title: Cell cycle-dependent activity of the novel dual PI3K-MTORC1/2 inhibitor NVP-BGT226 in acute leukemia.
abstract: BACKGROUND
  Dysregulation of the PI3Kinase/AKT pathway is involved in the pathogenesis of many human malignancies. In acute leukemia, the AKT pathway is frequently activated, however mutations in the PI3K/AKT pathway are uncommon. In some cases, constitutive AKT activation can be linked to gain-of-function tyrosine kinase (TK) mutations upstream of the PI3K/AKT pathway. Inhibitors of the PI3K/AKT pathway are attractive candidates for cancer drug development, but so far clinical efficacy of PI3K inhibitors against various neoplasms has been moderate. Furthermore, specific MTORC1 inhibitors, acting downstream of AKT, have the disadvantage of activating AKT via feed-back mechanisms. We now evaluated the antitumor efficacy of NVP-BGT226, a novel dual pan-PI3K and MTORC1/2 inhibitor, in acute leukemia.
  
  
  METHODS
  Native leukemia blasts were stained to analyze for AKT phosphorylation levels on a flow cytometer. Efficacy of NVP-BGT226 in comparison to a second dual inhibitor, NVP-BEZ235, was determined with regard to cellular proliferation, autophagy, cell cycle regulation and induction of apoptosis in in vitro and ex vivo cellular assays as well as on the protein level. An isogenic AKT-autoactivated Ba/F3 model, different human leukemia cell lines as well as native leukemia patient blasts were studied. Isobologram analyses were set up to calculate for (super) additive or antagonistic effects of two agents.
  
  
  RESULTS
  We show, that phosphorylation of AKT is frequently augmented in acute leukemia. NVP-BGT226 as well as NVP-BEZ235 profoundly and globally suppress AKT signaling pathways, which translates into potent antiproliferative effects. Furthermore, NVP-BGT226 has potent proapoptotic effects in vitro as well as in ex vivo native blasts. Surprisingly and in contrast, NVP-BEZ235 leads to a profound G1/G0 arrest preventing significant induction of apoptosis. Combination with TK inhibitors, which are currently been tested in the treatment of acute leukemia subtypes, overcomes cell cycle arrest and results in (super)additive proapoptotic effects for NVP-BGT226--but also for NVP-BEZ235. Importantly, mononuclear donor cells show lower phospho-AKT expression levels and consequently, relative insensitivity towards dual PI3K-MTORC1/2 inhibition.
  
  
  CONCLUSIONS
  Our data suggest a favorable antileukemic profile for NVP-BGT226 compared to NVP-BEZ235--which provides a strong rationale for clinical evaluation of the dual PI3K-MTORC1/2 inhibitor NVP-BGT226 in acute leukemia.
authors.affiliation: Department of Hematology, Oncology, Rheumatology, Immunology and Pulmology, University Hospital Tübingen, Otfried-Müller-Straße 10, 72076, Tübingen, Germany.
authors.forename: Kerstin Maria
authors.initials: KM
authors.lastname: Kampa-Schittenhelm
authors.forename: Michael Charles
authors.initials: MC
authors.lastname: Heinrich
authors.forename: Figen
authors.initials: F
authors.lastname: Akmut
authors.forename: Katharina Henriette
authors.initials: KH
authors.lastname: Rasp
authors.forename: Barbara
authors.initials: B
authors.lastname: Illing
authors.forename: Hartmut
authors.initials: H
authors.lastname: Döhner
authors.forename: Konstanze
authors.initials: K
authors.lastname: Döhner
authors.forename: Marcus Matthias
authors.initials: MM
authors.lastname: Schittenhelm
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007938:Leukemia / Q000235:genetics / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors*; D009154:Mutation; D051059:PTEN Phosphohydrolase / Q000172:deficiency / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011804:Quinolines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*
chemical_list: D000970:Antineoplastic Agents; D007093:Imidazoles; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D011804:Quinolines; D058570:TOR Serine-Threonine Kinases; C570852:8-(6-methoxypyridin-3-yl)-3-methyl-1-(4-piperazin-1-yl-3-trifluoromethylphenyl)-1,3-dihydroimidazo(4,5-c)quinolin-2-one