Meijer A E, Jernberg A R-M, Heiden T, Stenerlöw B, Persson L M, Tilly N, Lind B K, Edgren M R
Department of Oncology-Pathology, Division of Medical Radiation Physics, Karolinska Institutet, Stockholm, Sweden.
Int J Radiat Biol. 2005 Apr;81(4):261-72. doi: 10.1080/09553000500141215.
The aim was to investigate and compare the influence of linear energy transfer (LET), dose and time on the induction of apoptosis in a human melanoma cell line exposed to accelerated light boron ((10)B) ions and photons. Cells were exposed in vitro to doses up to 6 Gy accelerated boron ions (40, 80, 125 and 160 eV nm(-1)) and up to 12 Gy photons (0.2 eV nm(-1)). The induction of apoptosis was measured up to 9 days after irradiation using morphological characterization of apoptotic cells and bodies. In parallel, measurements of cell-cycle distribution, monitored by DNA flow cytometry, and cell survival based on the clonogenic cell survival assay, were performed. In addition, the induction and repair of DNA double-strand breaks (DSB), using pulsed-field gel electrophoresis (PFGE) were studied. Accelerated boron ions induced a significant increase in apoptosis as compared with photons at all time points studied. At 1-5 h the percentage of radiation-induced apoptotic cells increased with both dose and LET. At the later time points (24-216 h) the apoptotic response was more complex and did not increase in a strictly LET-dependent manner. The early premitotic apoptotic cells disappeared at 24 h following exposure to the highest LET (160 eV nm(-1)). A postmitotic apoptotic response was seen after release of the dose-, time- and LET-dependent G2/M accumulations. The loss of clonogenic ability was dose- and LET-dependent and the fraction of un-rejoined DSB increased with increasing LET. Despite the LET-dependent clonogenic cell killing, it was not possible to measure quantitatively a LET-dependent apoptotic response. This was due to the different time course of appearance and disappearance of apoptotic cells.
目的是研究和比较线性能量传递（LET）、剂量和时间对暴露于加速光硼（¹⁰B）离子和光子的人黑色素瘤细胞系中细胞凋亡诱导的影响。细胞在体外暴露于高达6 Gy的加速硼离子（40、80、125和160 eV nm⁻¹）和高达12 Gy的光子（0.2 eV nm⁻¹）。使用凋亡细胞和凋亡小体的形态学特征，在照射后长达9天测量细胞凋亡的诱导情况。同时，通过DNA流式细胞术监测细胞周期分布，并基于克隆形成细胞存活试验进行细胞存活测量。此外，使用脉冲场凝胶电泳（PFGE）研究DNA双链断裂（DSB）的诱导和修复。在所有研究的时间点，与光子相比，加速硼离子诱导细胞凋亡显著增加。在1 - 5小时，辐射诱导的凋亡细胞百分比随剂量和LET增加。在后期时间点（24 - 216小时），凋亡反应更为复杂，并非严格以LET依赖的方式增加。暴露于最高LET（160 eV nm⁻¹）后，早期有丝分裂前凋亡细胞在24小时消失。在剂量、时间和LET依赖的G2/M积累解除后，观察到有丝分裂后凋亡反应。克隆形成能力的丧失是剂量和LET依赖的，未重新连接的DSB比例随LET增加而增加。尽管克隆形成细胞杀伤具有LET依赖性，但无法定量测量LET依赖性凋亡反应。这是由于凋亡细胞出现和消失的时间进程不同。
