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Regulation of PSA secretion and survival signaling by calcium‐independent phopholipase A 2 β in prostate cancer cells
Author(s) -
Nicotera Thomas M.,
Schuster David P.,
Bourhim Mustapha,
Chadha Kailash,
Klaich Gary,
Corral David A.
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.20968
Subject(s) - lncap , prostate cancer , du145 , secretion , endocrinology , prostate , medicine , biology , autocrine signalling , cancer research , cancer , receptor
BACKGROUND Serum prostate specific antigen (PSA) levels in prostate cancer patients serve as a useful biomarker for diagnosing and monitoring prostate cancer. Recently, secreted PSA has been characterized as an autocrine survival factor through activation of Akt and induction of AR. In the normal prostate, PSA is secreted in the lumen of prostatic ducts to lyse proteins in the seminal coagulum. METHODS However, the mechanism for constitutive PSA secretion from benign prostate and its transport across the prostate‐blood barrier into serum are unknown. Regulation of peptide secretion by iPLA 2 ‐β has been reported in non‐prostatic tissue and in prostate tissue iPLA 2 ‐β is reported to be under androgen regulation. We investigated whether iPLA 2 plays a role for in PSA secretion by comparing iPLA 2 activity and expression in normal prostate epithelial RWPE‐1 cells and in LNCaP prostate cancer cells. Expression of the two active iPLA 2 ‐β mRNA splice variants, LH‐iPLA 2 and SH‐iPLA 2 , were increased and the inhibitory ankyrin‐iPLA 2 isoform was markedly reduced in LNCaP cells as compared to normal prostate epithelial RWPE‐1 cells. RESULTS These changes are consistent with a higher enzymatic activity in LNCaP cells. The iPLA 2 ‐β‐specific inhibitor BEL inhibited PSA secretion and induced apoptosis in LNCaP cells. iPLA 2 knockdown using SiRNA inhibited PSA secretion, downregulated AR and induced apoptosis. Exogenous PSA suppressed BEL‐induced apoptosis and neutralizing anti‐PSA antibody blocked the survival effect of PSA. CONCLUSIONS These data indicate that iPLA 2 ‐β participates in regulating PSA secretion and supports the concept that secreted PSA provides an autocrine survival function in LNCaP cells. Prostate 69:1270–1280, 2009. © 2009 Wiley‐Liss, Inc.