title: Induction of a heat shock factor 1-dependent stress response alters the cytotoxic activity of hsp90-binding agents.
abstract: In addition to its classic role in the cellular stress response, heat shock protein 90 (Hsp90) plays a critical but less well appreciated role in regulating signal transduction pathways that control cell growth and survival under basal, nonstress conditions. Over the past 5 years, the antitumor antibiotics geldanamycin and radicicol have become recognized as selective Hsp90-binding agents (HBA) with a novel ability to alter the activity of many of the receptors, kinases, and transcription factors involved in these cancer-associated pathways. As a consequence of their interaction with Hsp90, however, these agents also induce a marked cellular heat shock response. To study the mechanism of this response and assess its relevance to the anticancer action of the HBA, we verified that the compounds could activate a reporter construct containing consensus binding sites for heat shock factor 1 (HSF1), the major transcriptional regulator of the vertebrate heat shock response. We then used transformed fibroblasts derived from HSF1 knock-out mice to show that unlike conventional chemotherapeutics, HBA increased the synthesis and cellular levels of heat shock proteins in an HSF1-dependent manner. Compared with transformed fibroblasts derived from wild-type mice, HSF1 knock-out cells were significantly more sensitive to the cytotoxic effects of HBA but not to doxorubicin or cisplatin. Consistent with these in vitro data, we found that systemic administration of an HBA led to marked increases in the level of Hsp72 in both normal mouse tissues and human tumor xenografts. We conclude that HBA are useful probes for studying molecular mechanisms regulating the heat shock response both in cells and in whole animals. Moreover, induction of the heat shock response by HBA will be an important consideration in the clinical application of these drugs, both in terms of modulating their cytotoxic activity as well as monitoring their biological activity in individual patients.
authors.affiliation: Department of Pediatrics, Steele Memorial Children's Research Center, University of Arizona, Tucson 85724, USA.
authors.forename: R
authors.initials: R
authors.lastname: Bagatell
authors.forename: G D
authors.initials: GD
authors.lastname: Paine-Murrieta
authors.forename: C W
authors.initials: CW
authors.lastname: Taylor
authors.forename: E J
authors.initials: EJ
authors.lastname: Pulcini
authors.forename: S
authors.initials: S
authors.lastname: Akinaga
authors.forename: I J
authors.initials: IJ
authors.lastname: Benjamin
authors.forename: L
authors.initials: L
authors.lastname: Whitesell
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000378:metabolism / Q000494:pharmacology*; D016227:Benzoquinones; D002472:Cell Transformation, Viral; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000076249:Heat Shock Transcription Factors; D018869:Heat-Shock Response / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D047029:Lactams, Macrocyclic; D007783:Lactones / Q000378:metabolism / Q000494:pharmacology; D018942:Macrolides; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D016513:Mice, SCID; D027383:Papillomaviridae; D011809:Quinones / Q000378:metabolism / Q000494:pharmacology; D017828:Rifabutin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D018841:HSP90 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D047029:Lactams, Macrocyclic; D007783:Lactones; D018942:Macrolides; D011809:Quinones; D014157:Transcription Factors; D017828:Rifabutin; C112765:tanespimycin; C035359:monorden; C001277:geldanamycin