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Prostate cancer stem cells (CSCs) are defined by their extensive self-renewal, differentiation, and tumor initiation properties. It is now clear that CSCs are involved in tumor growth and recurrence, and resistance to conventional treatments. Thus, the strategy that suppresses stemness and consequently tumorigenic potential of CSCs could be considered for the management of prostate cancer. The objectives of this study were to examine the molecular mechanisms by which NPV-LDE-225 / Erismodegib (smoothened inhibitor) regulates stem cell characteristics in prostate cancer. Effects of NPV-LDE-225 on CSC's viability, sphere formation, apoptosis, transcriptional activity, and epithelial-mesenchymal transition (EMT) were measured. NPV-LDE-225 inhibited cell viability and spheroid formation, and induced apoptosis by activation of caspase-3 and cleavage of PARP. NPV-LDE-225 induced expression of Bax and Bak, and inhibited the expression of Bcl-2, Bcl-XL, XIAP, cIAP1, cIAP2 and survivin. NPV-LDE-225 inhibited Gli transcriptional activity, Gli-DNA interaction, and the expression of Gli1, Gli2, Patched1 and Patched 2 in prostate CSCs. Interestingly, NPV-LDE-225 induced PDCD4 and apoptosis and inhibited cell viability by suppressing miR-21. Furthermore, NPV-LDE-225 inhibited pluripotency maintaining factors Nanog, Oct4, cMyc and Sox-2. The inhibition of Bmi-1 by NPV-LDE-225 was regulated by up-regulation of miR-128. NPV-LDE-225 suppressed EMT by up-regulating E-cadherin and inhibiting N-cadherin, Snail, Slug and Zeb1 through regulating miR-200 family. Finally, NPV-LDE-225 inhibited CSC tumor growth which was associated with the suppression of Gli1, Gli2, Patched-1, Patched-2, Cyclin D1 and PCNA, and cleaved caspase-3 and PARP in tumor tissues derived from NOD/SCID IL2Rϒnull mice. Overall, our findings suggest that inhibition of the Shh signaling pathway in CSCs is a potential therapeutic strategy for prostate cancer. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A261. Citation Format: Rajesh Nanta, Daniel Meeker, Mariana Rodova, Peter J. Van Veldhuizen, Sharmila Shankar, Rakesh K. Srivastava. NPV-LDE-225 (Erismodegib) inhibits human prostate cancer stem cell growth in NOD/SCID IL2γnull mice by regulating Bmi-1 and microRNA-128. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A261.