Abstract
Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) exhibits specific tumoricidal activity and is under development for cancer therapy. Mismatch-repair-deficient colonic tumors evade TRAIL-induced apoptosis through mutational inactivation of Bax, but chemotherapeutics including Camptosar (CPT-11) restore TRAIL sensitivity. However, the signaling pathways in restoring TRAIL sensitivity remain to be elucidated. Here, we imaged p53 transcriptional activity in Bax-/- carcinomas by using bioluminescence, in vivo, and find that p53 is required for sensitization to TRAIL by CPT-11. Small interfering RNAs directed at proapoptotic p53 targets reveal TRAIL receptor KILLER/DR5 contributes significantly to TRAIL sensitization, whereas Bak plays a minor role. Caspase 8 inhibition protects both CPT-11 pretreated wild-type and Bax-/- HCT116 cells from TRAIL-induced apoptosis, whereas caspase 9 inhibition only rescued the wild-type HCT116 cells from death induced by TRAIL. The results suggest a conversion in the apoptotic mechanism in HCT116 colon carcinoma from a type II pathway involving Bax and the mitochondria to a type I pathway involving efficient extrinsic pathway caspase activation. In contrast to Bax-/- cells, Bak-deficient human cancers undergo apoptosis in response to TRAIL or CPT-11, implying that these proteins have nonoverlapping functions. Our studies elucidate a mechanism for restoration of TRAIL sensitivity in MMR-deficient Bax-/- human cancers through p53-dependent activation of KILLER/DR5 and reconstitution of a type I death pathway. Efforts to identify agents that up-regulate DR5 may be useful in cancer therapies restoring TRAIL sensitivity.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenoviridae / genetics
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Animals
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Antineoplastic Agents / pharmacology
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Antineoplastic Agents, Phytogenic / pharmacology
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Apoptosis
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Apoptosis Regulatory Proteins
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Base Pair Mismatch
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Camptothecin / analogs & derivatives*
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Camptothecin / metabolism
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Carcinoma / drug therapy*
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Carcinoma / genetics
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Caspase 8
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Caspase 9
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Caspase Inhibitors
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Caspases / metabolism
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Cell Death
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Cell Line
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Cell Line, Tumor
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Colonic Neoplasms / drug therapy*
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Colonic Neoplasms / genetics
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DNA Damage
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DNA Repair
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Enzyme Inhibitors / pharmacology
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Etoposide / pharmacology
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Flow Cytometry
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Humans
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Irinotecan
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Luciferases / metabolism
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Membrane Glycoproteins / metabolism
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Mice
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2*
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RNA, Small Interfering / metabolism
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Receptors, TNF-Related Apoptosis-Inducing Ligand
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Receptors, Tumor Necrosis Factor / genetics
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Receptors, Tumor Necrosis Factor / physiology
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TNF-Related Apoptosis-Inducing Ligand
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Time Factors
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Transcription, Genetic
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Transfection
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Tumor Necrosis Factor-alpha / metabolism
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Tumor Suppressor Protein p53 / genetics
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Tumor Suppressor Protein p53 / metabolism
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Tumor Suppressor Protein p53 / physiology*
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bcl-2-Associated X Protein
Substances
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Antineoplastic Agents
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Antineoplastic Agents, Phytogenic
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Apoptosis Regulatory Proteins
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BAX protein, human
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Bax protein, mouse
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Caspase Inhibitors
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Enzyme Inhibitors
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Membrane Glycoproteins
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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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
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TNF-Related Apoptosis-Inducing Ligand
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TNFRSF10B protein, human
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TNFSF10 protein, human
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Tnfrsf10b protein, mouse
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Tnfsf10 protein, mouse
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Tumor Necrosis Factor-alpha
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Tumor Suppressor Protein p53
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bcl-2-Associated X Protein
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Etoposide
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Irinotecan
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Luciferases
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CASP8 protein, human
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CASP9 protein, human
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Casp8 protein, mouse
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Casp9 protein, mouse
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Caspase 8
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Caspase 9
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Caspases
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Camptothecin