title: Inhibition of p53-murine double minute 2 interaction by nutlin-3A stabilizes p53 and induces cell cycle arrest and apoptosis in Hodgkin lymphoma.
abstract: OBJECTIVE
  p53 is frequently expressed but rarely mutated in Hodgkin and Reed-Sternberg (HRS) cells of Hodgkin's lymphoma (HL). p53 protein levels are regulated by murine double minute 2 (MDM2) through a well-established autoregulatory feedback loop. In this study, we investigated the effects of nutlin-3A, a recently developed small molecule that antagonizes MDM2 and disrupts the p53-MDM2 interaction, on p53-dependent cell cycle arrest and apoptosis in cultured HRS cells.
  
  
  METHODS
  HL cell lines carrying wild-type (wt) or mutated p53 gene were treated with the potent MDM2 inhibitor nutlin-3A or a 150-fold less active enantiomer, nutlin-3B.
  
  
  RESULTS
  We show that nutlin-3A, but not nutlin-3B, stabilizes p53 in cultured HRS cells carrying wt p53 gene resulting in p53-dependent cell cycle arrest and apoptosis. Cell cycle arrest was associated with up-regulation of the cyclin-dependent kinase inhibitor p21. Nutlin-3A-induced apoptotic cell death was accompanied by Bax and Puma up-regulation and caspase-3 cleavage and was abrogated, in part, by inhibition of caspase-9 and caspase-3 activity. By contrast, no effects on cell cycle or apoptosis were found in HL cell lines harboring mutated p53 gene. Furthermore, combined treatment with nutlin-3A and doxorubicin revealed enhanced cytotoxicity in HRS cells with wt p53 gene. Blocking of nuclear export by leptomycin B, or inhibition of proteasome by MG132, stabilized p53 at a level comparable with that of nutlin-3A treatment in HRS cells with wt p53.
  
  
  CONCLUSIONS
  These data suggest that nutlin-3A stabilized p53 by preventing MDM2-mediated p53 degradation in HRS cells. wt p53 stabilization and activation by nutlin-3A may be a novel therapeutic approach for patients with HL.
authors.affiliation: Department of Hematopathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
authors.forename: Elias
authors.initials: E
authors.lastname: Drakos
authors.forename: Athanasios
authors.initials: A
authors.lastname: Thomaides
authors.forename: L Jeffrey
authors.initials: LJ
authors.lastname: Medeiros
authors.forename: Jiang
authors.initials: J
authors.lastname: Li
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Leventaki
authors.forename: Marina
authors.initials: M
authors.lastname: Konopleva
authors.forename: Michael
authors.initials: M
authors.lastname: Andreeff
authors.forename: George Z
authors.initials: GZ
authors.lastname: Rassidakis
mesh_terms: D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002470:Cell Survival; D016158:Genes, p53; D006689:Hodgkin Disease / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010879:Piperazines / Q000494:pharmacology*; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics* / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D010879:Piperazines; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C482205:nutlin 3; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2