放射诱导对乳腺癌细胞株MDA-MB-231和MCF-7细胞周期及细胞凋亡的影响

Effect of radiation-induction on cell cycle and apoptosis in breast cancer cell lines MDA-MB-231 and MCF-7

目的研究经放射诱导的乳腺癌细胞株MDA-MB-231和MCF-7细胞周期和细胞凋亡的变化特点，探讨其与放射敏感性间的联系。方法使用6 MV X线对MCF-7和MDA-MB-231细胞进行照射，采用克隆形成实验拟合细胞存活曲线，计算放射生物学参数：平均致死剂量（D0）、准域剂量（Dq）和2 Gy照射的存活分数（SF2），比较肿瘤细胞放射敏感性；Hoechst 33342染色法检测肿瘤细胞的凋亡率，PI染色检测细胞周期。结果经6 MV X线照射后，MDA-MB-231细胞的存活曲线较MCF-7细胞右移；MDA-MB-231细胞D0、Dq和SF2值均大于MCF-7细胞（1.603±0.023比1.233±0.027、1.76±0.04比1.03±0.10、0.639 3±0.008 2比0.398 1±0.018 5，t值分别为-17.981、-11.745、-20.596，P值分别为0.000、0.003、0.000）。MCF-7细胞在2、4、8 Gy照射后24 h及同一剂量6 Gy照射后12 h和48 h的凋亡率均高于MDA-MB-231细胞（t值分别为4.441、7.299、10.499、6.375、7.743，P值分别为0.011、0.002、0.000、0.003、0.001）。和未照射相比，这两种细胞照射后均出现了不同程度的G2期阻滞，MDA-MB-231细胞组中G2/M期细胞比例随照射后时间及剂量的增加而逐渐增高，直至照射后48 h也未见细胞周期的明显恢复；而MCF-7细胞在受到8 Gy照射后24 h及6 Gy照射后48 h，这种阻滞就开始逐渐解除，随之出现G0/G1期细胞比例增高[（65.80±0.56）%、（62.53±0.67）%]。结论2~8 Gy 6 MV X线照射可诱导MCF-7细胞发生G1和G2期阻滞，MDA-MB-231细胞发生G2期阻滞，从而导致MCF-7细胞出现更多的凋亡，这也可能是造成两者放射敏感性差异的原因之一。

ObjectiveTo investigate the properties of radiation-induced changes of cell cycle and apoptosis in breast cancer cell lines MDA-MB-231 and MCF-7, and to further explore its relationship with radiosensitivity.MethodsThe two cell lines MCF-7 and MDA-MB-231 were irradiated with 6 MV X-rays. The cell survival curves were fitted by clonogenic formation assay, then according to the radiosensitivity parameters average lethal dose （D0）, quasi-threshold dose （Dq） and survival fraction after 2 Gy irradiation （SF2）, the radiosensitivity of the two cell lines was compared. The apoptosis rate and cell cycle distribution of the two cell lines were detected by Hoechst 33342 and PI staining.ResultsThe survival curve of MDA-MB-231 cell line shifted to the right compared with that of MCF-7 cell line. The values of D0, Dq and SF2 of MDA-MB-231 cell line were higher than those of MCF-7 cell line （1.603±0.023 vs. 1.233±0.027, 1.76±0.04 vs. 1.03±0.10, 0.639 3±0.008 2 vs. 0.398 1±0.018 5, t values were -17.981, -11.745, -20.596, P values were 0.000, 0.003, 0.000）. The apoptosis rate of MCF-7 cell line was significantly higher than that of MDA-MB-231 cell line at the doses of 2, 4, 8 Gy irradiated 24 h and at the 12, 48 h after 6 Gy X-irradiation （t values were 4.441, 7.299, 10.499, 6.375, 7.743, P values were 0.011, 0.002, 0.000, 0.003, 0.001）. Compared with the non-irradiated group, G2 phase arrest appeared in both cell lines after irradiation. The percentage of the G2/M phase in MDA-MB-231 cell line increased as the time or dosage accumulated. Furthmore, the percentage didn＇t go down even after 48 hours later. However, the blockage began to gradually release in MCF-7 cell line at the dose of 8 Gy irradiated 24 h and the 48 h after 6 Gy X-irradiation. Followed with that, it turned out the percentage of the G0/G1 phase increased [（65.80±0.56）%, （62.53±0.67）%].Conclusions6 MV X-irradiation with the doses of 2-8 Gy can induce the cell cycle arrest at G1 and G2 phase in MCF-7 cell line, G2 phase in MDA-MB-231 cell line. Thus more apoptosis appears in MCF-7 cell line, which may cause the difference in radiosensitivity between the two cell lines.