Laboratoire de Neurosciences Expérimentales et Cliniques (LNEC), Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 1084, Université de Poitiers, F-86073 Poitiers, France.
Département de Cancérologie Biologique, Centre Hospitalo-Universitaire de Poitiers, F-86021 Poitiers, France.
Int J Mol Sci. 2018 Oct 3;19(10):3018. doi: 10.3390/ijms19103018.
"Glioma Stem Cells" (GSCs) are known to play a role in glioblastoma (GBM) recurrence. Homologous recombination (HR) defects and cell cycle checkpoint abnormalities can contribute concurrently to the radioresistance of GSCs. DNA repair protein RAD51 homolog 1 (RAD51) is a crucial protein for HR and its inhibition has been shown to sensitize GSCs to irradiation. The aim of this study was to examine the consequences of ionizing radiation (IR) for cell cycle progression in GSCs. In addition, we intended to assess the potential effect of RAD51 inhibition on cell cycle progression. Five radiosensitive GSC lines and five GSC lines that were previously characterized as radioresistant were exposed to 4Gy IR, and cell cycle analysis was done by fluorescence-activated cell sorting (FACS) at 24, 48, 72, and 96 h with or without RAD51 inhibitor. Following 4Gy IR, all GSC lines presented a significant increase in G2 phase at 24 h, which was maintained over 72 h. In the presence of RAD51 inhibitor, radioresistant GSCs showed delayed G2 arrest post-irradiation for up to 48 h. This study demonstrates that all GSCs can promote G2 arrest in response to radiation-induced DNA damage. However, following RAD51 inhibition, the cell cycle checkpoint response differed. This study contributes to the characterization of the radioresistance mechanisms of GSCs, thereby supporting the rationale of targeting RAD51-dependent repair pathways in view of radiosensitizing GSCs.
“神经胶质瘤干细胞”（GSCs）被认为在胶质母细胞瘤（GBM）复发中起作用。同源重组（HR）缺陷和细胞周期检查点异常可能同时导致 GSCs 的放射抵抗。DNA 修复蛋白 RAD51 同源物 1（RAD51）是 HR 的关键蛋白，其抑制已被证明可使 GSCs 对辐射敏感。本研究旨在研究电离辐射（IR）对 GSCs 细胞周期进展的影响。此外，我们还旨在评估 RAD51 抑制对细胞周期进展的潜在影响。将五种放射敏感的 GSC 系和五种先前被表征为放射抗性的 GSC 系暴露于 4Gy IR 下，并在有或没有 RAD51 抑制剂的情况下通过荧光激活细胞分选（FACS）在 24、48、72 和 96 h 时进行细胞周期分析。在接受 4Gy IR 后，所有 GSC 系在 24 h 时均明显增加 G2 期，该期持续至 72 h。在 RAD51 抑制剂存在的情况下，放射抗性 GSC 在照射后延迟至 48 h 才出现 G2 期阻滞。本研究表明，所有 GSCs 都可以促进 G2 期阻滞以应对辐射诱导的 DNA 损伤。然而，在 RAD51 抑制后，细胞周期检查点反应不同。本研究有助于阐明 GSCs 的放射抵抗机制，从而支持针对 RAD51 依赖性修复途径以增强 GSCs 放射敏感性的原理。
