Department of General Surgery, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, 310000, Hangzhou, Zhejiang, China.
Department of General Surgery, Huzhou Hospital, Zhejiang University School of Medicine, 313003, Huzhou, Zhejiang, China.
Cell Death Dis. 2019 Feb 13;10(2):142. doi: 10.1038/s41419-019-1366-y.
Pancreatic cancer is one of the most aggressive tumors and patients have poor survival rates. Fisetin, a natural flavonoid, was recently reported to have antitumor effects in various cancer models. Autophagy is a conserved catabolic process that maintains cellular homoeostasis in response to stress, and together with apoptosis, determines cell fate. Herein, we examined the effect of fisetin on pancreatic cancer. We reveal that fisetin inhibits PANC-1 cell proliferation using a real-time cell analysis system. Moreover, the in vivo antitumor effect of fisetin was verified in pancreatic cancer using a luciferase-expressing murine xenograft pancreatic cancer model. We found that the AMPK/mTOR signaling pathway was enhanced after fisetin treatment; however, autophagy was not diminished by adding the AMPK inhibitor compound C. Thus, we hypothesized that an another autophagy regulating pathway existed. RNA-seq analysis revealed that the unfolded protein response pathway, which is activated by ER stress, was enriched. We also found that the stress-induced transcription factor p8 was increased in fisetin-treated PANC-1 cells, and that fisetin-induced autophagy was blocked by silencing p8. We revealed that p8-dependent autophagy was AMPK-independent, and that p8 regulated ATF6, ATF4, and PERK in response to ER stress via p53/PKC-α-mediated signaling. Furthermore, mitophagy was associated with Parkin and PINK1 in response to mitochondrial stress. Interestingly, ATF4 and ATF6 were increased in cells treated with fisetin and compound C. Moreover, inhibiting the AMPK/mTOR pathway with compound C may upregulate p8-dependent autophagy. Thus, there may be crosstalk between the AMPK/mTOR and p8-dependent pathways.
胰腺癌是最具侵袭性的肿瘤之一，患者的生存率较差。根皮素是一种天然黄酮类化合物，最近有研究报道其在多种癌症模型中具有抗肿瘤作用。自噬是一种保守的分解代谢过程，可在应激下维持细胞内稳态，并与细胞凋亡一起决定细胞命运。在此，我们研究了根皮素对胰腺癌的影响。我们发现根皮素通过实时细胞分析系统抑制 PANC-1 细胞的增殖。此外，我们在含有荧光素酶的小鼠异种移植胰腺癌模型中验证了根皮素的体内抗肿瘤作用。我们发现根皮素处理后 AMPK/mTOR 信号通路增强；然而，添加 AMPK 抑制剂化合物 C 并没有减少自噬。因此，我们假设存在另一种自噬调节途径。RNA-seq 分析显示，内质网应激激活的未折叠蛋白反应途径被富集。我们还发现，应激诱导转录因子 p8 在根皮素处理的 PANC-1 细胞中增加，并且 p8 沉默阻断了根皮素诱导的自噬。我们揭示了 p8 依赖性自噬与 AMPK 无关，并且 p8 通过 p53/PKC-α 介导的信号通路调节 ER 应激下的 ATF6、ATF4 和 PERK。此外，线粒体应激与 Parkin 和 PINK1 相关的线粒体自噬。有趣的是，用根皮素和化合物 C 处理的细胞中 ATF4 和 ATF6 增加。此外，用化合物 C 抑制 AMPK/mTOR 通路可能会上调 p8 依赖性自噬。因此，AMPK/mTOR 通路和 p8 依赖性通路之间可能存在串扰。
