Page 373 - 2014 Printable Abstract Book
P. 373
an effort to identify and screen potential mediators that may inhibit the eventual development of
radiation-induced fibrosis, we sought to determine whether the novel thioredoxin mimetic R-910 would
inhibit radiation-induced lung cell apoptosis when delivered either immediately before or 24 hours after
radiation. Methods: C57BL/6 female mice received 14 Gy radiation targeted to the thorax delivered by a
Philips X-ray Therapy Unit. R-910 was delivered via intraperitoneal injection either immediately before
(Day 0) or 24 hours post-radiation (Day 1) at a dose of 125 mg/kg. R-910 dosing was repeated 4 hours
post-radiation on Day 0 and continued twice/day at 125 mg/kg/injection on Days 1 - 6. Mice were
euthanized on Day 7 and lungs were examined for evidence of apoptosis by TUNEL assay. Results:
Untreated irradiated mice showed evidence of apoptosis in the lung on Day 7 post-radiation with 6 - 7%
of the cells being scored as TUNEL positive. This amount of apoptosis was significantly higher than that
observed in unirradiated control mice (< 0.5% TUNEL positive). Treatment with R-910 initiated either
immediately before radiation or 24 hours post-radiation significantly inhibited the development of lung
cell apoptosis as compared to irradiated mice. Levels of TUNEL positive cells in R-910 treated mice were
not significantly different than unirradiated control mice (< 3% TUNEL positive). Conclusion: Treatment of
irradiated mice with R-910, a thioredoxin mimetic, inhibits the development of lung cell apoptosis
apparent in irradiated control mice at Day 7 post-radiation. The efficacy of R-910 in inhibiting apoptosis
was not diminished by delaying treatment until 24 hours post-radiation. These results suggest that R-910
may be a good therapeutic candidate for testing in our radiation-induced pulmonary fibrosis model.
Funding: Lovelace Respiratory Research Institute.
(PS7-36) Radiosensitization of glioma cells by TP53-induced glycolysis and apoptosis regulator
1
1;2
knockdown is dependent on thioredoxin-1 nuclear translocation. Fenju Liu ; Haowen Zhang ; Cheng
1
1
1
3
Gu ; Jianjun Liu ; Jiahua Yu ; and Guomei Tai , School of Radiation Medicine and Protection, Medical
1
College of Soochow University, Suzhou, China ; Collaborative Innovation Center of Radiation Medicine of
2
Jiangsu Higher Education Institutions, Suzhou, China ; and Ren ji Hospital, School of Medicine, Shanghai
3
Jiao Tong University, Shanghai, China
TP53-induced glycolysis and apoptosis regulator (TIGAR) knockdown is proven to enhance the
radiosensitivity of glioma cells, but the mechanisms are not fully understood. Thioredoxin-1 (TRX1) is a
redox-sensitive oxidoreductase, which plays important roles in DNA damage response via nuclear
translocation in irradiated cells. Because the TRX1-dependent DNA damage signal transduction relies on
NADPH to maintain the reduced state of TRX1, and TIGAR functions to increase NADPH generation via
pentose phosphate pathway under oxidative stress, in this study, the role of TRX1 in TIGAR interference-
induced radiosensitization was investigated. It was demonstrated that ionizing radiation (IR)-induced
nuclear translocation of TRX1 was significantly hindered by TIGAR abrogation and reversed by wild-type
(WT)-TRX1 over-expression. In addition, WT-TRX1 over-expression could accelerate the process of DNA
damage repair postponed by TIGAR knockdown in glioma cells being irradiated. The reduction process of
IR-oxidized TRX1 was also delayed by TIGAR knockdown but restored by WT-TRX1 over-expression.
Therefore, we conclude that TIGAR knockdown-induced radiosensitization of glioma cells may be
dependent on the inhibition of TRX1 nuclear translocation. Finally, by using TIGAR shRNA lentivirus-based
gene therapy, it was proven TIGAR interference could radiosensitize glioma in vivo, and the mechanism
was correlated to the inhibition of TRX1 nuclear translocation.
371 | P a g e
radiation-induced fibrosis, we sought to determine whether the novel thioredoxin mimetic R-910 would
inhibit radiation-induced lung cell apoptosis when delivered either immediately before or 24 hours after
radiation. Methods: C57BL/6 female mice received 14 Gy radiation targeted to the thorax delivered by a
Philips X-ray Therapy Unit. R-910 was delivered via intraperitoneal injection either immediately before
(Day 0) or 24 hours post-radiation (Day 1) at a dose of 125 mg/kg. R-910 dosing was repeated 4 hours
post-radiation on Day 0 and continued twice/day at 125 mg/kg/injection on Days 1 - 6. Mice were
euthanized on Day 7 and lungs were examined for evidence of apoptosis by TUNEL assay. Results:
Untreated irradiated mice showed evidence of apoptosis in the lung on Day 7 post-radiation with 6 - 7%
of the cells being scored as TUNEL positive. This amount of apoptosis was significantly higher than that
observed in unirradiated control mice (< 0.5% TUNEL positive). Treatment with R-910 initiated either
immediately before radiation or 24 hours post-radiation significantly inhibited the development of lung
cell apoptosis as compared to irradiated mice. Levels of TUNEL positive cells in R-910 treated mice were
not significantly different than unirradiated control mice (< 3% TUNEL positive). Conclusion: Treatment of
irradiated mice with R-910, a thioredoxin mimetic, inhibits the development of lung cell apoptosis
apparent in irradiated control mice at Day 7 post-radiation. The efficacy of R-910 in inhibiting apoptosis
was not diminished by delaying treatment until 24 hours post-radiation. These results suggest that R-910
may be a good therapeutic candidate for testing in our radiation-induced pulmonary fibrosis model.
Funding: Lovelace Respiratory Research Institute.
(PS7-36) Radiosensitization of glioma cells by TP53-induced glycolysis and apoptosis regulator
1
1;2
knockdown is dependent on thioredoxin-1 nuclear translocation. Fenju Liu ; Haowen Zhang ; Cheng
1
1
1
3
Gu ; Jianjun Liu ; Jiahua Yu ; and Guomei Tai , School of Radiation Medicine and Protection, Medical
1
College of Soochow University, Suzhou, China ; Collaborative Innovation Center of Radiation Medicine of
2
Jiangsu Higher Education Institutions, Suzhou, China ; and Ren ji Hospital, School of Medicine, Shanghai
3
Jiao Tong University, Shanghai, China
TP53-induced glycolysis and apoptosis regulator (TIGAR) knockdown is proven to enhance the
radiosensitivity of glioma cells, but the mechanisms are not fully understood. Thioredoxin-1 (TRX1) is a
redox-sensitive oxidoreductase, which plays important roles in DNA damage response via nuclear
translocation in irradiated cells. Because the TRX1-dependent DNA damage signal transduction relies on
NADPH to maintain the reduced state of TRX1, and TIGAR functions to increase NADPH generation via
pentose phosphate pathway under oxidative stress, in this study, the role of TRX1 in TIGAR interference-
induced radiosensitization was investigated. It was demonstrated that ionizing radiation (IR)-induced
nuclear translocation of TRX1 was significantly hindered by TIGAR abrogation and reversed by wild-type
(WT)-TRX1 over-expression. In addition, WT-TRX1 over-expression could accelerate the process of DNA
damage repair postponed by TIGAR knockdown in glioma cells being irradiated. The reduction process of
IR-oxidized TRX1 was also delayed by TIGAR knockdown but restored by WT-TRX1 over-expression.
Therefore, we conclude that TIGAR knockdown-induced radiosensitization of glioma cells may be
dependent on the inhibition of TRX1 nuclear translocation. Finally, by using TIGAR shRNA lentivirus-based
gene therapy, it was proven TIGAR interference could radiosensitize glioma in vivo, and the mechanism
was correlated to the inhibition of TRX1 nuclear translocation.
371 | P a g e
