title: Osteopontin-c mediates the upregulation of androgen responsive genes in LNCaP cells through PI3K/Akt and androgen receptor signaling.
abstract: Androgen receptor (AR) signaling is a key pathway modulating prostate cancer (PCa) progression. Several steps in this pathway have been investigated in order to propose novel treatment strategies for advanced PCa. Total osteopontin (OPN) has been described as a biomarker for PCa, in addition to its role in activating the progression of this tumor. Based on the known effects of the OPNc splice variant on PCa progression, the present study investigated whether this isoform can also modulate AR signaling. In order to test this, anin vitromodel was used in which LNCaP cells were cultured in the presence of conditioned medium (CM) secreted by PCa cells overexpressing OPNc (OPNc-CM). The activation of AR signaling was evaluated by measuring the expression levels of AR-responsive genes (ARGs) using quantitative polymerase chain reaction and specific oligonucleotides. The data demonstrated that all nine tested ARGs (Fgf8,TMPRSS2,Greb1,Cdk2,Ndrg1,Cdk1,Pmepa1,PsaandAr) are significantly upregulated in response to OPNc-CM compared with LNCaP cells cultured in CM secreted by control cells transfected with empty expression vector. The specific involvement of OPNc was demonstrated by depleting OPNc from OPNc-CM using an anti-OPNc neutralizing antibody. In addition, by using a phosphoinositide 3-kinase (PI3K)-specific inhibitor and AR antagonists, such as flutamide and bicalutamide, it was also observed that upregulation of ARGs in response to OPNc-CM involves PI3K signaling and depends on the AR. In conclusion, these data indicated that OPNc is able to activate AR signaling through the PI3K pathway and the AR. These data further corroborate our previous data, revealing the OPNc splice variant to be a key molecule that is able to modulate key signaling pathways involved in PCa progression.
authors: Molecular Carcinogenesis Program, Research Coordination, National Institute of Cancer, Rio de Janeiro 22743-051, Brazil.
authors: Tatiana Martins
authors: TM
authors: Tilli
authors: Institute of Molecular Pathology and Immunology, University of Porto, Porto 4200-465, Portugal.
authors: Luciana Bueno
authors: LB
authors: Ferreira
authors: Molecular Carcinogenesis Program, Research Coordination, National Institute of Cancer, Rio de Janeiro 22743-051, Brazil ; Natural Sciences Department, Health and Humanities Institute, Fluminense Federal University, Rio das Ostras, Rio de Janeiro 28895-532, Brazil.
authors: Etel Rodrigues Pereira
authors: ER
authors: Gimba
keywords: OPNc; androgen receptor signaling; osteopontin; splice variant