FLT3 expressing leukemias are selectively sensitive to inhibitors of the molecular chaperone heat shock protein 90 through destabilization of signal transduction-associated kinases.
OBJECTIVE
We conducted studies to evaluate the hypothesis that FLT3 is a client of heat shock protein (Hsp) 90 and inhibitors of Hsp90 may be useful for therapy of leukemia.


METHODS
The effects of the Hsp90-inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) on cell growth, expression of signal transduction kinases, apoptosis, FLT3 phosphorylation and interaction with Hsp90 was determined in FLT3(+) human leukemias.


RESULTS
We found that FLT3 is included in a multiprotein complex that includes Hsp90 and p23. 17-AAG inhibited FLT3 phosphorylation and interaction with Hsp90. FLT3(+) leukemias were significantly more sensitive to the Hsp90 inhibitors 17-AAG and Herbimycin A in cell growth assays than FLT3-negative leukemias. Cells transfected with FLT3 became sensitive to 17-AAG. Cell cycle inhibition and apoptosis were induced by 17-AAG. Cells with constitutive expression of FLT3, as a result of internal tandem duplication, were the most sensitive; cells with wild-type FLT3 were intermediate in sensitivity, and FLT3-negative cells were the least sensitive. 17-AAG resulted in reduced cellular mass of FLT3, RAF, and AKT. The mass of another Hsp, Hsp70, was increased. The expression level of MLL-AF4 fusion protein was not reduced by 17-AAG in human leukemia cells.


CONCLUSIONS
FLT3(+) leukemias are sensitive to 17-AAG and Herbimycin A. 17-AAG inhibits leukemia cells with either FLT3-internal tandem duplication or wild-type FLT3, in part through destabilization of client kinases including FLT3, RAF, and AKT. 17-AAG is potentially useful for therapy of FLT3-expressing leukemias, including the mixed lineage leukemia fusion gene leukemias.
Yao
Qing
Q
University of Minnesota Cancer Center, Minneapolis, Minnesota 55455, USA.
Nishiuchi
Ritsuo
R
Li
Quanzhi
Q
Kumar
Ashish R
AR
Hudson
Wendy A
WA
Kersey
John H
JH
D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones; D002453:Cell Cycle / Q000187:drug effects; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability / Q000187:drug effects*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000378:metabolism; D047029:Lactams, Macrocyclic; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors / Q000737:chemistry; D051788:Myeloid-Lymphoid Leukemia Protein; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D016133:Polymerase Chain Reaction; D011233:Precipitin Tests; D000071876:Prostaglandin-E Synthases; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017828:Rifabutin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D051941:fms-Like Tyrosine Kinase 3
D016227:Benzoquinones; D004791:Enzyme Inhibitors; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; C113855:MLL-AF4 fusion protein, human; C474558:MLL-AF9 fusion protein, human; D018832:Molecular Chaperones; D015514:Oncogene Proteins, Fusion; D011518:Proto-Oncogene Proteins; D051788:Myeloid-Lymphoid Leukemia Protein; D017828:Rifabutin; C112765:tanespimycin; C497970:FLT3 protein, human; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019908:Proto-Oncogene Proteins c-raf; D019746:Intramolecular Oxidoreductases; D000071876:Prostaglandin-E Synthases