Sigma‐1 receptor (S1R) regulates reactive oxygen species (ROS) accumulation via nuclear factor erythroid 2‐related factor 2 (NRF2), which plays a vital role in ferroptosis. Sorafenib is a strong inducer of ferroptosis but not of apoptosis. However, the mechanism of sorafenib‐induced ferroptosis in hepatocellular carcinoma (HCC) remains unclear. In this study, we found for the first time that sorafenib induced most of S1Rs away from nucleus compared to control groups in Huh‐7 cells, and ferrostatin‐1 completely blocked the translocation. S1R protein expression, but not mRNA expression, in HCC cells was significantly up‐regulated by sorafenib. Knockdown of NRF2, but not of p53 or hypoxia‐inducible factor 1‐alpha (HIF1α), markedly induced S1R mRNA expression in HCC cells. Inhibition of S1R (by RNAi or antagonists) increased sorafenib‐induced HCC cell death in vitro and in vivo. Knockdown of S1R blocked the expression of glutathione peroxidase 4 (GPX4), one of the core targets of ferroptosis, in vitro and in vivo. Iron metabolism and lipid peroxidation increased in the S1R knockdown groups treated with sorafenib compared to the control counterpart. Ferritin heavy chain 1 (FTH1) and transferrin receotor protein 1 (TFR1), both of which are critical for iron metabolism, were markedly up‐regulated in HCC cells treated with erastin and sorafenib, whereas knockdown of S1R inhibited these increases. In conclusion, we demonstrate that S1R protects HCC cells against sorafenib and subsequent ferroptosis. A better understanding of the role of S1R in ferroptosis may provide novel insight into this biological process.

Primary liver cancer is the second most frequent cause of cancer‐related deaths. Ferroptosis, a recognized form of regulated cell death, recently gains attention. MicroRNA‐214‐3p (miR‐214) plays a regulatory role in hepatocarcinogenesis. However, the role of miR‐214 in cellular ferroptosis is unclear. This study aimed at elucidating whether miR‐214 could regulate ferroptosis of liver cancer. In vitro, HepG2 and Hep3B cancer cells were treated with erastin, a ferroptosis inducer, and then erastin was demonstrated to suppress the cell viability. Moreover, pre‐miR‐214 overexpression caused that HepG2 and Hep3B cells were more susceptible to erastin, whereas anti‐miR‐214 sponge showed the opposite effect. Additionally, pre‐miR‐214 overexpression increased the malondialdehyde and reactive oxygen species levels, upregulated Fe2+ concentration, and decreased glutathione levels in cancer cells exposed to erastin. Further, erastin enhanced the activation of transcription factor 4 (ATF4) in HepG2 and Hep3B cells, and pre‐miR‐214 overexpression inhibited ATF4 expression. The luciferase reporter data validated ATF4 as a direct target of miR‐214. Cancer cells transfected with ATF4 overexpression plasmid rendered lower susceptible to miR‐214‐induced ferroptotic death. In vivo, erastin significantly reduced the size and weight of xenografted tumors, and miR‐214 elevated the ferroptosis‐promoting effects of erastin and decreased ATF4 expression. In summary, our study demonstrates that the ferroptosis‐promoting effects of miR‐214 in hepatoma cells are attributed at least to its inhibitory effects on ATF4, which may provide a new target for therapy of hepatoma regarding ferroptosis.

As the most aggressive tumor, the outcome of pancreatic cancer (PACA) has not improved observably over the last decade. Anatomy-based TNM staging does not exactly identify treatment-sensitive patients, and an ideal biomarker is urgently needed for precision medicine. Based on expression files of 1280 patients from 10 multicenter cohorts, we screened 32 consensus prognostic genes. Ten machine-learning algorithms were transformed into 76 combinations, of which we selected the optimal algorithm to construct an artificial intelligence-derived prognostic signature (AIDPS) according to the average C-index in the nine testing cohorts. The results of the training cohort, nine testing cohorts, Meta-Cohort, and three external validation cohorts (290 patients) consistently indicated that AIDPS could accurately predict the prognosis of PACA. After incorporating several vital clinicopathological features and 86 published signatures, AIDPS exhibited robust and dramatically superior predictive capability. Moreover, in other prevalent digestive system tumors, the nine-gene AIDPS could still accurately stratify the prognosis. Of note, our AIDPS had important clinical implications for PACA, and patients with low AIDPS owned a dismal prognosis, higher genomic alterations, and denser immune cell infiltrates as well as were more sensitive to immunotherapy. Meanwhile, the high AIDPS group possessed observably prolonged survival, and panobinostat may be a potential agent for patients with high AIDPS. Overall, our study provides an attractive tool to further guide the clinical management and individualized treatment of PACA.

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