title: Dual mTORC2/mTORC1 targeting results in potent suppressive effects on acute myeloid leukemia (AML) progenitors.
abstract: OBJECTIVE
  To determine whether mTORC2 and rapamycin-insensitive (RI)-mTORC1 complexes are present in acute myeloid leukemia (AML) cells and to examine the effects of dual mTORC2/mTORC1 inhibition on primitive AML leukemic progenitors.
  
  
  METHODS
  Combinations of different experimental approaches were used, including immunoblotting to detect phosphorylated/activated forms of elements of the mTOR pathway in leukemic cell lines and primary AML blasts; cell-proliferation assays; direct assessment of mRNA translation in polysomal fractions of leukemic cells; and clonogenic assays in methylcellulose to evaluate leukemic progenitor-colony formation.
  
  
  RESULTS
  mTORC2 complexes are active in AML cells and play critical roles in leukemogenesis. RI-mTORC1 complexes are also formed and regulate the activity of the translational repressor 4E-BP1 in AML cells. OSI-027 blocks mTORC1 and mTORC2 activities and suppresses mRNA translation of cyclin D1 and other genes that mediate proliferative responses in AML cells. Moreover, OSI-027 acts as a potent suppressor of primitive leukemic precursors from AML patients and is much more effective than rapamycin in eliciting antileukemic effects in vitro.
  
  
  CONCLUSIONS
  Dual targeting of mTORC2 and mTORC1 results in potent suppressive effects on primitive leukemic progenitors from AML patients. Inhibition of the mTOR catalytic site with OSI-027 results in suppression of both mTORC2 and RI-mTORC1 complexes and elicits much more potent antileukemic responses than selective mTORC1 targeting with rapamycin.
authors.affiliation: Robert H. Lurie Comprehensive Cancer Center and Division of Hematology/Oncology, Northwestern University Medical School and Jesse Brown VA Medical Center, Chicago, Illinois, USA.
authors.forename: Jessica K
authors.initials: JK
authors.lastname: Altman
authors.forename: Antonella
authors.initials: A
authors.lastname: Sassano
authors.forename: Surinder
authors.initials: S
authors.lastname: Kaur
authors.forename: Heather
authors.initials: H
authors.lastname: Glaser
authors.forename: Barbara
authors.initials: B
authors.lastname: Kroczynska
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Redig
authors.forename: Suzanne
authors.initials: S
authors.lastname: Russo
authors.forename: Sharon
authors.initials: S
authors.lastname: Barr
authors.forename: Leonidas C
authors.initials: LC
authors.lastname: Platanias
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011506:Proteins / Q000037:antagonists & inhibitors*; D016601:RNA-Binding Proteins / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000037:antagonists & inhibitors*; D020298:U937 Cells
chemical_list: D000903:Antibiotics, Antineoplastic; D051017:Apoptosis Regulatory Proteins; C493245:CRTC2 protein, human; D046912:Multiprotein Complexes; C114487:PDCD4 protein, human; D011506:Proteins; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D019938:Cyclin D1; D000076222:Mechanistic Target of Rapamycin Complex 1; D051058:Oncogene Protein v-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus