title: Simultaneous activation of p53 and inhibition of XIAP enhance the activation of apoptosis signaling pathways in AML.
abstract: Activation of p53 by murine double minute (MDM2) antagonist nutlin-3a or inhibition of X-linked inhibitor of apoptosis (XIAP) induces apoptosis in acute myeloid leukemia (AML) cells. We demonstrate that concomitant inhibition of MDM2 by nutlin-3a and of XIAP by small molecule antagonists synergistically induced apoptosis in p53 wild-type OCI-AML3 and Molm13 cells. Knockdown of p53 by shRNA blunted the synergy, and down-regulation of XIAP by antisense oligonucleotide (ASO) enhanced nutlin-3a-induced apoptosis, suggesting that the synergy was mediated by p53 activation and XIAP inhibition. This is supported by data showing that inhibition of both MDM2 and XIAP by their respective ASOs induced significantly more cell death than either ASO alone. Importantly, p53 activation and XIAP inhibition enhanced apoptosis in blasts from patients with primary AML, even when the cells were protected by stromal cells. Mechanistic studies demonstrated that XIAP inhibition potentiates p53-induced apoptosis by decreasing p53-induced p21 and that p53 activation enhances XIAP inhibition-induced cell death by promoting mitochondrial release of second mitochondria-derived activator of caspases (SMAC) and by inducing the expression of caspase-6. Because both XIAP and p53 are presently being targeted in ongoing clinical trials in leukemia, the combination strategy holds promise for expedited translation into the clinic.
authors.affiliation: Department of Stem Cell Transplantation and Cellular Therapy, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Bing Z
authors.initials: BZ
authors.lastname: Carter
authors.forename: Duncan H
authors.initials: DH
authors.lastname: Mak
authors.forename: Wendy D
authors.initials: WD
authors.lastname: Schober
authors.forename: Erich
authors.initials: E
authors.lastname: Koller
authors.forename: Clemencia
authors.initials: C
authors.lastname: Pinilla
authors.forename: Lyubomir T
authors.initials: LT
authors.lastname: Vassilev
authors.forename: John C
authors.initials: JC
authors.lastname: Reed
authors.forename: Michael
authors.initials: M
authors.lastname: Andreeff
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001752:Blast Crisis / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D053178:Caspase 6 / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects / Q000235:genetics; D055785:Gene Knockdown Techniques; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D017154:Stromal Cells / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; C412403:DIABLO protein, human; C499605:Diablo protein, mouse; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D010879:Piperazines; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; C482205:nutlin 3; C497206:MDM2 protein, human; C497207:Mdm2 protein, mouse; D051736:Proto-Oncogene Proteins c-mdm2; C505514:CASP6 protein, human; C505516:Casp6 protein, mouse; D053178:Caspase 6