Characterization of a novel androgen receptor (AR) coregulator RIPK1 and related chemicals that suppress AR-mediated prostate cancer growth via peptide and chemical screening

// Cheng-Lung Hsu 1 , Jai-Shin Liu 2 , Ting-Wei Lin 3 , Ying-Hsu Chang 4 , Yung-Chia Kuo 1 , An-Chi Lin 1 , Huei-Ju Ting 5 , See-Tong Pang 4 , Li-Yu Lee 6 , Wen-Lung Ma 7 , Chun-Cheng Lin 3 and Wen-Guey Wu 2 1 Division of Hematology-Oncology, Departments of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan 333, Taiwan 2 Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 300, Taiwan 3 Department of Chemistry, National Tsing-Hua University, Hsinchu 300, Taiwan 4 Division of Urology, Department of Surgery, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan 333, Taiwan 5 Department of Biological Science and Technology, National University of Tainan, Tainan 700, Taiwan 6 Department of Pathology, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan 333, Taiwan 7 Sex Hormone Research Center, China Medical University Hospital, Taichung 104, Taiwan Correspondence to: Cheng-Lung Hsu, email: hsu2221@adm.cgmh.org.tw Wen-Guey Wu, email: wgwu@life.nthu.edu.tw Chun-Cheng Lin, email: cclin66@mx.nthu.edu.tw Keywords: FxxLF, RIPK1, androgen receptor, prostate cancer, oxadiazole Received: November 04, 2016      Accepted: April 27, 2017      Published: May 13, 2017 ABSTRACT Using bicalutamide-androgen receptor (AR) DNA binding domain-ligand binding domain as bait, we observed enrichment of FxxFY motif-containing peptides. Protein database searches revealed the presence of receptor-interacting protein kinase 1 (RIPK1) harboring one FxxFY motif. RIPK1 interacted directly with AR and suppressed AR transactivation in a dose-dependent manner. Domain mapping experiments showed that the FxxFY motif in RIPK1 is critical for interactions with AR and the death domain of RIPK1 plays a crucial role in its inhibitory effect on transactivation. In terms of tissue expression, RIPK1 levels were markedly higher in benign prostate hyperplasia and non-cancerous tissue regions relative to the tumor area. With the aid of computer modeling for screening of chemicals targeting activation function 2 (AF-2) of AR, we identified oxadiazole derivatives as good candidates and subsequently generated a small library of these compounds. A number of candidates could effectively suppress AR transactivation and AR-related functions in vitro and in vivo with tolerable toxicity via inhibiting AR-peptide, AR-coregulator and AR N-C interactions. Combination of these chemicals with antiandrogen had an additive suppressive effect on AR transcriptional activity. Our collective findings may pave the way in creating new strategies for the development and design of anti-AR drugs.