Abstract
The c-KIT receptor tyrosine kinase is constitutively activated and oncogenic in the majority of gastrointestinal stromal tumors. The identification of selective inhibitors of c-KIT, such as imatinib, has provided a novel therapeutic approach in the treatment of this chemotherapy refractory tumor. However, despite the clinical importance of these findings and the potential it provides as a model system for understanding targeted therapy, this approach has not yielded curative outcomes in most patients, and the biochemical pathways connecting c-KIT inhibition to cell death are not completely understood. Here, we show that inhibition of c-KIT with imatinib in gastrointestinal stromal tumors (GISTs) triggered the up-regulation of the proapoptotic protein BIM via both transcriptional and post-translational mechanisms. The inhibition of c-KIT by imatinib increased levels of the dephosphorylated and deubiquitinated form of BIM as well as triggered the accumulation of the transcription factor FOXO3a on the BIM promoter to activate transcription of BIM mRNA. Furthermore, using RNA interference directed against BIM, we demonstrated that BIM knockdown attenuated the effects of imatinib, suggesting that BIM functionally contributes to imatinib-induced apoptosis in GIST. The identification and characterization of the pathways that mediate imatinib-induced cell death in GIST provide for a better understanding of targeted therapy and may facilitate the development of new therapeutic approaches to further exploit these pathways.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Apoptosis / drug effects*
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Apoptosis Regulatory Proteins / physiology*
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Bcl-2-Like Protein 11
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Benzamides
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Blotting, Western
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Butadienes / pharmacology
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Cell Proliferation
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Chromatin Immunoprecipitation
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Drug Resistance, Neoplasm / drug effects*
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Enzyme Inhibitors / pharmacology
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Forkhead Box Protein O3
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Forkhead Transcription Factors / metabolism
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Gastrointestinal Stromal Tumors / drug therapy
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Gastrointestinal Stromal Tumors / metabolism
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Gastrointestinal Stromal Tumors / pathology*
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Gene Expression Regulation, Neoplastic / drug effects
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Humans
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Imatinib Mesylate
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Immunoprecipitation
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Membrane Proteins / physiology*
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Nitriles / pharmacology
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Piperazines / pharmacology*
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Protein Kinase Inhibitors / pharmacology*
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Proto-Oncogene Proteins / physiology*
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Proto-Oncogene Proteins c-kit / antagonists & inhibitors
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Proto-Oncogene Proteins c-kit / metabolism*
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Pyrimidines / pharmacology*
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RNA, Messenger / genetics
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RNA, Messenger / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Tumor Cells, Cultured
Substances
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Apoptosis Regulatory Proteins
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BCL2L11 protein, human
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Bcl-2-Like Protein 11
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Benzamides
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Butadienes
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Enzyme Inhibitors
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FOXO3 protein, human
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Forkhead Box Protein O3
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Forkhead Transcription Factors
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Membrane Proteins
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Nitriles
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Piperazines
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Protein Kinase Inhibitors
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Proto-Oncogene Proteins
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Pyrimidines
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RNA, Messenger
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U 0126
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Imatinib Mesylate
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Protein-Tyrosine Kinases
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Proto-Oncogene Proteins c-kit