Ferroptosis is triggered by a chain of intracellular labile iron‐dependent peroxidation of cell membrane phospholipids. Ferroptosis is important not only as a cause of ischaemic and neurodegenerative diseases but also as a mechanism of cancer suppression, and a better understanding of its regulatory mechanism is required. It has become clear that ferroptosis is finely controlled by two oxidative stress‐responsive transcription factors, NRF2 (NF‐E2‐related factor 2) and BACH1 (BTB and CNC homology 1). NRF2 and BACH1 inhibit and promote ferroptosis, respectively, by activating or suppressing the expression of genes in the major regulatory pathways of ferroptosis: intracellular labile iron metabolism, the GSH (glutathione) ‐GPX4 (glutathione peroxidase 4) pathway and the FSP1 (ferroptosis suppressor protein 1)‐CoQ (coenzyme Q) pathway. In addition to this, NRF2 and BACH1 control ferroptosis through the regulation of lipid metabolism and cell differentiation. This multifaceted regulation of ferroptosis by NRF2 and BACH1 is considered to have been acquired during the evolution of multicellular organisms, allowing the utilization of ferroptosis for maintaining homeostasis, including cancer suppression. In terms of cell–cell interaction, it has been revealed that ferroptosis has the property of propagating to surrounding cells along with lipid peroxidation. The regulation of ferroptosis by NRF2 and BACH1 and the propagation phenomenon could be used to realize anticancer cell therapy in the future. In this review, these points will be summarized and discussed.

Purpose: The epithelial-to-mesenchymal transition, the major process by which some cancer cells convert from an epithelial phenotype to a mesenchymal one, has been suggested to drive chemo-resistance and/or metastasis in patients with cancer. However, only a few studies have demonstrated the presence of CD45/CD326 doublypositive cells (CD45/CD326 DPC) in cancer. We deployed a combination of cell surface markers to elucidate the phenotypic heterogeneity in non-small cell lung cancer (NSCLC) cells and identified a new subpopulation that is doubly-positive for epithelial and non-epithelial cellsurface markers in both NSCLC cells and patients' malignant pleural effusions.Experimental Design: We procured a total of 39 patients' samples, solid fresh lung cancer tissues from 21 patients and malignant pleural effusion samples from 18 others, and used FACS and fluorescence microscopy to check their surface markers. We also examined the EGFR mutations in patients with known acquired EGFR mutations.Results: Our data revealed that 0.4% to 17.9% of the solid tumor tissue cells and a higher percentage of malignant pleural effusion cells harbored CD45/CD326 DPC expressing both epithelial and nonepithelial surface markers. We selected 3 EGFR mutation patients and genetically confirmed that the newly identified cell population really originated from cancer cells. We also found that higher proportions of CD45/CD326 DPC are significantly associated with poor prognosis.Conclusions: In conclusion, varying percentages of CD45/CD326 DPC exist in both solid cancer tissue and malignant pleural effusion in patients with NSCLC. This CD45/CD326 doubly-positive subpopulation can be an important key to clinical management of patients with NSCLC.

SummaryWe previously reported lower lymphocyte vitamin C levels in individuals with type 2 diabetes mellitus and in individuals with severe Parkinson's disease. Oxidative stress has been proposed to play a key role in the progression of Alzheimer's disease. Thus, the objective of this study was to investigate the association between peripheral levels of vitamin C and the progression of cognitive dysfunction in Alzheimer's disease. Fifty individuals with Alzheimer's disease being treated at Shizuoka General Hospital were consecutively enrolled in this study from December 2009 to March 2015 (76.069.7 y of age [mean6SD]; 32 men and 18 women; Mini-Mental State Examination Japanese version (MMSE-J) score range, 8-27). Plasma and lymphocyte vitamin C levels in fasting blood samples were measured. The association between the MMSE-J scores and vitamin C levels was estimated using Spearman's rank correlation coefficient () and the criteria defined by Swinscow. Spearman's  for the relationship between peripheral vitamin C levels and the MMSE-J score was 50.17 for plasma vitamin C and 50.26 for lymphocyte vitamin C. Thus, the associations were relatively weak based on the criteria. In contrast with type 2 diabetes mellitus and Parkinson's disease, lymphocyte vitamin C levels in the peripheral blood may not directly reflect the progression of cognitive dysfunction in Alzheimer's disease. Additional longitudinal studies are needed to evaluate the clinical importance of changes of peripheral vitamin C status in Alzheimer's disease.

Pancreatic ductal adenocarcinoma (PDAC) is the most lethal cancer, mainly because of its invasive and metastatic characteristics. Pancreatic intraepithelial neoplasia (PanIN) is one of the major precursor lesions of PDAC. Although epithelial‐to‐mesenchymal transition (EMT) is known to play an important role for these malignant behaviors, the association between PanIN and EMT has not been clearly understood. Therefore, we explored possible molecules for regulation of EMT immunohistochemically. Using surgically resected specimens from 71 PDAC patients, expressions of SNAIL, SLUG, TWIST1, and ZEB1 were investigated in high‐grade PanIN (HG‐PanIN) and PDAC. Results demonstrated that PDAC accompanied by SNAIL‐positive HG‐PanIN showed a significantly better relapse‐free survival (RFS) (median survival time (MST) of 11.3 months vs 4.4 months, P < 0.001) and overall survival overall survival (OS) (MST of 25.2 months vs 13.6 months, P < 0.001). In PDAC accompanied by SLUG‐positive HG‐PanIN, RFS and OS (P = 0.09 and P = 0.05) tended to have a better prognosis. In contrast, we could not find any significant prognostic benefits in the expression of TWIST1 or ZEB1 in PDAC accompanied by HG‐PanIN. Our present results suggest that (1) EMT may play an important role in the development of PDAC from HG‐PanIN, and (2) SNAIL may predict a distinct subgroup that shows a better prognosis.

Ferroptosis is a regulated cell death induced by iron-dependent lipid peroxidation. The heme-responsive transcription factor BTB and CNC homology 1 (BACH1) promotes ferroptosis by repressing the transcription of genes involved in glutathione (GSH) synthesis and intracellular labile iron metabolism, which are key regulatory pathways in ferroptosis. We found that BACH1 re-expression in Bach1−/− immortalized mouse embryonic fibroblasts (iMEFs) can induce ferroptosis upon 2-mercaptoethanol removal, without any ferroptosis inducers. In these iMEFs, GSH synthesis was reduced, and intracellular labile iron levels were increased upon BACH1 re-expression. We used this system to investigate whether the major ferroptosis regulators glutathione peroxidase 4 (Gpx4) and apoptosis-inducing factor mitochondria-associated 2 (Aifm2), the gene for ferroptosis suppressor protein 1, are target genes of BACH1. Neither Gpx4 nor Aifm2 was regulated by BACH1 in the iMEFs. However, we found that BACH1 represses AIFM2 transcription in human pancreatic cancer cells. These results suggest that the ferroptosis regulators targeted by BACH1 may vary across different cell types and animal species. Furthermore, we confirmed that the ferroptosis induced by BACH1 re-expression exhibited a propagating effect. BACH1 re-expression represents a new strategy for inducing ferroptosis after GPX4 or system Xc− suppression, and is expected to contribute to future ferroptosis research.