ChaC1

Ferroptosis is a regulated cell death nexus linking metabolism, redox biology and diseases including cancer. The aim of the present study was to identify a ferroptosis-related gene prognostic signature for stomach adenocarcinoma (STAD) by systematic analysis of transcriptional profiles from The Cancer Genome Atlas (TCGA), GEO and a clinical cohort from our centre. We developed a predictive model based on three ferroptosis-related genes (CHAC1, NOX4 and HIF1A), gene expression data and corresponding clinical outcomes were obtained from the TCGA database, and the reliability of this model was verified with GSE15459 and 51 queues in our centre. ROC curve showed better predictive ability using the risk score. Immune cell enrichment analysis demonstrated that the types of immune cells and their expression levels in the high-risk group were significantly different from those in the low-risk group. The experimental results confirmed that NOX4 was upregulated and CHAC1 was downregulated in the STAD tissues compared with the normal stomach mucosal tissues (p < 0.05). In sum, the ferroptosis-related gene signature can accurately predict the outcomes of patients with STAD, providing valuable insights for personalized treatment. As the signature also has relevance to the immune characteristics, it may help improve the efficacy of personalized immunotherapy.

To evaluate the validity of CHAC1 for predicting the prognosis of kidney renal clear cell carcinoma (KIRC) and to explore its therapeutic potential for KIRC, we conducted several bioinformatic analyses using the sequencing data and clinical information derived from online databases. We found CHAC1 is down-regulated in KIRC samples when compared with normal samples but up-regulated in KIRC samples with relatively higher malignancy and later stages. Univariate cox analysis and multivariate cox regression analysis were conducted and the results revealed up-regulated CHAC1 is an independent risk factor for poor prognosis of KIRC. Further, the nomogram model based on the result of multivariate cox regression analysis was constructed and effectively predicted patients' 1-year, 3-year and 5-year survival respectively. The correlation analyses showed CHAC1 is associated with the immune pathway markers of memory B cell, natural killer cell and type1 T helper cell as well as the checkpoint genes like ADORA2A, CD200, CD44, CD70, HHLA2, NRP1, PDCD1LG2 and TNFRSF18. Furthermore, experiments in vitro indicated CHAC1 could induce cell death in KIRC cell lines but had limited influence on cell migration and cell invasion. In conclusion, CHAC1 is found a valid indicator for poor prognosis of kidney renal clear cell carcinoma.

Dihydroartemisinin (DHA), an artemisinin derivate, has been investigated as a potential antitumor drug in primary liver cancer (PLC). Ferroptosis is a form of iron‑dependent cell death that can be driven by lipid peroxidation inducers. The present study aimed to determine whether and how DHA could promote the death of PLC cells by inducing ferroptosis. In total, four PLC cell lines with different p53 statuses, including Hep3B (p53 null), Huh7 (p53 mutant), PLC/PRF/5 (p53 mutant) and HepG2 (p53 wild‑type), were treated with various concentrations of DHA. The effects of DHA on all three branches of the unfolded protein response (UPR) were evaluated. To deactivate the UPRs, small interfering RNA was used to knockdown the expression of activating transcription factor (ATF)4, X‑box binding protein 1 (XBP1) or ATF6 in PLC cells. The effect of DHA on the promoter activity of Chac glutathione specific γ‑glutamylcyclotransferase 1 (CHAC1) was evaluated using a dual luciferase reporter assay. The results revealed that DHA‑induced death in PLC cells was irrelevant of the p53 status. PLC cells exposed to DHA displayed classic features of ferroptosis, such as increased lipid reactive oxygen species and malondialdehyde levels, an iron overload, and decreased activity or expression of glutathione (GSH), glutathione peroxidase 4, solute carrier family (SLC) 7 member 11 and SLC family 3 member 2. The antitumor effects of DHA in PLC cells were significantly weakened by two typical ferroptosis inhibitors, ferrostatin‑1 and deferoxamine mesylate salt, whereas the antitumor effects were augmented following iron overload. Furthermore, DHA activated all three branches of the UPR (eukaryotic translation initiation factor 2 α kinase 3/eukaryotic translation initiation factor 2A/ATF4, inositol‑requiring transmembrane kinase/endoribonuclease 1α/XBP1 and ATF6 branches) in vitro. Notably, DHA‑induced ferroptosis was significantly attenuated following the knockdown of ATF4, XBP1 or ATF6 expression. In addition, the promoter activity of CHAC1, a gene capable of degrading GSH, was enhanced by DHA, but weakened when the aforementioned three UPR transcription factors were knocked down. In conclusion, the findings of the present study suggested that DHA may effectively induce ferroptosis in PLC cells through the activation of anti‑survival UPRs and the upregulation of CHAC1 expression.