Cancer Therapy: Preclinical High-Throughput Cell-Based Screening of 4910 Known Drugs and Drug-like Small Molecules Identifies Disulfiram as an Inhibitor of Prostate Cancer Cell Growth

Purpose: To identify novel therapeutic opportunities for patients with prostate cancer, we applied high-throughput screening to systematically explore most currently marketed drugs and drug-like molecules for their efficacy against a panel of prostate cancer cells. Experimental Design:We carried out a high-throughput cell-based screening with proliferation as a primary end-point using a library of 4,910 drug-like small molecule compounds in four prostate cancer (VCaP, LNCaP, DU 145, and PC-3) and two nonmalignant prostate epithelial cell lines (RWPE-1 and EP156T). The EC50 values were determined for each cell type to identify cancer selective compounds. The in vivo effect of disulfiram (DSF) was studied in VCaP cell xenografts, and gene microarray and combinatorial studies with copper or zinc were done in vitro for mechanistic exploration. Results: Most of the effective compounds, including antineoplastic agents, were nonselective and found to inhibit both cancer and control cells in equal amounts. In contrast, histone deacetylase inhibitor trichostatin A, thiram, DSF, and monensin were identified as selective antineoplastic agents that inhibited VCaP and LNCaP cell proliferation at nanomolar concentrations. DSF reduced tumor growth in vivo, induced metallothionein expression, and reduced DNA replication by downregulating MCMmRNA expression. The effect of DSF was potentiated by copper in vitro. Conclusions: We identified three novel cancer-selective growth inhibitory compounds for human prostate cancer cells among marketed drugs. We then validated DSF as a potential prostate cancer therapeutic agent. These kinds of pharmacologically wellknown molecules can be readily translated to in vivo preclinical studies and clinical trials. (Clin Cancer Res 2009;15(19):6070–8) Besides surgery and radiation therapy, androgen deprivation remains the main first-line therapeutic option for prostate cancer patients, and the predominant therapy for patients with advanced and metastatic disease. However, hormonal therapy is not curative, and often, androgen-independent, drug-resistant disease develops. Such tumors remain virtually impossible to treat with current medications. The median survival time for men with androgen-independent cancer is around 2 years underlining the need to develop better therapies (1). The majority of prostate tumors from patients with an androgen-independent disease overexpress androgen receptor (AR), thereby sensitizing prostate cancer cells to low levels of androgens. Also other mechanisms behind androgen independency have been described, such as AR mutations activating the receptor in response to nonandrogenic ligands (2). Because AR plays an essential role also in androgen-independent prostate cancers, AR and its coregulators are potential drug targets for the disease. Recently, a frequent gene fusion between the androgen-regulated prostate-specific protease TMPRSS2 and the ERG transcription factor was discovered (3). In addition to TMPRSS2-ERG, other driver genes, as well as oncogenic ETS factors (e.g., ETV1, ETV4, and ETV5) have been identified as gene fusions in prostate tumors. It has been shown that ERG fusion gene may be bypassed at later stages of cancer progression, indicating Authors' Affiliations: Medical Biotechnology, VTT Technical Research Centre of Finland, Turku; Turku Centre for Biotechnology, University of Turku, Turku, Finland; Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden; and Institute for Molecular Medicine, Finland (FIMM), University of Helsinki, Helsinki, Finland Received 4/23/09; revised 6/17/09; accepted 6/17/09; published OnlineFirst 9/29/09. Grant support: Marie Curie Canceromics (MEXT-CT-2003-2728), EU-PRIMA project (contract # LSHC-CT-204-504587), Academy of Finland, Cancer Organizations of Finland, and Sigrid Juselius Foundation. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Note: Supplementary data for this article are available at Clinical Cancer Research Online (http://clincancerres.aacrjournals.org/). Requests for reprints: Olli Kallioniemi, Institute for Molecular Medicine, University of Helsinki and Medical Biotechnology, VTT Technical Research Centre of Finland, Itäinen Pitkäkatu 4, Turku, Finland. Phone: 358-40-5698192; Fax: 358-20-722-2840. E-mail: Olli. Kallioniemi@vtt.fi. F 2009 American Association for Cancer Research. doi:10.1158/1078-0432.CCR-09-1035 6070 Clin Cancer Res 2009;15(19) October 1, 2009 www.aacrjournals. org Published Online First on September 29, 2009 as 10.1158/1078-0432.CCR-09-1035 Research. on June 6, 2017. © 2009 American Association for Cancer clincancerres.aacrjournals. org Downloaded from Published OnlineFirst September 29, 2009; DOI: 10.1158/1078-0432.CCR-09-1035