Prostate cancer (PCa) growth initially depends on circulating androgens. Gonadotropin-releasing hormone (GnRH) agonists are currently used for the treatment of PCa. However, after an initial responsiveness to hormonal deprivation, PCa progresses and metastasizes. Recently, also GnRH antagonists have been used for clinical trials in patients with PCa and the results seem promising. The components of the plasminogen activator (PA) system (urokinase-type PA, uPA; PA inhibitors, PAI-1/2; uPA receptor, uPAR) have been implicated in the local degradation of the extracellular matrix (ECM) and PCa progression. The aim of this study was to test the possible effects of the treatment with an agonist (Leuprolide, GnRH-A) and an antagonist (Cetrorelix, GnRH-ANT) of GnRH on the expression and activity of uPA and PAI-1 in the conditioned media of DU145 and PC3, two PCa androgen-independent cell lines. The involvement of the PA system in the control of cellular migration was also investigated. The results obtained in DU145 and PC3 cells show that both GnRH-A and GnRH-ANT: i) inhibit cell proliferation; ii) significantly decrease the enzymatic activity and the secretion of uPA; iii) significantly increase the protein levels of PAI-1; iv) induce a significant decrease of the migratory and invasion PCa capabilities. This study suggests that GnRH analogues exhibit not only an antiproliferative effect, but also an anti-metastatic action exerted through the inhibition of the activity of PA system and might provide a rational basis for the development of clinical strategies for those tumours that progress towards an androgen-independent condition characterized by a higher metastatic potential.

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