title: In vitro biological characterization of a novel, synthetic diaryl pyrazole resorcinol class of heat shock protein 90 inhibitors.
abstract: The molecular chaperone heat shock protein 90 (HSP90) has emerged as an exciting molecular target. Derivatives of the natural product geldanamycin, such as 17-allylamino-17-demethoxy-geldanamycin (17-AAG), were the first HSP90 ATPase inhibitors to enter clinical trial. Synthetic small-molecule HSP90 inhibitors have potential advantages. Here, we describe the biological properties of the lead compound of a new class of 3,4-diaryl pyrazole resorcinol HSP90 inhibitor (CCT018159), which we identified by high-throughput screening. CCT018159 inhibited human HSP90beta with comparable potency to 17-AAG and with similar ATP-competitive kinetics. X-ray crystallographic structures of the NH(2)-terminal domain of yeast Hsp90 complexed with CCT018159 or its analogues showed binding properties similar to radicicol. The mean cellular GI(50) value of CCT018159 across a panel of human cancer cell lines, including melanoma, was 5.3 mumol/L. Unlike 17-AAG, the in vitro antitumor activity of the pyrazole resorcinol analogues is independent of NQO1/DT-diaphorase and P-glycoprotein expression. The molecular signature of HSP90 inhibition, comprising increased expression of HSP72 protein and depletion of ERBB2, CDK4, C-RAF, and mutant B-RAF, was shown by Western blotting and quantified by time-resolved fluorescent-Cellisa in human cancer cell lines treated with CCT018159. CCT018159 caused cell cytostasis associated with a G(1) arrest and induced apoptosis. CCT018159 also inhibited key endothelial and tumor cell functions implicated in invasion and angiogenesis. Overall, we have shown that diaryl pyrazole resorcinols exhibited similar cellular properties to 17-AAG with potential advantages (e.g., aqueous solubility, independence from NQO1 and P-glycoprotein). These compounds form the basis for further structure-based optimization to identify more potent inhibitors suitable for clinical development.
authors.affiliation: Haddow Laboratories, Cancer Research UK Centre for Cancer Therapeutics, The Institute of Cancer Research, 15 Cotswold Road, Belmont, Sutton, Surrey, UK.
authors.forename: Swee Y
authors.initials: SY
authors.lastname: Sharp
authors.forename: Kathy
authors.initials: K
authors.lastname: Boxall
authors.forename: Martin
authors.initials: M
authors.lastname: Rowlands
authors.forename: Chrisostomos
authors.initials: C
authors.lastname: Prodromou
authors.forename: S Mark
authors.initials: SM
authors.lastname: Roe
authors.forename: Alison
authors.initials: A
authors.lastname: Maloney
authors.forename: Marissa
authors.initials: M
authors.lastname: Powers
authors.forename: Paul A
authors.initials: PA
authors.lastname: Clarke
authors.forename: Gary
authors.initials: G
authors.lastname: Box
authors.forename: Sharon
authors.initials: S
authors.lastname: Sanderson
authors.forename: Lisa
authors.initials: L
authors.lastname: Patterson
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Matthews
authors.forename: Kwai-Ming J
authors.initials: KM
authors.lastname: Cheung
authors.forename: Karen
authors.initials: K
authors.lastname: Ball
authors.forename: Angela
authors.initials: A
authors.lastname: Hayes
authors.forename: Florence
authors.initials: F
authors.lastname: Raynaud
authors.forename: Richard
authors.initials: R
authors.lastname: Marais
authors.forename: Laurence
authors.initials: L
authors.lastname: Pearl
authors.forename: Sue
authors.initials: S
authors.lastname: Eccles
authors.forename: Wynne
authors.initials: W
authors.lastname: Aherne
authors.forename: Edward
authors.initials: E
authors.lastname: McDonald
authors.forename: Paul
authors.initials: P
authors.lastname: Workman
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D018360:Crystallography, X-Ray; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006574:Heterocyclic Compounds, 2-Ring / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008954:Models, Biological; D008958:Models, Molecular; D011485:Protein Binding; D011720:Pyrazoles / Q000737:chemistry / Q000494:pharmacology*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
chemical_list: C506244:CCT018159; D018841:HSP90 Heat-Shock Proteins; D006574:Heterocyclic Compounds, 2-Ring; D011720:Pyrazoles; D000251:Adenosine Triphosphatases