title: MicroRNA-21 inhibitor sensitizes human glioblastoma cells U251 (PTEN-mutant) and LN229 (PTEN-wild type) to taxol.
abstract: BACKGROUND
  Substantial data indicate that the oncogene microRNA 21 (miR-21) is significantly elevated in glioblastoma multiforme (GBM) and regulates multiple genes associated with cancer cell proliferation, apoptosis, and invasiveness. Thus, miR-21 can theoretically become a target to enhance the chemotherapeutic effect in cancer therapy. So far, the effect of downregulating miR-21 to enhance the chemotherapeutic effect to taxol has not been studied in human GBM.
  
  
  METHODS
  Human glioblastoma U251 (PTEN-mutant) and LN229 (PTEN wild-type) cells were treated with taxol and the miR-21 inhibitor (in a poly (amidoamine) (PAMAM) dendrimer), alone or in combination. The 50% inhibitory concentration and cell viability were determined by the MTT assay. The mechanism between the miR-21 inhibitor and the anticancer drug taxol was analyzed using the Zheng-Jun Jin method. Annexin V/PI staining was performed, and apoptosis and the cell cycle were evaluated by flow cytometry analysis. Expression of miR-21 was investigated by RT-PCR, and western blotting was performed to evaluate malignancy related protein alteration.
  
  
  RESULTS
  IC(50) values were dramatically decreased in cells treated with miR-21 inhibitor combine with taxol, to a greater extent than those treated with taxol alone. Furthermore, the miR-21 inhibitor significantly enhanced apoptosis in both U251 cells and LN229 cells, and cell invasiveness was obviously weakened. Interestingly, the above data suggested that in both the PTEN mutant and the wild-type GBM cells, miR-21 blockage increased the chemosensitivity to taxol. It is worth noting that the miR-21 inhibitor additively interacted with taxol on U251cells and synergistically on LN229 cells. Thus, the miR-21 inhibitor might interrupt the activity of EGFR pathways, independently of PTEN status. Meanwhile, the expression of STAT3 and p-STAT3 decreased to relatively low levels after miR-21 inhibitor and taxol treatment. The data strongly suggested that a regulatory loop between miR-21 and STAT3 might provide an insight into the mechanism of modulating EGFR/STAT3 signaling.
  
  
  CONCLUSIONS
  Taken together, the miR-21 inhibitor could enhance the chemo-sensitivity of human glioblastoma cells to taxol. A combination of miR-21 inhibitor and taxol could be an effective therapeutic strategy for controlling the growth of GBM by inhibiting STAT3 expression and phosphorylation.
authors.affiliation: Laboratory of Neuro-oncology, Tianjin Neurological Institute, Tianjin, PR China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ren
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhou
authors.forename: Mei
authors.initials: M
authors.lastname: Mei
authors.forename: Xu-Bo
authors.initials: XB
authors.lastname: Yuan
authors.forename: Lei
authors.initials: L
authors.lastname: Han
authors.forename: Guang-Xiu
authors.initials: GX
authors.lastname: Wang
authors.forename: Zhi-Fan
authors.initials: ZF
authors.lastname: Jia
authors.forename: Peng
authors.initials: P
authors.lastname: Xu
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Pu
authors.forename: Chun-Sheng
authors.initials: CS
authors.lastname: Kang
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000188:drug therapy*; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000188:drug therapy*; D006801:Humans; D020128:Inhibitory Concentration 50; D035683:MicroRNAs / Q000235:genetics*; D008954:Models, Biological; D051059:PTEN Phosphohydrolase / Q000235:genetics*; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation; D050796:STAT3 Transcription Factor / Q000378:metabolism; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D000972:Antineoplastic Agents, Phytogenic; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D013778:Tetrazolium Salts; D013844:Thiazoles; D066246:ErbB Receptors; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C022616:thiazolyl blue; D017239:Paclitaxel