Tianjin Key Laboratory of Radiation Medicine and Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin 300192, China.
Cancer Biol Med. 2021 Dec 1;19(8):1150-71. doi: 10.20892/j.issn.2095-3941.2021.0178.
We aimed to investigate the radiosensitizing efficacy of the poly-ADP-ribose polymerase (PARP) inhibitor, olaparib, and the Bloom syndrome protein (BLM) helicase inhibitor, ML216, in non-small cell lung cancer (NSCLC) cells.
Radiosensitization of NSCLC cells was assessed by colony formation and tumor growth assays. Mechanistically, the effects of ML216, olaparib, and radiation on cell and tumor proliferation, DNA damage, cell cycle, apoptosis, homologous recombination (HR) repair, and non-homologous end joining (NHEJ) repair activity were determined.
Both olaparib and ML216 enhanced the radiosensitivities of olaparib-sensitive H460 and H1299 cells, which was seen as decreased surviving fractions and Rad51 foci, increased total DNA damage, and γH2AX and 53BP1 foci ( < 0.05). The expressions of HR repair proteins were remarkably decreased in olaparib-treated H460 and H1299 cells after irradiation ( < 0.05), while olaparib combined with ML216 exerted a synergistic radiosensitization effect on olaparib-resistant A549 cells. In addition to increases of double strand break (DSB) damage and decreases of Rad51 foci, olaparib combined with ML216 also increased pDNA-PKcs (S2056) foci, abrogated G2 cell cycle arrest, and induced apoptosis in A549 lung cancer after irradiation and ( < 0.05). Moreover, Western blot showed that olaparib combined with ML216 and irradiation inhibited HR repair, promoted NHEJ repair, and inactivated cell cycle checkpoint signals both and ( < 0.05).
Taken together, these results showed the efficacy of PARP and BLM helicase inhibitors for radiosensitizing NSCLC cells, and supported the model that BLM inhibition sensitizes cells to PARP inhibitor-mediated radiosensitization, as well as providing the basis for the potential clinical development of this combination for tumors intrinsically resistant to PARP inhibitors and radiotherapy.
我们旨在研究聚 ADP-核糖聚合酶（PARP）抑制剂奥拉帕利和布鲁姆综合征蛋白（BLM）解旋酶抑制剂 ML216 对非小细胞肺癌（NSCLC）细胞的放射增敏作用。
通过集落形成和肿瘤生长实验评估 NSCLC 细胞的放射增敏作用。从机制上，检测 ML216、奥拉帕利和辐射对细胞和肿瘤增殖、DNA 损伤、细胞周期、细胞凋亡、同源重组（HR）修复和非同源末端连接（NHEJ）修复活性的影响。
奥拉帕利和 ML216 均增强了奥拉帕利敏感的 H460 和 H1299 细胞的放射敏感性，表现为存活分数降低，Rad51 焦点减少，总 DNA 损伤增加，γH2AX 和 53BP1 焦点增加（<0.05）。奥拉帕利处理后的 H460 和 H1299 细胞在照射后 HR 修复蛋白的表达显著降低（<0.05），而奥拉帕利联合 ML216 对奥拉帕利耐药的 A549 细胞发挥协同放射增敏作用。除了双链断裂（DSB）损伤增加和 Rad51 焦点减少外，奥拉帕利联合 ML216 还增加了 pDNA-PKcs（S2056）焦点，消除了 G2 细胞周期阻滞，并在照射后诱导 A549 肺癌细胞凋亡（<0.05）。此外，Western blot 显示，奥拉帕利联合 ML216 和照射抑制 HR 修复，促进 NHEJ 修复，并在照射后抑制细胞周期检查点信号（<0.05）。
综上所述，这些结果表明 PARP 和 BLM 解旋酶抑制剂对放射增敏 NSCLC 细胞有效，并支持了 BLM 抑制使细胞对 PARP 抑制剂介导的放射增敏敏感的模型，为该联合治疗方案在对 PARP 抑制剂和放疗固有耐药的肿瘤中的潜在临床开发提供了依据。
