title: Inhibition of heat shock protein 90 decreases ACTH production and cell proliferation in AtT-20 cells.
abstract: OBJECTIVE
  Cushing's disease is primarily caused by adrenocorticotropic hormone (ACTH)-producing pituitary adenomas. If excision of the tumor from the pituitary, which is the primary treatment for Cushing's disease, is unsuccessful, further medical therapy is needed to treat the resultant hypercortisolism. Some of the drugs used to treat this condition have shown potential therapeutic benefits, but a more effective treatment should be explored for the treatment of Cushing's disease. In the present study, we determined the effect of heat shock protein 90 inhibitors on ACTH production and cell proliferation of AtT-20 corticotroph tumor cells.
  
  
  METHODS
  AtT-20 pituitary corticotroph tumor cells were cultured. The expression levels of mouse proopiomelanocortin (POMC) and pituitary tumor transforming gene 1 (PTTG1) mRNA were evaluated using quantitative real-time PCR. Cellular DNA content was analyzed with fluorescence-activated cell sorting (FACS) analysis. The protein levels were determined by Western blot analysis.
  
  
  RESULTS
  Both 17-allylamino-17-demethoxygeldanamycin and CCT018159 decreased POMC mRNA levels in AtT-20 cells and ACTH levels in the culture medium of these cells, suggesting that both drugs suppress ACTH synthesis and secretion in corticotroph tumor cells. Both drugs also decreased cell proliferation and induced apoptosis. FACS analyses revealed that both agents increased the percentage of AtT-20 cells in the G2/M phase. These drugs decreased cell proliferation, presumably due to the induction of cell death and arrest of the cell cycle in AtT-20 cells. Tumor weight in mice xenografted with AtT-20 cells and treated with CCT018159 was lower than in AtT-20-xenografted control mice. CCT018159 also decreased plasma ACTH levels, and POMC and PTTG1 mRNA levels in the tumor cells.
  
  
  CONCLUSIONS
  CCT018159 inhibits ACTH production and corticotroph tumor cell proliferation in vitro and in vivo.
authors.affiliation: Department of Endocrinology and Metabolism, Hirosaki University Graduate School of Medicine, 5 Zaifu-cho, Hirosaki, Aomori, 036-8562, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Sugiyama
authors.forename: Kazunori
authors.initials: K
authors.lastname: Kageyama
authors.forename: Shingo
authors.initials: S
authors.lastname: Murasawa
authors.forename: Noriko
authors.initials: N
authors.lastname: Ishigame
authors.forename: Kanako
authors.initials: K
authors.lastname: Niioka
authors.forename: Makoto
authors.initials: M
authors.lastname: Daimon
mesh_terms: D049913:ACTH-Secreting Pituitary Adenoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000236:Adenoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000324:Adrenocorticotropic Hormone / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors*; D006574:Heterocyclic Compounds, 2-Ring / Q000494:pharmacology; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D051379:Mice; D009368:Neoplasm Transplantation; D011333:Pro-Opiomelanocortin / Q000187:drug effects / Q000235:genetics; D011720:Pyrazoles / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D064249:Securin / Q000187:drug effects / Q000235:genetics; D047368:Tumor Burden
chemical_list: D016227:Benzoquinones; C506244:CCT018159; D018841:HSP90 Heat-Shock Proteins; D006574:Heterocyclic Compounds, 2-Ring; D047029:Lactams, Macrocyclic; C578005:PTTG1 protein, mouse; D011720:Pyrazoles; D012333:RNA, Messenger; D064249:Securin; C112765:tanespimycin; D011333:Pro-Opiomelanocortin; D000324:Adrenocorticotropic Hormone