Oxidized analogs of Di(1H-indol-3-yl)methyl-4-substituted benzenes are NR4A1-dependent UPR inducers with potent and safe anti-cancer activity

// Marisa Sanchez 1, * , Zebin Xia 1, * , Elizabeth Rico-Bautista 1 , Xihua Cao 1 , Michael Cuddy 1 , David J. Castro 1, 3 , Ricardo G. Correa 1 , Liqun Chen 1 , Jinghua Yu 1 , Andrey Bobkov 1 , Vivian Ruvolo 4 , Michael Andreeff 4 , Robert G. Oshima 1 , Shu-Ichi Matsuzawa 1, 5 , John C. Reed 1, 6 , Xiao-Kun Zhang 1, 2 , Donna Hansel 7 , Dieter A. Wolf 1, 2 and Marcia I. Dawson 1 1 Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, USA 2 School of Pharmaceutical Sciences, Fujian Provincial Key Laboratory of Innovative Drug Target Research and Center for Stress Signaling Networks, Xiamen University, Xiamen, China 3 Oregon Health and Science University School of Medicine, Portland, OR, USA 4 Section of Molecular Hematology and Therapy, Department of Stem Cell Transplantation and Cellular Therapy, Department of Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, USA 5 Present address: Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan 6 Present address: Roche, Pharma Research and Early Development, Basel, Switzerland 7 Department of Pathology, University of California San Diego, San Diego, CA, USA * These authors contributed equally to this work Correspondence to: Dieter A. Wolf, email: dwolf@sbpdiscovery.org Keywords: orphan nuclear receptor 4A1; unfolded protein response; apoptosis; prostate cancer; oxidation products Received: February 04, 2017      Accepted: April 06, 2018      Published: May 18, 2018 ABSTRACT Di(1 H -indol-3-yl)(4-trifluoromethylphenyl)methane (DIM-Ph-4-CF 3 ) is an analog of orphan nuclear receptor 4A1 (NR4A1) ligand cytosporone B. We have synthesized several oxidation products of DIM-Ph-4-CF 3 , focusing on analogs with electron-withdrawing or donating groups at their phenyl ring 4-positions, and examined their anti-cancer activity and mechanism-of-action. Mesylates (DIM-Ph-4-X + OMs – s) having CF 3 , CO 2 Me and Cl groups were more effective inhibitors of cancer cell viability than their precursors. 19 F NMR spectroscopy and differential scanning calorimetry strongly indicated interactions of DIM-Ph-4-CF 3 + OMs – with the NR4A1 ligand binding domain, and compound-induced apoptosis of prostate cancer cells was dependent on NR4A1. DIM-Ph-4-CF3 + OMs – showed robust inhibition of LNCaP prostate cancer xenografts with no apparent toxicity. In vitro and in vivo , DIM-Ph-4-CF3 + OMs – activated proapoptotic unfolded protein response (UPR) signaling in prostate cancer cells. Independently of DIM-Ph-4-CF 3 + OMs – , the bulk of NR4A1 localized to the cytoplasm in various cancer cell lines, suggesting a cytoplasmic mechanism-of-action of DIM-Ph-4-CF 3 + OMs – in UPR induction and cell death. In summary, the data suggest that oxidized analogs of DIM-Ph-4-CF3 possess potent and safe anti-cancer activity which is mediated through UPR signaling downstream of NR4A1 binding.