ACSS2-mediated NF-κB activation promotes alkaliptosis in human pancreatic cancer cells.

Alkaliptosis is a recently discovered type of pH-dependent cell death used for tumor therapy. However, its underlying molecular mechanisms and regulatory networks are largely unknown. Here, we report that the acetate-activating enzyme acetyl-CoA short-chain synthase family member 2 (ACSS2) is a positive regulator of alkaliptosis in human pancreatic ductal adenocarcinoma (PDAC) cells. Using qPCR and western blot analysis, we found that the mRNA and protein expression of ACSS2 was upregulated in human PDAC cell lines (PANC1 and MiaPaCa2) in response to the classic alkaliptosis activator JTC801. Consequently, the knockdown of ACSS2 by shRNAs inhibited JTC801-induced cell death in PDAC cells, and was accompanied by an increase in cell clone formation and a decrease in intracellular pH. Mechanically, ACSS2-mediated acetyl-coenzyme A production and subsequent histone acetylation contributed to NF-κB-dependent CA9 downregulation, and this effect was enhanced by the histone deacetylase inhibitor trichostatin A. These findings may provide new insights for understanding the metabolic basis of alkaliptosis and establish a potential strategy for PDAC treatment.

MGST1 is a redox-sensitive repressor of ferroptosis in pancreatic cancer cells.

Ferroptosis is a type of nonapoptotic cell death driven by lipid peroxidation. Here, we show a key role of MGST1 in inhibiting ferroptosis in cell cultures and mouse xenograft models. Ferroptosis activators induce MGST1 upregulation in human pancreatic ductal adenocarcinoma (PDAC) cell lines in an NFE2L2-dependent manner. The genetic depletion of MGST1 or NFE2L2 has a similar effect in promoting ferroptosis, whereas the re-expression of MGST1 restores the resistance of NFE2L2-knockdown cells to ferroptosis. MGST1 inhibits ferroptotic cancer cell death partly by binding to ALOX5, resulting in reduced lipid peroxidation. The expression of MGST1 is positively correlated with NFE2L2 expression in pancreatic tumors, which is implicated in the poor prognosis of patients with PDAC. These findings not only provide a valuable insight into the defense mechanism against ferroptotic cell death, but also indicate that targeting the MGST1 redox-sensitive pathway may be a promising strategy for the treatment of PDAC.

PDK4 dictates metabolic resistance to ferroptosis by suppressing pyruvate oxidation and fatty acid synthesis.

Although induction of ferroptosis, an iron-dependent form of non-apoptotic cell death, has emerged as an anticancer strategy, the metabolic basis of ferroptotic death remains poorly elucidated. Here, we show that glucose determines the sensitivity of human pancreatic ductal carcinoma cells to ferroptosis induced by pharmacologically inhibiting system xc-. Mechanistically, SLC2A1-mediated glucose uptake promotes glycolysis and, thus, facilitates pyruvate oxidation, fuels the tricyclic acid cycle, and stimulates fatty acid synthesis, which finally facilitates lipid peroxidation-dependent ferroptotic death. Screening of a small interfering RNA (siRNA) library targeting metabolic enzymes leads to identification of pyruvate dehydrogenase kinase 4 (PDK4) as the top gene responsible for ferroptosis resistance. PDK4 inhibits ferroptosis by blocking pyruvate dehydrogenase-dependent pyruvate oxidation. Inhibiting PDK4 enhances the anticancer activity of system xc- inhibitors in vitro and in suitable preclinical mouse models (e.g., a high-fat diet diabetes model). These findings reveal metabolic reprogramming as a potential target for overcoming ferroptosis resistance.

NUPR1 is a critical repressor of ferroptosis.

Ferroptosis is a type of iron-dependent regulated cell death, representing an emerging disease-modulatory mechanism. Transcription factors play multiple roles in ferroptosis, although the key regulator for ferroptosis in iron metabolism remains elusive. Using NanoString technology, we identify NUPR1, a stress-inducible transcription factor, as a driver of ferroptosis resistance. Mechanistically, NUPR1-mediated LCN2 expression blocks ferroptotic cell death through diminishing iron accumulation and subsequent oxidative damage. Consequently, LCN2 depletion mimics NUPR1 deficiency with respect to ferroptosis induction, whereas transfection-enforced re-expression of LCN2 restores resistance to ferroptosis in NUPR1-deficient cells. Pharmacological or genetic blockade of the NUPR1-LCN2 pathway (using NUPR1 shRNA, LCN2 shRNA, pancreas-specific Lcn2 conditional knockout mice, or the small molecule ZZW-115) increases the activity of the ferroptosis inducer erastin and worsens pancreatitis, in suitable mouse models. These findings suggest a link between NUPR1-regulated iron metabolism and ferroptosis susceptibility.

Cathepsin B is a mediator of organelle-specific initiation of ferroptosis.

Ferroptosis is a type of non-apoptotic regulated cell death that involves excessive iron accumulation and subsequent lipid peroxidation. Although the antioxidant mechanisms of ferroptosis have been extensively studied recently, little is known about the interactions between the different organelles that control ferroptosis. Here, we show that the translocation of lysosomal cysteine protease cathepsin B (CTSB) into the nucleus is an important molecular event that mediates organelle-specific initiation of ferroptosis in human pancreatic cancer cells. Iron-dependent lysosomal membrane permeability triggers the release of CTSB from the lysosome to nucleus during ferroptosis. Mechanistically, nuclear CTSB accumulation causes DNA damage and subsequent activation of the stimulator of interferon response CGAMP interactor 1 (STING1/STING)-dependent DNA sensor pathway, which ultimately leads to autophagy-dependent ferroptosis. Consequently, the genetic inhibition of CTSB-dependent STING1 activation by RNAi prevents ferroptosis in cell culture and animal models. These new findings not only enhance our understanding of the mechanism by which organelles specifically trigger ferroptosis, but also may provide a potential way to enhance the anticancer activity of ferroptosis therapy.

Oxidative Damage and Antioxidant Defense in Ferroptosis.

Many new types of regulated cell death have been recently implicated in human health and disease. These regulated cell deaths have different morphological, genetic, biochemical, and functional hallmarks. Ferroptosis was originally described as a carcinogenic RAS-dependent non-apoptotic cell death, and is now defined as a type of regulated necrosis characterized by iron accumulation, lipid peroxidation, and the release of damage-associated molecular patterns (DAMPs). Multiple oxidative and antioxidant systems, acting together autophagy machinery, shape the process of lipid peroxidation during ferroptosis. In particular, the production of reactive oxygen species (ROS) that depends on the activity of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOXs) and the mitochondrial respiratory chain promotes lipid peroxidation by lipoxygenase (ALOX) or cytochrome P450 reductase (POR). In contrast, the glutathione (GSH), coenzyme Q10 (CoQ10), and tetrahydrobiopterin (BH4) system limits oxidative damage during ferroptosis. These antioxidant processes are further transcriptionally regulated by nuclear factor, erythroid 2-like 2 (NFE2L2/NRF2), whereas membrane repair during ferroptotic damage requires the activation of endosomal sorting complexes required for transport (ESCRT)-III. A further understanding of the process and function of ferroptosis may provide precise treatment strategies for disease.

Autophagy-Dependent Ferroptosis: Machinery and Regulation.

Macroautophagy (hereafter referred to as autophagy) is an evolutionarily conserved cellular process capable of degrading various biological molecules (e.g., protein, glycogen, lipids, DNA, and RNA) and organelles (e.g., mitochondria, endoplasmic reticulum [ER] ribosomes, lysosomes, and micronuclei) via the lysosomal pathway. Ferroptosis is a type of oxidative stress-dependent regulated cell death associated with iron accumulation and lipid peroxidation. The recently discovered role of autophagy, especially selective types of autophagy (e.g., ferritinophagy, lipophagy, clockophagy, and chaperone-mediated autophagy), in driving cells toward ferroptotic death motivated us to explore the functional interactions between metabolism, immunity, and cell death. Here, we describe types of selective autophagy and discuss the regulatory mechanisms and signaling pathways of autophagy-dependent ferroptosis. We also summarize chemical modulators that are currently available for triggering or blocking autophagy-dependent ferroptosis and that may be developed for therapeutic interventions in human diseases.

Alkaliptosis: a new weapon for cancer therapy.

Malignant tumors are one of the major causes of death worldwide, and the development of better treatments is urgently needed. There are many types of cancer treatment, such as surgery, chemotherapy, radiation therapy, immunotherapy, and targeted therapy, that might improve patient outcomes in a genotype- and stage-dependent manner. The main goal of cancer therapy is to inhibit biological capabilities of tumors and eventually eliminate the cancer cells. However, cancer cells are well known to escape apoptosis, a form of programmed cell death that was first described in studies of cell development and tissue remodelling. Increasing our understanding of cell death may result in new anticancer approaches that target types of nonapoptotic cell death, such as necroptosis, ferroptosis, autophagy-dependent cell death, and alkaliptosis. Notably, alkaliptosis, a pH-dependent form of regulated cell death, has been recently identified as a new strategy for cancer therapy across multiple tumor types, especially in pancreatic cancer.

Blastic plasmacytoid dendritic cell neoplasm in children: A review of two cases.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a newly characterized, rare malignant tumor of the skin and hematopoietic system. BPDCN occurs mainly in the elderly, whereas it is rarer among children, and has variable clinical manifestations. Optimal chemotherapeutic regimens for the treatment of BPDCN have not yet been determined and this tumor has a poor prognosis. In this study, two pediatric cases of BPDCN, including a 7-year-old female and a 9-year-old male patient, diagnosed at the Xiangya Hospital of Central South University over the past 2 years, were retrospectively reviewed. Both cases exhibited multiple organ involvement, although the clinical manifestations differed; they were diagnosed with BPDCN based on the clinical manifestations, pathological and immunohistochemical findings, which included positivity for CD4, CD56 and CD123. A high-risk acute lymphocytic leukemia (ALL) chemotherapy regimen was administered to both patients. The patient in the first case achieved a complete remission, but unfortunately her parents refused follow-up treatment and she succumbed to the disease 9 months after the initial diagnosis. The second patient was treated for a total of three courses with a chemotherapy regimen including daunorubicin, cytarabine and etoposide, followed by two courses of the high-risk ALL chemotherapy regimen; unfortunately, a remission was not achieved and the patient was scheduled to receive hematopoietic stem cell transplantation. Thus, not all pediatric BPDCN patients may be able to achieve complete remission following chemotherapy with the high-risk ALL regimen, and other treatment options must be investigated in the future.

[Recurrent pulmonary infection and oral mucosal ulcer].

An 8-year-old girl who had experienced intermittent cough and fever over a 3 year period, was admitted after experiencing a recurrence for one month. One year ago the patient experienced a recurrent oral mucosal ulcer. Physical examination showed vitiligo in the skin of the upper right back. Routine blood tests and immune function tests performed in other hospitals had shown normal results. Multiple lung CT scans showed pulmonary infection. The patient had recurrent fever and cough and persistent presence of some lesions after anti-infective therapy. The antitubercular therapy was ineffective. Routine blood tests after admission showed agranulocytosis. Gene detection was performed and she was diagnosed with dyskeratosis congenita caused by homozygous mutation in RTEL1. Patients with dyskeratosis congenita with RTEL1 gene mutation tend to develop pulmonary complications. Since RTEL1 gene sequence is highly variable with many mutation sites and patterns and can be inherited via autosomal dominant or recessive inheritance, this disease often has various clinical manifestations, which may lead to missed diagnosis or misdiagnosis. For children with unexplained recurrent pulmonary infection, examinations of the oral cavity, skin, and nails and toes should be taken and routine blood tests should be performed to exclude dyskeratosis congenita. There are no specific therapies for dyskeratosis congenita at present, and when bone marrow failure and pulmonary failure occur, hematopoietic stem cell transplantation and lung transplantation are the only therapies. Androgen and its derivatives are effective in some patients. Drugs targeting the telomere may be promising for patients with dyskeratosis congenita.