title: Bmi-1 promotes the aggressiveness of glioma via activating the NF-kappaB/MMP-9 signaling pathway.
abstract: BACKGROUND
  The prognosis of human glioma is poor, and the highly invasive nature of the disease represents a major impediment to current therapeutic modalities. The oncoprotein B-cell-specific Moloney murine leukemia virus integration site 1 protein (Bmi-1) has been linked to the development and progression of glioma; however, the biological role of Bmi-1 in the invasion of glioma remains unclear.
  
  
  METHODS
  A172 and LN229 glioma cells were engineered to overexpress Bmi-1 via stable transfection or to be silenced for Bmi-1 expression using RNA interfering method. Migration and invasiveness of the engineered cells were assessed using wound healing assay, Transwell migration assay, Transwell matrix penetration assay and 3-D spheroid invasion assay. MMP-9 expression and activity were measured using real-time PCR, ELISA and the gelatin zymography methods. Expression of NF-kappaB target genes was quantified using real-time PCR. NF-kappaB transcriptional activity was assessed using an NF-kappaB luciferase reporter system. Expression of Bmi-1 and MMP-9 in clinical specimens was analyzed using immunohistochemical assay.
  
  
  RESULTS
  Ectopic overexpression of Bmi-1 dramatically increased, whereas knockdown of endogenous Bmi-1 reduced, the invasiveness and migration of glioma cells. NF-kappaB transcriptional activity and MMP-9 expression and activity were significantly increased in Bmi-1-overexpressing but reduced in Bmi-1-silenced cells. The reporter luciferase activity driven by MMP-9 promoter in Bmi-1-overexpressing cells was dependent on the presence of a functional NF-kappaB binding site, and blockade of NF-kappaB signaling inhibited the upregulation of MMP-9 in Bmi-1 overexpressing cells. Furthermore, expression of Bmi-1 correlated with NF-kappaB nuclear translocation as well as MMP-9 expression in clinical glioma samples.
  
  
  CONCLUSIONS
  Bmi-1 may play an important role in the development of aggressive phenotype of glioma via activating the NF-kappaB/MMP-9 pathway and therefore might represent a novel therapeutic target for glioma.
authors.affiliation: Department of Pathophysiology, Guangzhou Medical University, Guangzhou, Guangdong 510182, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Jiang
authors.forename: Jueheng
authors.initials: J
authors.lastname: Wu
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Liping
authors.initials: L
authors.lastname: Liu
authors.forename: Libing
authors.initials: L
authors.lastname: Song
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Mengfeng
authors.initials: M
authors.lastname: Li
mesh_terms: D045744:Cell Line, Tumor; D055785:Gene Knockdown Techniques; D005910:Glioma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D010641:Phenotype; D063150:Polycomb Repressive Complex 1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C069077:BMI1 protein, human; D016328:NF-kappa B; D063150:Polycomb Repressive Complex 1; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9