Sequence-Dependent Potentiation of Paclitaxel-Mediated Apoptosis in Human Leukemia Cells by Inhibitors of the Mitogen-Activated Protein Kinase Kinase/Mitogen-Activated Protein Kinase Pathway

2001 ◽  
Vol 60 (1) ◽  
pp. 143-154 ◽  
Author(s):  
Chunrong Yu ◽  
Shujie Wang ◽  
Paul Dent ◽  
Steven Grant
Keyword(s):  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Human Leukemia Cells ◽  
Sequence Dependent ◽  
Mitogen Activated Protein ◽  
Kinase Pathway ◽  
Protein Kinase Kinase

Bortezomib and flavopiridol interact synergistically to induce apoptosis in chronic myeloid leukemia cells resistant to imatinib mesylate through both Bcr/Abl-dependent and -independent mechanisms

Blood ◽  
2004 ◽  
Vol 104 (2) ◽  
pp. 509-518 ◽  
Author(s):  
Yun Dai ◽  
Mohamed Rahmani ◽  
Xin-Yan Pei ◽  
Paul Dent ◽  
Steven Grant
Keyword(s):  
Protein Kinase ◽  
Imatinib Mesylate ◽  
Myelogenous Leukemia ◽  
Mitogen Activated Protein Kinase ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Down Regulation ◽  
Human Leukemia Cells ◽  
Mitogen Activated Protein ◽  
Induced Apoptosis

Abstract Interactions between the cyclin-dependent kinase (CDK) inhibitor flavopiridol and the proteasome inhibitor bortezomib were examined in Bcr/Abl+ human leukemia cells. Coexposure of K562 or LAMA84 cells to subtoxic concentration of flavopiridol (150-200 nM) and bortezomib (5-8 nM) resulted in a synergistic increase in mitochondrial dysfunction and apoptosis. These events were associated with a marked diminution in nuclear factor κB (NF-κB)/DNA binding activity; enhanced phosphorylation of SEK1/MKK4 (stress-activated protein kinase/extracellular signal-related kinase 1/mitogen-activated protein kinase kinase 4), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK); down-regulation of Bcr/Abl; and a marked reduction in signal transducer and activator of transcription 3 (STAT3) and STAT5 activity. In imatinib mesylate-resistant K562 cells displaying increased Bcr/Abl expression, bortezomib/flavopiridol treatment markedly increased apoptosis in association with down-regulation of Bcr/Abl and BclxL, and diminished phosphorylation of Lyn, Hck, CrkL, and Akt. Parallel studies were performed in imatinib mesylate-resistant LAMA84 cells exhibiting reduced expression of Bcr/Abl but a marked increase in expression/activation of Lyn and Hck. Flavopiridol/bortezomib effectively induced apoptosis in these cells in association with Lyn and Hck inactivation. The capacity of flavopiridol to promote bortezomib-mediated Bcr/Abl down-regulation and apoptosis was mimicked by the positive transcription elongation factor-b (P-TEFb) inhibitor DRB (5,6-dichloro 1-β-d-ribofuranosylbenzinida-sole). Finally, the bortezomib/flavopiridol regimen also potently induced apoptosis in Bcr/Abl- human leukemia cells. Collectively, these findings suggest that a strategy combining flavopiridol and bortezomib warrants further examination in chronic myelogenous leukemia and related hematologic malignancies. (Blood. 2004;104:509-518)

Synergistic antileukemic interactions between 17-AAG and UCN-01 involve interruption of RAF/MEK- and AKT-related pathways

Blood ◽  
2003 ◽  
Vol 102 (5) ◽  
pp. 1824-1832 ◽  
Author(s):  
Wentao Jia ◽  
Chunrong Yu ◽  
Mohamed Rahmani ◽  
Geoffrey Krystal ◽  
Edward A. Sausville ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Leukemia Cell ◽  
Cell Types ◽  
Mitogen Activated Protein Kinase ◽  
Leukemia Cells ◽  
Human Leukemia ◽  
Pronounced Increase ◽  
Akt Activation ◽  
Human Leukemia Cell ◽  
Human Leukemia Cells

Abstract Interactions between the protein kinase C (PKC) and Chk1 inhibitor UCN-01 and the heat shock protein 90 (Hsp90) antagonist 17-AAG have been examined in human leukemia cells in relation to effects on signal transduction pathways and apoptosis. Simultaneous exposure (30 hours) of U937 monocytic leukemia cells to minimally toxic concentrations of 17-AAG (eg, 400 nM) and UCN-01 (eg, 75 nM) triggered a pronounced increase in mitochondrial injury (ie, loss of mitochondrial membrane potential [Δψm]; cytosolic release of cytochrome c), caspase activation, and apoptosis. Synergistic induction of apoptosis was also observed in other human leukemia cell types (eg, Jurkat, NB4). Coexposure of human leukemia cells to 17-AAG and the PKC inhibitor bisindolylmaleimide (GFX) did not result in enhanced lethality, arguing against the possibility that the PKC inhibitory actions of UCN-01 are responsible for synergistic interactions. The enhanced cytotoxicity of this combination was associated with diminished Akt activation and marked down-regulation of Raf-1, MEK1/2, and mitogen-activated protein kinase (MAPK). Coadministration of 17-AAG and UCN-01 did not modify expression of Hsp90, Hsp27, phospho-JNK, or phospho-p38 MAPK, but was associated with further p34cdc2 dephosphorylation and diminished expression of Bcl-2, Mcl-1, and XIAP. In addition, inducible expression of both a constitutively active MEK1/2 or myristolated Akt construct, which overcame inhibition of ERK and Akt activation, respectively, significantly attenuated 17-AAG/UCN-01–mediated lethality. Together, these findings indicate that the Hsp90 antagonist 17-AAG potentiates UCN-01 cytotoxicity in a variety of human leukemia cell types and suggest that interference with both the Akt and Raf-1/MEK/MAP kinase cytoprotective signaling pathways contribute to this phenomenon.

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