The death of human cancer cells following photodynamic therapy: Apoptosis competence is necessary for Bcl-2 protection but not for induction of autophagy
The death of human cancer cells following photodynamic therapy: Apoptosis competence is necessary for Bcl-2 protection but not for induction of autophagy
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DOI：
10.1111/j.1751-1097.2007.00159.x
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发表时间：
2007-09-01
影响因子：
3.3
通讯作者：
Oleinick, Nancy L.
中科院分区：
文献类型：
--
作者：
Xue, Liang-Yan;Chiu, Song-Mao;Oleinick, Nancy L.
光动力疗法(PDT)是一种有效的细胞凋亡诱导剂，但在缺乏一种或多种介导细胞凋亡的因子的细胞中除外。最近的报道已经确定自噬是PDT后潜在的另一种细胞死亡过程。在这里，我们研究了光敏剂Pc4在缺乏促凋亡因子Bax的人癌细胞(人前列腺癌DU145细胞)或凋亡介导物caspase-3(人乳腺癌MCF-7v细胞)以及在具有凋亡能力的细胞(稳定高表达人前caspase-3的MCF-7c3细胞和中国仓鼠卵巢CHO 5A100细胞)中发生自噬的情况。此外，还对每个细胞系进行了稳定过表达和不稳定过表达的细胞株的研究。自噬是通过电子显微镜观察胞浆中双膜描绘的自噬小泡的存在和免疫印迹观察Pc4-PDT剂量和时间依赖性地增加自噬体膜成分Lc3-II的水平来鉴定的。在所有被研究的细胞系中都观察到了自噬，无论它们是否能够进行典型的凋亡，以及它们是否过度表达Bcl-2。稳定过表达的Bcl2的存在对PDT诱导的细胞凋亡和具有凋亡能力的细胞(MCF-7c3和CHO 5A100细胞)的克隆形成能力丧失具有保护作用。相反，在任何一种细胞系(MCF-7v和DU145细胞)中，过表达Bcl2并不能阻止自噬的发展，也不能阻止凋亡缺陷细胞(MCF-7v和DU145)中克隆形成的丧失。此外，自噬的抑制剂3-甲基腺嘌呤和Wortmannin对缺乏凋亡的细胞提供了比对有能力的细胞更大的保护作用。结果表明，在具有或不具有正常凋亡能力的人癌细胞中，自噬发生在PDT后的细胞死亡过程中。只有具有凋亡能力的细胞才能受到Bcl2的保护，使其免于细胞死亡。
Photodynamic therapy (PDT) is an efficient inducer of apoptosis in many types of cells, except in cells deficient in one or more of the factors that mediate apoptosis. Recent reports have identified autophagy as a potential alternative cell death process following PDT. Here we investigated the occurrence of autophagy after PDT with the photosensitizer Pc 4 in human cancer cells that are deficient in the pro-apoptotic factor Bax (human prostate cancer DU145 cells) or the apoptosis mediator caspase-3 (human breast cancer MCF-7v cells) and in apoptosis-competent cells (MCF-7c3 cells that stably overexpress human pro-caspase-3 and Chinese hamster ovary CHO 5A100 cells). Further, each of the cell lines was also studied with and without stably overexpressed Bcl-2. Autophagy was identified by electron microscopic observation of the presence of double-membrane-delineated auto-phagosomal vesicles in the cytosol and by immunoblot observation of the Pc 4-PDT dose- and time-dependent increase in the level of LC3-II, a component of the autophagosomal membrane. Autophagy was observed in all of the cell lines studied, whether or not they were capable of typical apoptosis and whether or not they overexpressed Bcl-2. The presence of stably overexpressed Bcl-2 in the cells protected against PDT-induced apoptosis and loss of clonogenicity in apoptosis-competent cells (MCF-7c3 and CHO 5A100 cells). In contrast, Bcl-2 overexpression did not protect against the development of autophagy in any of the cell lines or against loss of clonogenicity in apoptosis-deficient cells (MCF-7v and DU145 cells). Furthermore, 3-methyladenine and wortmannin, inhibitors of autophagy, provided greater protection against loss of viability to apoptosis-deficient than to apoptosis-competent cells. The results show that autophagy occurs during cell death following PDT in human cancer cells competent or not for normal apoptosis. Only the apoptosis-competent cells are protected by Bcl-2 against cell death.