Constitutive c-jun N-terminal kinase activity in acute myeloid leukemia derives from Flt3 and affects survival and proliferation.
OBJECTIVE
c-jun N-terminal kinase (JNK) has been implicated in proliferation and survival downstream from the tyrosine kinase oncogene, p210 BCR-ABL, in chronic myeloid leukemia. We studied whether a similar relationship between JNK and FMS-like tyrosine kinase 3 (Flt3) describes acute myeloid leukemia (AML).


METHODS
By immunoprecipitation, Flt3 was found to be activated and identified as the potential origin of JNK activity in a heavy majority of JNK+ve AML blasts tested. Often, Flt3 activity is associated with activating mutation of the gene locus. However, statistical linkage tied JNK activity with Flt3 expression levels rather than with mutation. An adaptor network to describe the signal cascade Flt3-to-JNK was uncovered.


RESULTS
Active Flt3 was linked to p85 phosphoinositide-3 (PI-3) kinase, and p85 with cbl and CrkII/CrkL by co-immunoprecipitaton assays from lysates of model cell lines and primary AML blasts. JNK1 co-immunoprecipitated from such lysates with p85-cbl-crkII/L and bound to Crk species SH3 domain in pull-down assay. siRNA-mediated depletion of Flt3 or of cbl, the adaptor at the nexus of this signaling group, inhibited JNK activity on substrate c-jun. Within AML blast cells influenced by Flt3 signaling, selective inhibition of JNK by a small molecule inhibitor, led to proliferative inhibition, apoptosis, and sensitizing cells to the anthracycline, daunorubicin. These effects occurred upon JNK inhibition without off-target inhibition of extracellular signal-regulated kinase or AKT pathways, and p38-kinase activation, an effector in the p53/p14 arf tumor suppressor pathway, was also maintained or augmented.


CONCLUSIONS
JNK is a bonafide signaling pathway from Flt3 in AML whose function for proliferation and survival is required in a significant AML cohort with active Flt3 signaling, by mutation or overexpression of Flt3.
Hartman
Amy D
AD
Walther Cancer Institute, Indianapolis, IN 46202, USA.
Wilson-Weekes
Annique
A
Suvannasankha
Attaya
A
Burgess
Gem S
GS
Phillips
Carissa A
CA
Hincher
Katie J
KJ
Cripe
Larry D
LD
Boswell
H Scott
HS
D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000235:genetics; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects / Q000235:genetics; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000201:enzymology* / Q000235:genetics; D048055:Mitogen-Activated Protein Kinase 8 / Q000378:metabolism*; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000378:metabolism; D040641:Quantitative Trait Loci / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D025803:Tumor Suppressor Protein p14ARF / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics / Q000378:metabolism*
D034741:RNA, Small Interfering; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D050721:Proto-Oncogene Proteins c-cbl; D019869:Phosphatidylinositol 3-Kinases; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3; D016044:Fusion Proteins, bcr-abl; D048055:Mitogen-Activated Protein Kinase 8; C067419:CBL protein, human