Pim-1 is up-regulated by constitutively activated FLT3 and plays a role in FLT3-mediated cell survival.
Constitutively activating internal tandem duplication (ITD) mutations of the receptor tyrosine kinase FLT3 (Fms-like tyrosine kinase 3) play an important role in leukemogenesis, and their presence is associated with poor prognosis in acute myeloid leukemia (AML). To better understand FLT3 signaling in leukemogenesis, we have examined the changes in gene expression induced by FLT3/ITD or constitutively activated wild-type FLT3 expression. Microarrays were used with RNA harvested before and after inhibition of FLT3 signaling. Pim-1 was found to be one of the most significantly down-regulated genes upon FLT3 inhibition. Pim-1 is a proto-oncogene and is known to be up-regulated by signal transducer and activator of transcription 5 (STAT5), which itself is a downstream target of FLT3 signaling. Quantitative polymerase chain reaction (QPCR) confirmed the microarray results and demonstrated approximately 10-fold decreases in Pim-1 expression in response to FLT3 inhibition. Pim-1 protein also decreased rapidly in parallel with decreasing autophosphorylation activity of FLT3. Enforced expression of either the 44-kDa or 33-kDa Pim-1 isotypes resulted in increased resistance to FLT3 inhibition-mediated cytotoxicity and apoptosis. In contrast, expression of a dominant-negative Pim-1 construct accelerated cytotoxicity in response to FLT3 inhibition and inhibited colony growth of FLT3/ITD-transformed BaF3 cells. These findings demonstrate that constitutively activated FLT3 signaling up-regulates Pim-1 expression in leukemia cells. This up-regulation contributes to the proliferative and antiapoptotic pathways induced by FLT3 signaling.
Kim
Kyu-Tae
KT
Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
Baird
Kristin
K
Ahn
Joon-Young
JY
Meltzer
Paul
P
Lilly
Michael
M
Levis
Mark
M
Small
Donald
D
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002227:Carbazoles / Q000494:pharmacology; D002460:Cell Line; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D005663:Furans; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008565:Membrane Proteins / Q000494:pharmacology; D051379:Mice; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology*; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051573:Proto-Oncogene Proteins c-pim-1; D012313:RNA / Q000096:biosynthesis; D020794:Receptor Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012091:Repetitive Sequences, Nucleic Acid; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics; D051941:fms-Like Tyrosine Kinase 3
D002227:Carbazoles; D005663:Furans; D007211:Indoles; C000715470:MAS1 protein, human; D008565:Membrane Proteins; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; C084881:flt3 ligand protein; D012313:RNA; C119379:lestaurtinib; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; C496634:PIM1 protein, human; C496636:Pim1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1