Abstract
Death ligands and their tumor necrosis factor receptor (TNFR) family receptors are the best-characterized and most efficient inducers of apoptotic signaling in somatic cells. In this study, we analyzed whether these prototypic activators of apoptosis are also expressed and able to be activated in human pluripotent stem cells. We examined human embryonic stem cells (hESC) and human-induced pluripotent stem cells (hiPSC) and found that both cell types express primarily TNF-related apoptosis-inducing ligand (TRAIL) receptors and TNFR1, but very low levels of Fas/CD95. We also found that although hESC and hiPSC contain all the proteins required for efficient induction and progression of extrinsic apoptotic signaling, they are resistant to TRAIL-induced apoptosis. However, both hESC and hiPSC can be sensitized to TRAIL-induced apoptosis by co-treatment with protein synthesis inhibitors such as the anti-leukemia drug homoharringtonine (HHT). HHT treatment led to suppression of cellular FLICE inhibitory protein (cFLIP) and Mcl-1 expression and, in combination with TRAIL, enhanced processing of caspase-8 and full activation of caspase-3. cFLIP likely represents an important regulatory node, as its shRNA-mediated down-regulation significantly sensitized hESC to TRAIL-induced apoptosis. Thus, we provide the first evidence that, irrespective of their origin, human pluripotent stem cells express canonical components of the extrinsic apoptotic system and on stress can activate death receptor-mediated apoptosis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Apoptosis / drug effects
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CASP8 and FADD-Like Apoptosis Regulating Protein / antagonists & inhibitors
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CASP8 and FADD-Like Apoptosis Regulating Protein / genetics*
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CASP8 and FADD-Like Apoptosis Regulating Protein / metabolism
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Caspase 3 / genetics
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Caspase 3 / metabolism
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Caspase 8 / genetics
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Caspase 8 / metabolism
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Cell Differentiation
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Cell Proliferation
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Drug Synergism
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Embryonic Stem Cells / cytology
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Embryonic Stem Cells / drug effects
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Embryonic Stem Cells / metabolism*
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Gene Expression Regulation
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Harringtonines / pharmacology
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Homoharringtonine
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Humans
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Myeloid Cell Leukemia Sequence 1 Protein / genetics
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Myeloid Cell Leukemia Sequence 1 Protein / metabolism
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Pluripotent Stem Cells / cytology
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Pluripotent Stem Cells / drug effects
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Pluripotent Stem Cells / metabolism*
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Protein Synthesis Inhibitors / pharmacology
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Receptors, TNF-Related Apoptosis-Inducing Ligand / genetics*
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Receptors, TNF-Related Apoptosis-Inducing Ligand / metabolism
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Receptors, Tumor Necrosis Factor, Type I / genetics
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Receptors, Tumor Necrosis Factor, Type I / metabolism
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Signal Transduction
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TNF-Related Apoptosis-Inducing Ligand / genetics*
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TNF-Related Apoptosis-Inducing Ligand / metabolism
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TNF-Related Apoptosis-Inducing Ligand / pharmacology
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fas Receptor / genetics
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fas Receptor / metabolism
Substances
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CASP8 and FADD-Like Apoptosis Regulating Protein
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FAS protein, human
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Harringtonines
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MCL1 protein, human
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Myeloid Cell Leukemia Sequence 1 Protein
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Protein Synthesis Inhibitors
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RNA, Small Interfering
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Receptors, TNF-Related Apoptosis-Inducing Ligand
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Receptors, Tumor Necrosis Factor, Type I
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TNF-Related Apoptosis-Inducing Ligand
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TNFRSF10A protein, human
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TNFSF10 protein, human
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fas Receptor
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Homoharringtonine
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Caspase 3
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Caspase 8