Inhibition of DNA-Dependent Protein Kinase Induces Accelerated Senescence in Irradiated Human Cancer Cells
Inhibition of DNA-Dependent Protein Kinase Induces Accelerated Senescence in Irradiated Human Cancer Cells
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DOI：
10.1158/1541-7786.mcr-11-0312
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发表时间：
2011-12-01
影响因子：
5.2
通讯作者：
Solomon, Benjamin
中科院分区：
文献类型：
--
作者：
Azad, Arun;Jackson, Susan;Solomon, Benjamin
DNA依赖性蛋白激酶（DNA-PK）在DNA双链断裂（DSB）修复中起关键作用，并主要参与调节细胞的辐射敏感性。在这里，我们确定DNA-PK作为一个关键的治疗目标，增加加速衰老的辐射人类癌细胞。我们发现，BEZ 235，一种新的抑制剂的DNA-PK和磷酸肌醇3-激酶（PI 3 K）/mTOR，废除辐射诱导的DSB修复，导致细胞放射增敏和辐射肿瘤异种移植物的生长延迟。重要的是，BEZ 235的辐射增强与显著的p53依赖性加速衰老表型相一致，其特征在于阳性β-半乳糖苷酶染色、G（2）-M细胞周期停滞、增大和扁平的细胞形态以及增加的p21表达和衰老相关的细胞因子分泌。由于这种对BEZ 235的衰老反应伴随着未修复的DNA DSB，我们检查了选择性靶向DNA-PK是否也诱导辐照细胞的加速衰老。值得注意的是，我们表明，DNA-PK的特异性药理学抑制，而不是PI 3 K或mTORC 1，延迟DSB修复，导致辐射后加速衰老。我们还表明，使用siRNA敲低PRKDC促进了辐射细胞中与BEZ 235相当的显著加速衰老表型。因此，在放射治疗的背景下，我们的数据表明，DNA-PK的抑制足以诱导加速衰老。这些结果验证了DNA-PK作为辐射癌细胞中的重要治疗靶点，并建立了加速衰老作为DNA-PK阻断诱导的放射增敏的新机制。Mol Cancer Res; 9（12）; 1696-707. (C)2011年AACR。
DNA-dependent protein kinase (DNA-PK) plays a pivotal role in the repair of DNA double-strand breaks (DSB) and is centrally involved in regulating cellular radiosensitivity. Here, we identify DNA-PK as a key therapeutic target for augmenting accelerated senescence in irradiated human cancer cells. We find that BEZ235, a novel inhibitor of DNA-PK and phosphoinositide 3-kinase (PI3K)/mTOR, abrogates radiation-induced DSB repair resulting in cellular radiosensitization and growth delay of irradiated tumor xenografts. Importantly, radiation enhancement by BEZ235 coincides with a prominent p53-dependent accelerated senescence phenotype characterized by positive beta-galactosidase staining, G(2)-M cell-cycle arrest, enlarged and flattened cellular morphology, and increased p21 expression and senescence-associated cytokine secretion. Because this senescence response to BEZ235 is accompanied by unrepaired DNA DSBs, we examined whether selective targeting of DNA-PK also induces accelerated senescence in irradiated cells. Significantly, we show that specific pharmacologic inhibition of DNA-PK, but not PI3K or mTORC1, delays DSB repair leading to accelerated senescence after radiation. We additionally show that PRKDC knockdown using siRNA promotes a striking accelerated senescence phenotype in irradiated cells comparable with that of BEZ235. Thus, in the context of radiation treatment, our data indicate that inhibition of DNA-PK is sufficient for the induction of accelerated senescence. These results validate DNA-PK as an important therapeutic target in irradiated cancer cells and establish accelerated senescence as a novel mechanism of radiosensitization induced by DNA-PK blockade. Mol Cancer Res; 9(12); 1696-707. (C) 2011 AACR.