Induction of endoplasmic reticulum stress by ellipticine plant alkaloids.
Anticancer drugs often show complex mechanisms of action, including effects on multiple cellular targets. Detailed understanding of these intricate effects is important for the understanding of cytotoxicity. In this study, we examined apoptosis induction by ellipticines, a class of cytotoxic plant alkaloids known to inhibit topoisomerase II. The potent ellipticine derivative 6-propanamine ellipticine (6-PA-ELL) induced rapid apoptosis in MDA-MB-231 breast cancer cells, preceded by a conformational change in Bak and cytochrome c release. Experiments using knock-out mouse embryo fibroblasts established that Bak was of particular importance for cytotoxicity. 6-PA-ELL increased the expression of the endoplasmic reticulum chaperones GRP78/BiP and GRP94, suggesting induction of endoplasmic reticulum stress. Induction of GRP78 expression was dependent on the endoplasmic reticulum stress response element (ERSE) of the GRP78 promoter. Examination of different ellipticine derivatives revealed a correlation between pro-apoptotic activity and the ability to induce GRP78 expression. Furthermore, 6-PA-ELL was found to induce splicing of the mRNA encoding the XBP1 transcription factor, characteristic of endoplasmic reticulum stress, and to induce activation of the endoplasmic reticulum-specific caspase-12 in mouse colon cancer cells. We finally demonstrate that 6-PA-ELL induces apoptotic signaling also in enucleated cells, consistent with the existence of a cytoplasmic target for this compound. Our data suggest that induction of endoplasmic reticulum stress may contribute to the cytotoxicity of ellipticines.
Hägg
Maria
M
Department of Oncology and Pathology, Cancer Center Karolinska, Karolinska Institute and Hospital, Stockholm, Sweden.
Berndtsson
Maria
M
Mandic
Aleksandra
A
Zhou
Rong
R
Shoshan
Maria C
MC
Linder
Stig
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053454:Caspase 12; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics; D004611:Ellipticines / Q000633:toxicity*; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011487:Protein Conformation / Q000187:drug effects; D012326:RNA Splicing / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000071701:Regulatory Factor X Transcription Factors; D020218:Response Elements / Q000235:genetics; D059005:Topoisomerase II Inhibitors; D014157:Transcription Factors / Q000235:genetics; D000071717:X-Box Binding Protein 1; D050998:bcl-2 Homologous Antagonist-Killer Protein
C494772:BAK1 protein, human; C494773:Bak1 protein, mouse; D004268:DNA-Binding Proteins; D004611:Ellipticines; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008565:Membrane Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D059005:Topoisomerase II Inhibitors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605544:Xbp1 protein, mouse; D050998:bcl-2 Homologous Antagonist-Killer Protein; C018551:glucose-regulated proteins; C034192:ellipticine; C506444:CASP12 protein, human; C506440:Casp12 protein, mouse; D053454:Caspase 12; D020169:Caspases