs were also characterized for in vitro toxicity against PSMA and nonPSMA producing human cancer cell lines. Analogs containing γ-linked glutamate residues were most efficiently hydrolyzed by PSMA, but were unstable in plasma. Analogs containing both α- and γ-linked acidic amino acids were less efficiently hydrolyzed by PSMA but were most stable in plasma. Analogs were 5-10 fold more selectively toxic in vitro in the presence of active PSMA. These studies have identified PSMA selective, plasma stable peptide substrates that can be incorporated into prodrugs targeted for activation by PSMA within prostate cancer sites.",
keywords = "Folate hydrolase, Methotrexate, NAALADase, Peptide, Prostate cancer, Prostate-specific membrane antigen, Substrate",
author = "Annastasiah Mhaka and Gady, {Alyssa M.} and Rosen, {D. Marc} and Lo, {Kin Ming} and Gillies, {Steven D.} and Denmeade, {Samuel R.}",
note = "Funding Information: aspartic acid The PSMA protein detectable in prostate cancers is an integral membrane protein and asparagine therefore has an extracellular domain that is accessible to agents in the extracellular peri-glutamine tumoral fluid making it possible to target this protein with antibodies and prodrugs. A b-nicotinamide a4de nLinae ndindu-es fiBnailo instecreisetinng casepe.c tD ofo P SMNA expression is that the PSMA mRNA is upregulated upon cleotide androgen withdrawal.10,11 In LNCaP cells, androgen has been found to downregulate 4-N[N-2,4diamino-6-pteridinyl- PSMA expression10 and in patient specimens an increase in immunohistochemically methyl)-N-methylamino-benzoate] detectable PSMA expression has been observed following androgen ablative therapy.11 In DHFR dihydrofolate reductase contrast, PSA expression is downregulated by androgen deprivation.12,13 Recently, Ross et al. demonstrated that prostate cancer cells expressed relatively increased levels of PSMA ACKNOWLEDGEMENTS compared to benign prostate tissue.14 In this study, increased PSMA expression correlated This work was supported by a grant from{\textcopyright} 200 with tumor grade, and pathological stage.14 Most importantly, this study demonstrated for Department of Defense Prostate Cancer Research the first time that overexpression of PSMA in primary prostate cancer is a predictive indicator Program DAMD17-00-1-0076 to SRD. for biochemical recurrence.14",
year = "2004",
month = jun,
doi = "10.4161/cbt.3.6.846",
language = "English (US)",
volume = "3",
pages = "551--558",
journal = "Cancer Biology and Therapy",
issn = "1538-4047",
publisher = "Landes Bioscience",
number = "6",
}