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MIR143 is pathologically downregulated and may function as a tumor suppressor in prostate cancer. Likewise, the urokinase plasminogen activator receptor (UPAR) is overexpressed in prostate carcinoma, representing a negative prognostic marker and putative therapeutic target gene. In this paper, we establish UPAR as a new direct target of MIR143. Luciferase reporter gene constructs identify one of the two in silico-predicted binding sites as functionally relevant for direct MIR143 binding to the 3′ UTR, and, concomitantly, transfection of MIR143 reduces UPAR protein levels in prostate carcinoma cells in vitro. Inhibitory effects on cell proliferation and colony formation, spheroid growth and integrity, and cell viability are extensively analyzed, and they are compared to direct small interfering RNA (siRNA)-mediated uPAR knockdown or combined microRNA (miRNA)-siRNA treatment. Switching to a therapeutically more relevant in vivo model, we demonstrate tumor-inhibitory effects of MIR143 replacement therapy by systemic treatment of mice bearing subcutaneous PC-3 tumor xenografts with MIR143 formulated in polymeric nanoparticles. This efficient, nanoparticle-mediated delivery of intact MIR143 mediates the marked downregulation of uPAR protein, but not mRNA levels, thus indicating translational inhibition rather than mRNA degradation. In summary, we identify UPAR as a direct target gene of MIR143, and we establish the therapeutic anti-tumor potential of nanoparticle-based MIR143 replacement in prostate cancer. Keywords: MIR143, urokinase plasminogen activator receptor, prostate cancer, miRNA replacement, PEI nanoparticles, xenograft

// Elke Nolte 1 , Sven Wach 1 , Izabella Thais Silva 2, 6 , Sabine Lukat 1 , Arif B. Ekici 3 , Jennifer Munkert 4 , Frieder Muller-Uri 4 , Wolfgang Kreis 4 , Claudia Maria Oliveira Simoes 2 , Julio Vera 5 , Bernd Wullich 1 , Helge Taubert 1 , Xin Lai 5 1 Department of Urology, University Hospital Erlangen, Erlangen, Germany 2 Department of Pharmaceutical Sciences, Universidade Federal de Santa Catarina, Florianopolis, Brazil 3 Institute of Human Genetics, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Erlangen, Germany 4 Department of Biology, Chair of Pharmaceutical Biology, Friedrich-Alexander-University Erlangen-Nurnberg, Erlangen, Germany 5 Laboratory of Systems Tumor Immunology, Department of Dermatology, University Hospital Erlangen, Friedrich-Alexander-University Erlangen-Nurnberg, Erlangen, Germany 6 Department of Pharmacy, Federal University of Minas Gerais, Belo Horizonte, Brazil Correspondence to: Xin Lai, email: xin.lai@uk-erlangen.de Keywords: 3β-[2-(1-amantadine)-1-on-ethylamine]-digitoxigenin, cardiac glycoside analog, human renal cell carcinoma cells, miRNA, cell cycle Received: June 21, 2016 Accepted: December 24, 2016 Published: January 14, 2017 ABSTRACT Cardiac glycosides are well known in the treatment of cardiovascular diseases; however, their application as treatment option for cancer patients is under discussion. We showed that the cardiac glycoside digitoxin and its analog AMANTADIG can inhibit the growth of renal cell carcinoma (RCC) cell lines and increase G2/M cell cycle arrest. To identify the signaling pathways and molecular basis of this G2/M arrest, microRNAs were profiled using microRNA arrays. Cardiac glycoside treatment significantly deregulated two microRNAs, miR-2278 and miR-670-5p. Pathway enrichment analysis showed that all cardiac glycoside treatments affected the MAPK and the axon guidance pathway. Within these pathways, three genes, MAPK1, NRAS and RAC2, were identified as in silico targets of the deregulated miRNAs. MAPK1 and NRAS are known regulators of G2/M cell cycle arrest. AMANTADIG treatment enhanced the expression of phosphorylated MAPK1 in 786-O cells. Secondly, we studied the expression of survivin known to be affected by cardiac glycosides and to regulate the G2/M cell phase. AMANTADIG treatment upregulated the expression of the pro-apoptotic survivin-2B variant in Caki-1 and 786-O cells. Moreover, treatment with AMANTADIG resulted in significantly lower survivin protein expression compared to 786-O control cells. Summarizing, treatment with all cardiac glycosides induced G2/M cell cycle arrest and downregulated the miR-2278 and miR-670-5p in microarray analysis. All cardiac glycosides affected the MAPK-pathway and survivin expression, both associated with the G2/M phase. Because cells in the G2/M phase are radio- and chemotherapy sensitive, cardiac glycosides like AMANTADIG could potentially improve the efficacy of radio- and/or chemotherapy in RCCs.