title: Role of Noxa in p53-independent fenretinide-induced apoptosis of neuroectodermal tumours.
abstract: Fenretinide-induced apoptosis of neuroectodermal tumour cells is mediated through generation of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, mitochondrial cytochrome c release and caspase activation. The present study describes the requirement of the BH3-domain only protein Noxa for this process and its regulation by p53. Noxa expression was induced by fenretinide in neuroblastoma and melanoma cells, including those with mutated p53, and this induction was abolished by antioxidants. Knockdown of p53 by RNA interference (RNAi) demonstrated upregulation of Noxa protein levels in response to fenretinide was p53-independent, although evidence suggested that Noxa may be transcriptionally regulated by p53. The ER stress-inducing agent thapsigargin also induced p53-independent Noxa expression. Conversely, Noxa transcription in response to the chemotherapeutic agents cisplatin or temozolomide was inhibited by p53 knockdown. Apoptosis in response to cisplatin or temozolomide was also inhibited by abrogation of p53 expression yet apoptosis in response to fenretinide or thapsigargin was unaffected. RNAi-mediated down-regulation of Noxa inhibited apoptosis in response to fenretinide or thapsigargin, whereas apoptosis induced by cisplatin or temozolomide was unaffected. These data demonstrate the importance of Noxa induction in determining the apoptotic response to fenretinide and emphasise the role of Noxa in p53-independent apoptosis.
authors.affiliation: Northern Institute for Cancer Research, School of Clinical and Laboratory Sciences, Newcastle University, Newcastle Upon Tyne, NE2 4HH, UK, J.L.Armstrong@ncl.ac.uk
authors.forename: Jane L
authors.initials: JL
authors.lastname: Armstrong
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Veal
authors.forename: Christopher P F
authors.initials: CP
authors.lastname: Redfern
authors.forename: Penny E
authors.initials: PE
authors.lastname: Lovat
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D017313:Fenretinide / Q000494:pharmacology / Q000627:therapeutic use; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008545:Melanoma / Q000188:drug therapy* / Q000378:metabolism; D009447:Neuroblastoma / Q000188:drug therapy* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D019284:Thapsigargin / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; C498702:PMAIP1 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D017313:Fenretinide; D019284:Thapsigargin; D053148:Caspase 3