title: Endoplasmic reticulum stress in the proapoptotic action of edelfosine in solid tumor cells.
abstract: The endoplasmic reticulum (ER) has been posited as a potential anticancer target. The synthetic antitumor alkyl-lysophospholipid analogue edelfosine accumulates in the ER of solid tumor cells. This ER accumulation of the drug leads to the inhibition of phosphatidylcholine and protein synthesis, G(2)-M arrest, depletion of ER-stored Ca(2+), Bax up-regulation and activation, transcriptional factor growth arrest and DNA damage-inducible gene 153 up-regulation, caspase-4 and caspase-8 activation, and eventually to apoptosis. Edelfosine prompted ER stress apoptotic signaling, but not the survival unfolded protein response. Edelfosine also induced persistent c-Jun NH(2)-terminal kinase (JNK) activation. Gene transfer-mediated overexpression of apoptosis signal-regulating kinase 1, which plays a crucial role in ER stress, enhanced edelfosine-induced JNK activation and apoptosis. Inhibition of JNK, caspase-4, or caspase-8 activation diminished edelfosine-induced apoptosis. Edelfosine treatment led to the generation of the p20 caspase-8 cleavage fragment of BAP31, directing proapoptotic signals between the ER and the mitochondria. bax(-/-)bak(-/-) double-knockout cells fail to undergo edelfosine-induced ER-stored Ca(2+) release and apoptosis. Wild-type and bax(-/-)bak(-/-) cells showed similar patterns of phosphatidylcholine and protein synthesis inhibition, despite their differences in drug sensitivity. Thus, edelfosine-induced apoptosis is dependent on Bax/Bak-mediated ER-stored Ca(2+) release, but phosphatidylcholine and protein synthesis inhibition is not critical. Transfection-enforced expression of Bcl-X(L), which localizes specifically in mitochondria, prevented apoptosis without inhibiting ER-stored Ca(2+) release. These data reveal that edelfosine induces an ER stress response in solid tumor cells, providing novel insights into the edelfosine-mediated antitumor activity. Our data also indicate that mitochondria are indispensable for this edelfosine-induced cell death initiated by ER stress.
authors.affiliation: Centro de Investigación del Cáncer, Instituto de Biología Molecular y Celular del Cáncer, Consejo Superior de Investigaciones Científicas-Universidad de Salamanca, Salamanca, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Nieto-Miguel
authors.forename: Rosalba I
authors.initials: RI
authors.lastname: Fonteriz
authors.forename: Laura
authors.initials: L
authors.lastname: Vay
authors.forename: Consuelo
authors.initials: C
authors.lastname: Gajate
authors.forename: Silvia
authors.initials: S
authors.lastname: López-Hernández
authors.forename: Faustino
authors.initials: F
authors.lastname: Mollinedo
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D020169:Caspases / Q000502:physiology; D019916:Choline-Phosphate Cytidylyltransferase / Q000037:antagonists & inhibitors; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000502:physiology; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010713:Phosphatidylcholines / Q000096:biosynthesis; D010742:Phospholipid Ethers / Q000494:pharmacology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000502:physiology; D051028:bcl-2-Associated X Protein / Q000502:physiology; D051020:bcl-X Protein / Q000502:physiology
chemical_list: D000970:Antineoplastic Agents; C494772:BAK1 protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D010713:Phosphatidylcholines; D010742:Phospholipid Ethers; D011500:Protein Synthesis Inhibitors; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C026659:edelfosine; D048031:JNK Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; C482858:MAP3K5 protein, human; D019916:Choline-Phosphate Cytidylyltransferase; D020169:Caspases; D002118:Calcium