Use of methotrexate-based peptide substrates to characterize the substrate specificity of Prostate-Specific Membrane Antigen (PSMA)
Use of methotrexate-based peptide substrates to characterize the substrate specificity of Prostate-Specific Membrane Antigen (PSMA)
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DOI：
10.4161/cbt.3.6.846
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发表时间：
2004-06-01
影响因子：
3.6
通讯作者：
Denmeade, SR
中科院分区：
文献类型：
--
作者：
Mhaka, A;Gady, AM;Denmeade, SR
前列腺特异性膜抗原（PSMA）是一种谷氨酸羧肽酶II，由正常和恶性前列腺上皮细胞以及许多肿瘤类型的新血管高度表达，但不表达正常组织中的内皮细胞。PSMA具有N-乙酰化α-连接的酸性二肽酶（NAALADase）的水解性质，并且还用作蝶酰聚-γ-谷氨酰羧肽酶（即，叶酸水解酶）。因此，PSMA可以靶向激活前列腺癌细胞外液中基于肽的前药。在本研究中，评价了基于甲氨蝶呤的肽类似物，以鉴定在人和小鼠血浆中对非特异性水解也稳定的PSMA选择性底物。还表征了这些甲氨蝶呤类似物对产生PSMA和非PSMA的人癌细胞系的体外毒性。含有γ-连接的谷氨酸残基的类似物被PSMA最有效地水解，但在血浆中不稳定。含有α-和γ-连接的酸性氨基酸的类似物被PSMA水解的效率较低，但在血浆中最稳定。在活性PSMA存在下，类似物在体外的选择性毒性高5-10倍。这些研究已经鉴定了PSMA选择性的、血浆稳定的肽底物，其可以掺入前列腺癌部位内被PSMA靶向激活的前药中。
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.