title: MicroRNA 128a increases intracellular ROS level by targeting Bmi-1 and inhibits medulloblastoma cancer cell growth by promoting senescence.
abstract: BACKGROUND
  MicroRNAs (miRNAs) are a class of short non-coding RNAs that regulate cell homeostasis by inhibiting translation or degrading mRNA of target genes, and thereby can act as tumor suppressor genes or oncogenes. The role of microRNAs in medulloblastoma has only recently been addressed. We hypothesized that microRNAs differentially expressed during normal CNS development might be abnormally regulated in medulloblastoma and are functionally important for medulloblastoma cell growth.
  
  
  RESULTS
  We examined the expression of microRNAs in medulloblastoma and then investigated the functional role of one specific one, miR-128a, in regulating medulloblastoma cell growth. We found that many microRNAs associated with normal neuronal differentiation are significantly down regulated in medulloblastoma. One of these, miR-128a, inhibits growth of medulloblastoma cells by targeting the Bmi-1 oncogene. In addition, miR-128a alters the intracellular redox state of the tumor cells and promotes cellular senescence.
  
  
  CONCLUSIONS
  Here we report the novel regulation of reactive oxygen species (ROS) by microRNA 128a via the specific inhibition of the Bmi-1 oncogene. We demonstrate that miR-128a has growth suppressive activity in medulloblastoma and that this activity is partially mediated by targeting Bmi-1. This data has implications for the modulation of redox states in cancer stem cells, which are thought to be resistant to therapy due to their low ROS states.
authors.affiliation: Department of Pediatrics, University of Colorado, Denver, Colorado, USA.
authors.forename: Sujatha
authors.initials: S
authors.lastname: Venkataraman
authors.forename: Irina
authors.initials: I
authors.lastname: Alimova
authors.forename: Rong
authors.initials: R
authors.lastname: Fan
authors.forename: Peter
authors.initials: P
authors.lastname: Harris
authors.forename: Nicholas
authors.initials: N
authors.lastname: Foreman
authors.forename: Rajeev
authors.initials: R
authors.lastname: Vibhakar
mesh_terms: D001483:Base Sequence; D001921:Brain / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016922:Cellular Senescence / Q000235:genetics*; D015536:Down-Regulation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D042541:Intracellular Space / Q000235:genetics / Q000378:metabolism*; D008527:Medulloblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D013481:Superoxides / Q000378:metabolism
chemical_list: C069077:BMI1 protein, human; C545189:MIRN128 microRNA, human; D035683:MicroRNAs; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D012097:Repressor Proteins; D013481:Superoxides; D063150:Polycomb Repressive Complex 1