Background: DNA-dependent protein kinase (DNA-PK) is a validated cancer therapeutic target involved in DNA damage response (DDR) and non-homologous end-joining (NHEJ) repair of DNA double-strand breaks (DSBs). Ku serves as a sensor of DSBs by binding to DNA ends and activating DNA-PK. Inhibition of DNA-PK is a common strategy to block DSB repair and improve efficacy of ionizing radiation (IR) therapy and radiomimetic drug therapies. We have previously developed Ku–DNA binding inhibitors (Ku-DBis) that block in vitro and cellular NHEJ activity, abrogate DNA-PK autophosphorylation, and potentiate cellular sensitivity to IR.Results and Conclusions: Here we report the discovery of oxindole Ku-DBis with improved cellular uptake and retained potent Ku-inhibitory activity. Variable monotherapy activity was observed in a panel of non-small cell lung cancer (NSCLC) cell lines, with ATM-null cells being the most sensitive and showing synergy with IR. BRCA1-deficient cells were resistant to single-agent treatment and antagonistic when combined with DSB-generating therapies. In vivo studies in an NSCLC xenograft model demonstrated that the Ku-DBi treatment blocked IR-dependent DNA-PKcs autophosphorylation, modulated DDR, and reduced tumor cell proliferation. This represents the first in vivo demonstration of a Ku-targeted DNA-binding inhibitor impacting IR response and highlights the potential therapeutic utility of Ku-DBis for cancer treatment.
背景：DNA依赖性蛋白激酶（DNA-PK）是经过验证的癌症治疗靶点，参与DNA损伤应答（DDR）及DNA双链断裂（DSBs）的非同源末端连接（NHEJ）修复。Ku蛋白通过结合DNA末端并激活DNA-PK，作为DSBs的感应器。抑制DNA-PK是阻断DSB修复并增强电离辐射（IR）疗法及拟辐射药物疗效的常用策略。我们先前开发的Ku-DNA结合抑制剂（Ku-DBis）能阻断体外及细胞内的NHEJ活性，消除DNA-PK自身磷酸化，并增强细胞对IR的敏感性。 结果与结论：本研究报道了具有改善细胞摄取能力并保持强效Ku抑制活性的羟吲哚类Ku-DBis的发现。在一组非小细胞肺癌（NSCLC）细胞系中观察到差异化的单药活性，其中ATM缺失细胞最为敏感且与IR治疗产生协同作用。BRCA1缺陷细胞对单药治疗具有耐药性，在与产生DSB的疗法联用时呈现拮抗效应。在NSCLC异种移植模型中的体内研究表明，Ku-DBi治疗可阻断IR依赖的DNA-PKcs自身磷酸化，调节DDR通路，并抑制肿瘤细胞增殖。这是首次在体内证实靶向Ku的DNA结合抑制剂能够影响IR应答，凸显了Ku-DBis在癌症治疗中的潜在应用价值。
Impact of Optimized Ku–DNA Binding Inhibitors on the Cellular and In Vivo DNA Damage Response
肿瘤(癌症)患者之家