Objectives: To investigate the biological effects of ¹²⁵I seeds continuous low dose rate (CLDR) radiation compared with ⁶⁰Co γ-ray high dose rate (HDR) radiation on non-small cell lung cancer (NSCLC) cells.
Materials and methods: A549, H1299 and BEAS-2B cells were exposed to ¹²⁵I seeds CLDR radiation and ⁶⁰Co γ-ray HDR radiation, respectively. 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 Caspase-3 and Cleaved-caspase-3, PARP and Cleaved-PARP, BAX and Bcl-2 were detected by western blotting assay.
Results: After irradiation with 125I seeds CLDR, there were 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 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, but we didn’t ruled out other possibilities which would be investigated in the future studies.