Abstract
Chronic lymphocytic leukemia (CLL) is an incurable disease characterized by failure of mature lymphocytes to undergo apoptosis. CLL cells are inherently resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Pretreatment with histone deacetylase inhibitors (HDACi) sensitizes CLL cells to TRAIL-mediated apoptosis primarily via TRAIL-R1 and offers a novel approach for the therapy of CLL and other malignancies. Depsipeptide (romidepsin), a HDACi, did not enhance TRAIL binding to TRAIL-R1, TRAIL-R1 aggregation, or internalization of TRAIL-R1, but it enhanced Fas-associated death domain protein (FADD) recruitment to TRAIL-R1 in the death-inducing signaling complex. Cotreatment with phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, dramatically inhibited the HDACi-mediated increase in FADD recruitment and sensitization to TRAIL-induced apoptosis and both of these were reversed by PKC inhibitors. Thus, enhanced FADD recruitment is a critical step in HDACi-mediated sensitization of CLL cells to TRAIL-induced apoptosis and this step is differentially affected by HDACi and phorbol 12-myristate 13-acetate. Using biotinylated TRAIL and streptactin-tagged TRAIL, we have identified several novel TRAIL receptor interacting proteins, including PKCbeta, lymphocyte-specific protease-1, Lyn, and Syk. These molecules may play an as yet unappreciated role in TRAIL signaling in CLL cells and inhibition of one or more of these kinases/phosphatases may provide a novel target to overcome TRAIL resistance.
MeSH terms
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Antineoplastic Combined Chemotherapy Protocols / pharmacology*
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Apoptosis / drug effects*
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Apoptosis Inducing Factor / metabolism
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Blotting, Western
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Depsipeptides / administration & dosage
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Depsipeptides / pharmacology
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Drug Synergism
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Fas-Associated Death Domain Protein / metabolism*
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Histone Deacetylase Inhibitors / administration & dosage
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Histone Deacetylase Inhibitors / pharmacology*
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Histone Deacetylases / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins / metabolism
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Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy*
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Leukemia, Lymphocytic, Chronic, B-Cell / metabolism
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Leukemia, Lymphocytic, Chronic, B-Cell / pathology
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Phosphorylation / drug effects
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Protein Kinase C / metabolism
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Protein Kinase C beta
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Protein Tyrosine Phosphatase, Non-Receptor Type 6 / metabolism
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Protein-Tyrosine Kinases / metabolism
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Receptors, TNF-Related Apoptosis-Inducing Ligand
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Receptors, Tumor Necrosis Factor / metabolism
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Signal Transduction / drug effects
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Syk Kinase
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TNF-Related Apoptosis-Inducing Ligand / administration & dosage
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TNF-Related Apoptosis-Inducing Ligand / pharmacology*
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Tetradecanoylphorbol Acetate / pharmacology
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Tumor Cells, Cultured
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src-Family Kinases / metabolism
Substances
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Apoptosis Inducing Factor
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Depsipeptides
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Fas-Associated Death Domain Protein
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Histone Deacetylase Inhibitors
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Intracellular Signaling Peptides and Proteins
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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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TNFRSF10A protein, human
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Protein-Tyrosine Kinases
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SYK protein, human
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Syk Kinase
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lyn protein-tyrosine kinase
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src-Family Kinases
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Protein Kinase C
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Protein Kinase C beta
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PTPN6 protein, human
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Protein Tyrosine Phosphatase, Non-Receptor Type 6
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Histone Deacetylases
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Tetradecanoylphorbol Acetate