Journal
INTERNATIONAL JOURNAL OF RADIATION BIOLOGY
Volume 93, Issue 8, Pages 764-770Publisher
TAYLOR & FRANCIS LTD
DOI: 10.1080/09553002.2017.1325025
Keywords
Hypoxia; radioresistance; autophagy; ROS; lung cancer cells
Funding
- National Nature Science Foundation of China [31570850, 81672985]
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Purpose: Tumor resistance towards radiation has been a big obstacle in the poor prognosis of lung cancer. It has been reported that hypoxia and autophagy partly contribute to this resistance. However, there is controversy over whether autophagy plays a positive role in cancer therapy or not. We aim to find out the specific mechanism of radiation resistance. Materials and methods: A549 cells were treated with conditioned medium (CM) under 12h hypoxia or normoxia before irradiation, followed by the measurement of clonogenic survival, reactive oxygen species (ROS), signal of mitochondria and autophagy flux. In some experiments, the A549 cells were respectively transfected with LC3 small interfering RNA (siRNA), or treated with Earle's Balanced Salt Solution (EBSS). Results: We found that hypoxia enhanced cell radioresistance by increasing the induction of autophagy. And after hypoxia stress, the number of mitochondria was reduced but the cellular ROS level was enhanced. It was significant that autophagy may enhance cell radioresistance by reducing ROS during hypoxic treatment. Conclusions: We elucidated the possible mechanisms of autophagy in regulating cancer cell death or survival. These results supply a new opinion about the intrinsic factor of radioresistance of hypoxia tumors.
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