Cancer Center of Daping Hospital, Army Medical University, Chongqing, 400000, China.
J Transl Med. 2023 Mar 9;21(1):183. doi: 10.1186/s12967-023-04022-9.
Apurinic/apyrimidinic endonuclease 1 (APE1) imparts radio-resistance by repairing isolated lesions via the base excision repair (BER) pathway, but whether and how it is involved in the formation and/or repair of DSBs remains mostly unknown.
Immunoblotting, fluorescent immunostaining, and the Comet assay were used to investigate the effect of APE1 on temporal DSB formation. Chromatin extraction, 53BP1 foci and co-immunoprecipitation, and rescue assays were used to evaluate non-homologous end joining (NHEJ) repair and APE1 effects. Colony formation, micronuclei measurements, flow cytometry, and xenograft models were used to examine the effect of APE1 expression on survival and synergistic lethality. Immunohistochemistry was used to detect APE1 and Artemis expression in cervical tumor tissues.
APE1 is upregulated in cervical tumor tissue compared to paired peri-tumor, and elevated APE1 expression is associated with radio-resistance. APE1 mediates resistance to oxidative genotoxic stress by activating NHEJ repair. APE1, via its endonuclease activity, initiates clustered lesion conversion to DSBs (within 1 h), promoting the activation of the DNA-dependent protein kinase catalytic subunit (DNA-PK), a key kinase in the DNA damage response (DDR) and NHEJ pathway. APE1 then participates in NHEJ repair directly by interacting with DNA- PK. Additionally, APE1 promotes NHEJ activity by decreasing the ubiquitination and degradation of Artemis, a nuclease with a critical role in the NHEJ pathway. Overall, APE1 deficiency leads to DSB accumulation at a late phase following oxidative stress (after 24 h), which also triggers activation of Ataxia-telangiectasia mutated (ATM), another key kinase of the DDR. Inhibition of ATM activity significantly promotes synergistic lethality with oxidative stress in APE1-deficient cells and tumors.
APE1 promotes NHEJ repair by temporally regulating DBS formation and repair following oxidative stress. This knowledge provides new insights into the design of combinatorial therapies and indicates the timing of administration and maintenance of DDR inhibitors for overcoming radio-resistance.
脱嘌呤/脱嘧啶核酸内切酶 1（APE1）通过碱基切除修复（BER）途径修复孤立损伤，赋予放射抗性，但它是否以及如何参与双链断裂（DSBs）的形成和/或修复在很大程度上尚不清楚。
采用免疫印迹、荧光免疫染色和彗星试验研究 APE1 对时间依赖性 DSB 形成的影响。采用染色质提取、53BP1 焦点和共免疫沉淀以及挽救试验评估非同源末端连接（NHEJ）修复和 APE1 效应。采用集落形成、微核测量、流式细胞术和异种移植模型研究 APE1 表达对存活和协同致死性的影响。采用免疫组织化学检测宫颈肿瘤组织中 APE1 和 Artemis 的表达。
与配对的肿瘤周围组织相比，宫颈肿瘤组织中 APE1 上调，并且 APE1 表达升高与放射抗性相关。APE1 通过激活 NHEJ 修复来介导对氧化遗传毒性应激的抗性。APE1 通过其内切酶活性，在 1 小时内启动簇状损伤转化为 DSB，促进 DNA 依赖性蛋白激酶催化亚基（DNA-PK）的激活，DNA-PK 是 DNA 损伤反应（DDR）和 NHEJ 途径的关键激酶。然后，APE1 通过与 DNA-PK 相互作用直接参与 NHEJ 修复。此外，APE1 通过减少在 NHEJ 途径中具有关键作用的核酸内切酶 Artemis 的泛素化和降解来促进 NHEJ 活性。总体而言，在氧化应激后（24 小时后），APE1 缺陷导致 DSB 在晚期积累，这也触发了 ATM（另一种 DDR 的关键激酶）的激活。在 APE1 缺陷细胞和肿瘤中，抑制 ATM 活性可显著促进与氧化应激的协同致死作用。
APE1 通过在氧化应激后临时调节 DSB 的形成和修复来促进 NHEJ 修复。这一发现为设计联合治疗方案提供了新的见解，并表明了 DDR 抑制剂的给药时间和维持时间，以克服放射抗性。
