The TMPRSS2-ERG Gene Fusion Blocks XRCC4-Mediated Nonhomologous End-Joining Repair and Radiosensitizes Prostate Cancer Cells to PARP Inhibition.
The TMPRSS2-ERG Gene Fusion Blocks XRCC4-Mediated Nonhomologous End-Joining Repair and Radiosensitizes Prostate Cancer Cells to PARP Inhibition.
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DOI：
10.1158/1535-7163.mct-14-0865
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发表时间：
2015-08
影响因子：
5.7
通讯作者：
Almasan A
中科院分区：
文献类型：
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作者：
Chatterjee P;Choudhary GS;Alswillah T;Xiong X;Heston WD;Magi-Galluzzi C;Zhang J;Klein EA;Almasan A
接触遗传毒性物质，例如电离辐射 (IR)，会产生 DNA 损伤，导致 DNA 双链断裂 (DSB)；当 DNA 修复受损时，IR 毒性就会增强。我们报道，PARP 抑制剂 (PARPi) 的放射增敏作用在表达 TMPRSS2-ERG 基因融合蛋白的前列腺癌 (PCa) 细胞中非常显着。在这里，我们发现 TMPRSS2-ERG 通过抑制 DNA-PKcs 来阻断非同源末端连接 (NHEJ) DNA 修复。含有 TMPRSS2-ERG 的 VCaP 细胞和稳定表达 TMPRSS2-ERG 的 PC3 细胞组成型地显示 γH2AX 和 53BP1 灶，表明在 VCaP 细胞中用 siRNA 消除 TMPRSS2-ERG 时不会出现持续性 DNA 损伤。 DNA 损伤的程度增强，并与 TMPRSS2-ERG 抑制 DNA-PKcs 功能的能力相关，如其自身的磷酸化（Thr2609、Ser2056）及其底物 Ser1778-53BP1 的磷酸化所示。 TMPRSS2-ERG 引起的 DNA-PKcs 缺陷破坏了染色质上关键 NHEJ 成分的稳定性。因此，XRCC4 没有被招募到染色质，其他 NHEJ 核心因子的保留减少。当 TMPRSS2-ERG 被 siRNA 耗尽时，DNA-PKcs 自磷酸化恢复到亲代细胞的水平。 IR后，表达TMPRSS2-ERG的PC3细胞的Rad51焦点和同源重组（HR）活性升高，表明HR补偿了这些细胞中的NHEJ缺陷，从而解决了为什么单独的TMPRSS2-ERG不会导致放射增敏。然而，TMPRSS2-ERG 的存在通过抑制 NHEJ DNA 修复增强了 PARPi 介导的放射增敏作用。 IR 与 PARPi 结合导致 TMPRSS2-ERG 表达细胞中 DNA 损伤增强。因此，通过抑制 NHEJ，TMPRSS2-ERG 在表达 TMPRSS2-ERG 的 PCa 患者中提供与 PARPi 的合成致死相互作用。
Exposure to genotoxic agents, such as ionizing radiation (IR) produces DNA damage leading to DNA double-strand breaks (DSBs); IR toxicity is augmented when the DNA repair is impaired. We reported that radiosensitization by a PARP inhibitor (PARPi) was highly prominent in prostate cancer (PCa) cells expressing the TMPRSS2-ERG gene fusion protein. Here, we show that TMPRSS2-ERG blocks non-homologous end-joining (NHEJ) DNA repair by inhibiting DNA-PKcs. VCaP cells, which harbor TMPRSS2-ERG and PC3 cells that stably express it displayed γH2AX and 53BP1 foci constitutively, indicating persistent DNA damage that was absent if TMPRSS2-ERG was depleted by siRNA in VCaP cells. The extent of DNA damage was enhanced and associated with TMPRSS2-ERG’s ability to inhibit DNA-PKcs function, as indicated by its own phosphorylation (Thr2609, Ser2056) and that of its substrate, Ser1778-53BP1. DNA-PKcs deficiency caused by TMPRSS2-ERG destabilized critical NHEJ components on chromatin. Thus, XRCC4 was not recruited to chromatin, with retention of other NHEJ core factors being reduced. DNA-PKcs autophosphorylation was restored to the level of parental cells when TMPRSS2-ERG was depleted by siRNA. Following IR, TMPRSS2-ERG-expressing PC3 cells had elevated Rad51 foci and homologous recombination (HR) activity, indicating that HR compensated for defective NHEJ in these cells, hence addressing why TMPRSS2-ERG alone did not lead to radiosensitization. However, the presence of TMPRSS2-ERG, by inhibiting NHEJ DNA repair, enhanced PARPi-mediated radiosensitization. IR in combination with PARPi resulted in enhanced DNA damage in TMPRSS2-ERG-expressing cells. Thus, by inhibiting NHEJ, TMPRSS2-ERG provides a synthetic lethal interaction with PARPi in PCa patients expressing TMPRSS2-ERG.