The FLT3 internal tandem duplication mutation prevents apoptosis in interleukin-3-deprived BaF3 cells due to protein kinase A and ribosomal S6 kinase 1-mediated BAD phosphorylation at serine 112.
Internal tandem duplication (ITD) mutations in the FLT3 tyrosine kinase have been detected in approximately 20% of acute myeloid leukemia (AML) patients. Patients harboring FLT3/ITD mutations have a relatively poor prognosis. FLT3/ITD results in constitutive autophosphorylation of the receptor and factor-independent survival. Previous studies have shown that FLT3/ITD activates the signal transducers and activators of transcription 5 (STAT5), p42/p44 mitogen-activated protein kinase [MAPK; extracellular signal-regulated kinase (ERK) 1/2], and phosphatidylinositol 3-kinase/Akt pathways. We herein provide biochemical and biological evidence that ribosomal S6 kinase 1 (RSK1) and protein kinase A (PKA) are the two principal kinases that mediate the antiapoptotic function of FLT3/ITD via phosphorylation of BAD at Ser112. Inhibiting both MAPK kinase (MEK)/ERK and PKA pathways by a combination of U0126 (10 micromol/L) and H-89 (5 micromol/L) reduced most of BAD phosphorylation at Ser112 and induced apoptosis to a level comparable with that induced by FLT3 inhibitor AG1296 (5 micromol/L) in BaF3/FLT3/ITD cells. RNA interference of RSK1 or PKA catalytic subunit reduced BAD phosphorylation and induced apoptosis. The MEK inhibitor U0126 and/or the PKA inhibitor H-89 greatly enhanced the efficacy of the FLT3 inhibitor AG1296, suggesting that combining FLT3/ITD downstream pathway inhibition with FLT3 inhibitors may be a viable therapeutic strategy for AML caused by a FLT3/ITD mutation.
Yang
Xinping
X
Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
Liu
Liyun
L
Sternberg
David
D
Tang
Liren
L
Galinsky
Ilene
I
DeAngelo
Daniel
D
Stone
Richard
R
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002070:Butadienes / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004357:Drug Synergism; D004789:Enzyme Activation; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D007377:Interleukin-3 / Q000172:deficiency* / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D034622:RNA Interference; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology; D020080:Tandem Repeat Sequences / Q000235:genetics; D020032:Tyrphostins / Q000494:pharmacology; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D051941:fms-Like Tyrosine Kinase 3
C494820:Bad protein, mouse; C494812:Bcl2l1 protein, mouse; D002070:Butadienes; D002352:Carrier Proteins; D007377:Interleukin-3; D007546:Isoquinolines; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; D020032:Tyrphostins; C113580:U 0126; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; C106250:6,7-dimethoxy-3-phenylquinoxaline; D012694:Serine; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C512964:Rps6ka1 protein, mouse; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide