Inhibition of eIF2α dephosphorylation enhances TRAIL-induced apoptosis in hepatoma cells.

Abstract

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an inducer of cancer cell death that holds promise in cancer therapy. Cancer cells are more susceptible than normal cells to the cell-death-inducing effects of TRAIL. However, a variety of cancer cells are resistant to TRAIL through complex mechanisms. Here, we investigate the effects of inhibition of eukaryotic initiation factor 2 subunit α (eIF2α) dephosphorylation on TRAIL-induced apoptosis in hepatoma cells. Treatment of hepatoma cells with salubrinal, an inhibitor of eIF2α dephosphorylation, enhances TRAIL-induced eIF2α phosphorylation, CCAAT/enhancer-binding protein homologous protein (CHOP) expression and caspase activation. Salubrinal enhances TRAIL-induced apoptosis, which could be abrogated by caspase inhibitor. Overexpression of phosphomimetic eIF2α (S51D) enhances TRAIL-induced CHOP expression, caspase 7 and PARP cleavage and apoptosis. By contrast, overexpression of phosphodeficient eIF2α (S51A) abrogates the stimulation of TRAIL-induced apoptosis by salubrinal. Moreover, knockdown of growth arrest and DNA damage-inducible protein 34 (GADD34), which recruits protein phosphatase 1 to dephosphorylate eIF2α, enhances TRAIL-induced eIF2α phosphorylation, CHOP expression, caspase activation and apoptosis. Furthermore, the sensitization of hepatoma cells to TRAIL by salubrinal is dependent on CHOP. Knockdown of CHOP abrogates the stimulation of TRAIL-induced caspase activation and apoptosis by salubrinal. Combination of salubrinal and TRAIL leads to increased expression of Bim, a CHOP-regulated proapoptotic protein. Bim knockdown blunts the stimulatory effect of salubrinal on TRAIL-induced apoptosis. Collectively, these findings suggest that inhibition of eIF2α dephosphorylation may lead to synthetic lethality in TRAIL-treated hepatoma cells.

• Authors: Y Teng, M Gao, J Wang, Q Kong, H Hua, T Luo, Y Jiang
• Journal: Cell death & disease (Cell Death Dis) Vol. 5 Pg. e1060 (Feb 13 2014) ISSN: 2041-4889 [Electronic] England
• PMID: 24525736 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Apoptosis Regulatory Proteins
• BCL2L11 protein, human
• Bcl-2-Like Protein 11
• Caspase Inhibitors
• DDIT3 protein, human
• Eukaryotic Initiation Factor-2
• Membrane Proteins
• Proto-Oncogene Proteins
• TNF-Related Apoptosis-Inducing Ligand
• TNFSF10 protein, human
• Transcription Factor CHOP
• Poly(ADP-ribose) Polymerases
• PPP1R15A protein, human
• Protein Phosphatase 1
• CASP7 protein, human
• Caspase 7

Topics

• Antineoplastic Agents (pharmacology)
• Apoptosis (drug effects)
• Apoptosis Regulatory Proteins (genetics, metabolism)
• Bcl-2-Like Protein 11
• Carcinoma, Hepatocellular (genetics, metabolism, pathology)
• Caspase 7 (metabolism)
• Caspase Inhibitors (pharmacology)
• Dose-Response Relationship, Drug
• Eukaryotic Initiation Factor-2 (genetics, metabolism)
• Hep G2 Cells
• Humans
• Liver Neoplasms (genetics, metabolism, pathology)
• Membrane Proteins (genetics, metabolism)
• Phosphorylation
• Poly(ADP-ribose) Polymerases (metabolism)
• Protein Phosphatase 1 (antagonists & inhibitors, genetics, metabolism)
• Proto-Oncogene Proteins (genetics, metabolism)
• RNA Interference
• Signal Transduction (drug effects)
• TNF-Related Apoptosis-Inducing Ligand (pharmacology)
• Transcription Factor CHOP (genetics, metabolism)
• Transfection