title: Tumour-suppressor microRNAs let-7 and mir-101 target the proto-oncogene MYCN and inhibit cell proliferation in MYCN-amplified neuroblastoma.
abstract: BACKGROUND
  MicroRNAs (miRNAs) regulate expression of many cancer-related genes through posttranscriptional repression of their mRNAs. In this study we investigate the proto-oncogene MYCN as a target for miRNA regulation.
  
  
  METHODS
  A luciferase reporter assay was used to investigate software-predicted miRNA target sites in the 3'-untranslated region (3'UTR) of MYCN. The miRNAs were overexpressed in cell lines by transfection of miRNA mimics or miRNA-expressing plasmids. Mutation of the target sites was used to validate MYCN 3'UTR as a direct target of several miRNAs. To measure miRNA-mediated suppression of endogenous N-myc protein, inhibition of proliferation and inhibition of clonogenic growth, miRNAs were overexpressed in a MYCN-amplified neuroblastoma cell line.
  
  
  RESULTS
  The results from this study show that MYCN is targeted by several miRNAs. In addition to the previously shown mir-34a/c, we experimentally validate mir-449, mir-19a/b, mir-29a/b/c, mir-101 and let-7e/mir-202 as direct MYCN-targeting miRNAs. These miRNAs were able to suppress endogenous N-myc protein in a MYCN-amplified neuroblastoma cell line. The let-7e and mir-202 were strong negative regulators of MYCN expression. The mir-101 and the let-7 family miRNAs let-7e and mir-202 inhibited proliferation and clonogenic growth when overexpressed in Kelly cells.
  
  
  CONCLUSIONS
  The tumour-suppressor miRNAs let-7 and mir-101 target MYCN and inhibit proliferation and clonogenic growth of MYCN-amplified neuroblastoma cells.
authors.affiliation: Department of Paediatrics, University Hospital of North-Norway, 9038 Tromsø, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Buechner
authors.forename: E
authors.initials: E
authors.lastname: Tømte
authors.forename: B H
authors.initials: BH
authors.lastname: Haug
authors.forename: J R
authors.initials: JR
authors.lastname: Henriksen
authors.forename: C
authors.initials: C
authors.lastname: Løkke
authors.forename: T
authors.initials: T
authors.lastname: Flægstad
authors.forename: C
authors.initials: C
authors.lastname: Einvik
mesh_terms: D001932:Brain Neoplasms / Q000235:genetics / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D015536:Down-Regulation / Q000235:genetics / Q000502:physiology; D005784:Gene Amplification / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D018390:Gene Targeting; D016147:Genes, Tumor Suppressor / Q000502:physiology; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000502:physiology*; D000071447:N-Myc Proto-Oncogene Protein; D009447:Neuroblastoma / Q000235:genetics / Q000473:pathology*; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics*; D015513:Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics*; D000090063:Proto-Oncogene Mas; D011519:Proto-Oncogenes / Q000235:genetics
chemical_list: C000715470:MAS1 protein, human; C549045:MIRN107 microRNA, human; C459801:MYCN protein, human; D035683:MicroRNAs; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D000090063:Proto-Oncogene Mas; C487931:mirnlet7 microRNA, human