Middleton Fiona K, Patterson Miranda J, Elstob Claire J, Fordham Sarah, Herriott Ashleigh, Wade Mark A, McCormick Aiste, Edmondson Richard, May Felicity E B, Allan James M, Pollard John R, Curtin Nicola J
Newcastle University, Northern Institute for Cancer Research, Newcastle upon Tyne, UK.
Vertex Pharmaceuticals (Europe) Limited, Milton Park, Abingdon, Oxfordshire, UK.
Oncotarget. 2015 Oct 20;6(32):32396-409. doi: 10.18632/oncotarget.6136.
ATR is an attractive target in cancer therapy because it signals replication stress and DNA lesions for repair and to S/G2 checkpoints. Cancer-specific defects in the DNA damage response (DDR) may render cancer cells vulnerable to ATR inhibition alone. We determined the cytotoxicity of the ATR inhibitor VE-821 in isogenically matched cells with DDR imbalance. Cell cycle arrest, DNA damage accumulation and repair were determined following VE-821 exposure.Defects in homologous recombination repair (HRR: ATM, BRCA2 and XRCC3) and base excision repair (BER: XRCC1) conferred sensitivity to VE-821. Surprisingly, the loss of different components of the trimeric non-homologous end-joining (NHEJ) protein DNA-PK had opposing effects. Loss of the DNA-binding component, Ku80, caused hypersensitivity to VE-821, but loss of its partner catalytic subunit, DNA-PKcs, did not. Unexpectedly, VE-821 was particularly cytotoxic to human and hamster cells expressing high levels of DNA-PKcs. High DNA-PKcs was associated with replicative stress and activation of the DDR. VE-821 suppressed HRR, determined by RAD51 focus formation, to a greater extent in cells with high DNA-PKcs.Defects in HRR and BER and high DNA-PKcs expression, that are common in cancer, confer sensitivity to ATR inhibitor monotherapy and may be developed as predictive biomarkers for personalised medicine.
ATR是癌症治疗中一个有吸引力的靶点，因为它能发出复制应激和DNA损伤信号，以进行修复并传至S/G2检查点。DNA损伤反应（DDR）中的癌症特异性缺陷可能使癌细胞单独易受ATR抑制的影响。我们测定了ATR抑制剂VE-821在DDR失衡的同基因匹配细胞中的细胞毒性。在暴露于VE-821后，测定细胞周期停滞、DNA损伤积累和修复情况。同源重组修复（HRR：ATM、BRCA2和XRCC3）和碱基切除修复（BER：XRCC1）中的缺陷使细胞对VE-821敏感。令人惊讶的是，三聚体非同源末端连接（NHEJ）蛋白DNA-PK的不同组分缺失产生了相反的效果。DNA结合组分Ku80的缺失导致对VE-821超敏，但其伙伴催化亚基DNA-PKcs的缺失则不然。出乎意料的是，VE-821对高表达DNA-PKcs的人和仓鼠细胞具有特别的细胞毒性。高DNA-PKcs与复制应激和DDR激活相关。通过RAD51焦点形成测定，VE-821在高DNA-PKcs的细胞中更大程度地抑制HRR。HRR和BER缺陷以及高DNA-PKcs表达在癌症中常见，使细胞对ATR抑制剂单一疗法敏感，可能被开发为个性化医疗的预测生物标志物。
