title: Sensitization of mesothelioma cells to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by heat stress via the inhibition of the 3-phosphoinositide-dependent kinase 1/Akt pathway.
abstract: Heat stress may enhance the effect of apoptosis-inducing agents in resistant tumor cells. One such agent is the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), which has attracted intense interest for its ability to induce apoptosis in tumors without affecting nonmalignant cells. We therefore tested whether heat stress potentiates TRAIL-induced apoptosis in mesothelioma cells, its cell type being resistant to TRAIL alone. We found that heat stress enhanced the apoptosis caused by TRAIL but not by chemotherapy. To explain this potentiation, we found that heat stress decreased Akt phosphorylation via the dissociation of heat shock protein 90 (Hsp90) from its client protein 3-phosphoinositide-dependent kinase 1 (PDK-1), a major Akt kinase. The role of Hsp90 and the Akt pathway was confirmed by showing that inhibitors of Hsp90 and the phosphatidyilinositol-3 kinase/Akt pathway reproduced the effect of heat stress on TRAIL-induced apoptosis and that the effect of inhibiting Hsp90 on TRAIL-induced apoptosis could be overcome by activating the Akt pathway with a constitutively active construct of the Akt kinase PDK-1. The effect of heat stress involved multiple steps of the apoptotic machinery. Heat stress potentiated the death receptor pathway, as shown by an increase in TRAIL-induced caspase 8 cleavage. Nonetheless, knockdown of Bid, the main intermediary molecule from the death receptor pathway to the mitochondria, inhibited the effect of heat stress, showing that mitochondrial amplification was required for potentiation by heat stress. In summary, these results support the novel concept that heat stress inhibits the Akt pathway by dissociating PDK-1 from its chaperone Hsp90, leading to potentiation of TRAIL-induced apoptosis in resistant malignant cells.
authors.affiliation: Laboratory of Surgical Research, Cardiovascular Research Institute, University of California-San Francisco, California 94110, USA.
authors.forename: Melissa H
authors.initials: MH
authors.lastname: Pespeni
authors.forename: Maki
authors.initials: M
authors.lastname: Hodnett
authors.forename: Keith S
authors.initials: KS
authors.lastname: Abayasiriwardana
authors.forename: Jérémie
authors.initials: J
authors.lastname: Roux
authors.forename: Marybeth
authors.initials: M
authors.lastname: Howard
authors.forename: V Courtney
authors.initials: VC
authors.lastname: Broaddus
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Pittet
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D005047:Etoposide / Q000494:pharmacology; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D008654:Mesothelioma / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000502:physiology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D018841:HSP90 Heat-Shock Proteins; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D005047:Etoposide; D064413:3-Phosphoinositide-Dependent Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D053181:Caspase 8