title: Alkyl-lysophospholipids activate the SAPK/JNK pathway and enhance radiation-induced apoptosis.
abstract: Alkyl-lysophospholipids (ALPs) represent a new class of antitumor drugs that induce apoptotic cell death in a variety of tumor cell lines. Although their precise mechanism of action is unknown, ALPs primarily act on the cell membrane, where they inhibit signaling through the mitogen-activated protein kinase (MAPK) pathway. Because stimulation of the stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) pathway is essential for radiation-induced apoptosis in certain cell types, we tested the effect of ALPs in combination with ionizing radiation on MAPK/SAPK signaling and apoptosis induction. Here, we present data showing that three ALPs, 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine, hexadecylphosphocholine, and the novel compound octadecyl-(1,1-dimethyl-piperidinio-4-yl)-phosphate (D-21266) induce time- and dose-dependent apoptosis in the human leukemia cell lines U937 and Jurkat T but not in normal vascular endothelial cells. Moreover, in combination with radiation, ALPs strongly enhance the induction of apoptosis in both leukemic cell lines. All tested ALPs not only prevented MAPK activation, but, like radiation, stimulated the SAPK/JNK cascade within minutes. A dominant-negative mutant of c-Jun inhibited radiation- and ALP-induced apoptosis, indicating a requirement for the SAPK/JNK pathway. Our data support the view that ALPs and ionizing radiation cause an enhanced apoptotic effect by modulating the balance between the mitogenic, antiapoptotic MAPK, and the apoptotic SAPK/JNK pathways. This type of modulation of specific signal transduction pathways in tumor cells may lead to the development of new therapeutic strategies.
authors.affiliation: Department of Radiotherapy, Antoni van Leeuwenhoek Ziekenhuis/The Netherlands Cancer Institute, Amsterdam.
authors.forename: G A
authors.initials: GA
authors.lastname: Ruiter
authors.forename: S F
authors.initials: SF
authors.lastname: Zerp
authors.forename: H
authors.initials: H
authors.lastname: Bartelink
authors.forename: W J
authors.initials: WJ
authors.lastname: van Blitterswijk
authors.forename: M
authors.initials: M
authors.lastname: Verheij
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000528:radiation effects; D005720:Gamma Rays; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells / Q000187:drug effects / Q000528:radiation effects; D019950:Mitogen-Activated Protein Kinase 1; D048291:Mitogen-Activated Protein Kinase 12; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010742:Phospholipid Ethers / Q000494:pharmacology*; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects* / Q000528:radiation effects; D020298:U937 Cells / Q000187:drug effects / Q000528:radiation effects
chemical_list: D010742:Phospholipid Ethers; D010767:Phosphorylcholine; C026659:edelfosine; C105905:perifosine; C039128:miltefosine; D011494:Protein Kinases; D048291:Mitogen-Activated Protein Kinase 12; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases