title: Synergistic interactions between DMAG and mitogen-activated protein kinase kinase 1/2 inhibitors in Bcr/abl+ leukemia cells sensitive and resistant to imatinib mesylate.
abstract: OBJECTIVE
  To characterize interactions between the heat shock protein 90 antagonist 17-dimethylaminoethylamino-17-demethoxygeldanamycin (DMAG) and the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase 1/2 inhibitor PD184352 in Bcr/abl(+) leukemia cells sensitive and resistant to imatinib mesylate.
  
  
  METHODS
  K562 and LAMA 84 cells were exposed to varying concentrations of DMAG and PD184352 for 48 hours; after which, mitochondrial integrity, caspase activation, and apoptosis were monitored. Parallel studies were done in imatinib mesylate-resistant cells, including BaF3 cells transfected with plasmids encoding clinically relevant Bcr/abl mutations conferring imatinib mesylate resistance (e.g., E255K, M351T, and T315I) and primary CD34(+) bone marrow cells from patients refractory to imatinib mesylate.
  
  
  RESULTS
  Cotreatment of Bcr/abl(+) cells with minimally toxic concentrations of DMAG and PD184352 resulted in synergistic induction of mitochondrial injury (cytochrome c release and Bax conformational change), events associated with the pronounced and sustained inactivation of ERK1/2 accompanied by down-regulation of Bcl-x(L). Conversely, cells ectopically expressing Bcl-x(L) displayed significant protection against PD184352/DMAG-mediated lethality. This regimen effectively induced apoptosis in K562 cells overexpressing Bcr/abl, in BaF3 cells expressing various clinically relevant Bcr/abl mutations, and in primary CD34(+) cells from patients resistant to imatinib mesylate, but was relatively sparing of normal CD34(+) bone marrow cells.
  
  
  CONCLUSIONS
  A regimen combining the heat shock protein 90 antagonist DMAG and the mitogen-activated protein kinase/ERK kinase 1/2 inhibitor potently induces apoptosis in Bcr/abl(+) cells, including those resistant to imatinib mesylate through various mechanisms including Bcr/abl kinase mutations, through a process that may involve sustained ERK1/2 inactivation and Bcl-x(L) down-regulation. This strategy warrants further attention in Bcr/abl(+) hematopoietic malignancies, particularly those resistant to Bcr/abl kinase inhibitors.
authors.affiliation: Department of Medicine, Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia, USA.
authors.forename: Tri K
authors.initials: TK
authors.lastname: Nguyen
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
authors.forename: Lora
authors.initials: L
authors.lastname: Kramer
authors.forename: Amie S
authors.initials: AS
authors.lastname: Corbin
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Druker
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000494:pharmacology*; D016227:Benzoquinones; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016044:Fusion Proteins, bcr-abl / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D047029:Lactams, Macrocyclic; D007938:Leukemia / Q000188:drug therapy* / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D011809:Quinones / Q000494:pharmacology*; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology; D012680:Sensitivity and Specificity; D013329:Structure-Activity Relationship; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D000970:Antineoplastic Agents; D001549:Benzamides; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D010879:Piperazines; D011743:Pyrimidines; D011809:Quinones; C448659:17-(dimethylaminoethylamino)-17-demethoxygeldanamycin; D017828:Rifabutin; C112765:tanespimycin; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl