title: KRIBB11 inhibits HSP70 synthesis through inhibition of heat shock factor 1 function by impairing the recruitment of positive transcription elongation factor b to the hsp70 promoter.
abstract: Heat shock factor 1 (HSF1) is the master switch for heat shock protein (HSP) expression in eukaryotes. A synthetic chemical library was screened to identify inhibitors of HSF1 using a luciferase reporter under the control of a heat shock element. A compound named KRIBB11 (N(2)-(1H-indazole-5-yl)-N(6)-methyl-3-nitropyridine-2,6-diamine) was identified for its activity in abolishing the heat shock-induced luciferase activity with an IC(50) of 1.2 μmol/liter. When the cells were exposed to heat shock in the presence of KRIBB11, the induction of HSF1 downstream target proteins such as HSP27 and HSP70 was blocked. In addition, treatment of HCT-116 cells with KRIBB11 induced growth arrest and apoptosis. Markers of apoptosis, such as cleaved poly(ADP-ribose) polymerase, were detected after KRIBB11 treatment. Biotinyl-KRIBB11 was synthesized as an affinity probe for the identification of KRIBB11 target proteins. Using affinity chromatography and competition assays, KRIBB11 was shown to associate with HSF1 in vitro. Chromatin immunoprecipitation analysis showed that KRIBB11 inhibited HSF1-dependent recruitment of p-TEFb (positive transcription elongation factor b) to the hsp70 promoter. Finally, intraperitoneal treatment of nude mice with KRIBB11 at 50 mg/kg resulted in a 47.4% (p < 0.05) inhibition of tumor growth without body weight loss. Immunoblotting assays showed that the expression of HSP70 was lower in KRIBB11-treated tumor tissue than in control tissues. Because HSPs are expressed at high levels in a wide range of tumors, these results strengthen the rationale for targeting HSF1 in cancer therapy.
authors.affiliation: Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Korea.
authors.forename: Young Ju
authors.initials: YJ
authors.lastname: Yoon
authors.forename: Joo Ae
authors.initials: JA
authors.lastname: Kim
authors.forename: Ki Deok
authors.initials: KD
authors.lastname: Shin
authors.forename: Dae-Seop
authors.initials: DS
authors.lastname: Shin
authors.forename: Young Min
authors.initials: YM
authors.lastname: Han
authors.forename: Yu Jin
authors.initials: YJ
authors.lastname: Lee
authors.forename: Jin Soo
authors.initials: JS
authors.lastname: Lee
authors.forename: Byoung-Mog
authors.initials: BM
authors.lastname: Kwon
authors.forename: Dong Cho
authors.initials: DC
authors.lastname: Han
mesh_terms: D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003959:Diamines / Q000494:pharmacology*; D016503:Drug Delivery Systems; D055551:HSP27 Heat-Shock Proteins / Q000096:biosynthesis; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D006801:Humans; D007191:Indazoles / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D042925:Positive Transcriptional Elongation Factor B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000631:Aminopyridines; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D003959:Diamines; C000619706:HSF1 protein, human; D055551:HSP27 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C057725:HSPB1 protein, human; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D007191:Indazoles; D018832:Molecular Chaperones; C556094:N2-(1H-indazole-5-yl)-N6-methyl-3-nitropyridine-2,6-diamine; D009363:Neoplasm Proteins; D014157:Transcription Factors; D011065:Poly(ADP-ribose) Polymerases; D042925:Positive Transcriptional Elongation Factor B