title: A novel, small molecule inhibitor of Hsc70/Hsp70 potentiates Hsp90 inhibitor induced apoptosis in HCT116 colon carcinoma cells.
abstract: OBJECTIVE
  The anti-apoptotic function of the 70 kDa family of heat shock proteins and their role in cancer is well documented. Dual targeting of Hsc70 and Hsp70 with siRNA induces proteasome-dependent degradation of Hsp90 client proteins and extensive tumor specific apoptosis as well as the potentiation of tumor cell apoptosis following pharmacological Hsp90 inhibition.
  
  
  METHODS
  We have previously described the discovery and synthesis of novel adenosine-derived inhibitors of the 70 kDa family of heat shock proteins; the first inhibitors described to target the ATPase binding domain. The in vitro activity of VER-155008 was evaluated in HCT116, HT29, BT474 and MDA-MB-468 carcinoma cell lines. Cell proliferation, cell apoptosis and caspase 3/7 activity was determined for VER-155008 in the absence or presence of small molecule Hsp90 inhibitors.
  
  
  RESULTS
  VER-155008 inhibited the proliferation of human breast and colon cancer cell lines with GI(50)s in the range 5.3-14.4 microM, and induced Hsp90 client protein degradation in both HCT116 and BT474 cells. As a single agent, VER-155008 induced caspase-3/7 dependent apoptosis in BT474 cells and non-caspase dependent cell death in HCT116 cells. VER-155008 potentiated the apoptotic potential of a small molecule Hsp90 inhibitor in HCT116 but not HT29 or MDA-MB-468 cells. In vivo, VER-155008 demonstrated rapid metabolism and clearance, along with tumor levels below the predicted pharmacologically active level.
  
  
  CONCLUSIONS
  These data suggest that small molecule inhibitors of Hsc70/Hsp70 phenotypically mimic the cellular mode of action of a small molecule Hsp90 inhibitor and can potentiate the apoptotic potential of a small molecule Hsp90 inhibitor in certain cell lines. The factors determining whether or not cells apoptose in response to Hsp90 inhibition or the combination of Hsp90 plus Hsc70/Hsp70 inhibition remain to be determined.
authors.affiliation: Vernalis (R&D) Ltd, Granta Park, Cambridge, CB21 6GB, UK. a.massey@vernalis.com
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Massey
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Williamson
authors.forename: Helen
authors.initials: H
authors.lastname: Browne
authors.forename: James B
authors.initials: JB
authors.lastname: Murray
authors.forename: Pawel
authors.initials: P
authors.lastname: Dokurno
authors.forename: Terry
authors.initials: T
authors.lastname: Shaw
authors.forename: Alba T
authors.initials: AT
authors.lastname: Macias
authors.forename: Zoe
authors.initials: Z
authors.lastname: Daniels
authors.forename: Stephanie
authors.initials: S
authors.lastname: Geoffroy
authors.forename: Melanie
authors.initials: M
authors.lastname: Dopson
authors.forename: Paul
authors.initials: P
authors.lastname: Lavan
authors.forename: Natalia
authors.initials: N
authors.lastname: Matassova
authors.forename: Geraint L
authors.initials: GL
authors.lastname: Francis
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Graham
authors.forename: Rachel
authors.initials: R
authors.lastname: Parsons
authors.forename: Yikang
authors.initials: Y
authors.lastname: Wang
authors.forename: Antony
authors.initials: A
authors.lastname: Padfield
authors.forename: Mike
authors.initials: M
authors.lastname: Comer
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Drysdale
authors.forename: Mike
authors.initials: M
authors.lastname: Wood
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology; D016503:Drug Delivery Systems; D004357:Drug Synergism; D005260:Female; D050883:HSC70 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D018840:HSP70 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D011684:Purine Nucleosides / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D050883:HSC70 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D011684:Purine Nucleosides; C550733:VER 155008; D053148:Caspase 3; D053179:Caspase 7