CR-UK/MRC Gray Institute for Radiation Oncology and Biology, Department of Oncology, University of Oxford, Oxford, UK.
Int J Radiat Oncol Biol Phys. 2012 Jul 15;83(4):1298-305. doi: 10.1016/j.ijrobp.2011.09.051. Epub 2012 Feb 14.
The open structure of euchromatin renders it susceptible to DNA damage by ionizing radiation (IR) compared with compact heterochromatin. The effect of chromatin configuration on the efficacy of Auger electron radiotherapy was investigated.
Chromatin structure was altered in MDA-MB-468 and 231-H2N human breast cancer cells by suberoylanilide hydroxamic acid (SAHA), 5-aza-2-deoxycytidine, or hypertonic treatment. The extent and duration of chromatin structural changes were evaluated using the micrococcal nuclease assay. DNA damage (γH2AX assay) and clonogenic survival were evaluated after exposure to (111)In-DTPA-hEGF, an Auger electron-emitting radiopharmaceutical, or IR. The intracellular distribution of (111)In-DTPA-hEGF after chromatin modification was investigated in cell fractionation experiments.
Chromatin remained condensed for up to 20 minutes after NaCl and in a relaxed state 24 hours after SAHA treatment. The number of γH2AX foci per cell was greater in MDA-MB-468 and 231-H2N cells after IR (0.5 Gy) plus SAHA (1 μM) compared with IR alone (16 ± 0.6 and 14 ± 0.3 vs. 12 ± 0.4 and 11 ± 0.2, respectively). More γH2AX foci were observed in MDA-MB-468 and 231-H2N cells exposed to (111)In-DTPA-hEGF (6 MBq/μg) plus SAHA vs. (111)In-DTPA-hEGF alone (11 ± 0.3 and 12 ± 0.7 vs. 9 ± 0.4 and 7 ± 0.3, respectively). 5-aza-2-deoxycytidine enhanced the DNA damage caused by IR and (111)In-DTPA-hEGF. Clonogenic survival was reduced in MDA-MB-468 and 231-H2N cells after IR (6 Gy) plus SAHA (1 μM) vs. IR alone (0.6% ± 0.01 and 0.3% ± 0.2 vs. 5.8% ± 0.2 and 2% ± 0.1, respectively) and after (111)In-DTPA-hEGF plus SAHA compared to (111)In-DTPA-hEGF alone (21% ± 0.4% and 19% ± 4.6 vs. 33% ± 2.3 and 32% ± 3.7). SAHA did not affect (111)In-DTPA-hEGF nuclear localization. Hypertonic treatment resulted in fewer γH2AX foci per cell after IR and (111)In-DTPA-hEGF compared to controls but did not significantly alter clonogenic survival.
Chromatin structure affects DNA damage and cell survival after exposure to Auger electron radiation.
与紧密的异染色质相比，常染色质的开放结构使其容易受到电离辐射（IR）的 DNA 损伤。研究了染色质结构对俄歇电子放射治疗效果的影响。
通过琥珀酰亚胺基羟肟酸（SAHA）、5-氮杂-2-脱氧胞苷或高渗处理改变 MDA-MB-468 和 231-H2N 人乳腺癌细胞的染色质结构。使用微球菌核酸酶测定法评估染色质结构变化的程度和持续时间。在暴露于（111）In-DTPA-hEGF（一种俄歇电子发射放射性药物）或 IR 后，评估 DNA 损伤（γH2AX 测定）和集落形成存活。在细胞分馏实验中研究了染色质修饰后（111）In-DTPA-hEGF 的细胞内分布。
NaCl 处理后，染色质在长达 20 分钟内保持凝聚状态，SAHA 处理 24 小时后呈松弛状态。与单独 IR（0.5 Gy）相比，IR 加 SAHA（1 μM）处理后的 MDA-MB-468 和 231-H2N 细胞中每个细胞的γH2AX 焦点数量更多（分别为 16±0.6 和 14±0.3 与 12±0.4 和 11±0.2）。与单独使用（111）In-DTPA-hEGF 相比，暴露于（111）In-DTPA-hEGF（6 MBq/μg）加 SAHA 的 MDA-MB-468 和 231-H2N 细胞中观察到更多的γH2AX 焦点（分别为 11±0.3 和 12±0.7 与 9±0.4 和 7±0.3）。5-氮杂-2-脱氧胞苷增强了 IR 和（111）In-DTPA-hEGF 引起的 DNA 损伤。与单独使用 IR（6 Gy）加 SAHA（1 μM）相比，IR 加 SAHA（1 μM）处理后的 MDA-MB-468 和 231-H2N 细胞的集落存活减少（分别为 0.6%±0.01 和 0.3%±0.2 与 5.8%±0.2 和 2%±0.1），与单独使用（111）In-DTPA-hEGF 相比，（111）In-DTPA-hEGF 加 SAHA 处理后的 MDA-MB-468 和 231-H2N 细胞的集落存活减少（分别为 21%±0.4%和 19%±4.6 与 33%±2.3 和 32%±3.7）。SAHA 不影响（111）In-DTPA-hEGF 的核定位。与对照组相比，高渗处理后 IR 和（111）In-DTPA-hEGF 处理后的每个细胞中的γH2AX 焦点数量减少，但对集落存活没有显著影响。
染色质结构影响暴露于俄歇电子辐射后的 DNA 损伤和细胞存活。
