title: FW-04-806 inhibits proliferation and induces apoptosis in human breast cancer cells by binding to N-terminus of Hsp90 and disrupting Hsp90-Cdc37 complex formation.
abstract: BACKGROUND
  Heat shock protein 90 (Hsp90) is a promising therapeutic target and inhibition of Hsp90 will presumably result in suppression of multiple signaling pathways. FW-04-806, a bis-oxazolyl macrolide compound extracted from China-native Streptomyces FIM-04-806, was reported to be identical in structure to the polyketide Conglobatin.
  
  
  METHODS
  We adopted the methods of chemproteomics, computational docking, immunoprecipitation, siRNA gene knock down, Quantitative Real-time PCR and xenograft models on the research of FW-04-806 antitumor mechanism, through the HER2-overexpressing breast cancer SKBR3 and HER2-underexpressing breast cancer MCF-7 cell line.
  
  
  RESULTS
  We have verified the direct binding of FW-04-806 to the N-terminal domain of Hsp90 and found that FW-04-806 inhibits Hsp90/cell division cycle protein 37 (Cdc37) chaperone/co-chaperone interactions, but does not affect ATP-binding capability of Hsp90, thereby leading to the degradation of multiple Hsp90 client proteins via the proteasome pathway. In breast cancer cell lines, FW-04-806 inhibits cell proliferation, caused G2/M cell cycle arrest, induced apoptosis, and downregulated Hsp90 client proteins HER2, Akt, Raf-1 and their phosphorylated forms (p-HER2, p-Akt) in a dose and time-dependent manner. Importantly, FW-04-806 displays a better anti-tumor effect in HER2-overexpressed SKBR3 tumor xenograft model than in HER2-underexpressed MCF-7 model. The result is consistent with cell proliferation assay and in vitro apoptosis assay applied for SKBR-3 and MCF-7. Furthermore, FW-04-806 has a favorable toxicity profile.
  
  
  CONCLUSIONS
  As a novel Hsp90 inhibitor, FW-04-806 binds to the N-terminal of Hsp90 and inhibits Hsp90/Cdc37 interaction, resulting in the disassociation of Hsp90/Cdc37/client complexes and the degradation of Hsp90 client proteins. FW-04-806 displays promising antitumor activity against breast cancer cells both in vitro and in vivo, especially for HER2-overexpressed breast cancer cells.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.affiliation: School of Pharmacy, Fujian Medical University, Basic Medicine Building North 205, No,88 Jiaotong Road, Fuzhou, Fujian 350004, China. miny@fjmu.edu.cn.
authors.forename: Min
authors.initials: M
authors.lastname: Ye
authors.forename: Lian-Ru
authors.initials: LR
authors.lastname: Zhang
authors.forename: Qun-Dan
authors.initials: QD
authors.lastname: Wu
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D018833:Chaperonins / Q000037:antagonists & inhibitors / Q000235:genetics*; D005260:Female; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D006801:Humans; D061986:MCF-7 Cells; D018942:Macrolides / Q000008:administration & dosage*; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors / Q000187:drug effects; D010080:Oxazoles / Q000008:administration & dosage; D011485:Protein Binding / Q000187:drug effects; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics
chemical_list: D018797:Cell Cycle Proteins; D018833:Chaperonins; D018841:HSP90 Heat-Shock Proteins; D018942:Macrolides; D046912:Multiprotein Complexes; D010080:Oxazoles; D018719:Erb-b2 Receptor Tyrosine Kinases; C498362:CDC37 protein, human; C022800:conglobatin; C508053:ERBB2 protein, human