sta-9090 and geldanamycin

The Hsp90 molecule, one of the most abundant heat shock proteins in mammalian cells, maintains homeostasis and prevents stress-induced cellular damage. Hsp90 is expressed under normal conditions at a level of about 1-2 Percent of total proteins, while its expression increases 2-10 fold in cancer cells. The two main constitutively expressed isoforms of Hsp90 are known as Hsp90-alpha and Hsp90-beta, and their upregulation is associated with tumor progression, invasion and formation of metastases, as well as development of drug resistance. The Hsp90 is a key target for many newly established, potent anticancer agents containing Hsp90 N-terminal ATP binding inhibitors, such as geldanamycin, and its analogues 17AAG and 17DMAG. The therapeutic usage of geldanamycin has been limited due to its poor water solubility and severe hepatotoxicity. Therefore, its analogues, including 17AAG, 17DMAG, Tanespimycin and Retaspimycin hydrochloride, with improved pharmacokinetic profiles, have been developed.

Topics: Animals; Antineoplastic Agents; Benzoquinones; Cyclin-Dependent Kinases; HSP90 Heat-Shock Proteins; Humans; Indoles; Lactams, Macrocyclic; Macrolides; Models, Biological; Mutation; Novobiocin; Proto-Oncogene Proteins c-raf; src-Family Kinases; Transforming Growth Factor beta; Triazoles; Tumor Suppressor Protein p53

Inflammation is an important component of cancer diathesis and treatment-refractory inflammation is a feature of many chronic degenerative lung diseases. HSP90 is a 90kDa protein which functions as an ATP-dependent molecular chaperone that regulates the signalling conformation and expression of multiple protein client proteins especially oncogenic mediators. HSP90 inhibitors are in clinical development as cancer therapies but the myeleosuppressive and neutropenic effect of first generation geldanamycin-class inhibitors has confounded studies on the effects on HSP90 inhibitors on inflammation. To address this we assessed the ability of Ganetespib, a non-geldanamycin HSP90 blocker, to suppress lipopolysaccharide (LPS)-induced cellular infiltrates, proteases and inflammatory mediator and transcriptional profiles. Ganetespib (10-100 mg/kg, i.v.) did not directly cause myelosuppression, as assessed by video micrography and basal blood cell count, but it strongly and dose-dependently suppressed LPS-induced neutrophil mobilization into blood and neutrophil- and mononuclear cell-rich steroid-refractory lung inflammation. Ganetespib also suppressed B cell and NK cell accumulation, inflammatory cytokine and chemokine induction and MMP9 levels. These data identify non-myelosuppresssive HSP90 inhibitors as potential therapies for inflammatory diseases refractory to conventional therapy, in particular those of the lung.

Topics: Animals; B-Lymphocytes; Benzoquinones; Cytokines; HSP90 Heat-Shock Proteins; Inflammation; Killer Cells, Natural; Lactams, Macrocyclic; Lipopolysaccharides; Lung; Male; Matrix Metalloproteinase 9; Mice; Mice, Inbred BALB C; Neutrophils; Triazoles

The two cytosolic/nuclear isoforms of the molecular chaperone HSP90, stress-inducible HSP90α and constitutively expressed HSP90β, fold, assemble and maintain the three-dimensional structure of numerous client proteins. Because many HSP90 clients are important in cancer, several HSP90 inhibitors have been evaluated in the clinic. However, little is known concerning possible unique isoform or conformational preferences of either individual HSP90 clients or inhibitors. In this report, we compare the relative interaction strength of both HSP90α and HSP90β with the transcription factors HSF1 and HIF1α, the kinases ERBB2 and MET, the E3-ubiquitin ligases KEAP1 and RHOBTB2, and the HSP90 inhibitors geldanamycin and ganetespib. We observed unexpected differences in relative client and drug preferences for the two HSP90 isoforms, with HSP90α binding each client protein with greater apparent affinity compared to HSP90β, while HSP90β bound each inhibitor with greater relative interaction strength compared to HSP90α. Stable HSP90 interaction was associated with reduced client activity. Using a defined set of HSP90 conformational mutants, we found that some clients interact strongly with a single, ATP-stabilized HSP90 conformation, only transiently populated during the dynamic HSP90 chaperone cycle, while other clients interact equally with multiple HSP90 conformations. These data suggest different functional requirements among HSP90 clientele that, for some clients, are likely to be ATP-independent. Lastly, the two inhibitors examined, although sharing the same binding site, were differentially able to access distinct HSP90 conformational states.

Topics: Adenosine Triphosphate; Amino Acid Sequence; Benzoquinones; Binding Sites; DNA-Binding Proteins; GTP-Binding Proteins; Heat Shock Transcription Factors; HEK293 Cells; HSP90 Heat-Shock Proteins; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Intracellular Signaling Peptides and Proteins; Kelch-Like ECH-Associated Protein 1; Lactams, Macrocyclic; Molecular Sequence Data; Mutation; Protein Binding; Protein Conformation; Protein Isoforms; Protein Kinase Inhibitors; Receptor, ErbB-2; Transcription Factors; Triazoles; Tumor Suppressor Proteins