Division of Radiation Health, Department of Pharmaceutical Sciences, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
Radiat Res. 2013 Feb;179(2):160-70. doi: 10.1667/RR3034.1. Epub 2012 Dec 21.
Our study was to elucidate the mechanisms whereby BMS-345541 (BMS, a specific IκB kinase β inhibitor) inhibits the repair of DNA double-strand breaks (DSBs) and evaluate whether BMS can sensitize MCF-7 breast cancer cells (MCF-7 cells) to ionizing radiation (IR) in an apoptosis-independent manner. In this study, MCF-7 cells were exposed to IR in vitro and in vivo with or without pretreatment of BMS. The effects of BMS on the repair of IR-induced DSBs by homologous recombination (HR) and non-homologous end-joining (NHEJ) were analyzed by the DR-GFP and EJ5-GFP reporter assays and IR-induced γ-H2AX, 53BP1, Brca1 and Rad51 foci assays. The mechanisms by which BMS inhibits HR were examined by microarray analysis and quantitative reverse transcription PCR. The effects of BMS on the sensitivity of MCF-7 cells to IR were determined by MTT and clonogenic assays in vitro and tumor growth inhibition in vivo in a xenograft mouse model. The results showed that BMS selectively inhibited HR repair of DSBs in MCF-7 cells, most likely by down-regulation of several genes that participate in HR. This resulted in a significant increase in the DNA damage response that sensitizes MCF-7 cells to IR-induced cell death in an apoptosis-independent manner. Furthermore, BMS treatment sensitized MCF-7 xenograft tumors to radiation therapy in vivo in an association with a significant delay in the repair of IR-induced DSBs. These data suggest that BMS is a novel HR inhibitor that has the potential to be used as a radiosensitizer to increase the responsiveness of cancer to radiotherapy.
我们的研究旨在阐明 BMS-345541（BMS，一种特定的 IκB 激酶 β 抑制剂）抑制 DNA 双链断裂（DSBs）修复的机制，并评估 BMS 是否可以以非凋亡方式使 MCF-7 乳腺癌细胞（MCF-7 细胞）对电离辐射（IR）敏感。在这项研究中，MCF-7 细胞在体外和体内接受 IR 照射，并在预处理 BMS 的情况下进行。通过 DR-GFP 和 EJ5-GFP 报告基因检测和 IR 诱导的 γ-H2AX、53BP1、Brca1 和 Rad51 焦点检测，分析 BMS 对同源重组（HR）和非同源末端连接（NHEJ）修复 IR 诱导的 DSBs 的影响。通过微阵列分析和定量逆转录 PCR 检查 BMS 抑制 HR 的机制。通过 MTT 和克隆形成测定法在体外和异种移植小鼠模型中体内肿瘤生长抑制，确定 BMS 对 MCF-7 细胞对 IR 敏感性的影响。结果表明，BMS 选择性抑制 MCF-7 细胞中 DSBs 的 HR 修复，最可能是通过下调参与 HR 的几个基因。这导致 DNA 损伤反应显著增加，使 MCF-7 细胞对 IR 诱导的细胞死亡产生非凋亡敏感性。此外，BMS 治疗使 MCF-7 异种移植肿瘤对体内放射治疗敏感，与 IR 诱导的 DSBs 修复显著延迟相关。这些数据表明，BMS 是一种新型的 HR 抑制剂，有可能作为放射增敏剂，增加癌症对放射治疗的反应性。
