title: Down-regulation of heat shock protein 70 improves arsenic trioxide and 17-DMAG effects on constitutive signal transducer and activator of transcription 3 activity.
abstract: OBJECTIVE
  Signal transducer and activator of transcription 3 (STAT3) has been shown to be constitutively active in approximately 50% of patients with acute myeloid leukemia and is associated with worse outcome. Arsenic trioxide (ATO) synergizes with the heat shock protein (HSP) 90 inhibitor, 17-DMAG, to down-regulate STAT3 activity. However, both agents up-regulate HSP70, an anti-apoptotic protein. We therefore examined whether down-regulating HSP70 with short interference (si) RNA will affect ATO and 17-DMAG effects on constitutive STAT3 activity.
  
  
  METHODS
  A semi-mechanistic pharmacodynamic model was used to characterize concentration-effect relationships of ATO and 17-DMAG effects on constitutive STAT3 activity and HSP70 expression with or without siRNA against HSP70 in a cell line model.
  
  
  RESULTS
  Treatment with siRNA for HSP70 resulted in a stronger degree of synergism on down-regulation of STAT3 activity by ATO and 17-DMAG. However, treatment with siRNA for HSP70 resulted in less synergism on up-regulation of HSP70 by the two drugs.
  
  
  CONCLUSIONS
  Down-regulation of HSP70 improves ATO and 17-DMAG effects on constitutive STAT3 activity. These results further provide a basis for studying the combined role of ATO with a HSP90 inhibitor such as 17-DMAG in AML with constitutive STAT3 activity.
authors.affiliation: Department of Medicine, Roswell Park Cancer Institute, Leukemia Section, Elm and Carlton Streets, Buffalo, NY 14263, USA. meir.wetzler@roswellpark.org
authors.forename: Sampa
authors.initials: S
authors.lastname: Ghoshal
authors.forename: Indranil
authors.initials: I
authors.lastname: Rao
authors.forename: Justin C
authors.initials: JC
authors.lastname: Earp
authors.forename: William J
authors.initials: WJ
authors.lastname: Jusko
authors.forename: Meir
authors.initials: M
authors.lastname: Wetzler
mesh_terms: D000465:Algorithms; D017209:Apoptosis / Q000187:drug effects; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D016227:Benzoquinones / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D018274:Electroporation; D018840:HSP70 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D010087:Oxides / Q000494:pharmacology*; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000378:metabolism*
chemical_list: D001152:Arsenicals; D016227:Benzoquinones; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D010087:Oxides; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C448659:17-(dimethylaminoethylamino)-17-demethoxygeldanamycin; D000077237:Arsenic Trioxide