title: Synergistic targeting of AML stem/progenitor cells with IAP antagonist birinapant and demethylating agents.
abstract: BACKGROUND
  Acute myeloid leukemia (AML) therapy has limited long-term efficacy because patients frequently develop disease relapse because of the inability of standard chemotherapeutic agents to target AML stem/progenitor cells. Here, we identify deregulated apoptotic components in AML stem/progenitor cells and investigate the individual and combinatorial effects of the novel inhibitor of apoptosis (IAP) protein antagonist and second mitochondrial-derived activator of caspases (SMAC) mimetic birinapant and demethylating epigenetic modulators.
  
  
  METHODS
  Protein expression was measured by reversed-phase protein array in AML patient (n = 511) and normal (n = 21) samples and by western blot in drug-treated cells. The antileukemic activity of birinapant and demethylating agents was assessed in vitro and in an in vivo AML mouse xenograft model (n = 10 mice per group). All statistical tests were two-sided.
  
  
  RESULTS
  Compared with bulk AML cells, CD34(+)38(-) AML stem/progenitors expressed increased cIAP1 and caspase-8 levels and decreased SMAC levels (one-way analysis of variance followed by Tukey's multiple comparison test, P < .001). Birinapant induced death receptor-/caspase-8-mediated apoptosis in AML cells, including in AML stem/progenitor cells, but not in normal CD34(+) cells. Demethylating agents modulated extrinsic apoptosis pathway components and, when combined with birinapant, were highly synergistic in vitro (combination index < 1), and also more effective in vivo (P < .001, by Student t test, for the median survival of birinapant plus 5-azacytadine vs birinapant alone or vs controls).
  
  
  CONCLUSIONS
  cIAP1, SMAC, and caspase-8 appear to play a role in AML stem cell survival, and synergistic targeting of these cells with birinapant and demethylating agents shows potential utility in leukemia therapy.
authors: Affiliations of authors: Section of Molecular Hematology and Therapy, Department of Leukemia (BZC, PYM, DHM, YS, YQ, HM, ROJ, TM, SMK, MA) and Department of Bioinformatics and Computational Biology (HY, KRC), University of Texas M.D. Anderson Cancer Center, Houston, TX; Division of Hematology and Oncology, Mayo Clinic, Scottsdale, AZ (JMB, RT).
authors: Bing Z
authors: BZ
authors: Carter
authors: Po Yee
authors: PY
authors: Mak
authors: Duncan H
authors: DH
authors: Mak
authors: Yuexi
authors: Y
authors: Shi
authors: Yihua
authors: Y
authors: Qiu
authors: James M
authors: JM
authors: Bogenberger
authors: Hong
authors: H
authors: Mu
authors: Raoul
authors: R
authors: Tibes
authors: Hui
authors: H
authors: Yao
authors: Kevin R
authors: KR
authors: Coombes
authors: Rodrigo O
authors: RO
authors: Jacamo
authors: Teresa
authors: T
authors: McQueen
authors: Steven M
authors: SM
authors: Kornblau
authors: Michael
authors: M
authors: Andreeff
mesh_terms: D000328:Adult; D000368:Aged; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology / Q000627:therapeutic use*; D051017:Apoptosis Regulatory Proteins; D001374:Azacitidine / Q000008:administration & dosage; D015153:Blotting, Western; D053181:Caspase 8 / Q000378:metabolism*; D019175:DNA Methylation / Q000187:drug effects*; D004151:Dipeptides / Q000008:administration & dosage; D004357:Drug Synergism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007211:Indoles / Q000008:administration & dosage; D051034:Inhibitor of Apoptosis Proteins / Q000037:antagonists & inhibitors*; D047908:Intracellular Signaling Peptides and Proteins / Q000819:agonists / Q000378:metabolism*; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D024101:Mitochondrial Proteins / Q000819:agonists / Q000378:metabolism*; D014411:Neoplastic Stem Cells; D040081:Protein Array Analysis
chemical_list: D000964:Antimetabolites, Antineoplastic; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D004151:Dipeptides; D007211:Indoles; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; C582429:birinapant; D053181:Caspase 8; D001374:Azacitidine