Ferroptosis, a recently discovered form of iron-dependent cell death, requires an increased level of lipid-reactive oxygen species (ROS). Ferritinophagy, a ferritin degradation pathway, depends on a selective autophagic cargo receptor (NCOA4). By screening various types of natural compounds, formosanin C (FC) was identified as a novel ferroptosis inducer, characterized by attenuations of FC-induced viability inhibition and lipid ROS formation in the presence of ferroptosis inhibitor. FC also induced autophagic flux, evidenced by preventing autophagic marker LC3-II degradation and increasing yellow LC3 puncta in tandem fluorescent-tagged LC3 (mRFP-GFP) reporter plasmid (ptfLC3) transfected cells when combined with autophagic flux inhibitor. It is noteworthy that FC-induced ferroptosis and autophagic flux were stronger in HepG2 cells expressing higher NCOA4 and lower ferritin heavy chain 1 (FTH1) levels, agreeing with the results of gene expression analysis using CTRP and PRISM, indicating that FTH1 expression level exhibited a significant negative correlation with the sensitivity of the cells to a ferroptosis inducer. Confocal and electron microscopy confirmed the pronounced involvement of ferritinophagy in FC-induced ferroptosis in the cells with elevated NCOA4. Since ferroptosis is a non-apoptotic form of cell death, our data suggest FC has chemotherapeutic potential against apoptosis-resistant HCC with a higher NCOA4 expression via ferritinophagy.

中文翻译：

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皂苷Formosaanin C诱导人肝癌细胞中的铁蛋白吞噬作用和肥大症。

Ferroptosis是最近发现的铁依赖性细胞死亡的一种形式，需要增加脂质反应性氧（ROS）的水平。铁蛋白吞噬（铁蛋白降解途径）取决于选择性自噬货物受体（NCOA4）。通过筛选各种类型的天然化合物，Formosacanin C（FC）被鉴定为一种新型的促肥大病诱导剂，其特征是在存在促肥大病抑制剂的情况下减弱了FC诱导的活力抑制和脂质ROS的形成。FC还诱导自噬通量，与自噬通量抑制剂联合使用时，可防止自噬标记LC3-II降解并在串联荧光标记的LC3（mRFP-GFP）报告质粒（ptfLC3）的转染细胞中增加黄色LC3点的出现。值得注意的是，FC诱导的肥大病和自噬通量在表达更高NCOA4和更低铁蛋白重链1（FTH1）水平的HepG2细胞中更强，这与使用CTRP和PRISM进行基因表达分析的结果一致，表明FTH1表达水平显示出与细胞对肥大症诱导物的敏感性显着负相关。共聚焦和电子显微镜证实，在NCOA4升高的细胞中，铁蛋白吞噬明显参与了FC诱导的肥大病。由于ferroptosis是细胞死亡的一种非凋亡形式，因此我们的数据表明FC具有抗凋亡的HCC的化学治疗潜力，并且通过铁蛋白吞噬作用具有更高的NCOA4表达。这表明FTH1表达水平与细胞对肥大症诱导物的敏感性呈显着负相关。共聚焦和电子显微镜证实，在NCOA4升高的细胞中，铁蛋白吞噬明显参与了FC诱导的肥大病。由于ferroptosis是细胞死亡的一种非凋亡形式，因此我们的数据表明FC具有抗凋亡的HCC的化学治疗潜力，并且通过铁蛋白吞噬作用具有更高的NCOA4表达。这表明FTH1表达水平与细胞对肥大症诱导物的敏感性呈显着负相关。共聚焦和电子显微镜证实，在NCOA4升高的细胞中，铁蛋白吞噬明显参与了FC诱导的肥大病。由于ferroptosis是细胞死亡的一种非凋亡形式，因此我们的数据表明FC具有抗凋亡的HCC的化学治疗潜力，并且通过铁蛋白吞噬作用具有更高的NCOA4表达。