Dipartimento di Scienze della Vita, Università di Modena e Reggio Emilia, via Campi 213/D, Modena, Italy.
PLoS One. 2013;8(1):e53664. doi: 10.1371/journal.pone.0053664. Epub 2013 Jan 11.
The activation of autophagy has been extensively described as a pro-survival strategy, which helps to keep cells alive following deprivation of nutrients/growth factors and other stressful cellular conditions. In addition to cytoprotective effects, autophagy can accompany cell death. Autophagic vacuoles can be observed before or during cell death, but the role of autophagy in the death process is still controversial. A complex interplay between autophagy and apoptosis has come to light, taking into account that numerous genes, such as p53 and Bcl-2 family members, are shared between these two pathways.
METHODOLOGY/PRINCIPAL FINDINGS: In this study we showed a potent and irreversible cytotoxic activity of the stable Curcumin derivative bis-DeHydroxyCurcumin (bDHC) on human colon cancer cells, but not on human normal cells. Autophagy is elicited by bDHC before cell death as demonstrated by increased autophagosome formation -measured by electron microscopy, fluorescent LC3 puncta and LC3 lipidation- and autophagic flux -measured by interfering LC3-II turnover. The accumulation of poly-ubiquitinated proteins and ER-stress occurred upstream of autophagy induction and resulted in cell death. Cell cycle and Western blot analyses highlighted the activation of a mitochondrial-dependent apoptosis, which involves caspase 7, 8, 9 and Cytochrome C release. Using pharmacological inhibitions and RNAi experiments, we showed that ER-stress induced autophagy has a major role in triggering bDHC-cell death.
CONCLUSION/SIGNIFICANCE: Our findings describe the mechanism through which bDHC promotes tumor selective inhibition of proliferation, providing unequivocal evidence of the role of autophagy in contrasting the proliferation of colon cancer cells.
自噬的激活已被广泛描述为一种促进生存的策略，它有助于在营养物质/生长因子剥夺和其他应激细胞条件下保持细胞存活。除了细胞保护作用外，自噬还可以伴随着细胞死亡。自噬泡可以在细胞死亡之前或期间观察到，但自噬在死亡过程中的作用仍存在争议。自噬和细胞凋亡之间存在复杂的相互作用，考虑到许多基因，如 p53 和 Bcl-2 家族成员，在这两条途径之间是共享的。
方法/主要发现：在这项研究中，我们展示了稳定的姜黄素衍生物双去氢姜黄素（bDHC）对人结肠癌细胞具有强大且不可逆的细胞毒性作用，但对人正常细胞没有这种作用。自噬是由 bDHC 引起的，这可以通过电镜观察到的自噬体形成增加、荧光 LC3 斑点和 LC3 脂质化以及自噬流增加来证明，自噬流通过干扰 LC3-II 周转来测量。多聚泛素化蛋白和内质网应激的积累发生在自噬诱导的上游，并导致细胞死亡。细胞周期和 Western blot 分析突出了线粒体依赖性凋亡的激活，涉及半胱天冬酶 7、8、9 和细胞色素 C 的释放。通过药理学抑制和 RNAi 实验，我们表明内质网应激诱导的自噬在触发 bDHC 细胞死亡中起主要作用。
结论/意义：我们的研究结果描述了 bDHC 促进肿瘤选择性增殖抑制的机制，为自噬在拮抗结肠癌细胞增殖中的作用提供了明确的证据。
