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，患者的生存率很低。非瑟酮是一种天然黄酮类化合物，最近有报道称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，可维持细胞内稳态以应对应激，并与细胞凋亡一起决定细胞命运。在此，我们研究了非瑟酮对胰腺癌的作用。我们使用实时细胞分析系统揭示非瑟酮抑制 PANC-1 细胞增殖。此外，使用表达荧光素酶的小鼠异种移植胰腺癌模型验证了非瑟酮在胰腺癌中的体内抗肿瘤作用。我们发现非瑟酮处理后 AMPK/mTOR 信号通路增强；然而，添加AMPK抑制剂化合物C并没有减弱自噬。因此，我们假设存在另一种自噬调节途径。 RNA-seq 分析表明，由 ER 应激激活的未折叠蛋白反应途径得到了富集。我们还发现，在非瑟酮处理的 PANC-1 细胞中，应激诱导的转录因子 p8 增加，并且沉默 p8 可以阻断非瑟酮诱导的自噬。我们发现 p8 依赖性自噬不依赖于 AMPK，并且 p8 通过 p53/PKC-α 介导的信号传导调节 ATF6、ATF4 和 PERK 以响应 ER 应激。此外，线粒体自噬与 Parkin 和 PINK1 相关，以响应线粒体应激。有趣的是，用非瑟酮和化合物 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 和 p8 依赖性途径之间可能存在串扰。