Cysteine Dioxygenase 1 Mediates Erastin-Induced Ferroptosis in Human Gastric Cancer Cells

Identification and Validation of a Prognostic Signature for Prostate Cancer Based on Ferroptosis-Related Genes

Ferroptosis, an iron-dependent form of selective cell death, is involved in the development of many cancers. However, ferroptosis related genes (FRGs) in prostate cancer (PCa) are not been well studied. In this study, we collected the mRNA expression profiles and clinical information of PCa patients from TCGA and MSKCC databases. The univariate, LASSO, and multivariate Cox regression analyses were performed to construct a prognostic signature. Seven FRGs, AKR1C3, ALOXE3, ATP5MC3, CARS1, MT1G, PTGS2, and TFRC, were included to establish a risk model, which was validated in the MSKCC dataset. The results showed that the high-risk group was apparently correlated with copy number alteration load, tumor burden mutation, immune cell infiltration, mRNAsi, immunotherapy, and bicalutamide response. Moreover, we found that TFRC overexpression induced the proliferation and invasion of PCa cell lines in vitro. These results demonstrate that this risk model can accurately predict prognosis, suggesting that FRGs are promising prognostic biomarkers and potential drug targets in PCa patients.

Designer exosomes for targeted and efficient ferroptosis induction in cancer via chemo-photodynamic therapy

Background: Efficient and specific induction of cell death in liver cancer is urgently needed. In this study, we aimed to design an exosome-based platform to deliver ferroptosis inducer (Erastin, Er) and photosensitizer (Rose Bengal, RB) into tumor tissues with high specificity. Methods: Exosome donor cells (HEK293T) were transfected with control or CD47-overexpressing plasmid. Exosomes were isolated and loaded with Er and RB via sonication method. Hepa1-6 cell xenograft C57BL/6 model was injected with control and engineered exosomes via tail vein. In vivo distribution of the injected exosomes was analyzed via tracking the fluorescence labeled exosomes. Photodynamic therapy was conducted by 532 nm laser irradiation. The therapeutic effects on hepatocellular carcinoma and toxic side-effects were systemically analyzed. Results: CD47 was efficiently loaded on the exosomes from the donor cells when CD47 was forced expressed by transfection. CD47 surface functionalization (ExosCD47) made the exosomes effectively escape the phagocytosis of mononuclear phagocyte system (MPS), and thus increased the distribution in tumor tissues. Erastin and RB could be effectively encapsulated into exosomes after sonication, and the drug-loaded exosomes (Er/RB@ExosCD47) strongly induced ferroptosis both in vitro and in vivo in tumor cells after irradiation of 532 nm laser. Moreover, compared with the control exosomes (Er/RB@ExosCtrl), Er/RB@ExosCD47 displayed much lower toxicity in liver. Conclusion: The engineered exosomes composed of CD47, Erastin, and Rose Bengal, induce obvious ferroptosis in hepatocellular carcinoma (HCC) with minimized toxicity in liver and kidney. The proposed exosomes would provide a promising strategy to treat types of malignant tumors.

Molecular identification of an immunity- and Ferroptosis-related gene signature in non-small cell lung Cancer

Background

Lung cancer is one of the dominant causes of cancer-related deaths worldwide. Ferroptosis, an iron-dependent form of programmed cell death, plays a key role in cancer immunotherapy. However, the role of immunity- and ferroptosis-related gene signatures in non-small cell lung cancer (NSCLC) remain unclear.

Methods

RNA-seq data and clinical information pertaining to NSCLC were collected from The Cancer Genome Atlas dataset. Univariate and multivariate Cox regression analyses were performed to identify ferroptosis-related genes. A receiver operating characteristic (ROC) model was established for sensitivity and specificity evaluation. Gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed to explore the function roles of differentially expressed genes.

Results

A signature composed of five ferroptosis-related genes was established to stratify patients into high- and low-risk subgroups. In comparison with patients in the low-risk group, those in the high-risk one showed significantly poor overall survival in the training and validation cohorts (P < 0.05). Multivariate Cox regression analysis indicated risk score to be an independent predictor of overall survival (P < 0.01). Further, the 1-, 2-, and 3-year ROCs were 0.623 vs. 0.792 vs. 0.635, 0.644 vs. 0.792 vs. 0.634, and 0.631 vs. 0.641 vs. 0.666 in one training and two validation cohorts, respectively. Functional analysis revealed that immune-related pathways were enriched and associated with abnormal activation of immune cells.

Conclusions

We identified five immunity- and ferroptosis-related genes that may be involved in NSCLC progression and prognosis. Targeting ferroptosis-related genes seems to be an alternative to clinical therapy for NSCLC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08541-w.

The role of non-apoptotic cell death in the treatment and drug-resistance of digestive tumors

Tumor cell apoptosis evasion is one of the main reasons for easy metastasis occurrence, chemotherapy resistance, and the low five-year survival rate of digestive system tumors. Current research has shown that non-apoptotic cell death plays an important role in tumors of the digestive system. Therefore, increasing the proportion of non-apoptotic tumor cells is one of the effective methods of improving therapeutic efficacies for digestive system tumors. Non-apoptotic cell death modes mainly include autophagic cell death, pyroptosis, ferroptosis, in addition to other cell death modes. This review covers a systematic review relating to the research progress made into autophagic cell death, pyroptosis, ferroptosis, and other cell death modes in the treatment of digestive system tumors. It also highlights how treatment is a reasonable prospect based on clinical experience and provides reliable guidance for the further development of digestive system tumor treatments.

H-ferritin suppression and pronounced mitochondrial respiration make Hepatocellular Carcinoma cells sensitive to RSL3-induced ferroptosis

Ferroptosis is a form of regulated cell death dependent on iron, reactive oxygen species and characterized by the accumulation of lipid peroxides. It can be experimentally initiated by chemicals, such as erastin and RSL3, that modulate GPX4 activity, the cellular antioxidant machinery that avert lipid peroxidation. The study aimed to investigate mitochondrial respiration and ferritin function as biomarkers of ferroptosis sensitivity of HepG2 and HA22T/VGH, two Hepatocellular Carcinoma (HCC) cell line models. Cell viability was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay, labile iron levels were determined using Calcein-AM fluorescence microscopy, ferritin, glutathione and lipid peroxidation were assayed with commercially available kits. The Seahorse assay was used to investigate mitochondrial function in the cells. The study shows that highly differentiated HepG2 cells were more sensitive to RSL3-induced ferroptosis than the poorly differentiated HA22T/VGH (HCC) cell line (RSL3 IC₅₀ 0.07 μM in HepG2 vs 0.3 μM in HA22T/VGH). Interestingly, HepG2 exhibited higher mitochondrial respiration and lower glycolytic activity than HA22T/VGH and were more sensitive to RSL3-induced ferroptosis, indicating a mitochondrial-specific mechanism of action of RSL3. Interestingly, iron metabolism seems to be involved in this different sensitivity, specifically, the downregulation of H-ferritin (but not of L-subunit), makes HA22T/VGH more sensitive toward both RSL3-and iron-induced ferroptosis. Hence only the H-ferritin seems involved in the protection from this cell death process.

MEF2C silencing downregulates NF2 and E-cadherin and enhances Erastin-induced ferroptosis in meningioma

BACKGROUND

Ferroptosis, a programmed cell death characterized by lipid peroxidation, is implicated in various diseases including cancer. Although cell density-dependent E-cadherin and Merlin/Neurofibromin (NF2) loss can modulate ferroptosis, the role of ferroptosis and its potential link to NF2 status and E-cadherin expression in meningioma remain unknown.

METHODS

Relationship between ferroptosis modulators expression and NF2 mutational status was examined in 35 meningiomas (10 NF2 loss and 25 NF2 wildtype). The impact of NF2 and E-cadherin on ferroptosis were examined by LDH release, lipid peroxidation and western blot assays in IOMM-Lee, CH157 and patient-derived meningioma cell models. Luciferase reporter and chromatin immunoprecipitation assays were used to assess the ability of MEF2C (myocyte enhancer factor 2C) to drive expression of NF2 and CDH1 (E-cadherin). Therapeutic efficacy of Erastin-induced ferroptosis was tested in xenograft mouse models.

RESULTS

Meningioma cells with NF2 inactivation were susceptible to Erastin-induced ferroptosis. Meningioma cells grown at higher density increased expression of E-Cadherin, which suppressed Erastin-induced ferroptosis. Maintaining NF2 and E-cadherin inhibited ferroptosis-related lipid peroxidation and meningioma cell death. MEF2C was found to drive the expression of both NF2 and E-cadherin. MEF2C silencing enhanced Erastin-induced ferroptotic meningioma cell death and lipid peroxidation levels in vitro, which was limited by forced expression of MEF2C targets, NF2 and E-Cadherin. In vivo, anti-meningioma effect of Erastin was augmented by MEF2C knockdown and was counteracted by NF2 or E-Cadherin.

CONCLUSIONS

NF2 loss and low E-cadherin create susceptibility to ferroptosis in meningioma. MEF2C could be a new molecular target in ferroptosis-inducing therapies for meningioma.

Hydrogen sulfide in longevity and pathologies: Inconsistency is malodorous

Hydrogen sulfide (H₂S) is one of the biologically active gases (gasotransmitters), which plays an important role in various physiological processes and aging. Its production in the course of methionine and cysteine catabolism and its degradation are finely balanced, and impairment of H₂S homeostasis is associated with various pathologies. Despite the strong geroprotective action of exogenous H₂S in C. elegans, there are controversial effects of hydrogen sulfide and its donors on longevity in other models, as well as on stress resistance, age-related pathologies and aging processes, including regulation of senescence-associated secretory phenotype (SASP) and senescent cell anti-apoptotic pathways (SCAPs). Here we discuss that the translation potential of H₂S as a geroprotective compound is influenced by a multiplicity of its molecular targets, pleiotropic biological effects, and the overlapping ranges of toxic and beneficial doses. We also consider the challenges of the targeted delivery of H₂S at the required dose. Along with this, the complexity of determining the natural levels of H₂S in animal and human organs and their ambiguous correlations with longevity are reviewed.

The construction and analysis of a ferroptosis-related gene prognostic signature for pancreatic cancer

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 pancreatic cancer (PCa) by systematic analysis of transcriptional profiles from Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx). Altogether 14 ferroptosis-relevant genes with potential prognostic values were identified, based on which a risk score formula was constructed. According to the risk scores, we classified the patients into a high- and a low-risk score group. It was verified in Gene Expression Omnibus (GEO) and ICGC (International Cancer Genome Consortium) datasets. The Kaplan-Meier survival curves demonstrated that patients with lower risk scores had significantly favorable overall survival (OS) (P < 0.0001). The area under the receiver operating curve (ROC) for 12, 18 and 24 months was about 0.8 in all patients. The result of immune status analysis revealed that the signature significantly associated with the immune infiltration and immune checkpoint blockade (ICB) proteins. In addition, we used quantitative real time PCR (q-rtPCR) and Human Protein Atlas (HPA) to validate the expression of the key genes. Collectively, the signature is valuable for survival prediction of PCa patients. As the signature also has relevance with the immune characteristics, it may help improve the efficacy of personalized immunotherapy.

Short overview on the relevance of microRNA-reactive oxygen species (ROS) interactions and lipid peroxidation for modulation of oxidative stress-mediated signalling pathways in cancer treatment

OBJECTIVES

Modulation of oxidative stress-mediated signalling pathways is constantly getting more attention as a valuable therapeutic strategy in cancer treatment. Although complexity of redox signalling pathways might represent a major hurdle, the development of advanced -omics technologies allow thorough studies on cancer-specific biology, which is essential to elucidate the impact of these signalling pathways in cancer cells. The scope of our review is to provide updated information about recent developments in cancer treatment.

KEY FINDINGS

In recent years identifying oxidative stress-mediated signalling pathways is a major goal of cancer research assuming it may provide novel therapeutic approaches through the development of agents that may have better tissue penetration and therefore affect specific redox signalling pathways. In this review, we discuss some recent studies focussed on the modulation of oxidative stress-related signalling pathways as a novel anti-cancer treatment, with a particular emphasis on the induction of lipid peroxidation.

CONCLUSIONS

Characterization and modulation of oxidative stress-mediated signalling pathways and lipid peroxidation products will continue to foster novel interest and further investigations, which may pave the way for more effective, selective, and personalized integrative biomedicine treatment strategies.

The Multifaceted Regulation of Mitochondria in Ferroptosis

Ferroptosis is characterized as a novel form of regulated cell death, which is initiated by the lethal accumulation of lipid peroxidation catalyzed by cellular labile free iron. This iron driven cell death sharply differs from other well characterized forms of regulated cell death at morphological, genetic and biochemical levels. Increasing research has elaborated a high relevance between dysregulated ferroptosis and the pathogenesis of degenerative diseases and organs injury in human patients. Additionally, targeted induction of ferroptosis is considered as a potentially therapeutic design for the clinical intervention of other therapy-resistant cancers. It is well understood that mitochondria, the cellular powerhouse, determine several types of regulated cell death. Recently, compromised mitochondrial morphology and functionalities have been primarily formulated in ferroptosis. Several mitochondria associated proteins and metabolic processes have been elaborated to fine-tune ferroptotic program. Herein, we critically review the recent advances in this booming field, with focus on summarizing the multifaceted mitochondrial regulation of ferroptosis and providing a perspective on the potential biochemical basis. Finally, we are attempting to shed light on an integrative view on the possibility of mitochondria- and ferroptosis-targeting therapeutics as novel treatment designs for the intervention of ferroptosis related diseases.

Cysteine metabolic circuitries: druggable targets in cancer

To enable survival in adverse conditions, cancer cells undergo global metabolic adaptations. The amino acid cysteine actively contributes to cancer metabolic remodelling on three different levels: first, in its free form, in redox control, as a component of the antioxidant glutathione or its involvement in protein s-cysteinylation, a reversible post-translational modification; second, as a substrate for the production of hydrogen sulphide (H2S), which feeds the mitochondrial electron transfer chain and mediates per-sulphidation of ATPase and glycolytic enzymes, thereby stimulating cellular bioenergetics; and, finally, as a carbon source for epigenetic regulation, biomass production and energy production. This review will provide a systematic portrayal of the role of cysteine in cancer biology as a source of carbon and sulphur atoms, the pivotal role of cysteine in different metabolic pathways and the importance of H2S as an energetic substrate and signalling molecule. The different pools of cysteine in the cell and within the body, and their putative use as prognostic cancer markers will be also addressed. Finally, we will discuss the pharmacological means and potential of targeting cysteine metabolism for the treatment of cancer.

Construction and Validation of a Ferroptosis-Related Prognostic Model for Gastric Cancer

BACKGROUND

Gastric cancer (GC), an extremely aggressive tumor with a very different prognosis, is the third leading cause of cancer-related mortality. We aimed to construct a ferroptosis-related prognostic model that can be distinguished prognostically.

METHODS

The gene expression and the clinical data of GC patients were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus database (GEO). The ferroptosis-related genes were obtained from the FerrDb. Using the "limma" R package and univariate Cox analysis, ferroptosis-related genes with differential expression and prognostic value were identified in the TCGA cohort. Last absolute shrinkage and selection operator (LASSO) Cox regression was applied to shrink ferroptosis-related predictors and construct a prognostic model. Functional enrichment, ESTIMATE algorithm, and single-sample gene set enrichment analysis (ssGSEA) were applied for exploring the potential mechanism. GC patients from the GEO cohort were used for validation.

RESULTS

An 8-gene prognostic model was constructed and stratified GC patients from TCGA and meta-GEO cohort into high-risk groups or low-risk groups. GC patients in high-risk groups have significantly poorer OS compared with those in low-risk groups. The risk score was identified as an independent predictor for OS. Functional analysis revealed that the risk score was mainly associated with the biological function of extracellular matrix (ECM) organization and tumor immunity.

CONCLUSION

In conclusion, the ferroptosis-related model can be utilized for the clinical prognostic prediction in GC.

Inhibition of SRSF9 enhances the sensitivity of colorectal cancer to erastin-induced ferroptosis by reducing glutathione peroxidase 4 expression

Ferroptosis, a newly iron-dependent form of cell death, is often accompanied by the damage of membrane lipid peroxide. Recently, the ferroptosis inducer erastin has been reported to exhibit potential anti-cancer activities. The aim of this study was to investigate the effects of SRSF9 on the sensitivity of colorectal cancer (CRC) to erastin and explore the underlying molecular mechanism. Short hairpin RNAs (shRNAs) or SRSF9 overexpression vector (SRSF9-OE) was transfected into erastin-induced human CRC cells to inhibit or overexpress SRSF9. Results showed that SRSF9 inhibition promoted the cell death induced by erastin, conversely, SRSF9 overexpression augmented the resistance to erastin-induced death in human CRC cells. SRSF9 decreased lipid peroxide damage which was a key event during erastin-induced ferroptosis in human CRC cells. Furthermore, we found that SRSF9 inhibition increased erastin-induced ferroptosis by downregulating GPX4 level. In an In vivo study, SRSF9 shRNA or SRSF9-OE stably transfected human CRC cells were subcutaneously injected into the right flank of nude mice. SRSF9 overexpression partly abolished the tumor growth inhibition and ferroptosis induced by erastin. Our data indicated SRSF9's regulation of GPX4 as an essential mechanism driving CRC tumorigenesis and resistance of erastin-induced ferroptosis. This molecular mechanism may provide a novel method for improving the sensitivity of CRC to erastin.

Ferroptosis: molecular mechanisms and health implications

Cell death can be executed through different subroutines. Since the description of ferroptosis as an iron-dependent form of non-apoptotic cell death in 2012, there has been mounting interest in the process and function of ferroptosis. Ferroptosis can occur through two major pathways, the extrinsic or transporter-dependent pathway and the intrinsic or enzyme-regulated pathway. Ferroptosis is caused by a redox imbalance between the production of oxidants and antioxidants, which is driven by the abnormal expression and activity of multiple redox-active enzymes that produce or detoxify free radicals and lipid oxidation products. Accordingly, ferroptosis is precisely regulated at multiple levels, including epigenetic, transcriptional, posttranscriptional and posttranslational layers. The transcription factor NFE2L2 plays a central role in upregulating anti-ferroptotic defense, whereas selective autophagy may promote ferroptotic death. Here, we review current knowledge on the integrated molecular machinery of ferroptosis and describe how dysregulated ferroptosis is involved in cancer, neurodegeneration, tissue injury, inflammation, and infection.

System Xc-: a key regulatory target of ferroptosis in cancer

Ferroptosis is a type of oxidative stress-dependent regulated necrosis characterized by excessive lipid peroxide accumulation. This novel cell death modality has been implicated in preventing cancer progression. Cancer cells tend to modulate their redox state to prevent excessive peroxidation, eventually facilitating tumor growth. System Xc^- (a cystine/glutamate antiporter system) is a promising target in cancer cells for ferroptosis induction. The overexpression of system Xc^-, especially its core subunit xCT, has been reported in several tumors, and these high expression levels were closely related to cancer cell proliferation, invasion, metastasis and the tumor microenvironment. xCT might serve as a novel biomarker, and its upregulation almost always indicates drug tolerance and poor survival. Therefore, system Xc^- inhibition may enhance chemotherapy sensitivity and optimize patient prognosis. Here, we elaborate on the mediation of ferroptosis by suppressing system Xc^- and the relevant underlying molecular mechanism in cancer cells. The spotlight on this approach to cancer treatment is creating a new horizon and pointing to future opportunities.

Cathepsin B is an executioner of ferroptosis

Ferroptosis is a necrotic form of cell death caused by inactivation of the glutathione system and uncontrolled iron-mediated lipid peroxidation. Increasing evidence implicates ferroptosis in a wide range of diseases from neurotrauma to cancer, highlighting the importance of identifying an executioner system that can be exploited for clinical applications. In this study, using pharmacological and genetic models of ferroptosis, we observed that lysosomal membrane permeabilization and cytoplasmic leakage of cathepsin B unleashes structural and functional changes in mitochondria and promotes a not previously reported cleavage of histone H3. Inhibition of cathepsin-B robustly rescued cellular membrane integrity and chromatin degradation. We show that these protective effects are independent of glutathione peroxidase-4 and are mediated by preventing lysosomal membrane damage. This was further confirmed when cathepsin B knockout primary fibroblasts remained unaffected in response to various ferroptosis inducers. Our work identifies new and yet-unrecognized aspects of ferroptosis and identifies cathepsin B as a mediator of ferroptotic cell death.

Ferroptosis as a novel form of regulated cell death: Implications in the pathogenesis, oncometabolism and treatment of human cancer

The treatment of cancer mainly involves surgical excision supplemented by radiotherapy and chemotherapy. Chemotherapy drugs act by interfering with tumor growth and inducing the death of cancer cells. Anti-tumor drugs were developed to induce apoptosis, but some patient’s show apoptosis escape and chemotherapy resistance. Therefore, other forms of cell death that can overcome the resistance of tumor cells are important in the context of cancer treatment. Ferroptosis is a newly discovered iron-dependent, non-apoptotic type of cell death that is highly negatively correlated with cancer development. Ferroptosis is mainly caused by the abnormal increase in iron-dependent lipid reactive oxygen species and the imbalance of redox homeostasis. This review summarizes the progression and regulatory mechanism of ferroptosis in cancer and discusses its possible clinical applications in cancer diagnosis and treatment.

Emerging Strategies in Anticancer Combination Therapy Employing Silica-Based Nanosystems

Combination therapy has emerged as one of the most promising approaches for cancer treatment. However, beyond remotely-triggered therapies that require advanced infrastructures and optimization, new combination therapies based on internally triggered cell-killing effects have also demonstrated promising therapeutic profiles. In this revision, the focus is on self-triggered strategies able to improve the therapeutic effect of drug delivery nanosystems. As reviewed, ferroptosis, hypoxia, and immunotherapy show potency enough to treat satisfactorily tumors in vivo. However, the interest of combining those with chemotherapeutics, especially with carriers based on mesoporous silica, has provided a new generation of therapeutic nanomedicines with potential enough to achieve complete tumor remission in murine models.

Targeting ferroptosis in breast cancer

Ferroptosis is a recently discovered distinct type of regulated cell death caused by the accumulation of lipid-based ROS. Metabolism and expression of specific genes affect the occurrence of ferroptosis, making it a promising therapeutic target to manage cancer. Here, we describe the current status of ferroptosis studies in breast cancer and trace the key regulators of ferroptosis back to previous studies. We also compare ferroptosis to common regulated cell death patterns and discuss the sensitivity to ferroptosis in different subtypes of breast cancer. We propose that viewing ferroptosis-related studies from a historical angle will accelerate the development of ferroptosis-based biomarkers and therapeutic strategies in breast cancer.

Galangin attenuated cerebral ischemia-reperfusion injury by inhibition of ferroptosis through activating the SLC7A11/GPX4 axis in gerbils

AIMS

To evaluate the impact of galangin treatment on cerebral ischemia-reperfusion (I/R) injury in gerbils and to identify potential mechanisms of the protective effect of galangin on hippocampal neurons after I/R injury.

PRINCIPAL METHODS

A cerebral ischemia model using bilateral common carotid artery ligation in gerbils was established. The Morris water maze (MWM) test was used to evaluate the learning and memory ability of gerbils. The cell viability was evaluated with an MTT assay. The levels of lipid peroxide biomarkers were measured to estimate the injury due to lipid peroxide. The morphology was detected by electron micrography, immunofluorescence and Nissl staining. Western blot and quantitative real-time polymerase chain reaction (qRT-PCR) were used to measure the molecular characteristics.

KEY FINDINGS

In the MWM, gerbils treated with galangin after I/R injury showed significant improvements in learning and memory. In addition, galangin treatment reduced the levels of lipid peroxide in the brains of gerbils that underwent I/R as well as reduced the amount of cell death and increased the expression of SLC7A11 and glutathione peroxidase 4 (GPX4). Furthermore, the expression of the marker of ferroptosis was decreased in galangin-treated gerbils, and the effect of galangin was weakened when SLC7A11 was knocked down. These results show that galangin can inhibit ferroptosis by enhancing the expressions of SLC7A11 and GPX4 as well as reduce neuronal cell death.

SIGNIFICANCE

Galangin inhibits ferroptosis through activation of the SLC7A11/GPX4 axis and has a protective effect on hippocampal neurons in gerbils after I/R.

Metabolism of Sulfur-Containing Amino Acids: How the Body Copes with Excess Methionine, Cysteine, and Sulfide

Metabolism of excess methionine (Met) to homocysteine (Hcy) by transmethylation is facilitated by the expression of methionine adenosyltransferase (MAT) I/III and glycine N-methyltransferase (GNMT) in liver, and a lack of either enzyme results in hypermethioninemia despite normal concentrations of MATII and methyltransferases other than GNMT. The further metabolism of Hcy by the transsulfuration pathway is facilitated by activation of cystathionine β-synthase (CBS) by S-adenosylmethionine (SAM) as well as the relatively high KM of CBS for Hcy. Transmethylation plus transsulfuration effects catabolism of the Met molecule along with transfer of the sulfur atom of Met to serine to synthesize cysteine (Cys). Oxidation and excretion of Met sulfur depend upon Cys catabolism and sulfur oxidation pathways. Excess Cys is oxidized by cysteine dioxygenase 1 (CDO1) and further metabolized to taurine or sulfate. Some Cys is normally metabolized by desulfhydration pathways, and the hydrogen sulfide (H2S) produced is further oxidized to sulfate. If Cys or Hcy concentrations are elevated, Cys or Hcy desulfhydration can result in excess H2S and thiosulfate production. Excess Cys or Met may also promote their limited metabolism by transamination pathways.

Ferroptosis: An emerging approach for targeting cancer stem cells and drug resistance

Resistance to chemotherapeutic agents remains a major challenge in the fierce battle against cancer. Cancer stem cells (CSCs) are a small population of cells in tumors that possesses the ability to self-renew, initiate tumors, and cause resistance to conventional anticancer agents. Targeting this population of cells was proven as a promising approach to eliminate cancer recurrence and improve the clinical outcome. CSCs are less susceptible to death by classical anticancer agents inducing apoptosis. CSCs can be eradicated by ferroptosis, which is a non-apoptotic-regulated mechanism of cell death. The induction of ferroptosis is an attractive strategy to eliminate tumors due to its ability to selectively target aggressive CSCs. The current review critically explored the crosstalk and regulatory pathways controlling ferroptosis, which can selectively induce CSCs death. In addition, successful chemotherapeutic agents that achieve better therapeutic outcomes through the induction of ferroptosis in CSCs were discussed to highlight their promising clinical impact.

Computational repositioning of dimethyl fumarate for treating alcoholic liver disease

Alcoholic liver disease (ALD) is a chronic alcohol-induced disorder of the liver for which there are few effective therapies for severe forms of ALD and for those who do not achieve alcohol abstinence. In this study, we used a systematic drug-repositioning bioinformatics approach querying a large compendium of gene-expression profiles to identify candidate U.S. Food and Drug Administration (FDA)–approved drugs to treat ALD. One of the top compounds predicted to be therapeutic for ALD by our approach was dimethyl fumarate (DMF), an nuclear factor erythroid 2-related factor 2 (NRF2) inducer. We experimentally validated DMF in liver cells and in vivo. Our work demonstrates that DMF is able to significantly upregulate the NRF2 protein level, increase NRF2 phosphorylation, and promote NRF2 nuclear localization in liver cells. DMF also reduced the reactive oxygen species (ROS) level, lipid peroxidation, and ferroptosis. Furthermore, DMF treatment could prevent ethanol-induced liver injury in ALD mice. Our results provide evidence that DMF might serve as a therapeutic option for ALD in humans, and support the use of computational repositioning to discover therapeutic options for ALD.

Real-Time Imaging Redox Status in Biothiols and Ferric Metabolism of Cancer Cells in Ferroptosis Based on Switched Fluorescence Response of Gold Carbon Dots

Ferroptosis is an iron-dependent form of regulated cell death. In this study, a ratiometric fluorescent probe, gold carbon dots (GCDs) consisting of carbon skeleton and gold nanoclusters, was used for in situ imaging to monitor redox status in biothiols (glutathione and cysteine) and ferric metabolism of cancer cells in ferroptosis. The as-prepared GCDs can selectively respond to biothiols, interestingly, the fluorescence may be switched to sense ferric ions without interference by biothiols under proper conditions. The robust GCDs-probe exhibits excellent photobleaching resistance and can reversibly respond to intracellular biothiols/ferric ion with high temporal resolution. The 8 h real-time imaging of living cells was employed to track the fluctuation of biothiols, showing the change of redox status in ferroptosis. In addition, release of ferric ions in cells was monitored. The real-time imaging of depletion of biothiols and release of ferric ion in cells indicates the GCDs-probe can monitor how the ferroptosis regulates redox status in biothiols and ferric metabolism.

Insight Into the Role of Ferroptosis in Non-neoplastic Neurological Diseases

Ferroptosis is an iron-dependent form of cell death characterized by the accumulation of intracellular lipid reactive oxygen species (ROS). Ferroptosis is significantly different from other types of cell death including apoptosis, autophagy, and necrosis, both in morphology and biochemical characteristics. The mechanisms that are associated with ferroptosis include iron metabolism, lipid oxidation, and other pathophysiological changes. Ferroptosis inducers or inhibitors can influence its occurrence through different pathways. Ferroptosis was initially discovered in tumors, though recent studies have confirmed that it is also closely related to a variety of neurological diseases including neurodegenerative disease [Alzheimer’s disease (AD), Parkinson’s disease (PD), etc.] and stroke. This article reviews the definition and characteristics of ferroptosis, the potential mechanisms associated with its development, inducers/inhibitors, and its role in non-neoplastic neurological diseases. We hope to provide a theoretical basis and novel treatment strategies for the treatment of central nervous system diseases by targeting ferroptosis.

The Mechanism of Ferroptosis and Applications in Tumor Treatment

Iron-dependent ferroptosis is a new form of cell death in recent years, which is driven by lipid peroxidation. The lethal lipid accumulation caused by glutathione depletion or inactivation of glutathione peroxidase 4 (GPX4) is characteristic of the ferroptosis process. In recent years, with the in-depth study of ferroptosis, various types of diseases have been reported to be related to ferroptosis. In other words, ferroptosis, which has attracted widespread attention in the fields of biochemistry, oncology, and especially materials science, can undoubtedly provide a new way for patients. This review introduces the relevant mechanisms of ferroptosis, the relationship between ferroptosis and various cancers, as well as the application of ferroptosis in tumor treatment. We also sorted out the genes and drugs that regulate ferroptosis. Moreover, small molecule compound-induced ferroptosis has a strong inhibitory effect on tumor growth in a drug-resistant environment, which can enhance the sensitivity of chemotherapeutic drugs, suggesting that ferroptosis is very important in the treatment of tumor drug resistance, but the details are still unclear. How to use ferroptosis to fight cancer, and how to prevent drug-resistant tumor cells have become the focus and direction of research. At the end of the article, some existing problems related to ferroptosis are summarized for future research.

The Relationship between Ferroptosis and Tumors: A Novel Landscape for Therapeutic Approach

BACKGROUND

Ferroptosis is a newly discovered form of iron-dependent oxidative cell death characterized by lethal accumulation of lipid-based reactive oxygen species (ROS). It is distinct from other forms of cell death including apoptosis, necrosis, and autophagy in terms of morphology, biochemistry and genetics.

DISCUSSION

Ferroptosis can be induced by system xc- inhibitors or glutathione peroxidase 4 (GPx4) inhibitors, as well as drugs such as sorafenib, sulfasalazine (SAS), and artesunate (ART). Ferroptosis has been recently shown to be critical in regulating growth of tumors, such as hepatocellular carcinoma (HCC), renal cell carcinoma (RCC), non-small cell lung cancer (NSCLC), ovarian cancer, pancreatic carcinoma, and diffuse large B cell lymphoma (DLBCL). Ferroptosis is also associated with resistance to chemotherapeutic drugs and the anti-tumor efficacy of immunotherapy.

CONCLUSION

This review summarizes the mechanism of ferroptosis and its relationship with different types of tumors, to advance our understanding of cell death and to find a novel approach for clinical cancer management.

Targeting apoptosis in cancer therapy

For over three decades, a mainstay and goal of clinical oncology has been the development of therapies promoting the effective elimination of cancer cells by apoptosis. This programmed cell death process is mediated by several signalling pathways (referred to as intrinsic and extrinsic) triggered by multiple factors, including cellular stress, DNA damage and immune surveillance. The interaction of apoptosis pathways with other signalling mechanisms can also affect cell death. The clinical translation of effective pro-apoptotic agents involves drug discovery studies (addressing the bioavailability, stability, tumour penetration, toxicity profile in non-malignant tissues, drug interactions and off-target effects) as well as an understanding of tumour biology (including heterogeneity and evolution of resistant clones). While tumour cell death can result in response to therapy, the selection, growth and dissemination of resistant cells can ultimately be fatal. In this Review, we present the main apoptosis pathways and other signalling pathways that interact with them, and discuss actionable molecular targets, therapeutic agents in clinical translation and known mechanisms of resistance to these agents.

Actinidia chinensis Planch prevents proliferation and migration of gastric cancer associated with apoptosis, ferroptosis activation and mesenchymal phenotype suppression

Actinidia chinensis Planch (ACP) was the kiwifruit plant Chinese kiwifruit Actinidia chinensis Planch Root, which had been approved to be an anti-tumor drug widespread in clinical. However, the specific mechanism of ACP in resistance to gastric cancer remained unclear. Therefore, our study was dedicated to investigate the anti-proliferation and anti-migration effects of ACP on gastric cancer cells and its molecular mechanisms. Firstly, we utilized HPLC-MS to analyze the composition of ACP decoction, the results showed that ACP contained two main anti-tumor components, Ursolic acid and Oleanolic acid. The proliferation and migration ability of HGC-27 were examined by CCK-8 and cell scratch tests respectively. In addition, we also investigated HGC-27 cells apoptosis, mesenchymal phenotype and ferroptosis after ACP rat drug-containing serum (ACPs) treatment. EGFP-expressing lentiviral vectors were utilized to construct HGC-27 cells which containing green fluorescence. Then we take advantages of containing green fluorescence cells to establish a zebrafish xenograft model in vivo. The CCK-8 and cell scratch experiments verified that ACPs significantly inhibited proliferation and migration of HGC-27 in vitro. ACPs increased cells apoptosis rate, while were rescued by apoptosis inhibitor Z-VAD-FMK. Furthermore, ACPs downregulated the expression levels of Vimentin protein and Snail protein markedly. Intriguingly, ACPs increased the accumulation of ROS via inhibited the glutathione peroxidase 4 (GPx4) and xCT (SLC7A11) proteins, while were inhibited by Ferrostatin-1 (Fer-1) significantly. Furthermore, the zebrafish xenograft study further confirmed that administration of ACP suppressed the xenograft growth and metastasis of transplanted HGC-27 cells in vivo. In conclusion, ACP was a promising antineoplastic agent for the treatment of gastric cancer by regulating apoptosis, ferroptosis and mesenchymal phenotype.

CAF secreted miR-522 suppresses ferroptosis and promotes acquired chemo-resistance in gastric cancer

BACKGROUND

Ferroptosis is a novel mode of non-apoptotic cell death induced by build-up of toxic lipid peroxides (lipid-ROS) in an iron dependent manner. Cancer-associated fibroblasts (CAFs) support tumor progression and drug resistance by secreting various bioactive substances, including exosomes. Yet, the role of CAFs in regulating lipid metabolism as well as ferroptosis of cancer cells is still unexplored and remains enigmatic.

METHODS

Ferroptosis-related genes in gastric cancer (GC) were screened by using mass spectrum; exosomes were isolated by ultra-centrifugation and CAF secreted miRNAs were determined by RT-qPCR. Erastin was used to induce ferroptosis, and ferroptosis levels were evaluated by measuring lipid-ROS, cell viability and mitochondrial membrane potential.

RESULTS

Here, we provide clinical evidence to show that arachidonate lipoxygenase 15 (ALOX15) is closely related with lipid-ROS production in gastric cancer, and that exosome-miR-522 serves as a potential inhibitor of ALOX15. By using primary stromal cells and cancer cells, we prove that exosome-miR-522 is mainly derived from CAFs in tumor microenvironment. Moreover, heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was found to mediate miR-522 packing into exosomes, and ubiquitin-specific protease 7 (USP7) stabilizes hnRNPA1 through de-ubiquitination. Importantly, cisplatin and paclitaxel promote miR-522 secretion from CAFs by activating USP7/hnRNPA1 axis, leading to ALOX15 suppression and decreased lipid-ROS accumulation in cancer cells, and ultimately result in decreased chemo-sensitivity.

CONCLUSIONS

The present study demonstrates that CAFs secrete exosomal miR-522 to inhibit ferroptosis in cancer cells by targeting ALOX15 and blocking lipid-ROS accumulation. The intercellular pathway, comprising USP7, hnRNPA1, exo-miR-522 and ALOX15, reveals new mechanism of acquired chemo-resistance in GC.

Ferroptosis: past, present and future

Ferroptosis is a new type of cell death that was discovered in recent years and is usually accompanied by a large amount of iron accumulation and lipid peroxidation during the cell death process; the occurrence of ferroptosis is iron-dependent. Ferroptosis-inducing factors can directly or indirectly affect glutathione peroxidase through different pathways, resulting in a decrease in antioxidant capacity and accumulation of lipid reactive oxygen species (ROS) in cells, ultimately leading to oxidative cell death. Recent studies have shown that ferroptosis is closely related to the pathophysiological processes of many diseases, such as tumors, nervous system diseases, ischemia-reperfusion injury, kidney injury, and blood diseases. How to intervene in the occurrence and development of related diseases by regulating cell ferroptosis has become a hotspot and focus of etiological research and treatment, but the functional changes and specific molecular mechanisms of ferroptosis still need to be further explored. This paper systematically summarizes the latest progress in ferroptosis research, with a focus on providing references for further understanding of its pathogenesis and for proposing new targets for the treatment of related diseases.

Ferroptosis in Carcinoma: Regulatory Mechanisms and New Method for Cancer Therapy

Ferroptosis is a new form of programmed cell death with characteristic accumulation of reactive oxygen species (ROS) resulting from iron accumulation and lipid peroxidation. Ferroptosis is involved in many diseases, including cancer, and induction of ferroptosis has shown attractive antitumour activities. In this review, we summarize recent findings on the regulatory mechanisms of key regulators of ferroptosis, including the catalytic subunit solute carrier family 7 member 11 (SLC7A11), the glutathione peroxidase 4 (GPX4), p53 and non-coding RNAs, the correlations between ferroptosis and iron homeostasis or autophagy, ferroptosis-inducing agents and nanomaterials and the diagnostic and prognostic value of ferroptosis-associated genes in TCGA data.

Epigenetic regulation of AURKA by miR-4715-3p in upper gastrointestinal cancers

Aurora kinase A (AURKA) is frequently overexpressed in several cancers. miRNA sequencing and bioinformatics analysis indicated significant downregulation of miR-4715-3p. We found that miR-4715-3p has putative binding sites on the 3UTR region of AURKA. Upper gastrointestinal adenocarcinoma (UGC) tissue samples and cell models demonstrated significant overexpression of AURKA with downregulation of miR-4715-3p. Luciferase reporter assays confirmed binding of miR-4715-3p on the 3UTR region of AURKA. miR-4715-3p mediated a reduction in AURKA levels leading to G2/M delay, chromosomal polyploidy, and cell death. We also detected a remarkable decrease in GPX4, an inhibitor of ferroptosis, with an increase in cleaved PARP and caspase-3. Inhibition of AURKA using siRNA produced similar results, suggesting a possible link between AURKA and GPX4. Analysis of UGC samples and cell models demonstrated increased methylation levels of several CpG nucleotides upstream of miR-4715-3p. 5-Aza-2'-deoxycytidine induced demethylation of several CpG nucleotides, restoring miR-4715-3p expression, leading to downregulation of AURKA. In conclusion, our data identified a novel epigenetic mechanism mediating silencing of miR-4715-3p and induction of AURKA in UGCs. Inhibition of AURKA or reconstitution of miR-4715-3p inhibited GPX4 and induced cell death, suggesting a link between AURKA and ferroptosis.

Targeted exosome-encapsulated erastin induced ferroptosis in triple negative breast cancer cells

Ferroptosis is an iron‐dependent, lipid peroxide‐driven cell death caused by inhibition of the cystine/glutamate transporter, which is of importance for the survival of triple‐negative breast cancer (TNBC) cells. Erastin is a low molecular weight chemotherapy drug that induces ferroptosis; however, poor water solubility and renal toxicity have limited its application. Exosomes, as drug delivery vehicles with low immunogenicity, high biocompatibility and high efficiency, have attracted increasing attention in recent years. Herein, we developed a formulation of erastin‐loaded exosomes labeled with folate (FA) to form FA‐vectorized exosomes loaded with erastin (erastin@FA‐exo) to target TNBC cells with overexpression of FA receptors. The characterization, drug release, internalization and anti–tumor effect in vitro of erastin@FA‐exo were determined. Erastin@FA‐exo could increase the uptake efficiency of erastin into MDA‐MB‐231 cells; compared with erastin@exo and free erastin, erastin@FA‐exo has a better inhibitory effect on the proliferation and migration of MDA‐MB‐231 cells. Furthermore, erastin@FA‐exo promoted ferroptosis with intracellular depletion of glutathione and reactive oxygen species overgeneration. Western blot analyses revealed that erastin@FA‐exo suppressed expression of glutathione peroxidase 4 (GPX4) and upregulated expression of cysteine dioxygenase (CDO1). We conclude that targeting and biocompatibility of exosome‐based erastin preparations provide an innovative and powerful delivery platform for anti–cancer therapy.

The role of ferroptosis in digestive system cancer

Ferroptosis is a type of regulated cell death dependent on iron and reactive oxygen species. Ferroptosis is distinct from other cell death modalities, including apoptosis, autophagy and necrosis. Dysregulated ferroptosis has been implicated in a number of diseases, including neuropathy, ischemia reperfusion injury, acute kidney failure and cancer. The digestive system consists of several organs. The morbidity and mortality rates of digestive system cancer are high. The current review summarizes the role of ferroptosis in digestive system cancer. A large number of molecules, including tumor protein p53, retinoblastoma protein, nuclear factor E2-related factor 2, KH RNA binding domain containing signal transduction associated 1, cysteine dioxygenase type 1, metallothionein-1G, nuclear receptor coactivator 4, CDGSH iron sulfur domain 1, heat shock protein family A (Hsp70) member 5 and acyl-CoA synthetase long chain family member 4, regulate ferroptosis in digestive system cancer. Drugs such as cisplatin, baicalein, haloperidol, artesunate, piperlongumine, saponin and bromelain may cause cancer cell death by inducing ferroptosis. An improved understanding of ferroptosis in digestive system cancer may give rise to novel diagnostic and making therapeutic strategies.

Ferroptosis at the crossroads of cancer-acquired drug resistance and immune evasion

Ferroptosis is a recently recognized cell death modality that is morphologically, biochemically and genetically distinct from other forms of cell death and that has emerged to play an important role in cancer biology. Recent discoveries have highlighted the metabolic plasticity of cancer cells and have provided intriguing insights into how metabolic rewiring is a critical event for the persistence, dedifferentiation and expansion of cancer cells. In some cases, this metabolic reprogramming has been linked to an acquired sensitivity to ferroptosis, thus opening up new opportunities to treat therapy-insensitive tumours. However, it is not yet clear what metabolic determinants are critical for therapeutic resistance and evasion of immune surveillance. Therefore, a better understanding of the processes that regulate ferroptosis sensitivity should ultimately aid in the discovery of novel therapeutic strategies to improve cancer treatment. In this Perspectives article, we provide an overview of the known mechanisms that regulate sensitivity to ferroptosis in cancer cells and how the modulation of metabolic pathways controlling ferroptosis might reshape the tumour niche, leading to an immunosuppressive microenvironment that promotes tumour growth and progression.

Cystine-glutamate antiporter xCT deficiency suppresses tumor growth while preserving antitumor immunity

xCT, the cystine–glutamate antiporter, has been implicated in supporting both tumor growth and T cell proliferation; thus, antitumor effects of systemic xCT inhibition may be blunted by compromised antitumor immunity. This report details the unexpected finding that xCT is dispensable for T cell proliferation in vivo and for antitumor immune responses. Consequently, tumor cell xCT loss acts synergistically with the immunotherapeutic agent anti–CTLA-4, laying the foundation for utilizing specific xCT inhibitors clinically to expand the efficacy of existing anticancer immunotherapeutics.

T cell-invigorating cancer immunotherapies have near-curative potential. However, their clinical benefit is currently limited, as only a fraction of patients respond, suggesting that these regimens may benefit from combination with tumor-targeting treatments. As oncogenic progression is accompanied by alterations in metabolic pathways, tumors often become heavily reliant on antioxidant machinery and may be susceptible to increases in oxidative stress. The cystine–glutamate antiporter xCT is frequently overexpressed in cancer and fuels the production of the antioxidant glutathione; thus, tumors prone to redox stress may be selectively vulnerable to xCT disruption. However, systemic inhibition of xCT may compromise antitumor immunity, as xCT is implicated in supporting antigen-induced T cell proliferation. Therefore, we utilized immune-competent murine tumor models to investigate whether cancer cell expression of xCT was required for tumor growth in vivo and if deletion of host xCT impacted antitumor immune responses. Deletion of xCT in tumor cells led to defective cystine uptake, accumulation of reactive oxygen species, and impaired tumor growth, supporting a cancer cell-autonomous role for xCT. In contrast, we observed that, although T cell proliferation in culture was exquisitely dependent on xCT expression, xCT was dispensable for T cell proliferation in vivo and for the generation of primary and memory immune responses to tumors. These findings prompted the combination of tumor cell xCT deletion with the immunotherapeutic agent anti–CTLA-4, which dramatically increased the frequency and durability of antitumor responses. Together, these results identify a metabolic vulnerability specific to tumors and demonstrate that xCT disruption can expand the efficacy of anticancer immunotherapies.

Ferroptosis, a new form of cell death: opportunities and challenges in cancer

Ferroptosis is a novel type of cell death with distinct properties and recognizing functions involved in physical conditions or various diseases including cancers. The fast-growing studies of ferroptosis in cancer have boosted a perspective for its usage in cancer therapeutics. Here, we review the current findings of ferroptosis regulation and especially focus on the function of ncRNAs in mediating the process of cell ferroptotic death and on how ferroptosis was in relation to other regulated cell deaths. Aberrant ferroptosis in diverse cancer types and tissues were summarized, and we elaborated recent data about the novel actors of some “conventional” drugs or natural compounds as ferroptosis inducers in cancer. Finally, we deliberate future orientation for ferroptosis in cancer cells and current unsettled issues, which may forward the speed of clinical use of ferroptosis induction in cancer treatment.

MSC-regulated lncRNA MACC1-AS1 promotes stemness and chemoresistance through fatty acid oxidation in gastric cancer

Chemotherapy is the preferred treatment for advanced stage gastric cancer (GC) patients and chemotherapy resistance is the major obstacle to effective cancer therapy. Increasing evidence suggests that mesenchymal stem cells (MSCs) make important contributions to development of drug resistance. However, the underlying mechanism remains elusive. In this study, we discovered that abundant MSCs in tumor tissues predicted a poor prognosis in GC patients. MSCs promoted stemness and chemoresistance in GC cells through fatty acid oxidation (FAO) in vitro and in vivo. Mechanically, transforming growth factor β1 (TGF-β1) secretion by MSCs activated SMAD2/3 through TGF-β receptors and induced long non-coding RNA (lncRNA) MACC1-AS1 expression in GC cells, which promoted FAO-dependent stemness and chemoresistance through antagonizing miR-145-5p. Moreover, pharmacologic inhibition of FAO with etomoxir (ETX) attenuated MSC-induced FOLFOX regiment resistance in vivo. These results suggest that FAO plays an important role in MSC-mediated stemness and chemotherapy resistance in GC and FAO inhibitors in combination with chemotherapeutic drugs present as a promising strategy to overcome chemoresistance.

Role of ferroptosis in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is a complicated disease with low survival rate due to frequent recurrence and the lack of efficient therapies. For advanced HCC, sorafenib, as the only approved first-line drug for HCC, improves the survival to some extent, but depressingly with severe adverse effects and emerging resistance conditions, which cause a poor prognosis. Ferroptosis is a new recognized way of non-apoptosis-regulated cell death, characterized by the iron-dependent accumulation of lipid hydroperoxides, showing a tremendous promising in the therapy of cancer, especially in HCC. To provide ideas for the diagnosis and treatment of HCC, we summarized the role of ferroptosis in HCC.

METHODS

The relevant literature from PubMed is reviewed in this article.

RESULTS

Interestingly enough, investigators have found sorafenib can induce ferroptosis in HCC. Moreover, recent researches reported increasing pathways and mechanisms related to ferroptosis in HCC such as TP53 and Rb, and strategies to improve sorafenib resistance by targeting ferroptosis. In addition, other drugs were reported to induce ferroptosis in HCC such as erastin and showed good efficacy in vivo and in vitro.

CONCLUSION

In this review, we summarize pathways and mechanisms of ferroptosis in HCC and other digestive system neoplasms such as gastric cancer, pancreatic cancer and colorectal cancer and point out the trends of ferroptosis in HCC.

Activation of ferritinophagy is required for the RNA-binding protein ELAVL1/HuR to regulate ferroptosis in hepatic stellate cells

Ferroptosis is a recently recognized form of regulated cell death that is characterized by lipid peroxidation. However, the molecular mechanisms regulating ferroptosis are largely unknown. In this study, we report that the RNA-binding protein ELAVL1/HuR plays a crucial role in regulating ferroptosis in liver fibrosis. Upon exposure to ferroptosis-inducing compounds, ELAVL1 protein expression was remarkably increased through the inhibition of the ubiquitin-proteasome pathway. ELAVL1 siRNA led to ferroptosis resistance, whereas ELAVL1 plasmid contributed to classical ferroptotic events. Interestingly, upregulated ELAVL1 expression also appeared to increase autophagosome generation and macroautophagic/autophagic flux, which was the underlying mechanism for ELAVL1-enhanced ferroptosis. Autophagy depletion completely impaired ELAVL1-mediated ferroptotic events, whereas autophagy induction showed a synergistic effect with ELAVL1. Importantly, ELAVL1 promoted autophagy activation via binding to the AU-rich elements within the F3 of the 3'-untranslated region of BECN1/Beclin1 mRNA. The internal deletion of the F3 region abrogated the ELAVL1-mediated BECN1 mRNA stability, and, in turn, prevented ELAVL1-enhanced ferroptosis. In mice, treatment with sorafenib alleviated murine liver fibrosis by inducing hepatic stellate cell (HSC) ferroptosis. HSC-specific knockdown of ELAVL1 impaired sorafenib-induced HSC ferroptosis in murine liver fibrosis. Noteworthy, we retrospectively analyzed the effect of sorafenib on HSC ferroptosis in advanced fibrotic patients with hepatocellular carcinoma receiving sorafenib monotherapy. Attractively, ELAVL1 upregulation, ferritinophagy activation, and ferroptosis induction occurred in primary human HSCs from the collected human liver tissue. Overall, these results reveal novel molecular mechanisms and signaling pathways of ferroptosis, and also identify ELAVL1-autophagy-dependent ferroptosis as a potential target for the treatment of liver fibrosis. Abbreviations: ACTA2/alpha-SMA: actin, alpha 2, smooth muscle, aorta; ACTB/beta-actin: actin beta; ARE: AU-rich element; ATG: autophagy related; BDL: bile duct ligation; BECN1: beclin 1; BSO: buthionine sulfoximine; COL1A1: collagen type I alpha 1 chain; ELAVL1/HuR: ELAV like RNA binding protein 1; FDA: fluorescein diacetate; FTH1: ferritin heavy chain 1; GOT1/AST: glutamic-oxaloacetic transaminase 1; GPT/ALT: glutamic-pyruvic transaminase; GPX4: glutathione peroxidase 4; GSH: glutathione; HCC: hepatocellular carcinoma; HSC: hepatic stellate cell; LCM: laser capture microdissection; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MDA: malondialdehydep; NCOA4: nuclear receptor coactivator 4; PTGS2: prostaglandin-endoperoxide synthase 2; ROS: reactive oxygen species; SQSTM1/p62: sequestosome 1; TBIL: total bilirubin; TEM: transmission electron microscopy; TGFB1: trasforming growth factor beta 1; UTR: untranslated region; VA-Lip-ELAVL1-siRNA: vitamin A-coupled liposomes carrying ELAVL1-siRNA.

Ferritinophagy/ferroptosis: Iron-related newcomers in human diseases

Nuclear receptor coactivator 4 mediated ferritinophagy is an autophagic phenomenon that specifically involves ferritin to release intracellular free iron. Ferritinophagy is implicated in maintaining efficient erythropoiesis. Notably, ferritinophagy also plays a central role in driving some pathological processes, including Parkinson's disease (PD) and urinary tract infections. Some evidence has demonstrated that ferritinophagy is critical to induce ferroptosis. Ferroptosis is a newly nonapoptotic form of cell death, characterized by the accumulation of iron-based lipid reactive oxygen species. Ferroptosis plays an important role in inhibiting some types of cancers, such as hepatocellular carcinoma, pancreatic carcinoma, prostate cancer, and breast cancer. Conversely, the activation of ferroptosis accelerates neurodegeneration diseases, including PD and Alzheimer's disease. Therefore, in this review, we summarize the regulatory mechanisms related to ferritinophagy and ferroptosis. Moreover, the distinctive effects of ferritinophagy in human erythropoiesis and some pathologies, coupled with the promotive or inhibitory role of tumorous and neurodegenerative diseases mediated by ferroptosis, are elucidated. Obviously, activating or inhibiting ferroptosis could be exploited to achieve desirable therapeutic effects on diverse cancers and neurodegeneration diseases. Interrupting ferritinophagy to control iron level might provide a potentially therapeutic avenue to suppress urinary tract infections.