Department of Radiotherapy and Radiation Oncology, University of Rostock, Südring 75, Rostock, Germany.
Strahlenther Onkol. 2012 Feb;188(2):177-84. doi: 10.1007/s00066-011-0029-4. Epub 2012 Jan 12.
A combined modality treatment employing radiation and chemotherapy plays a central role in the management of solid tumors. In our study, we examined the cytotoxic and radiosensitive effect of the microtubule stabilizer epothilone B on two human epithelial tumor cell lines in vitro and its influence on the microtubule assembly.
Cancer cells were treated with epothilone B in proliferation assays and in combination with radiation in colony-forming assays. For the analysis of ionizing radiation-induced DNA damage and the influence of the drug on its repair a γH2AX foci assay was used. To determine the effect of epothilone B on the microtubule assembly in cells and on purified tubulin, immunofluorescence staining and tubulin polymerization assay, respectively, were conducted.
Epothilone B induced a concentration- and application-dependent antiproliferative effect on the cells, with IC(50) values in the low nanomolar range. Colony forming assays showed a synergistic radiosensitive effect on both cell lines which was dependent on incubation time and applied concentration of epothilone B. The γH2AX assays demonstrated that ionizing radiation combined with the drug resulted in a concentration-dependent increase in the number of double-strand breaks and suggested a reduction in DNA repair capacity. Epothilone B produced enhanced microtubule bundling and abnormal spindle formation as revealed by immunofluorescence microscopy and caused microtubule formation from purified tubulin.
The results of this study showed that epothilone B displays cytotoxic antitumor activity at low nanomolar concentrations and also enhances the radiation response in the tumor cells tested; this may be induced by a reduced DNA repair capacity triggered by epothilone B. It was also demonstrated that epothilone B in fact targets microtubules in a more effective manner than paclitaxel.
采用放疗和化疗相结合的综合治疗方法在实体瘤的治疗中起着核心作用。在我们的研究中，我们在体外检查了微管稳定剂埃坡霉素 B 对两种人上皮肿瘤细胞系的细胞毒性和放射敏感性作用及其对微管组装的影响。
在增殖试验中用埃坡霉素 B 处理癌细胞，并在集落形成试验中与放射治疗联合使用。为了分析电离辐射诱导的 DNA 损伤和药物对其修复的影响，我们使用了γH2AX 焦点检测法。为了确定埃坡霉素 B 对细胞中微管组装和纯化微管蛋白的影响，分别进行了免疫荧光染色和微管蛋白聚合试验。
埃坡霉素 B 对细胞表现出浓度和应用依赖性的抗增殖作用，IC（50）值在低纳摩尔范围内。集落形成试验显示出对两种细胞系的协同放射敏感性作用，这种作用依赖于埃坡霉素 B 的孵育时间和应用浓度。γH2AX 检测法表明，电离辐射与药物联合使用会导致双链断裂数量的浓度依赖性增加，并提示 DNA 修复能力降低。埃坡霉素 B 导致微管束集增强和异常纺锤体形成，如免疫荧光显微镜所示，并导致从纯化的微管蛋白形成微管。
这项研究的结果表明，埃坡霉素 B 在低纳摩尔浓度下表现出细胞毒性抗肿瘤活性，并且增强了所测试的肿瘤细胞的放射反应；这可能是由埃坡霉素 B 触发的 DNA 修复能力降低引起的。此外，还证明埃坡霉素 B 实际上比紫杉醇更有效地靶向微管。
