title: Minnelide Inhibits Androgen Dependent, Castration Resistant Prostate Cancer Growth by Decreasing Expression of Androgen Receptor Full Length and Splice Variants.
abstract: BACKGROUND
  With almost 30,000 deaths per year, prostate cancer is the second-leading cause of cancer-related death in men. Androgen Deprivation Therapy (ADT) has been the corner stone of prostate cancer treatment for decades. However, despite an initial response of prostate cancer to ADT, this eventually fails and the tumors recur, resulting in Castration Resistant Prostate Cancer (CRPC). Triptolide, a diterpene triepoxide, has been tested for its anti-tumor properties in a number of cancers for over a decade. Owing to its poor solubility in aqueous medium, its clinical application had been limited. To circumvent this problem, we have synthesized a water-soluble pro-drug of triptolide, Minnelide, that is currently being evaluated in a Phase 1 clinical trial against gastrointestinal tumors. In the current study, we assessed the therapeutic potential of Minnelide and its active compound triptolide against androgen dependent prostate cancer both in vitro as well as in vivo.
  
  
  METHODS
  Cell viability was measured by a MTT based assay after treating prostate cancer cells with multiple doses of triptolide. Apoptotic cell death was measured using a caspase 3/7 activity. Androgen Receptor (AR) promoter-binding activity was evaluated by using luciferase reporter assay. For evaluating the effect in vivo, 22Rv1 cells were implanted subcutaneously in animals, following which, treatment was started with 0.21 mg/kg Minnelide.
  
  
  RESULTS
  Our study showed that treatment with triptolide induced apoptotic cell death in CRPC cells. Triptolide treatment inhibited AR transcriptional activity and decreased the expression of AR and its splice variants both at the mRNA and the protein level. Our studies show that triptolide inhibits nuclear translocation of Sp1, resulting in its decreased transcriptional activity leading to downregulation of AR and its splice variants in prostate cancer cells. In vivo, Minnelide (0.21 mg/kg) regressed subcutaneous tumors derived from CRPC 22RV1 at our study endpoint. Our animal studies further confirmed that Minnelide was more efficacious than the standard of care therapies, Docetaxel and Enzalutamide.
  
  
  CONCLUSIONS
  Our study indicates that Minnelide is very effective as a therapeutic option against CRPC at a dose that is currently tolerated by patients in the ongoing clinical trials. Prostate 77: 584-596, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Department of Urology, Institute for Prostate and Urologic Cancers, University of Minnesota, Minneapolis, Minnesota.|Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Sumit
authors.initials: S
authors.lastname: Isharwal
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Shrey
authors.initials: S
authors.lastname: Modi
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Nivedita
authors.initials: N
authors.lastname: Arora
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Charles
authors.initials: C
authors.lastname: Uhlrich
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Bhuwan
authors.initials: B
authors.lastname: Giri
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Usman
authors.initials: U
authors.lastname: Barlass
authors.affiliation: Department of Urology, Institute for Prostate and Urologic Cancers, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Ayman
authors.initials: A
authors.lastname: Soubra
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Rohit
authors.initials: R
authors.lastname: Chugh
authors.affiliation: Department of Urology, Institute for Prostate and Urologic Cancers, University of Minnesota, Minneapolis, Minnesota.|Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota.|Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Dehm
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.|Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Vikas
authors.initials: V
authors.lastname: Dudeja
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.|Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Ashok
authors.initials: A
authors.lastname: Saluja
authors.affiliation: Department of Surgery, University of Minnesota, Minneapolis, Minnesota.|Miller School of Medicine, University of Miami, Miami, Florida.
authors.forename: Sulagna
authors.initials: S
authors.lastname: Banerjee
authors.affiliation: Department of Urology, Institute for Prostate and Urologic Cancers, University of Minnesota, Minneapolis, Minnesota.
authors.forename: Badrinath
authors.initials: B
authors.lastname: Konety
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D004224:Diterpenes; D004305:Dose-Response Relationship, Drug; D004852:Epoxy Compounds; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D010755:Organophosphates / Q000494:pharmacology* / Q000627:therapeutic use; D010616:Phenanthrenes / Q000494:pharmacology* / Q000627:therapeutic use; D064129:Prostatic Neoplasms, Castration-Resistant / Q000188:drug therapy / Q000378:metabolism*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D011897:Random Allocation; D011944:Receptors, Androgen / Q000096:biosynthesis* / Q000235:genetics; D047368:Tumor Burden / Q000187:drug effects / Q000502:physiology; D023041:Xenograft Model Antitumor Assays
chemical_list: C410798:AR protein, human; D004224:Diterpenes; D004852:Epoxy Compounds; D010755:Organophosphates; D010616:Phenanthrenes; D020033:Protein Isoforms; D011944:Receptors, Androgen; C579022:14-O-phosphonooxymethyltriptolide disodium salt
keywords: Androgen receptor; CRPC; Minnelide; Sp1; splice variant; triptolide