The hierarchical relationship between MAPK signaling and ROS generation in human leukemia cells undergoing apoptosis in response to the proteasome inhibitor Bortezomib

Exp Cell Res. 2004 May 1;295(2):555-66. doi: 10.1016/j.yexcr.2004.02.001.


The hierarchy of events accompanying induction of apoptosis by the proteasome inhibitor Bortezomib was investigated in Jurkat lymphoblastic and U937 myelomonocytic leukemia cells. Treatment of Jurkat or U937 cells with Bortezomib resulted in activation of c-Jun-N-terminal kinase (JNK) and p38 MAPK (mitogen-activated protein kinase), inactivation of extracellular signal-regulating kinase 1/2 (ERK1/2), cytochrome c release, caspase-9, -3, and -8 activation, and apoptosis. Bortezomib-mediated cytochrome c release and caspase activation were blocked by the pharmacologic JNK inhibitor SP600125, but lethality was not diminished by the p38 MAPK inhibitor SB203580. Inducible expression of a constitutively active MEK1 construct blocked Bortezomib-mediated ERK1/2 inactivation, significantly attenuated Bortezomib lethality, and unexpectedly prevented JNK activation. Conversely, pharmacologic MEK/ERK1/2 inhibition promoted Bortezomib-mediated JNK activation and apoptosis. Lastly, the antioxidant N-acetyl-l-cysteine (LNAC) attenuated Bortezomib-mediated reactive oxygen species (ROS) generation, ERK inactivation, JNK activation, mitochondrial dysfunction, and apoptosis. In contrast, enforced MEK1 and ERK1/2 activation or JNK inhibition did not modify Bortezomib-induced ROS production. Together, these findings suggest that in human leukemia cells, Bortezomib-induced oxidative injury operates at a proximal point in the cell death cascade to antagonize cytoprotective ERK1/2 signaling, promote activation of the stress-related JNK pathway, and to trigger mitochondrial dysfunction, caspase activation, and apoptosis. They also suggest the presence of a feedback loop wherein Bortezomib-mediated ERK1/2 inactivation contributes to JNK activation, thereby amplifying the cell death process.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anthracenes / pharmacology
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects*
  • Boronic Acids / pharmacology*
  • Bortezomib
  • Caspases / drug effects
  • Caspases / metabolism
  • Cytochromes c / drug effects
  • Cytochromes c / metabolism
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Imidazoles / pharmacology
  • JNK Mitogen-Activated Protein Kinases
  • Jurkat Cells
  • Leukemia / drug therapy*
  • Leukemia / enzymology
  • Leukemia / pathology
  • MAP Kinase Signaling System
  • Membrane Potentials / drug effects
  • Mitochondria / drug effects
  • Mitogen-Activated Protein Kinase Kinases / metabolism*
  • Mitogen-Activated Protein Kinases / drug effects
  • Mitogen-Activated Protein Kinases / metabolism
  • Models, Biological
  • Protease Inhibitors / pharmacology
  • Pyrazines / pharmacology*
  • Pyridines / pharmacology
  • Reactive Oxygen Species / metabolism*
  • Signal Transduction / drug effects*
  • U937 Cells


  • Anthracenes
  • Antineoplastic Agents
  • Boronic Acids
  • Enzyme Inhibitors
  • Imidazoles
  • Protease Inhibitors
  • Pyrazines
  • Pyridines
  • Reactive Oxygen Species
  • pyrazolanthrone
  • Bortezomib
  • Cytochromes c
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinase Kinases
  • Caspases
  • SB 203580