Abstract: ObjectiveTo investigate the effect of regulating glucose metabolism by silent information regulator 6 （SIRT6） on radiosensitivity of nonsmall cell lung cancer A549 cells. MethodsThe adenovirus vector AdSIRT6 expressing SIRT6 was constructed， and mRNA levels of SIRT6 were detected by fluorescence quantitative realtime PCR （QPCR） at 24 h after transfection with different transfection intensities （0， 25， 50， 100， 200 pfu／cell） of AdSIRT6. According to the experimental design， A549 cells were divided into control group， empty load（Adnull） group and overexpression （AdSIRT6） group， and the virus concentration of Adnull group and AdSIRT6 group were 200 pfu／cell. The survival fraction （SF） of 3 groups after 0， 2， 4， 6， 8 and 10 Gy Xray irradiation were detected by colony formation assay， and the cell survival curve was drawn and the sensitivity enhancement ratio （SER） was calculated according to the multitarget model. Flow cytometry was used to detect the cell cycle and apoptosis at 48 h in 3 groups after 4 Gy Xray irradiation. The mRNA levels of pyruvate dehydrogenase 2 （PKM2）， lactate dehydrogenase A （LDHA） and hexokinase （HK） in glycolysis were detected by QPCR after 48 h irradiation with 4 Gy Xray. Glucose levels were measured by glucose kit after transfection for 12， 24， 36 and 48 h. 
ResultsQPCR results showed that in the range of 25200 pfu／cell， the mRNA levels of SIRT6 increased with the increasing intensity of transfection （P＜0001）. The mRNA levels of SIRT6 were 1012±0016， 1356±0185， 2243±0695， 4887±1169 and 7241±1425 for A549 cells transfected with 0， 25， 50， 100， 200 pfu／cell. The mRNA levels of SIRT6 were higher in 50， 100， 200 pfu／cell than in control group （P＜005）， and the followup test selected the strongest expression of 200 pfu／cell. The clone formation experiment showed that there was no significant difference in SF between Adnull group and control group after 0， 2， 4， 6， 8 and 10 Gy Xray irradiation （P＞005）， while the SF in AdSIRT6 group after 410 Gy Xray irradiation was lower than that in Adnull group and control group （P＜005）. The cell survival curve of the multitarget model showed that the SER was 176. Compared with control group and Adnull group， the percentage of G0／G1 phase cells and apoptotic rate in AdSIRT6 group were increased， while the percentage of S phase cells and the mRNA levels of PKM2， LDHA and HK were decreased （P＜005）. The glucose consumption of AdSIRT6 group decreased after 12， 24， 36 and 48 h of transfection， lower than those of control group and Adnull group （P＜005）. 
ConclusionOverexpression of SIRT6 can inhibit the formation of key enzymes during glycolysis in A549 cells to inhibit glycolysis as well as radiosensitivity， and lead to G0／G1 arrest and apoptosis.

Key words: Nonsmall cell lung cancer, Silent information regulator 6 （SIRT6）, Radiosensitivity, Glycolysis