title: Radiosensitization effect of overexpression of adenovirus-mediated SIRT6 on A549 non-small cell lung cancer cells.
abstract: OBJECTIVE
  To explore the radiosensitization effect of overexpression of silent information regulator 6 (SIRT6) on A549 non-small cell lung cancer (NSCLC) cells.
  
  
  METHODS
  Adenovirus vector Ad-SIRT6 causing overexpression of SIRT6 was established. Western blotting and MTT assay were adopted to detect the level of SIRT6 protein and the inhibitory rate of A549 cell proliferation after different concentrations of adenovirus transduction (0, 25, 100, 200, and 400 pfu/cell) for 24 h. Control group, Ad-null group and Ad-SIRT6 group were designed in this experiment and virus concentration of the latter two groups was 200 pfu/cell. Colony formation assays were employed to test survival fraction (SF) of the 3 groups after 0, 2, 4, 6, 8, 10 X-ray irradiation. Flow cytometry was used to detect the status of cell cycle of 3 groups after 48 h of 4 Gy X-ray irradiation and Western blotting was used to determine the expression of apoptosis-related genes of 3 groups after 48 h of 4 Gy X-ray irradiation.
  
  
  RESULTS
  In the range of 25 ~ 400 pfu/cell, the inhibitory rate of A549 cell proliferation increased as adenovirus concentration raised. The inhibitory rates under the concentrations of 0, 25, 100, 200, and 400 pfu/cell were 0%, 4.23 ± 0.34%, 12.7 ± 2.57%, 22.6 ± 3.38%, 32.2 ± 3.22%, 38.7 ± 4.09% and 47.8 ± 5.58% and there were significantly differences among groups (P < .05). SF in Ad-SIRT6 group was lower than Ad-null and control groups after 4 ~ 10 Gy X-ray irradiation (P < 0.05) and the sensitization enhancement ratio (SER) was 1.35 when compared with control group. Moreover, after 48 h of 4 Gy X-ray irradiation, there appeared a significant increase in G1-phase cell proportion, up-regulated expression of the level of apoptosis-promoting genes (Bax and Cleaved caspase-3), but a obvious decline in S-phase and G2-phase cell proportion and a significant decrease of the level of apoptosis- inhibiting gene (Bal-2) in the Ad-SIRT6 group (P<0.05).
  
  
  CONCLUSIONS
  The over-expression of adenovirus-mediated SIRT6, which has radiosensitization effect on A549 cells of NSCLC, can inhibit the proliferation of A549 cells and cause G0/G1 phase retardation as well as induce apoptosis of cells.
authors.affiliation: Department of Radiation Oncology, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China E-mail : shixl@126.com.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cai
authors.forename: Zhao-Ying
authors.initials: ZY
authors.lastname: Sheng
authors.forename: Shi-Xiong
authors.initials: SX
authors.lastname: Liang
mesh_terms: D000256:Adenoviridae; D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics*; D053148:Caspase 3 / Q000378:metabolism / Q000528:radiation effects; D059447:Cell Cycle Checkpoints / Q000235:genetics / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics / Q000528:radiation effects; D005822:Genetic Vectors; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*; D037761:Sirtuins / Q000235:genetics*; D014162:Transfection; D015854:Up-Regulation; D014965:X-Rays; D051028:bcl-2-Associated X Protein / Q000378:metabolism / Q000528:radiation effects
chemical_list: D051028:bcl-2-Associated X Protein; C505407:CASP3 protein, human; D053148:Caspase 3; C516592:SIRT6 protein, human; D037761:Sirtuins