title: Co-administration of the mTORC1/TORC2 inhibitor INK128 and the Bcl-2/Bcl-xL antagonist ABT-737 kills human myeloid leukemia cells through Mcl-1 down-regulation and AKT inactivation.
abstract: Effects of concurrent inhibition of mTORC1/2 and Bcl-2/Bcl-xL in human acute myeloid leukemia cells were examined. Tetracycline-inducible Bcl-2/Bcl-xL dual knockdown markedly sensitized acute myeloid leukemia cells to the dual TORC1/2 inhibitor INK128 in vitro as well as in vivo. Moreover, INK128 co-administered with the Bcl-2/xL antagonist ABT-737 sharply induced cell death in multiple acute myeloid leukemia cell lines, including TKI-resistant FLT3-ITD mutants and primary acute myeloid leukemia blasts carrying various genetic aberrations e.g., FLT3, IDH2, NPM1, and Kras, while exerting minimal toxicity toward normal hematopoietic CD34(+) cells. Combined treatment was particularly active against CD34(+)/CD38(-)/CD123(+) primitive leukemic progenitor cells. The INK128/ABT-737 regimen was also effective in the presence of a protective stromal microenvironment. Notably, INK128 was more potent than the TORC1 inhibitor rapamycin in down-regulating Mcl-1, diminishing AKT and 4EBP1 phosphorylation, and potentiating ABT-737 activity. Mcl-1 ectopic expression dramatically attenuated INK128/ABT-737 lethality, indicating an important functional role for Mcl-1 down-regulation in INK128/ABT-737 actions. Immunoprecipitation analysis revealed that combined treatment markedly diminished Bax, Bak, and Bim binding to all major anti-apoptotic Bcl-2 members (Bcl-2/Bcl-xL/Mcl-1), while Bax/Bak knockdown reduced cell death. Finally, INK128/ABT-737 co-administration sharply attenuated leukemia growth and significantly prolonged survival in a systemic acute myeloid leukemia xenograft model. Analysis of subcutaneous acute myeloid leukemia-derived tumors revealed significant decrease in 4EBP1 phosphorylation and Mcl-1 protein level, consistent with results obtained in vitro. These findings demonstrate that co-administration of dual mTORC1/mTORC2 inhibitors and BH3-mimetics exhibits potent anti-leukemic activity in vitro and in vivo, arguing that this strategy warrants attention in acute myeloid leukemia.
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Mandy Mayo
authors.initials: MM
authors.lastname: Aust
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Elisa
authors.initials: E
authors.lastname: Hawkins
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Parker
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Masey
authors.initials: M
authors.lastname: Ross
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Maciej
authors.initials: M
authors.lastname: Kmieciak
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Leonid Borisovich
authors.initials: LB
authors.lastname: Reshko
authors.affiliation: Department of Pathology, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Rizzo
authors.affiliation: Department of Pathology, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Catherine I
authors.initials: CI
authors.lastname: Dumur
authors.affiliation: Department of Pathology, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ferreira-Gonzalez
authors.affiliation: Department of Medicine, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA Department of Biochemistry, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA Department of Pharmacology, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA Department of Human and Molecular Genetics, Virginia Commonwealth University, the Virginia Institute for Molecular Medicine, and the Massey Cancer Center, Richmond, VA, USA stgrant@vcu.edu.
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D000818:Animals; D001583:Benzoxazoles / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein / Q000378:metabolism*; D009596:Nitrophenols / Q000494:pharmacology*; D000090243:Nucleophosmin; D010879:Piperazines / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020298:U937 Cells; D023041:Xenograft Model Antitumor Assays; D051020:bcl-X Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000225:Adenine / Q000031:analogs & derivatives
chemical_list: D001583:Benzoxazoles; D001713:Biphenyl Compounds; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; D000090243:Nucleophosmin; D010879:Piperazines; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D011743:Pyrimidines; D013449:Sulfonamides; D058570:TOR Serine-Threonine Kinases; D051020:bcl-X Protein; C501332:ABT-737; C000595707:BCL2 protein, human; C494811:BCL2L1 protein, human; C579095:MCL1 protein, human; C000716967:NPM1 protein, human; C000715570:Npm1 protein, mouse; C572449:sapanisertib; D000225:Adenine