Ribotoxic stress sensitizes glioblastoma cells to death receptor induced apoptosis: requirements for c-Jun NH2-terminal kinase and Bim.
A prominent feature of glioblastoma is its resistance to death receptor-mediated apoptosis. In this study, we explored the possibility of modulating death receptor-induced cell death with the c-Jun-NH2-terminal kinase (JNK) activator anisomycin. Anisomycin activates JNK by inactivating the ribosome and inducing "ribotoxic stress." We found that anisomycin and death receptor ligand anti-Fas antibody CH-11 or tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) synergistically induce apoptosis in multiple human glioblastoma cell lines. For example, in U87 cells, anisomycin reduced the IC50 of CH-11 by more than 20-fold (from 500 to 25 ng/mL). Cell viability in response to anisomycin, CH-11, and their combination was 79%, 91%, and 28% (P<0.001), respectively. Anisomycin and TRAIL were found to be similarly synergistic in glioblastoma cells maintained as tumor xenografts. The potentiation of death receptor-dependent cell death by anisomycin was specific because emetine, another ribosome inhibitor that does not induce ribotoxic stress or activate JNK, did not have a similar effect. Synergistic cell death was predominantly apoptotic involving both extrinsic and intrinsic pathways. Expression of Fas, FasL, FLIP, and Fas-associated death domain (FADD) was not changed following treatment with anisomycin+CH-11. JNK was activated 10- to 22-fold by anisomycin+CH-11 in U87 cells. Inhibiting JNK activation with pharmacologic inhibitors of JNKK and JNK or with dominant negative mitogen-activated protein kinase (MAPK) kinase kinase 2 (MEKK2) significantly prevented cell death induced by the combination of anisomycin+CH-11. We further found that anisomycin+CH-11 up-regulated the proapoptotic protein Bim by approximately 14-fold. Simultaneously inhibiting Bim expression and JNK activation additively desensitized U87 cells to anisomycin+CH-11. These findings show that anisomycin-induced ribotoxic stress sensitizes glioblastoma cells to death receptor-induced apoptosis via a specific mechanism requiring both JNK activation and Bim induction.
Xia
Shuli
S
Kennedy Krieger Research Institute, Department of Neurology, School of Medicine, Johns Hopkins University, 707 N. Broadway, Baltimore, MD 21205, USA.
Li
Yang
Y
Rosen
Eliot M
EM
Laterra
John
J
D000841:Anisomycin / Q000494:pharmacology*; D000906:Antibodies / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D004357:Drug Synergism; D053222:Fas Ligand Protein / Q000378:metabolism; D005434:Flow Cytometry; D005909:Glioblastoma / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D053218:Receptors, Death Domain / Q000378:metabolism; D012270:Ribosomes / Q000187:drug effects*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000378:metabolism
D000906:Antibodies; D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C481004:CH-11 anti-fas antibody, human; C491901:FAS protein, human; D053222:Fas Ligand Protein; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D053218:Receptors, Death Domain; D053221:TNF-Related Apoptosis-Inducing Ligand; D019014:fas Receptor; D000841:Anisomycin; D045304:Cytochromes c; D048031:JNK Mitogen-Activated Protein Kinases; D020169:Caspases