title: Piperlongumine induces rapid depletion of the androgen receptor in human prostate cancer cells.
abstract: BACKGROUND
  Androgen receptor (AR) signaling is regarded as the driving force in prostate carcinogenesis, and its modulation represents a logical target for prostate cancer (PC) prevention and treatment. Natural products are the most consistent source of small molecules for drug development. In this study, we investigate the functional impact of piperlongumine (PL), a naturally occurring alkaloid present in the Long pepper (Piper longum), on AR expression in PC cells and delineate its mechanism of action.
  
  
  METHODS
  Expression and transcriptional activity of AR was examined by western blotting and luciferase reporter assay, respectively. CellTiter Blue assay was utilized to quantify cell proliferation. Reactive oxygen species (ROS) generation was examined by staining cells with a ROS indicator CM-H(2) DCFDA, followed by flow cytometry analysis.
  
  
  RESULTS
  The results of our experiments demonstrate that PL rapidly reduces AR protein levels in PC cells via proteasome-mediated ROS-dependent mechanism. Moreover, PL effectively depletes a modified AR lacking the ligand-binding domain, shedding light on a new paradigm in the treatment approach to prostatic carcinoma that expresses mutated constitutively active AR. Importantly, PL effectively depletes AR in PC cells at low micromolar concentrations, while concurrently exerting a significant inhibitory effect on AR transcriptional activity and proliferation of PC cells.
  
  
  CONCLUSIONS
  Our investigation demonstrates for the first time that PL induces rapid depletion of the AR in PC cells. As such, PL may afford novel opportunities for both prevention and treatment of prostatic malignancy.
authors.affiliation: Department of Surgical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Konstantin V
authors.initials: KV
authors.lastname: Golovine
authors.forename: Peter B
authors.initials: PB
authors.lastname: Makhov
authors.forename: Ervin
authors.initials: E
authors.lastname: Teper
authors.forename: Alexander
authors.initials: A
authors.lastname: Kutikov
authors.forename: Daniel
authors.initials: D
authors.lastname: Canter
authors.forename: Robert G
authors.initials: RG
authors.lastname: Uzzo
authors.forename: Vladimir M
authors.initials: VM
authors.lastname: Kolenko
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004148:Dioxolanes / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D010881:Piperidones
chemical_list: D000970:Antineoplastic Agents; D004148:Dioxolanes; D046988:Proteasome Endopeptidase Complex; D017382:Reactive Oxygen Species; D011944:Receptors, Androgen; C498077:piperlongumine; D010881:Piperidones