Pharmacological Inhibitors of the Mitogen-activated Protein Kinase (MAPK) Kinase/MAPK Cascade Interact Synergistically with UCN-01 to Induce Mitochondrial Dysfunction and Apoptosis in Human Leukemia Cells

Division of Hematology/Oncology, Medical College of Virginia, Richmond, Virginia 23298, USA.
Cancer Research (Impact Factor: 9.33). 08/2001; 61(13):5106-15.
Source: PubMed

ABSTRACT Interactions between the checkpoint abrogator UCN-01 and several pharmacological inhibitors of the mitogen-activated protein kinase (MAPK) kinase (MEK)/MAPK pathway have been examined in a variety of human leukemia cell lines. Exposure of U937 monocytic leukemia cells to a marginally toxic concentration of UCN-01 (e.g., 150 nM) for 18 h resulted in phosphorylation/activation of p42/44 MAPK. Coadministration of the MEK inhibitor PD184352 (10 microM) blocked UCN-01-induced MAPK activation and was accompanied by marked mitochondrial damage (e.g., cytochrome c release and loss of DeltaPsi(m)), caspase activation, DNA fragmentation, and apoptosis. Similar interactions were noted in the case of other MEK inhibitors (e.g., PD98059; U0126) as well as in multiple other leukemia cell types (e.g., HL-60, Jurkat, CCRF-CEM, and Raji). Coadministration of PD184352 and UCN-01 resulted in reduced binding of the cdc25C phosphatase to 14-3-3 proteins, enhanced dephosphorylation/activation of p34(cdc2), and diminished phosphorylation of cyclic AMP-responsive element binding protein. The ability of UCN-01, when combined with PD184352, to antagonize cdc25C/14-3-3 protein binding, promote dephosphorylation of p34(cdc2), and potentiate apoptosis was mimicked by the ataxia telangectasia mutation inhibitor caffeine. In contrast, cotreatment of cells with UCN-01 and PD184352 did not substantially increase c-Jun-NH(2)-terminal kinase activation nor did it alter expression of Bcl-2, Bcl-x(L), Bax, or X-inhibitor of apoptosis. However, coexposure of U937 cells to UCN-01 and PD184352 induced a marked increase in p38 MAPK activation. Moreover, SB203580, which inhibits multiple kinases including p38 MAPK, partially antagonized cell death. Lastly, although UCN-01 +/- PD184352 did not induce p21(CIP1), stable expression of a p21(CIP1) antisense construct significantly increased susceptibility to this drug combination. Together, these findings indicate that exposure of leukemic cells to UCN-01 leads to activation of the MAPK cascade and that interruption of this process by MEK inhibition triggers perturbations in several signaling and cell cycle regulatory pathways that culminate in mitochondrial injury, caspase activation, and apoptosis. They also raise the possibility that disrupting multiple signaling pathways, e.g., by combining UCN-01 with MEK inhibitors, may represent a novel antileukemic strategy.

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Available from: Yun Dai, Oct 08, 2014
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    • "Flavopiridol causes an inhibition of the cell cycle in G1 or G2, based on the inhibition of CDK [4]. Other studies have shown that leukemic cells are particularly sensitive when survival pathway inhibitors are combined with mitotic inhibitors [9]. Moreover, combination of bortezomib with mitotic inhibitors (such as paclitaxel) are currently in clinical trials for the treatment of non-small-cell lung carcinoma (NSCLC) and other solid tumors [10]. "
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    PLoS ONE 10/2013; 8(10):e77390. DOI:10.1371/journal.pone.0077390 · 3.23 Impact Factor
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    • "To test whether RA bypassed this requirement, we used three pharmacological inhibitors (Figure 4). SU5402 inhibits the FGF receptor tyrosine kinase [18]; PD184352 and PD0325901 are both able to block MEK1/2, upstream of ERK1/2 [19,20]. All of these inhibitors are able to block neural specification of ESCs [7,21,22]. "
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    BMC Cell Biology 08/2009; 10(1):57. DOI:10.1186/1471-2121-10-57 · 2.34 Impact Factor
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    • "Even more intriguing is the ability of MEK inhibitors to synergistically induce apoptosis in leukemic cells when combined with an array of different signal transduction inhibitors and/or apoptosis modulators. Among these, 7-hydroxystaurosporine (UCN-01), a PKC/Chk1 inhibitor endowed with potent pro-apoptotic activity, particularly in haematopoietic cells, has been recently shown to result in the activation of the MEK/ERK MAPK module, when used at marginally toxic concentrations (Dai et al., 2001); under these conditions, simultaneous MEK blockade by different inhibitors, such as CI-1040, PD98059, and U0126 synergistically triggered mitochondrial damage, caspase activation, DNA fragmentation, and apoptosis in multiple lymphoid and myeloid cell lines and in drug-sensitive and – resistant myeloma cell lines and primary samples (Dai et al., 2001; Dai et al., 2002), suggesting that this combination strategy could have a broad applicability in haematological malignancies. At a molecular level, MAPK activation by UCN-01 is partly dependent on Chk1 activity, while the pro-apoptotic effect of combined UCN-01 and MEK inhibitors appears to require both Chk1 inhibition and cdc2 activation (Pei et al., 2006). "
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