title: Betulinic acid-induced apoptosis in glioma cells: A sequential requirement for new protein synthesis, formation of reactive oxygen species, and caspase processing.
abstract: Betulinic acid (BA), a pentacyclic triterpene, is an experimental cytotoxic agent for malignant melanoma. Here, we show that BA triggers apoptosis in five human glioma cell lines. BA-induced apoptosis requires new protein, but not RNA, synthesis, is independent of p53, and results in p21 protein accumulation in the absence of a cell cycle arrest. BA-induced apoptosis involves the activation of caspases that cleave poly(ADP ribose)polymerase. Interactions of death ligand/receptor pairs of the CD95/CD95 ligand family do not mediate BA-induced caspase activation. BA enhances the levels of BAX and BCL-2 proteins but does not alter the levels of BCL-xS or BCL-xL. Ectopic expression of BCL-2 prevents BA-induced caspase activation, DNA fragmentation, and cell death. Furthermore, BA induces the formation of reactive oxygen species that are essential for BA-triggered cell death. The generation of reactive oxygen species is blocked by BCL-2 and requires new protein synthesis but is unaffected by caspase inhibitors, suggesting that BA toxicity sequentially involves new protein synthesis, formation of reactive oxygen species, and activation of crm-A-insensitive caspases.
authors.affiliation: Laboratory of Molecular Neuro-Oncology, Department of Neurology, University of Tübingen, School of Medicine, Tübingen, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Wick
authors.forename: C
authors.initials: C
authors.lastname: Grimmel
authors.forename: B
authors.initials: B
authors.lastname: Wagenknecht
authors.forename: J
authors.initials: J
authors.lastname: Dichgans
authors.forename: M
authors.initials: M
authors.lastname: Weller
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division; D002470:Cell Survival; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D053938:DNA Fragmentation; D004789:Enzyme Activation; D053222:Fas Ligand Protein; D005910:Glioma; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D053978:Pentacyclic Triterpenes; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000502:physiology*; D014315:Triterpenes / Q000633:toxicity*; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000187:drug effects / Q000502:physiology; D000094062:Betulinic Acid
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C494826:BAX protein, human; C494811:BCL2L1 protein, human; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D015853:Cysteine Proteinase Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D009842:Oligopeptides; D053978:Pentacyclic Triterpenes; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014315:Triterpenes; C108637:aspartyl-glutamyl-valyl-aspartal; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor; D003513:Cycloheximide; D020169:Caspases; D000094062:Betulinic Acid