Triptolide Inhibits the Proliferation of Prostate Cancer Cells and Down-Regulates SUMO-Specific Protease 1 Expression Weiwei Huang1., Tiantian He1,2., Chengsen Chai1, Yuan Yang 1 , Yahong Zheng 1 , Pei Zhou 1 , Xiaoxia Qiao 1 , Bin Zhang 1 , Zengzhen Liu1, Junru Wang 1 , Changhong Shi3, Liping Lei4, Kun Gao 5 , Hewei Li6, Sue Zhong4, Libo Yao 3 , Meng-Er Huang 2 , Ming Lei1* 1 Key Laboratory of Agricultural Molecular Biology, College of Life Science, Northwest A&F University, Yangling, Shaanxi Province, People’s Republic of China, 2 UMR3348 Centre National de la Recherche Scientifique, Institut Curie, Universite´ Paris-Sud 11, Orsay, France, 3 State Key laboratory of Tumor Biology, The Fourth Military Medical University, Xi’an, Shaanxi Province, People’s Republic of China, 4 Xi’an San-Yao Bio-pharmaceutical Corporation, Xi’an, Shaanxi Province, People’s Republic of China, 5 State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu Province, People’s Republic of China, 6 School of Chinese Materia Medica, Beijing University of Chinese Medicine, Beijing, People’s Republic of China Abstract Recently, traditional Chinese medicine and medicinal herbs have attracted more attentions worldwide for its anti-tumor efficacy. Celastrol and Triptolide, two active components extracted from the Chinese herb Tripterygium wilfordii Hook F (known as Lei Gong Teng or Thunder of God Vine), have shown anti-tumor effects. Celastrol was identified as a natural 26 s proteasome inhibitor which promotes cell apoptosis and inhibits tumor growth. The effect and mechanism of Triptolide on prostate cancer (PCa) is not well studied. Here we demonstrated that Triptolide, more potent than Celastrol, inhibited cell growth and induced cell death in LNCaP and PC-3 cell lines. Triptolide also significantly inhibited the xenografted PC-3 tumor growth in nude mice. Moreover, Triptolide induced PCa cell apoptosis through caspases activation and PARP cleavage. Unbalance between SUMOylation and deSUMOylation was reported to play an important role in PCa progression. SUMO-specific protease 1 (SENP1) was thought to be a potential marker and therapeutical target of PCa. Importantly, we observed that Triptolide down-regulated SENP1 expression in both mRNA and protein levels in dose-dependent and time- dependent manners, resulting in an enhanced cellular SUMOylation in PCa cells. Meanwhile, Triptolide decreased AR and c- Jun expression at similar manners, and suppressed AR and c-Jun transcription activity. Furthermore, knockdown or ectopic SENP1, c-Jun and AR expression in PCa cells inhibited the Triptolide anti-PCa effects. Taken together, our data suggest that Triptolide is a natural compound with potential therapeutic value for PCa. Its anti-tumor activity may be attributed to mechanisms involving down-regulation of SENP1 that restores SUMOylation and deSUMOyaltion balance and negative regulation of AR and c-Jun expression that inhibits the AR and c-Jun mediated transcription in PCa. Citation: Huang W, He T, Chai C, Yang Y, Zheng Y, et al. (2012) Triptolide Inhibits the Proliferation of Prostate Cancer Cells and Down-Regulates SUMO-Specific Protease 1 Expression. PLoS ONE 7(5): e37693. doi:10.1371/journal.pone.0037693 Editor: Matthew Bogyo, Stanford University, United States of America Received April 19, 2011; Accepted April 26, 2012; Published May 30, 2012 Copyright: 2012 Huang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was funded by National Forestry Public Welfare Industry Research Project (201204603), Program for New Century Excellent Talents in University (NCET-08-0467) and 100 Talents Program of Shaanxi Province of China to Ming Lei. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist, although two co-authors are from a commercial company (Bio- pharmaceutical Corporation) who contributed some reagents or analysis tools for the experiments involved in this paper. The company also has no financial or non-financial competing interests exist. This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials. * E-mail: leiming70@hotmail.com . These authors contributed equally to this work. Introduction The steady increase in the incidence and mortality rates of cancers urges researchers to make great effort on searching for novel anti-tumor drugs or therapies. Extracted compounds from natural herbs, such as Taxol, have been widely used in cancer therapy. Traditional Chinese medicine promises an important and useful alternative in cancer treatment. Many active compounds extracted from Chinese herbs have shown anti-tumor efficacy. Triptolide and Celastrol, two active components extracted from the Chinese herb Tripterygium wilfordii Hook F (known as Lei Gong Teng or Thunder of God Vine) used for rheumatoid arthritis therapy, have shown anti-tumor effect and apoptosis induction [1,2]. Celastrol has been identified as a natural proteasome inhibitor that causes the accumulation of ubiquitinated proteins and proteasome substrates IkB-a, Bax, and p27. Celastrol also induces apoptosis in PCa cells and shrinks the xenografted tumor in mice [1]. Triptolide is a diterpene lactone with potent immunosuppressive effects and anti-tumor properties in different cancers, including melanoma [2], breast cancer [3], pancreatic cancer [4], prostate cancer (PCa) [5] and others. Triptolide induces cell apoptosis via inhibiting HSP70 in pancreatic cancer cells [4,6], and interrupts the IL6R-JAK/STAT pathway in colon cancer cells [7]. In human anaplastic thyroid carcinoma cells, Triptolide significantly reduces the expression of the NF-kappa B PLoS ONE | www.plosone.org 1 May 2012 | Volume 7 | Issue 5 | e37693