Institute of Cancer Sciences, Wolfson Wohl Cancer Research Centre, University of Glasgow, Glasgow, United Kingdom.
School of Pharmacy and Pharmaceutical Sciences, Faculty of Health Sciences and Wellbeing, University of Sunderland, Sunderland, United Kingdom.
Cancer Res. 2018 Sep 1;78(17):5060-5071. doi: 10.1158/0008-5472.CAN-18-0569. Epub 2018 Jul 5.
Glioblastoma (GBM) is a lethal primary brain tumor characterized by treatment resistance and inevitable tumor recurrence, both of which are driven by a subpopulation of GBM cancer stem-like cells (GSC) with tumorigenic and self-renewal properties. Despite having broad implications for understanding GSC phenotype, the determinants of upregulated DNA-damage response (DDR) and subsequent radiation resistance in GSC are unknown and represent a significant barrier to developing effective GBM treatments. In this study, we show that constitutive DDR activation and radiation resistance are driven by high levels of DNA replication stress (RS). CD133 GSC exhibited reduced DNA replication velocity and a higher frequency of stalled replication forks than CD133 non-GSC ; immunofluorescence studies confirmed these observations in a panel of orthotopic xenografts and human GBM specimens. Exposure of non-GSC to low-level exogenous RS generated radiation resistance , confirming RS as a novel determinant of radiation resistance in tumor cells. GSC exhibited DNA double-strand breaks, which colocalized with "replication factories" and RNA: DNA hybrids. GSC also demonstrated increased expression of long neural genes (>1 Mbp) containing common fragile sites, supporting the hypothesis that replication/transcription collisions are the likely cause of RS in GSC. Targeting RS by combined inhibition of ATR and PARP (CAiPi) provided GSC-specific cytotoxicity and complete abrogation of GSC radiation resistance These data identify RS as a cancer stem cell-specific target with significant clinical potential. These findings shed new light on cancer stem cell biology and reveal novel therapeutics with the potential to improve clinical outcomes by overcoming inherent radioresistance in GBM. .
胶质母细胞瘤（GBM）是一种致命的原发性脑肿瘤，其特征为治疗抵抗和不可避免的肿瘤复发，这两者均由具有致瘤性和自我更新特性的 GBM 癌症干细胞样细胞（GSC）亚群驱动。尽管对理解 GSC 表型具有广泛的意义，但上调 DNA 损伤反应（DDR）的决定因素以及 GSC 随后的辐射抗性仍然未知，这是开发有效的 GBM 治疗方法的重大障碍。在这项研究中，我们表明，DDR 的组成性激活和辐射抗性是由高水平的 DNA 复制应激（RS）驱动的。CD133 GSC 比 CD133 非 GSC 的 DNA 复制速度更低，且停滞的复制叉频率更高；免疫荧光研究在一系列原位异种移植和人 GBM 标本中证实了这些观察结果。非 GSC 暴露于低水平的外源性 RS 会产生辐射抗性，从而证实 RS 是肿瘤细胞辐射抗性的一个新决定因素。GSC 表现出 DNA 双链断裂，这些断裂与“复制工厂”和 RNA:DNA 杂交体共定位。GSC 还表现出长神经基因（>1 Mbp）的表达增加，这些基因包含常见的脆弱位点，这支持了复制/转录碰撞是 GSC 中 RS 的可能原因的假说。通过联合抑制 ATR 和 PARP（CAiPi）来靶向 RS ，提供了 GSC 特异性的细胞毒性，并完全消除了 GSC 的辐射抗性。这些数据确定了 RS 作为一种癌症干细胞特异性靶标，具有重要的临床潜力。这些发现为癌症干细胞生物学提供了新的认识，并揭示了新的治疗方法，有可能通过克服 GBM 固有的放射抗性来改善临床结果。
