Related Experiment Video
Updated: Aug 25, 2026
Specificity Analysis of Protein Lysine Methyltransferases Using SPOT Peptide Arrays
Published on: November 29, 2014
Use of methotrexate-based peptide substrates to characterize the substrate specificity of prostate-specific membrane
Annastasiah Mhaka1, Alyssa M Gady, D Marc Rosen
1The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, The Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
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 alpha-linked acidic dipeptidase (NAALADase) and also functions as a pteroyl poly-gamma-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 gamma-linked glutamate residues were most efficiently hydrolyzed by PSMA, but were unstable in plasma. Analogs containing both alpha- and gamma-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.
Insights
Researchers developed novel methotrexate-based peptide analogs to target Prostate-Specific Membrane Antigen (PSMA) for prostate cancer prodrug activation. These analogs show enhanced stability and selective toxicity, paving the way for targeted cancer therapies.
Area of Science:
- Biochemistry
- Oncology
- Drug Discovery
Background:
- Prostate-Specific Membrane Antigen (PSMA) is a key enzyme overexpressed in prostate cancer.
- PSMA exhibits carboxypeptidase and folate hydrolase activities, making it a viable target for prodrug activation.
- Targeting PSMA offers a strategy for localized drug delivery and enhanced therapeutic efficacy in prostate cancer treatment.
Purpose of the Study:
- To identify and characterize novel methotrexate-based peptide analogs as selective substrates for Prostate-Specific Membrane Antigen (PSMA).
- To evaluate the stability of these analogs in plasma and their in vitro toxicity against cancer cell lines.
- To develop PSMA-activated prodrugs for targeted prostate cancer therapy.
Main Methods:
- Synthesis and evaluation of methotrexate-based peptide analogs with varying amino acid linkages.
- Assessment of PSMA-mediated hydrolysis and plasma stability of the synthesized analogs.
- In vitro cytotoxicity assays using PSMA-expressing and non-expressing human cancer cell lines.
Main Results:
- Peptide analogs with gamma-linked glutamate residues were efficiently hydrolyzed by PSMA but lacked plasma stability.
- Analogs with both alpha- and gamma-linked acidic amino acids demonstrated lower PSMA hydrolysis but superior plasma stability.
- The developed analogs exhibited 5-10 fold greater selective toxicity in vitro when PSMA was present.
Conclusions:
- Novel PSMA-selective and plasma-stable peptide substrates were identified.
- These substrates can be incorporated into prodrugs for targeted activation by PSMA at prostate cancer sites.
- The findings support the development of PSMA-targeted prodrug strategies for improved prostate cancer treatment.
