title: Repression of BIRC5/survivin by FOXO3/FKHRL1 sensitizes human neuroblastoma cells to DNA damage-induced apoptosis.
abstract: The phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB) pathway regulates survival and chemotherapy resistance of neuronal cells, and its deregulation in neuroblastoma (NB) tumors predicts an adverse clinical outcome. Here, we show that inhibition of PI3K-PKB signaling in human NB cells induces nuclear translocation of FOXO3/FKHRL1, represses the prosurvival protein BIRC5/Survivin, and sensitizes to DNA-damaging agents. To specifically address whether FKHRL1 contributes to Survivin regulation, we introduced a 4-hydroxy-tamoxifen-regulated FKHRL1(A3)ERtm allele into NB cells. Conditional FKHRL1 activation repressed Survivin transcription and protein expression. Transgenic Survivin exerted a significant antiapoptotic effect and prevented the accumulation of Bim and Bax at mitochondria, the loss of mitochondrial membrane potential as well as the release of cytochrome c during FKHRL1-induced apoptosis. In concordance, Survivin knockdown by retroviral short hairpin RNA technology accelerated FKHRL1-induced apoptosis. Low-dose activation of FKHRL1 sensitized to the DNA-damaging agents doxorubicin and etoposide, whereas the overexpression of Survivin diminished FKHRL1 sensitization to these drugs. These results suggest that repression of Survivin by FKHRL1 facilitates FKHRL1-induced apoptosis and sensitizes to cell death induced by DNA-damaging agents, which supports the central role of PI3K-PKB-FKHRL1 signaling in drug resistance of human NB.
authors.affiliation: Tyrolean Cancer Research Institute, A-6020 Innsbruck, Austria. petra.obexer@i-med.ac.at
authors.forename: Petra
authors.initials: P
authors.lastname: Obexer
authors.forename: Judith
authors.initials: J
authors.lastname: Hagenbuchner
authors.forename: Thomas
authors.initials: T
authors.lastname: Unterkircher
authors.forename: Nora
authors.initials: N
authors.lastname: Sachsenmaier
authors.forename: Christoph
authors.initials: C
authors.lastname: Seifarth
authors.forename: Günther
authors.initials: G
authors.lastname: Böck
authors.forename: Verena
authors.initials: V
authors.lastname: Porto
authors.forename: Kathrin
authors.initials: K
authors.lastname: Geiger
authors.forename: Michael
authors.initials: M
authors.lastname: Ausserlechner
mesh_terms: D000483:Alleles; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology; D004354:Drug Screening Assays, Antitumor; D005047:Etoposide / Q000494:pharmacology; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009447:Neuroblastoma / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D000077022:Survivin; D019076:Transgenes
chemical_list: C107489:BIRC5 protein, human; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000077022:Survivin; D005047:Etoposide; D004317:Doxorubicin; D051057:Proto-Oncogene Proteins c-akt