title: Down-regulation of BTG1 by miR-454-3p enhances cellular radiosensitivity in renal carcinoma cells.
abstract: BACKGROUND
  B cell translocation gene 1 (BTG1) has long been recognized as a tumor suppressor gene. Recent reports demonstrated that BTG1 plays an important role in progression of cell cycle and is involved in cellular response to stressors. However, the microRNAs mediated regulatory mechanism of BTG1 expression has not been reported so far. MicroRNAs can effectively influence tumor radiosensitivity by preventing cell cycle progression, resulting in enhancement of the cytotoxicity of radiotherapy efficacy. This study aimed to demonstrating the effects of microRNAs on the BTG1 expression and cellular radiosensitivity.
  
  
  METHODS
  The human renal carcinoma 786-O cells were treated with 5 Gy of X-rays. Expressions of BTG1 gene and miR-454-3p, which was predicted to target BTG1 by software algorithm, were analyzed by quantitative polymerase chain reaction. Protein expressions were assessed by Western blot. Luciferase assays were used to quantify the interaction between BTG1 3'-untranslated region (3'-UTR) and miR-454-3p. The radiosensitivity was quantified by the assay of cell viability, colony formation and caspase-3 activity.
  
  
  RESULTS
  The expression of the BTG1 gene in 786-O cells was significantly elevated after treatments with X-ray irradiation, DMSO, or serum starvation. The up-regulation of BTG1 after irradiation reduced cellular radiosensitivity as demonstrated by the enhanced cell viability and colony formation, as well as the repressed caspase-3 activity. In comparison, knock down of BTG1 by siRNA led to significantly enhanced cellular radiosensitivity. It was found that miR-454-3p can regulate the expression of BTG1 through a direct interaction with the 3'-UTR of BTG1 mRNA. Decreasing of its expression level correlates well with BTG1 up-regulation during X-ray irradiation. Particularly, we observed that over-expression of miR-454-3p by transfection inhibited the BTG1 expression and enhanced the radiosensitivity. In addition, cell cycle analysis showed that over-expression of miR-454-3p shifted the cell cycle arrest from G2/M phase to S phase.
  
  
  CONCLUSIONS
  Our results indicate that BTG1 is a direct target of miR-454-3p. Down-regulation of BTG1 by miR-454-3p renders tumor cells sensitive to radiation. These results may shed light on the potential application in tumor radiotherapy.
authors.forename: Xin
authors.initials: X
authors.lastname: Wu
authors.forename: Nan
authors.initials: N
authors.lastname: Ding
authors.forename: Wentao
authors.initials: W
authors.lastname: Hu
authors.forename: Jinpeng
authors.initials: J
authors.lastname: He
authors.forename: Shuai
authors.initials: S
authors.lastname: Xu
authors.forename: Hailong
authors.initials: H
authors.lastname: Pei
authors.forename: Junrui
authors.initials: J
authors.lastname: Hua
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Department of Space Radiobiology, Key Laboratory of Heavy Ion Radiation Biology and Medicine, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 509 Nanchang Road, Lanzhou 730000, China. jufangwang@impcas.ac.cn.
authors.forename: Jufang
authors.initials: J
authors.lastname: Wang
mesh_terms: D015153:Blotting, Western; D002292:Carcinoma, Renal Cell / Q000235:genetics*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000528:radiation effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007680:Kidney Neoplasms / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics*; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D014162:Transfection
chemical_list: C583712:MIRN454 microRNA, human; D035683:MicroRNAs; D009363:Neoplasm Proteins; C074086:BTG1 protein, human