title: Targeting of mTOR is associated with decreased growth and decreased VEGF expression in acute myeloid leukaemia cells.
abstract: BACKGROUND
  The mammalian target of rapamycin (mTOR) has recently been implicated in leukaemic cell growth, tumour-associated angiogenesis and expression of vascular endothelial growth factor (VEGF). We examined whether mTOR plays a role as regulator of growth and VEGF-expression in acute myeloid leukaemia (AML). Three mTOR-targeting drugs, rapamycin, everolimus (RAD001) and CCI-779, were applied. The effects of these drugs on growth, survival, apoptosis and VEGF expression in primary AML cells and various AML cell lines were examined.
  
  
  METHODS
  Growth of AML cells and AML-derived cell lines was assessed by (3)H-thymidine incorporation, survival was examined by light- and electron microscopy, by Tunel assay and by AnnexinV-staining, and the expression of VEGF by Northern blotting, RT-PCR and ELISA.
  
  
  RESULTS
  Rapamycin was found to counteract growth in the AML cell lines U937 and KG1a as well as in primary AML cells in 14/18 patients examined. The effects of rapamycin and its derivatives were dose-dependent (IC(50): 10 pM-100 nM). It was also found that exposure to mTOR-targeting drugs resulted in apoptosis and in decreased expression of VEGF in leukaemic cells.
  
  
  CONCLUSIONS
  mTOR-targeting drugs exert antileukaemic effects on AML cells in vitro through multiple actions, including direct inhibition of proliferation, induction of apoptosis and suppression of VEGF. Based on this study and other studies, mTOR can be regarded as a potential drug target in AML.
authors.affiliation: Medical University of Vienna, Vienna, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Böhm
authors.forename: K J
authors.initials: KJ
authors.lastname: Aichberger
authors.forename: M
authors.initials: M
authors.lastname: Mayerhofer
authors.forename: H
authors.initials: H
authors.lastname: Herrmann
authors.forename: S
authors.initials: S
authors.lastname: Florian
authors.forename: M-T
authors.initials: MT
authors.lastname: Krauth
authors.forename: S
authors.initials: S
authors.lastname: Derdak
authors.forename: P
authors.initials: P
authors.lastname: Samorapoompichit
authors.forename: K
authors.initials: K
authors.lastname: Sonneck
authors.forename: A
authors.initials: A
authors.lastname: Vales
authors.forename: K V
authors.initials: KV
authors.lastname: Gleixner
authors.forename: W F
authors.initials: WF
authors.lastname: Pickl
authors.forename: W R
authors.initials: WR
authors.lastname: Sperr
authors.forename: P
authors.initials: P
authors.lastname: Valent