title: Pharmacologic mitogen-activated protein/extracellular signal-regulated kinase kinase/mitogen-activated protein kinase inhibitors interact synergistically with STI571 to induce apoptosis in Bcr/Abl-expressing human leukemia cells.
abstract: Interactions between the kinase inhibitor STI571 and pharmacological antagonists of the mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) cascade have been examined in human myeloid leukemia cells (K562 and LAMA 84) that express the Bcr-Abl kinase. Exposure of K562 cells to concentrations of STI571 that minimally induced apoptosis (e.g., approximately 200 nM) resulted in early suppression (i.e., at 6 h) of p42/44 MAPK phosphorylation followed at later intervals (i.e., > or =24 h) by a marked increase in p42/44 MAPK phosphorylation/activation. Coadministration of a nontoxic concentration of the MEK1/2 inhibitor PD184352 (5 microM) prevented STI571-mediated activation of p42/44 MAPK. Cells exposed to STI571 in combination with PD184352 for 48 h demonstrated a very dramatic increase in mitochondrial dysfunction (e.g., loss of DeltaPsim and cytosolic cytochrome c release) associated with procaspase-3 activation, poly(ADP-ribose) polymerase cleavage, and the appearance of the characteristic morphological features of apoptosis. Similar results were obtained using other pharmacological MEK1/2 inhibitors (e.g., PD 98059 and U0126) as well as another leukemic cell line that expresses Bcr-Abl (e.g., LAMA 84). However, synergistic induction of apoptosis by STI571 and PD184352 was not observed in human myeloid leukemia cells that do not express the Bcr-Abl kinase (e.g., HL-60 and U937) nor in normal human peripheral blood mononuclear cells. Synergistic potentiation of STI571-mediated lethality by PD184352 was associated with multiple perturbations in signaling and apoptotic regulatory pathways, including caspase-dependent down-regulation of Bcr-Abl and Bcl-2; caspase-independent down-regulation of Bcl-x(L) and Mcl-1; activation of JNK, p38 MAPK, and p34(cdc2); and diminished phosphorylation of Stat5 and CREB. Significantly, coexposure to PD184352 strikingly increased the lethality of a pharmacologically achievable concentration of STI571 (i.e., 1-2 microM) in resistant K562 cells expressing marked increases in Bcr-Abl protein levels. Together, these findings raise the possibility that treatment of Bcr-Abl-expressing cells with STI571 elicits a cytoprotective MAPK activation response and that interruption of the latter pathway (e.g., by pharmacological MEK1/2 inhibitors) is associated with a highly synergistic induction of mitochondrial damage and apoptosis. They also indicate that in the case of Bcr-Abl-positive cells, simultaneous interruption of two signal transduction pathways may represent an effective antileukemic strategy.
authors.affiliation: Division of Hematology/Oncology, Medical College of Virginia, Richmond, Virginia 23298, USA.
authors.forename: Chunrong
authors.initials: C
authors.lastname: Yu
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Krystal
authors.forename: Lyuba
authors.initials: L
authors.lastname: Varticovksi
authors.forename: Robert
authors.initials: R
authors.lastname: McKinstry
authors.forename: Mohamed
authors.initials: M
authors.lastname: Rahmani
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D051697:Activating Transcription Factor 1; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001549:Benzamides / Q000494:pharmacology*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016044:Fusion Proteins, bcr-abl / Q000096:biosynthesis*; D016193:G1 Phase / Q000187:drug effects; D018922:HL-60 Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D006801:Humans; D000068877:Imatinib Mesylate; D048031:JNK Mitogen-Activated Protein Kinases; D020014:K562 Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D008894:Milk Proteins; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology*; D016192:Resting Phase, Cell Cycle / Q000187:drug effects; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors; D020298:U937 Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology
chemical_list: C120227:2-(2-chloro-4-iodophenylamino)-N-cyclopropylmethoxy-3,4-difluorobenzamide; D051697:Activating Transcription Factor 1; D000970:Antineoplastic Agents; D001549:Benzamides; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D008894:Milk Proteins; D010879:Piperazines; D011743:Pyrimidines; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D000068877:Imatinib Mesylate; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases