A Comparison Of Biological Effects Between ¹²⁵I Seeds Continuous Low Dose Rate Radiation And ⁶⁰Co High Dose Rate Gamma Radiation On Non Small Cell Lung Cancer Cells

Objectives: To investigate the biological effects of continuous low dose rate（CLDR） radiation compared with high dose rate（HDR） radiation on non-small cell lung cancer（NSCLC） cells and the mechanisms for the anti-proliferative effectMaterials and methods: A549, H1299 and BEAS-2B cell lines were exposed to ¹²⁵I seeds CLDR radiation and ⁶⁰Co γ-ray HDR radiation, respectively, at 2, 4, 6, 8Gy. The survival fraction was determined by colony-forming assay. The cell cycle and the cell apoptosis were detected by flowcytometry（FCM）. The expression of apoptosis related proteins Bcl-2, BAX, Caspase-3 and PARP were detected by western blotting assay.Results: After irradiation with ¹²⁵I seeds CLDR, a lower survival fraction, an obvious cell cycle arrest（G1 arrest and G2/M arrest in A549 and H1299 cells） and a higher apoptotic ratio occured compared with ⁶⁰Co γ-ray HDR radiation on A549 and H1299 cells. Moreover, Western blot assay revealed that ¹²⁵I seeds CLDR radiation remarkably up-regulated the expression of BAX, Cleaved-caspase-3 and Cleaved-PARP proteins, down-regulated the expression of Bcl-2 proteins compared with ⁶⁰Co γ-ray HDR radiation on A549 and H1299 cells. However, for normal BEAS-2B cells, there were little change on apoptotic ratio and apoptosis related proteins under the same treatment.Conclusion: Firstly, ¹²⁵I seeds CLDR radiation led to a remarkable growth inhibition on A549 and H1299 cells compared with ⁶⁰Co HDR γ-ray radiation; with A549 cells were the most sensitive to radiation, followed by H1299 cells, the normal BEAS-2B cells were relative radio-resistance to A549 and H1299 cells. Secondly, the imbalance of Bcl-2/BAX ratio and the activation of Caspase-3, PARP proteins might play a key role in the anti-proliferative effects induced by ¹²⁵I seeds CLDR radiation.