Blocked autophagy sensitizes resistant carcinoma cells to radiation therapy
Blocked autophagy sensitizes resistant carcinoma cells to radiation therapy
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DOI：
10.1158/0008-5472.can-07-0562
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发表时间：
2008-03-01
期刊：
影响因子：
11.2
通讯作者：
Mayer, Andreas
中科院分区：
文献类型：
--
作者：
Apel, Anja;Herr, Ingrid;Mayer, Andreas
在接受化疗或放射治疗的肿瘤细胞中，自噬或“自噬”经常被激活。自噬是否代表了一种生存机制，或者更确切地说，是导致细胞死亡，仍然存在争议。为了解决这个问题，我们研究了自噬在辐射敏感和辐射抵抗的人类癌细胞系中对伽玛射线的反应所起的作用。我们发现，在每个细胞系中，辐射诱导的自噬小体的积累伴随着与自噬相关的基因Beclin 1、atg3、atg4b、atg4c、atg5和atg12的强烈的mRNA诱导。逆转录-聚合酶链式反应和Western印迹分析显示，转导特定靶向siRNAs后，这些基因的下调持续时间长达8天。每个自噬相关基因的阻断与辐射后自噬小体的积累显著减少有关。克隆存活法显示，大多数被抑制的自噬相关基因，单独或联合使用，导致耐药癌细胞对辐射增敏，而未处理的耐药细胞而不是敏感细胞在自噬被抑制时存活得更好。同样，在不同的敏感癌细胞和抑制不同的自噬基因时，也观察到放射增敏或相反。突变型p53对自噬小体的积累没有影响，但如预期的那样略微增加了克隆存活率，因为突变型p53通过赋予细胞对凋亡的抵抗来保护细胞。在我们的系统中，短期抑制自噬伴随着放射治疗导致耐药癌细胞中放射治疗的细胞毒性增强。
Autophagy or "self eating" is frequently activated in tumor cells treated with chemotherapy or irradiation. Whether autophagy represents a survival mechanism or rather contributes to cell death remains controversial. To address this issue, the role of autophagy in radiosensitive and radioresistant human cancer cell lines in response to gamma-irradiation was examined. We found irradiation-induced accumulation of autophagosomes accompanied by strong mRNA induction of the autophagy-related genes beclin 1, atg3, atg4b, atg4c, atg5, and atg12 in each cell line. Transduction of specific target-siRNAs led to down-regulation of these genes for up to 8 days as shown by reverse transcription-PCR and Western blot analysis. Blockade of each autophagy-related gene was associated with strongly diminished accumulation of autophagosomes after irradiation. As shown by clonogenic survival, the majority of inhibited autophagy-related genes, each alone or combined, resulted in sensitization of resistant carcinoma cells to radiation, whereas untreated resistant cells but not sensitive cells survived better when autophagy was inhibited. Similarly, radiosensitization or the opposite was observed in different sensitive carcinoma cells and upon inhibition of different autophagy genes. Mutant p53 had no effect on accumulation of autophagosomes but slightly increased clonogenic survival, as expected, because mutated p53 protects cells by conferring resistance to apoptosis. In our system, short-time inhibition of autophagy along with radiotherapy lead to enhanced cytotoxicity of radiotherapy in resistant cancer cells.