title: The sensitivity of the Ewing's sarcoma family of tumours to fenretinide-induced cell death is increased by EWS-Fli1-dependent modulation of p38(MAPK) activity.
abstract: The Ewing's sarcoma family of tumours (ESFT) are small round cell tumours characterized by the non-random EWS-ETS gene rearrangements. We have previously demonstrated that ESFT are highly sensitive to fenretinide-induced death, effected in part through a reactive oxygen species (ROS)-dependent pathway. Here, we demonstrate for the first time that the sensitivity of ESFT cells to fenretinide-induced cell death is decreased following downregulation of the oncogenic fusion protein EWS-Fli1; siRNA targeting EWS-Fli1 attenuated fenretinide-induced cell death in cell lines expressing EWS-Fli1, but not EWS-ERG. This decrease in cell death was independent of the level of ROS produced following exposure to fenretinide, but was effected through EWS-Fli1-dependent modulation of p38(MAPK) activity. Furthermore, inhibition of p38(MAPK) activity and knockdown of EWS-Fli1 reduced fenretinide-induced mitochondrial permeabilization, cytochrome c release, caspase and PARP cleavage, consistent with the hypothesis that p38(MAPK) is critical for activation of the death cascade by fenretinide in ESFT cells. These data demonstrate that expression of EWS-Fli1 enhances fenretinide-induced cell death in ESFT and that this is effected at least in part through modulation of p38(MAPK) activity.
authors: Candlelighter's Children's Cancer Research Laboratory, Cancer Research UK Clinical Centre, St James's University Hospital, Leeds, UK.
authors: S S
authors: SS
authors: Myatt
authors: S A
authors: SA
authors: Burchill
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D015536:Down-Regulation; D018274:Electroporation; D017313:Fenretinide / Q000494:pharmacology*; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051789:Proto-Oncogene Protein c-fli-1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D034802:RNA-Binding Protein EWS; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012512:Sarcoma, Ewing / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C450460:EWS-ERG fusion protein, human; C106031:EWS-FLI fusion protein; D015514:Oncogene Proteins, Fusion; D051789:Proto-Oncogene Protein c-fli-1; D034741:RNA, Small Interfering; D034802:RNA-Binding Protein EWS; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D017313:Fenretinide; D045304:Cytochromes c; D011065:Poly(ADP-ribose) Polymerases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases