title: Combined IFN-gamma and retinoic acid treatment targets the N-Myc/Max/Mad1 network resulting in repression of N-Myc target genes in MYCN-amplified neuroblastoma cells.
abstract: The MYCN protooncogene is involved in the control of cell proliferation, differentiation, and survival of neuroblasts. Deregulation of MYCN by gene amplification contributes to neuroblastoma development and is strongly correlated to advanced disease and poor outcome, emphasizing the urge for new therapeutic strategies targeting MYCN function. The transcription factor N-Myc, encoded by MYCN, regulates numerous genes together with its partner Max, which also functions as a cofactor for the Mad/Mnt family of Myc antagonists/transcriptional repressors. We and others have previously reported that IFN-gamma synergistically potentiates retinoic acid (RA)-induced sympathetic differentiation and growth inhibition in neuroblastoma cells. This study shows that combined treatment of MYCN-amplified neuroblastoma cells with RA+IFN-gamma down-regulates N-Myc protein expression through increased protein turnover, up-regulates Mad1 mRNA and protein, and reduces N-Myc/Max heterodimerization. This results in a shift of occupancy at the ornithine decarboxylase N-Myc/Mad1 target promoter in vivo from N-Myc/Max to Mad1/Max predominance, correlating with histone H4 deacetylation, indicative of a chromatin structure typical of a transcriptionally repressed state. This is further supported by data showing that RA+IFN-gamma treatment strongly represses expression of N-Myc/Mad1 target genes ornithine decarboxylase and hTERT. Our results suggest that combined IFN-gamma and RA signaling can form a basis for new therapeutic strategies targeting N-Myc function for patients with high-risk, MYCN-amplified neuroblastoma.
authors.affiliation: Department of Plant Biology and Forest Genetics, Uppsala Genetic Center, Swedish University of Agricultural Sciences, University of Uppsala, University Hospital, Uppsala, Sweden.
authors.forename: Cihan
authors.initials: C
authors.lastname: Cetinkaya
authors.forename: Anne
authors.initials: A
authors.lastname: Hultquist
authors.forename: Yingtao
authors.initials: Y
authors.lastname: Su
authors.forename: Siqin
authors.initials: S
authors.lastname: Wu
authors.forename: Fuad
authors.initials: F
authors.lastname: Bahram
authors.forename: Sven
authors.initials: S
authors.lastname: Påhlman
authors.forename: Irina
authors.initials: I
authors.lastname: Guzhova
authors.forename: Lars-Gunnar
authors.initials: LG
authors.lastname: Larsson
mesh_terms: D000107:Acetylation; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D015152:Blotting, Northern; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D019281:Dimerization; D004359:Drug Therapy, Combination; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D007371:Interferon-gamma / Q000627:therapeutic use; D000071447:N-Myc Proto-Oncogene Protein; D009447:Neuroblastoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism*; D009955:Ornithine Decarboxylase / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014212:Tretinoin / Q000627:therapeutic use; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D050976:Basic-Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins; D002843:Chromatin; D006657:Histones; C501384:MAD1L1 protein, human; C459801:MYCN protein, human; C067850:Myc associated factor X; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D012097:Repressor Proteins; D014212:Tretinoin; D007371:Interferon-gamma; D009955:Ornithine Decarboxylase