Flavopiridol induces mitochondrial-mediated apoptosis in murine glioma GL261 cells via release of cytochrome c and apoptosis inducing factor.
Glioblastoma (GBM) remains one of the most challenging solid cancers to treat due to its highly proliferative, angiogenic and invasive nature. The small molecule CDK inhibitor, flavopiridol, has demonstrated antitumor activity in human xenograft models and is currently in clinical trials showing efficacy in patients with advanced disease. We have developed an experimental animal model using the murine glioma GL261 cells as a novel in vivo system to screen potential therapeutic agents for GBM. Results of in vitro testing demonstrate that flavopiridol has several relevant clinical characteristics such as its ability to: 1. inhibit cell growth; 2. inhibit cell migration; 3. decrease expression of cyclin D1, CDK4 and p21; 4. induce apoptosis in cells with high levels of p27 expression; and 5. decrease the expression of the anti-apoptotic protein Bcl-2. The mechanism by which flavopiridol induces apoptosis is mitochondrial-mediated. We demonstrate by electron microscopy and immunohistochemistry that drug treatment induces mitochondrial damage that was accompanied by the release of cytochrome c into the cytosol together with the translocation of apoptosis inducing factor (AIF) into the nucleus. This finding in murine glioma cells differs from the mechanism of flavopiridolinduced cell death reported by us for human glioma cells (Alonso et al., Mol Cancer Ther 2003; 2:139) where drug treatment induced a caspase- and cytochrome c-independent pathway in the absence of detectable damage to mitochondria. In apoptotic human glioma cells only translocation of AIF into the nucleus occurred. Thus, the same drug kills different types of glioma cells by different mitochondrial-dependent pathways.
Department of Pathology MSB531, New York University Medical Center, 550 First Avenue, New York, NY 10016, USA. newcoe01@med.nyu.edu
Elizabeth W
EW
Newcomb
Cristina
C
Tamasdan
Yolanda
Y
Entzminger
Judith
J
Alonso
David
D
Friedlander
Diana
D
Crisan
Douglas C
DC
Miller
David
D
Zagzag
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D051033:Apoptosis Inducing Factor; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D003574:Cytochrome c Group / Q000378:metabolism; D003603:Cytotoxins / Q000633:toxicity; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005057:Eukaryotic Cells / Q000187:drug effects* / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology*; D005420:Flavoproteins / Q000378:metabolism; D016195:G2 Phase / Q000187:drug effects; D005909:Glioblastoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D051033:Apoptosis Inducing Factor; D018797:Cell Cycle Proteins; D003574:Cytochrome c Group; D003603:Cytotoxins; D005419:Flavonoids; D005420:Flavoproteins; D008565:Membrane Proteins; C494830:AIFM1 protein, mouse; D010880:Piperidines; C077990:alvocidib