title: Molecular imaging of the efficacy of heat shock protein 90 inhibitors in living subjects.
abstract: Heat shock protein 90 alpha (Hsp90 alpha)/p23 and Hsp90 beta/p23 interactions are crucial for proper folding of proteins involved in cancer and neurodegenerative diseases. Small molecule Hsp90 inhibitors block Hsp90 alpha/p23 and Hsp90 beta/p23 interactions in part by preventing ATP binding to Hsp90. The importance of isoform-selective Hsp90 alpha/p23 and Hsp90 beta/p23 interactions in determining the sensitivity to Hsp90 was examined using 293T human kidney cancer cells stably expressing split Renilla luciferase (RL) reporters. Interactions between Hsp90 alpha/p23 and Hsp90 beta/p23 in the split RL reporters led to complementation of RL activity, which was determined by bioluminescence imaging of intact cells in cell culture and living mice using a cooled charge-coupled device camera. The three geldanamycin-based and seven purine-scaffold Hsp90 inhibitors led to different levels of inhibition of complemented RL activities (10-70%). However, there was no isoform selectivity to both classes of Hsp90 inhibitors in cell culture conditions. The most potent Hsp90 inhibitor, PU-H71, however, led to a 60% and 30% decrease in RL activity (14 hr) in 293T xenografts expressing Hsp90 alpha/p23 and Hsp90 beta/p23 split reporters respectively, relative to carrier control-treated mice. Molecular imaging of isoform-specific Hsp90 alpha/p23 and Hsp90 beta/p23 interactions and efficacy of different classes of Hsp90 inhibitors in living subjects have been achieved with a novel genetically encoded reporter gene strategy that should help in accelerating development of potent and isoform-selective Hsp90 inhibitors.
authors.affiliation: Department of Radiology, Stanford University School of Medicine, Stanford, California 94305-5427, USA.
authors.forename: Carmel T
authors.initials: CT
authors.lastname: Chan
authors.forename: Ramasamy
authors.initials: R
authors.lastname: Paulmurugan
authors.forename: Olivier S
authors.initials: OS
authors.lastname: Gheysens
authors.forename: Joungnam
authors.initials: J
authors.lastname: Kim
authors.forename: Gabriela
authors.initials: G
authors.lastname: Chiosis
authors.forename: Sanjiv Sam
authors.initials: SS
authors.lastname: Gambhir
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D052117:Benzodioxoles / Q000494:pharmacology*; D016227:Benzoquinones / Q000737:chemistry; D045744:Cell Line, Tumor; D004354:Drug Screening Assays, Antitumor / Q000379:methods*; D017930:Genes, Reporter / Q000235:genetics; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic / Q000737:chemistry; D049410:Luciferases, Renilla / Q000032:analysis / Q000235:genetics; D051379:Mice; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009154:Mutation; D010750:Phosphoproteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D025941:Protein Interaction Mapping / Q000379:methods; D011687:Purines / Q000378:metabolism / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D052117:Benzodioxoles; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; C493165:HSP90AB1 protein, human; D047029:Lactams, Macrocyclic; D018832:Molecular Chaperones; D010750:Phosphoproteins; D011687:Purines; C526550:9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-; D049410:Luciferases, Renilla; C490849:PTGES3 protein, human; D000071876:Prostaglandin-E Synthases; C001277:geldanamycin