Farnesyltransferase inhibitors interact synergistically with the Chk1 inhibitor UCN-01 to induce apoptosis in human leukemia cells through interruption of both Akt and MEK/ERK pathways and activation of SEK1/JNK.

Abstract

Interactions between the Chk1 inhibitor UCN-01 and the farnesyltransferase inhibitor L744832 were examined in human leukemia cells. Combined exposure of U937 cells to subtoxic concentrations of UCN-01 and L744832 resulted in a dramatic increase in mitochondrial dysfunction, apoptosis, and loss of clonogenicity. Similar interactions were noted in other leukemia cells (HL-60, Raji, Jurkat) and primary acute myeloid leukemia (AML) blasts. Coadministration of L744832 blocked UCN-01-mediated phosphorylation of mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK), leading to down-regulation of phospho-cyclic adenosine monophosphate responsive element-binding protein (phospho-CREB) and -p90(RSK) and activation of p34(cdc2) and stress-activated protein kinase/ERK kinase/c-Jun N-terminal kinase (SEK/JNK). Combined treatment also resulted in pronounced reductions in levels of phospho-Akt, -glycogen synthase kinase-3 (-GSK-3), -p70(S6K), -mammalian target of rapamycin (-mTOR), -forkhead transcription factor (-FKHR), -caspase-9, and -Bad. Ectopic expression of Bcl-2 or Bcl-xL but not dominant-negative caspase-8 blocked UCN-01/L744832-mediated mitochondrial dysfunction and apoptosis but did not prevent activation of p34(cdc2) and JNK or inactivation of MEK/ERK and Akt. Enforced expression of myristoylated Akt but not constitutively active MEK significantly attenuated UCN-01/L744832-induced apoptosis. However, dual transfection with Akt and MEK resulted in further protection from UCN-01/L744832-mediated lethality. Finally, down-regulation of JNK1 by siRNA significantly reduced the lethality of the UCN-01/L744832 regimen. Together, these findings suggest that farnesyltransferase inhibitors interrupt the cytoprotective Akt and MAPK pathways while reciprocally activating SAPK/JNK in leukemia cells exposed to UCN-01 and, in so doing, dramatically increase mitochondria-dependent apoptosis.

• Authors: Yun Dai, Mohamed Rahmani, Xin-Yan Pei, Payal Khanna, Song Iy Han, Clint Mitchell, Paul Dent, Steven Grant
• Journal: Blood (Blood) Vol. 105 Issue 4 Pg. 1706-16 (Feb 15 2005) ISSN: 0006-4971 [Print] United States
• PMID: 15494423 (Publication Type: Journal Article, 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.)

Chemical References

• Enzyme Inhibitors
• L 744832
• Protein Kinase Inhibitors
• Proto-Oncogene Proteins
• 7-hydroxystaurosporine
• Methionine
• Alkyl and Aryl Transferases
• Farnesyltranstransferase
• Protein Kinases
• AKT1 protein, human
• CHEK1 protein, human
• Checkpoint Kinase 1
• Protein Serine-Threonine Kinases
• Proto-Oncogene Proteins c-akt
• Extracellular Signal-Regulated MAP Kinases
• JNK Mitogen-Activated Protein Kinases
• MAP Kinase Kinase 4
• Caspases
• Staurosporine

Topics

• Acute Disease
• Alkyl and Aryl Transferases (antagonists & inhibitors)
• Antineoplastic Combined Chemotherapy Protocols
• Apoptosis (drug effects)
• Caspases (metabolism)
• Cell Transformation, Neoplastic (drug effects)
• Checkpoint Kinase 1
• Dose-Response Relationship, Drug
• Drug Synergism
• Enzyme Activation (drug effects)
• Enzyme Inhibitors (metabolism)
• Extracellular Signal-Regulated MAP Kinases (antagonists & inhibitors)
• Farnesyltranstransferase
• HL-60 Cells
• Humans
• JNK Mitogen-Activated Protein Kinases (metabolism)
• Jurkat Cells
• Leukemia, Myeloid (drug therapy, enzymology, pathology)
• MAP Kinase Kinase 4 (metabolism)
• MAP Kinase Signaling System (drug effects)
• Membrane Potentials (drug effects)
• Methionine (analogs & derivatives, toxicity)
• Mitochondria (drug effects)
• Protein Kinase Inhibitors (metabolism)
• Protein Kinases (metabolism)
• Protein Serine-Threonine Kinases (antagonists & inhibitors)
• Proto-Oncogene Proteins (antagonists & inhibitors)
• Proto-Oncogene Proteins c-akt
• Staurosporine (analogs & derivatives, metabolism, toxicity)
• U937 Cells