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Expression of prostate‐specific membrane antigen (PSMA), increases cell folate uptake and proliferation and suggests a novel role for PSMA in the uptake of the non‐polyglutamated folate, folic acid
Author(s) -
Yao Veronica,
Berkman Clifford E.,
Choi Joseph K.,
O'Keefe Denise S.,
Bacich Dean J.
Publication year - 2009
Publication title -
the prostate
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.295
H-Index - 123
eISSN - 1097-0045
pISSN - 0270-4137
DOI - 10.1002/pros.21065
Subject(s) - glutamate carboxypeptidase ii , cell growth , prostate cancer , chemistry , biochemistry , cell , cancer research , cell culture , biology , cancer , medicine , genetics
BACKGROUND Prostate specific membrane antigen (PSMA) is a unique folate hydrolase that is significantly upregulated in prostate cancer. In a mouse model, PSMA is able to facilitate prostate carcinogenesis, however, little is known about the mechanism by which this occurs. As PSMA is able to hydrolyze polyglutamated folates, and cancer cells proliferate directly in response to available folate, we examined if expression of human PSMA in PC‐3 cells confers a proliferative advantage in a microenvironment with physiologically relevant folate levels. METHODS Proliferation and folate uptake of PC‐3 prostate cancer cells expressing human‐PSMA or vector alone was assessed in media containing low (LF; 1 nM), physiological (PF; 25 nM), or high (HF; 2.3 µM) folate with or without poly‐γ‐glutamated folate (Pte‐Glu 5 ) or folic acid, and a specific inhibitor of the enzymatic activity of PSMA, 2‐(phosphonomethyl)‐pentanedioic acid (2‐PMPA). Folic acid was tested for its ability to competitively inhibit the enzymatic activity of PSMA. RESULTS Proliferation of PC‐3‐PSMA cells grown in the presence of poly‐γ‐glutamated folate, was significantly higher than that of PC‐3‐vector cells, an advantage which was attenuated by the addition of 2‐PMPA. In media containing physiologic levels of folate, PSMA expression increased folic acid uptake approximately twofold over non‐expressing cells. Folic acid was able to inhibit hydrolysis of N ‐[4‐(phenylazo)‐benzoyl]‐glutamyl‐γ‐glutamic acid (PABGgG) by PSMA in a competitive inhibition assay. CONCLUSION These findings implicate PSMA in both the metabolism of polyglutamated folates, and in the uptake of monoglutamated folates. Under conditions of LF or PF levels, PSMA gives cells expressing it a proliferative advantage. Prostate 70: 305–316, 2010. © 2009 Wiley‐Liss, Inc.