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.
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.
Dai
Yun
Y
Department of Medicine, Virginia Commonwealth University/Medical College of Virginia, Richmond VA, 23298, USA.
Rahmani
Mohamed
M
Pei
Xin-Yan
XY
Khanna
Payal
P
Han
Song Iy
SI
Mitchell
Clint
C
Dent
Paul
P
Grant
Steven
S
D000208:Acute Disease; D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors*; D000971:Antineoplastic Combined Chemotherapy Protocols; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D000071877:Checkpoint Kinase 1; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors*; D051231:Farnesyltranstransferase; D018922:HL-60 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019169:Jurkat Cells; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D008715:Methionine / Q000031:analogs & derivatives* / Q000633:toxicity; D008928:Mitochondria / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors*; D051057:Proto-Oncogene Proteins c-akt; D019311:Staurosporine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000633:toxicity; D020298:U937 Cells
D004791:Enzyme Inhibitors; C096898:L 744832; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; C054852:7-hydroxystaurosporine; D008715:Methionine; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase; D011494:Protein Kinases; C494918:AKT1 protein, human; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020169:Caspases; D019311:Staurosporine