Torin2 enhances the radiosensitivity of MCF-7 breast cancer cells by downregulating the mTOR signaling pathway and ATM phosphorylation
Torin2 enhances the radiosensitivity of MCF-7 breast cancer cells by downregulating the mTOR signaling pathway and ATM phosphorylation
复制标题
DOI：
10.3892/mmr.2017.7848
复制
发表时间：
2018-01-01
影响因子：
3.4
通讯作者：
Wang, Ge
中科院分区：
文献类型：
--
作者：
Luo, Jia;Pi, Guocheng;Wang, Ge
放射治疗在乳腺癌的综合治疗中占有重要地位。然而，由于固有的放射抵抗性，辅助放射治疗的临床结果可能受到限制，因此有必要探索有效的放射增敏方法，以改善接受放射治疗的患者的临床结果。本研究旨在探讨雷帕霉素（mTOR）抑制剂Torin 2的新机制靶点是否增强MCF-7乳腺癌细胞的放射敏感性。进行细胞计数试剂盒-8（CCK-8）测定以测量Torin 2对细胞增殖的影响，同时采用克隆形成测定来确定Torin 2与辐射组合对MCF-7细胞增殖的影响。使用流式细胞术分析Torin 2和/或辐射对细胞周期的影响。此外，通过蛋白质印迹分析测量磷脂酰肌醇3-激酶/Akt/mTOR途径的组分的蛋白质表达，以及参与DNA损伤修复的蛋白质的表达。结果表明，Torin 2在MCF-7细胞中表现出更高的效力，而MDA-MB-231细胞对Torin 2的敏感性较低。与单独照射相比，用20 nM Torin 2预处理后再照射导致-H2 A组蛋白家族成员X的水平增加。辐射诱导Akt/mTOR信号通路活化，并上调磷酸化（p）-Akt（473）和p-真核翻译起始因子4 E结合蛋白1（4 EBP 1）的表达（37/46）。值得注意的是，用Torin 2预处理减弱了辐射诱导的Akt/mTOR信号通路的激活。此外，Torin 2通过减少共济失调毛细血管扩张症突变的激活部分阻断辐射诱导的双链断裂的修复，并使MCF-7细胞对辐射敏感。结论：放疗前给予Torin 2可增强乳腺癌细胞的体外放疗效应，为临床合理应用放疗联合Torin 2治疗乳腺癌提供了依据。
Radiotherapy has an important role in the comprehensive treatment of breast cancer. However, the clinical outcome of adjuvant radiotherapy may be limited due to intrinsic radioresistance, it is necessary to explore efficient radiosensitization methods that improve the clinical outcome of patients undergoing radiotherapy. The present study aimed to investigate whether the novel mechanistic target of rapamycin (mTOR) inhibitor Torin2 enhances the radiosensitivity of MCF-7 breast cancer cells. A Cell Counting Kit-8 (CCK-8) assay was performed to measure the effect of Torin2 on cell proliferation, while clonogenic assays were employed to determine the effect of Torin2 in combination with radiation on the proliferation of MCF-7 cells. The effect of Torin2 and/or radiation on the cell cycle was analyzed using flow cytometry. Furthermore, the protein expression of components of the phosphatidylinositol 3-kinase/Akt/mTOR pathway, and the expression of proteins involved in DNA damage repair, was measured by western blot analysis. The results demonstrated that Torin2 exhibited a higher potency in MCF-7 cells, while MDA-MB-231 cells were less sensitive to Torin2. Compared with irradiation alone, pretreatment with 20 nM Torin2 followed by irradiation resulted in an increased level of -H2A histone family member X. Radiation induced the activation of the Akt/mTOR signaling pathway and upregulated the expression of phosphorylated (p)-Akt(473) and p-eukaryotic translation initiation factor 4E binding protein 1 (4EBP1)(37/46). Notably, pretreatment with Torin2 attenuated the radiation-induced activation of the Akt/mTOR signaling pathway. In addition, Torin2 partially blocked the repair of double-strand breaks induced by radiation by reducing the activation of ataxia telangiectasia-mutated, and sensitized MCF-7 cells to radiation. In conclusion, administration of Torin2 prior to irradiation enhanced the radiotherapeutic effect on breast cancer cells in vitro, and these results may provide a foundation for the rational use of combined therapy with irradiation and Torin2 for breast cancer in clinical practice.