Suppression of basal autophagy reduces lung cancer cell proliferation and enhances caspase-dependent and -independent apoptosis by stimulating ROS formation
Suppression of basal autophagy reduces lung cancer cell proliferation and enhances caspase-dependent and -independent apoptosis by stimulating ROS formation
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DOI：
10.4161/auto.20123
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发表时间：
2012-07-01
期刊：
影响因子：
13.3
通讯作者：
Zhivotovsky, Boris
中科院分区：
文献类型：
--
作者：
Kaminskyy, Vitaliy O.;Piskunova, Tatiana;Zhivotovsky, Boris
自噬是参与细胞器和大分子周转的分解代谢过程，根据条件的不同，可能导致细胞死亡或保持细胞存活。我们发现，一些肺癌细胞系和肿瘤样本的特征是脂化的LC3水平增加。自噬敏化的非小细胞肺癌(NSCLC)细胞对顺铂诱导的凋亡的抑制作用；然而，在用依托泊苷处理的细胞中，这种反应被减弱。抑制自噬刺激ROS的形成和顺铂处理对ROS的积累有协同作用。使用针对细胞内隔室的遗传编码的过氧化氢探针，我们发现自噬抑制促进了顺铂处理的细胞胞浆和线粒体中过氧化氢的形成。抑制自噬条件下细胞死亡的增加部分依赖于caspase，但抗氧化剂NAC或羟基自由基清除剂，而不是超氧化物歧化酶或MnSOD类似物，可减少细胞色素c的释放，并取消细胞对顺铂诱导的细胞凋亡的敏感性。这种对ROS的抑制阻止了线粒体对AIF和HTRA2的处理和释放。此外，抑制基础自噬活跃的NSCLC细胞的自噬减少了它们的增殖，但对细胞周期分布没有显著影响。依托泊苷抑制细胞增殖，延缓S期细胞积聚，可延缓依托泊苷诱导的细胞凋亡执行期。这些结果表明，自噬抑制导致抑制NSCLC细胞的增殖，并通过刺激ROS的形成而使其对顺铂诱导的caspase依赖和非依赖的凋亡敏感。
Autophagy is a catabolic process involved in the turnover of organelles and macromolecules which, depending on conditions, may lead to cell death or preserve cell survival. We found that some lung cancer cell lines and tumor samples are characterized by increased levels of lipidated LC3. Inhibition of autophagy sensitized non-small cell lung carcinoma (NSCLC) cells to cisplatin-induced apoptosis; however, such response was attenuated in cells treated with etoposide. Inhibition of autophagy stimulated ROS formation and treatment with cisplatin had a synergistic effect on ROS accumulation. Using genetically encoded hydrogen peroxide probes directed to intracellular compartments we found that autophagy inhibition facilitated formation of hydrogen peroxide in the cytosol and mitochondria of cisplatin-treated cells. The enhancement of cell death under conditions of inhibited autophagy was partially dependent on caspases, however, antioxidant NAC or hydroxyl radical scavengers, but not the scavengers of superoxide or a MnSOD mimetic, reduced the release of cytochrome c and abolished the sensitization of the cells to cisplatin-induced apoptosis. Such inhibition of ROS prevented the processing and release of AIF (apoptosis-inducing factor) and HTRA2 from mitochondria. Furthermore, suppression of autophagy in NSCLC cells with active basal autophagy reduced their proliferation without significant effect on the cell-cycle distribution. Inhibition of cell proliferation delayed accumulation of cells in the S phase upon treatment with etoposide that could attenuate the execution stage of etoposide-induced apoptosis. These findings suggest that autophagy suppression leads to inhibition of NSCLC cell proliferation and sensitizes them to cisplatin-induced caspase-dependent and -independent apoptosis by stimulation of ROS formation.