^125I粒子持续低剂量率照射胰腺癌细胞株PANC-1相对生物效应的研究

Relative biological effectiveness of ^125 I seeds for low-dose-rate irradiation of PANC-1

目的探讨国产6711型^125I粒子的相对生物效应，并对其照射杀伤PANC-1细胞的效果进行了初步探讨。方法PANC-1细胞处于指数生长期时，行^125I粒子离体照射；在初始剂量率为2．59cGy／h时，分别给予1、2、4、6、8和10Gy照射。^60Co照射作为对照组，吸收剂量率为2．21Gy／min，给予相同剂量照射。用锥虫蓝染色法检测细胞死亡比率，并比较在4Gy照射后培养12、24、48和72h细胞死亡率随时间变化。采用克隆形成实验，计算细胞克隆形成率，绘制生存曲线，得出生物学参数，并测定^125I粒子与^60Co的相对生物效应。结果在相同剂量照射下，^125I持续低剂量率照射与^60Co照射相比，当≥4Gy时，细胞死亡率明显增高。在4Gy照射后，随着时间延长细胞死亡率增高，两者相比有明显差异。从生存曲线分析，^125I粒子持续低剂量率照射细胞存活分数比^60Co低，^125I粒子相对于^60Co的生物效应为1．45。结论^125I粒子持续低剂量率照射与^60Co高剂量率照射相比，细胞杀伤效应更强；测定的相对生物效应与其他研究者测量的结果相似；将为临床^125I粒子治疗肿瘤提供一定的参考价值。

Objective To investigate the relative biological effectiveness（RBE） of National Model 6711 ^125I seeds and the response patterns of PANC-1 exposed to ^125I seeds irradiation. Methods PANC-1 cells in exponential growth were irradiated at initial dose rate of 2.59 cGy/h in vitro and exposed to 1, 2, 4, 6, 8 and 10 Gy. Meanwhile, the other part of cells were exposed to the same doses by ^60Co at dose rate of 2.21 Gy/min. After irradiation, the cells were stained by trypan blue to measure the cellular mortality rate and to compare the changes along with plating times of 12, 24, 48 and 72 h after 4 Gy. Tbe colonies were counted to obtain the plating efficiencies by colony-forming assay and the cell surviving fraction was calculated to plot cell survival curves, and RBE of ^125I seeds relative to ^60Co was determined. Results The cell death rate for continuous low- dose-rate （LDR） irradiation by ^125I seeds was greater than ^60Co at the same doses above or equal to 4 Gy. After 4 Gy irradiation, the cellular mortality rates were increased with times. The difference was significant between ^125 I seeds and ^60 Co. The survival fractions of ^125I were lower than those of ^60 Co, and the RBE of ^125I relative to ^60 Co was determined to be 1.45. Conclusion The cell-killing effects for continuous low-dose-rate （LDR） irradiation by ^125I seeds are greater than acute high-dose-rate of ^60 Co.