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    Edelfosine and perifosine induce selective apoptosis in multiple myeloma by recruitment of death receptors and downstream signaling molecules into lipid rafts

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    Multiple myeloma (MM) is an incurable B-cell malignancy, requiring new therapeutic strategies. We have found that synthetic alkyl-lysophospholipids (ALPs) edelfosine and perifosine induced apoptosis in MM cell lines and patient MM cells, whereas normal B and T lymphocytes were spared. ALPs induced recruitment of Fas/CD95 death receptor, Fas-associated death domain-containing protein, and procaspase-8 into lipid rafts, leading to the formation of the death-inducing signaling complex (DISC) and apoptosis. TNF-related apoptosis-inducing ligand receptor-1/death receptor 4 (TRAIL-R1/DR4) and TRAIL-R2/DR5, as well as Bid, were also recruited into lipid rafts, linking death receptor and mitochondrial signaling pathways. ALPs induced mitochondrial cytochrome c release. Bcl-XL overexpression prevented cytochrome c release and apoptosis. A Fas/CD95-deficient MM subline expressing DR4 and DR5 was resistant to edelfosine. Fas/CD95 retrovirus transduction bestowed edelfosine sensitivity in these cells. A Fas/CD95 mutant lacking part of the intracellular domain was ineffective. Lipid raft disruption prevented ALP-induced Fas/CD95 clustering, DISC formation, and apoptosis. ALP-induced apoptosis was Fas/CD95 ligand (FasL/CD95L) independent. ALP-induced recruitment of death receptors in lipid rafts potentiated MM cell killing by FasL/CD95L and TRAIL. These data uncover a novel lipid raft-mediated therapy in MM involving concentration of death receptors in membrane rafts, with Fas/CD95 playing a major role in ALP-mediated apoptosis. © 2007 by The American Society of Hematology.This work was supported by grants from Fondo de Investigación Sanitaria and European Commission (FIS-FEDER 06/0813, 04/ 0843, 02/1199), Ministerio de Educación y Ciencia (SAF2005- 04293), Fundación de Investigación Médica Mutua Madrileña (FMM), Fundación “la Caixa” (BM05-30-0), and Junta de Castilla y León (CSI04A05), and by the Ramón y Cajal Program from the Ministerio de Educación y Ciencia of Spain (C.G.).Peer Reviewe
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