Autophagy-Dependent Ferroptosis in Cancer

Macropinocytosis inhibits alkaliptosis in pancreatic cancer cells through fatty acid uptake

Alkaliptosis, a form of regulated cell death, is characterized by lysosomal dysfunction and intracellular pH alkalinization. The pharmacological induction of alkaliptosis using the small molecule compound JTC801 has emerged as a promising anticancer strategy in various types of cancers, particularly pancreatic ductal adenocarcinoma (PDAC). In this study, we investigate a novel mechanism by which macropinocytosis, an endocytic process involving the uptake of extracellular material, promotes resistance to alkaliptosis in human PDAC cells. Through lipid metabolomics analysis and functional studies, we demonstrate that the inhibition of alkaliptosis by fatty acids, such as oleic acid, is not dependent on endogenous synthetic pathways but rather on exogenous uptake facilitated by macropinocytosis. Consequently, targeting macropinocytosis through pharmacological approaches (e.g. using EIPA or EHoP-016) or genetic interventions (e.g. RAC1 knockdown) effectively enhances JTC801-induced alkaliptosis in human PDAC cells. These findings provide compelling evidence that the modulation of macropinocytosis can increase the sensitivity of cancer cells to alkaliptosis inducers.

Ferroptosis, a therapeutic target for cardiovascular diseases, neurodegenerative diseases and cancer

The identification of ferroptosis represents a pivotal advancement in the field of cell death research, revealing an entirely novel mechanism of cellular demise and offering new insights into the initiation, progression, and therapeutic management of various diseases. Ferroptosis is predominantly induced by intracellular iron accumulation, lipid peroxidation, or impairments in the antioxidant defense system, culminating in membrane rupture and consequent cell death. Studies have associated ferroptosis with a wide range of diseases, and by enhancing our comprehension of its underlying mechanisms, we can formulate innovative therapeutic strategies, thereby providing renewed hope for patients.

Nrf2 inhibition and NCOA4-mediated ferritinophagy activation synergistically exacerbated S-3'-hydroxy-7', 2', 4'-trimethoxyisoxane induced ferroptosis in lung cancer cells

S-3'-hydroxy-7', 2', 4'-trimethoxyisoxane (ShtIX) is a novel isoflavane compound that exhibits significant anticancer activity against a variety of cancer cells. Our previous studies have confirmed that ShtIX induced ferroptosis by inhibiting Nr2/HO-1 pathway in non-small cell lung cancer (NSCLC) cells, both in vitro and vivo. Recent research has increasingly recognized ferroptosis as an autophagy-dependent form of cell death. However, it has not been previously explored whether ShtIX can activate autophagy during ferroptosis and its relationship with ferroptosis. In the present study, we discovered that ShtIX was able to trigger autophagy, and the activation of autophagy is essential for ShtIX-induced ferroptosis. These findings demonstrated that ShtIX induced an autophagy-dependent form of ferroptosis in NSCLC cells. Intriguingly, the autophagy triggered by ShtIX is independent of ferroptosis. Furthermore, our results indicated that ShtIX degraded ferritin through autophagy and promoted NCOA4-mediated ferritinophagy, which contributed significantly to ShtIX-induced ferroptosis in NSCLC cells. Additionally, the knockdown Nrf2 reinforced ShtIX-induced NCOA4-mediated ferritinophagy, while the inhibition of autophagy attenuated the suppressive effect of ShtIX on Nrf2 and HO-1. Taken together, our work uncovers a new mechanism by which ShtIX induced ferroptosis through inhibition the Nrf2 pathway and activation of NCOA4-mediated ferritinophagy in NSCLC cells. Targeting ferritinophagy to regulate ferroptosis offers a novel therapeutic strategy for the treatment of lung cancer with ShtIX.

Ferroptosis contributes to the progression of female-specific neoplasms, from breast cancer to gynecological malignancies in a manner regulated by non-coding RNAs: Mechanistic implications

Ferroptosis, a recently identified type of non-apoptotic cell death, triggers the elimination of cells in the presence of lipid peroxidation and in an iron-dependent manner. Indeed, ferroptosis-stimulating factors have the ability of suppressing antioxidant capacity, leading to the accumulation of reactive oxygen species (ROS) and the subsequent oxidative death of the cells. Ferroptosis is involved in the pathophysiological basis of different maladies, such as multiple cancers, among which female-oriented malignancies have attracted much attention in recent years. In this context, it has also been unveiled that non-coding RNA transcripts, including microRNAs, long non-coding RNAs, and circular RNAs have regulatory interconnections with the ferroptotic flux, which controls the pathogenic development of diseases. Furthermore, the potential of employing these RNA transcripts as therapeutic targets during the onset of female-specific neoplasms to modulate ferroptosis has become a research hotspot; however, the molecular mechanisms and functional alterations of ferroptosis still require further investigation. The current review comprehensively highlights ferroptosis and its association with non-coding RNAs with a focus on how this crosstalk affects the pathogenesis of female-oriented malignancies, from breast cancer to ovarian, cervical, and endometrial neoplasms, suggesting novel therapeutic targets to decelerate and even block the expansion and development of these tumors.

Cytoglobin augments ferroptosis through autophagic degradation of ferritin in colorectal cancer cells

Autophagy has gained importance in the context of ferroptosis. Nevertheless, a deeper understanding of the regulatory mechanism governing autophagy-dependent ferroptosis is necessary. Cytoglobin (CYGB), a member of the globin family, exhibits antifibrotic effects, regulates cellular reactive oxygen species, and stimulates tumor inhibition. Herein, we present further insights into the role of CYGB in ferroptosis regulation. Our investigation confirmed that CYGB impedes cell proliferation and migration. Furthermore, a significant association between CYGB and the lysosomal pathway was suggested based on the RNA sequencing data analysis. Elevated lysosomal signal and colocalization of CYGB with lysosome-associated membrane glycoprotein 1 (LAMP1) were observed. Moreover, upregulated autophagy and augmented ferroptosis induced by RSL3 were confirmed in CYGB-overexpression cells with an obviously increased colocalization of nuclear receptor coactivator 4 (NCOA4) and LC3B. The autophagy inhibitor bafilomycin or chloroquine alleviated autophagy-dependent degradation of ferritin protein under RSL3 treated condition. Additionally, a colocalization of CYGB with the transferrin receptor (TFR) was confirmed. Our results demonstrate an important functional pathway by which CYGB regulates ferroptosis through TFR-binding and autophagic degradation of ferritin, and provide a potential pathway for the treatment of colorectal cancer.

Macroautophagy/autophagy promotes resistance to KRASG12D-targeted therapy through glutathione synthesis

KRASG12D mutation-driven pancreatic ductal adenocarcinoma (PDAC) represents a major challenge in medicine due to late diagnosis and treatment resistance. Here, we report that macroautophagy (hereafter autophagy), a cellular degradation and recycling process, contributes to acquired resistance against novel KRASG12D-targeted therapy. The KRASG12D protein inhibitor MRTX1133 induces autophagy in KRASG12D-mutated PDAC cells by blocking MTOR activity, and increased autophagic flux prevents apoptosis. Mechanistically, autophagy facilitates the generation of glutamic acid, cysteine, and glycine for glutathione synthesis. Increased glutathione levels reduce reactive oxygen species production, which impedes CYCS translocation from mitochondria to the cytosol, ultimately preventing the formation of the APAF1 apoptosome. Consequently, genetic interventions (utilizing ATG5 or BECN1 knockout) or pharmacological inhibition of autophagy (with chloroquine, bafilomycin A1, or spautin-1) enhance the anticancer activity of MRTX1133 in vitro and in various animal models (subcutaneous, patient-derived xenograft, and orthotopic). Moreover, the release of histones by apoptotic cells triggers an adaptive immune response when combining an autophagy inhibitor with MRTX1133 in immunocompetent mice. These findings establish a new strategy to overcome KRASG12D-targeted therapy resistance by inhibiting autophagy-dependent glutathione synthesis.

USP13 facilitates a ferroptosis-to-autophagy switch by activation of the NFE2L2/NRF2-SQSTM1/p62-KEAP1 axis dependent on the KRAS signaling pathway

Macroautophagy/autophagyis a lysosomal-regulated degradation process that participates incellular stress and then promotes cell survival or triggers celldeath. Ferroptosis was initially described as anautophagy-independent, iron-regulated, nonapoptotic cell death.However, recent studies have revealed that autophagy is positivelyassociated with sensitivity to ferroptosis. Nonetheless, themolecular mechanisms by which these two types of regulated cell death(RCD) modulate each other remain largely unclear. Here, we screened85 deubiquitinating enzymes (DUBs) and found that overexpression ofUSP13 (ubiquitin specific peptidase 13) could significantlyupregulate NFE2L2/NRF2 (NFE2 like bZIP transcription factor 2)protein levels. In addition, in 39 cases of KRAS-mutated lungadenocarcinoma (LUAD), we found that approximately 76% of USP13overexpression is positively correlated with NFE2L2 overexpression.USP13 interacts with and catalyzes the deubiquitination of thetranscription factor NFE2L2. Additionally, USP13 depletion promotesan autophagy-to-ferroptosis switch invitro andin xenograft tumor mouse models, through the activation of theNFE2L2-SQSTM1/p62 (sequestosome 1)-KEAP1 axis in KRAS mutant cellsand tumor tissues. Hence, targeting USP13 effectively switchedautophagy-to-ferroptosis, thereby inhibiting KRAS (KRASproto-oncogene, GTPase) mutant LUAD, suggesting the therapeuticpromise of combining autophagy and ferroptosis in the KRAS-mutantLUAD.

ITCH inhibits alkaliptosis in human pancreatic cancer cells through YAP1-dependent SLC16A1 activation

Alkaliptosis is a type of pH-dependent cell death and plays an emerging role in tumor suppression. However, the key modulation mechanism of alkaliptosis remains largely unknown. In particular, the nucleus, as the centre of genetic and metabolic regulation, is crucial for the regulation of cellular life. It is not known whether nuclear proteins are involved in the regulation of alkaliptosis. Here, we isolated nuclear proteins to perform a proteomics that identified itchy E3 ubiquitin protein ligase (ITCH) as a natural inhibitor of alkaliptosis in human pancreatic ductal adenocarcinoma (PDAC) cells. The downregulation of ITCH protein is associated with the induction of alkaliptosis in three human PDAC cell lines (SW1990, MiaPaCa2, and PANC1). Functionally, increasing ITCH expression reduces JTC801-induced growth inhibition and cell death. In contrast, knocking down ITCH using specific shRNA increases JTC801-induced cell growth inhibition in the short or long term, resulting in increased cell death. Mechanistically, JTC801-induced ITCH inhibition blocks large tumor suppressor kinase 1 (LATS1) ubiquitination, which in turn suppresses Yes1 associated transcriptional regulator (YAP1)-dependent the transcriptional activation of solute carrier family 16 member 1 (SLC16A1), a proton-linked monocarboxylate transporter that inhibits JTC801-induced alkaliptosis. Additionally, decreased expression of ITCH is associated with longer survival times in patients with PDAC. Collectively, our results establish an ITCH-dependent pathway that regulates alkaliptotic sensitivity in PDAC cells and deepen the understanding of alkaliptosis in targeted therapy.

Ferroptosis: a potential target for acute lung injury

Acute lung injury (ALI) is caused by a variety of intrapulmonary and extrapulmonary factors and is associated with high morbidity and mortality. Oxidative stress is an important part of the pathological mechanism of ALI. Ferroptosis is a mode of programmed cell death distinguished from others and characterized by iron-dependent lipid peroxidation. This article reviews the metabolic regulation of ferroptosis, its role in the pathogenesis of ALI, and the use of ferroptosis as a therapeutic target regarding the pharmacological treatment of ALI.

Protein modification and degradation in ferroptosis

Ferroptosis is a form of iron-related oxidative cell death governed by an integrated redox system, encompassing pro-oxidative proteins and antioxidative proteins. These proteins undergo precise control through diverse post-translational modifications, including ubiquitination, phosphorylation, acetylation, O-GlcNAcylation, SUMOylation, methylation, N-myristoylation, palmitoylation, and oxidative modification. These modifications play pivotal roles in regulating protein stability, activity, localization, and interactions, ultimately influencing both the buildup of iron and lipid peroxidation. In mammalian cells, regulators of ferroptosis typically undergo degradation via two principal pathways: the ubiquitin-proteasome system, which handles the majority of protein degradation, and autophagy, primarily targeting long-lived or aggregated proteins. This comprehensive review aims to summarize recent advances in the post-translational modification and degradation of proteins linked to ferroptosis. It also discusses strategies for modulating ferroptosis through protein modification and degradation systems, providing new insights into potential therapeutic applications for both cancer and non-neoplastic diseases.

Cetylpyridinium chloride triggers paraptosis to suppress pancreatic tumor growth via the ERN1-MAP3K5-p38 pathway

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive solid malignancy with low 5-year survival and limited treatment options. We conducted an unbiased screening using FDA-approved drug and demonstrated that cetylpyridinium chloride (CPC), a component commonly found in mouthwash and known for its robust bactericidal and antifungal attributes, exhibits anticancer activity against human PDAC cells. CPC inhibited PDAC cell growth and proliferation by inducing paraptosis, rather than apoptosis. Mechanistically, CPC induced paraptosis through the initiation of endoplasmic reticulum stress, leading to the accumulation of misfolded proteins. Subsequently, the endoplasmic reticulum stress to nucleus signaling 1 (ERN1)-mitogen-activated protein kinase kinase kinase 5 (MAP3K5)-p38 mitogen-activated protein kinase (MAPK) signaling pathway was activated, ultimately culminating in the induction of paraptosis. In vivo experiments, including those involving patient-derived xenografts, orthotopic models, and genetically engineered mouse models of PDAC, provided further evidence of CPC's effectiveness in suppressing the growth of pancreatic tumors.

Alkaliptosis induction counteracts paclitaxel-resistant ovarian cancer cells via ATP6V0D1-mediated ABCB1 inhibition

Paclitaxel serves as the cornerstone chemotherapy for ovarian cancer, yet its prolonged administration frequently culminates in drug resistance, presenting a substantial challenge. Here we reported that inducing alkaliptosis, rather than apoptosis or ferroptosis, effectively overcomes paclitaxel resistance. Mechanistically, ATPase H+ transporting V0 subunit D1 (ATP6V0D1), a key regulator of alkaliptosis, plays a pivotal role by mediating the downregulation of ATP-binding cassette subfamily B member 1 (ABCB1), a multidrug resistance protein. Both ATP6V0D1 overexpression through gene transfection and pharmacological enhancement of ATP6V0D1 protein stability using JTC801 effectively inhibit ABCB1 upregulation, resulting in growth inhibition in drug-resistant cells. Additionally, increasing intracellular pH to alkaline (pH 8.5) via sodium hydroxide application suppresses ABCB1 expression, whereas reducing the pH to acidic conditions (pH 6.5) with hydrochloric acid amplifies ABCB1 expression in drug-resistant cells. Collectively, these results indicate a potentially effective therapeutic strategy for targeting paclitaxel-resistant ovarian cancer by inducing ATP6V0D1-dependent alkaliptosis.

Molecular characteristics and immune microenvironment of gastrointestinal stromal tumours: targets for therapeutic strategies

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours, arising mainly from the interstitial cells of Cajal (ICCs) of the gastrointestinal tract. As radiotherapy and chemotherapy are generally ineffective for GISTs, the current primary treatment is surgical resection. However, surgical resection is not choice for most patients. Therefore, new therapeutic strategies are urgently needed. Targeted therapy, represented by tyrosine kinase inhibitors (TKIs), and immunotherapy, represented by immune checkpoint inhibitor therapies and chimeric antigen receptor T-cell immunotherapy (CAR-T), offer new therapeutic options in GISTs and have shown promising treatment responses. In this review, we summarize the molecular classification and immune microenvironment of GISTs and discuss the corresponding targeted therapy and immunotherapy options. This updated knowledge may provide more options for future therapeutic strategies and applications in GISTs.

LncRNA STARD7-AS1 suppresses cervical cancer cell proliferation while promoting autophagy by regulating miR-31-5p/TXNIP axis to inactivate the mTOR signaling

OBJECTIVE

Cervical cancer (CC) is a serious gynecologic health issue for women worldwide. Long non-coding RNA (lncRNA) has been well-documented in controlling malignant behavior of various cancer cells. The role of lncRNA STARD7-AS1 in regulating CC cell proliferation and autophagy and its possible mechanism were investigated in this work.

METHODS

RNA expression and protein levels were quantified by reverse transcription quantitative polymerase chain reaction and western blotting. The location of STARD7-AS1 in CC cells was examined using subcellular fraction assays. Cell Counting Kit-8 assays and colony forming assays were performed to measure CC cell viability and proliferation. Autophagy in CC cells was evaluated using macrophage-derived chemokine (MDC) staining and transmission electron microscopy. The binding between microRNA (miR)-31-5p and STARD7-AS1 (or thioredoxin-interacting protein [TXNIP]) was determined by performing luciferase reporter, RNA pull-down or RNA immunoprecipitation assays.

RESULTS

STARD7-AS1 overexpression significantly suppressed CC cell viability and proliferation while notably inducing autophagy. STARD7-AS1 upregulated TXNIP expression via interaction with miR-31-5p. In addition, the effects of STARD7-AS1 on CC cell proliferation and autophagy were reversed by TXNIP silencing. The suppressive effect of STARD7-AS1 overexpression on phosphorylated levels of mTOR and S6K1 was countervailed by TXNIP deficiency.

CONCLUSION

In conclusion, lncRNA STARD7-AS1 inhibits CC cell proliferation and promotes cell autophagy by targeting the miR-31-5p/TXNIP axis to inactivate the mTOR signaling.

Decoding ferroptosis: Revealing the hidden assassin behind cardiovascular diseases

The discovery of regulatory cell death processes has driven innovation in cardiovascular disease (CVD) therapeutic strategies. Over the past decade, ferroptosis, an iron-dependent form of regulated cell death driven by excessive lipid peroxidation, has been shown to drive the development of multiple CVDs. This review provides insights into the evolution of the concept of ferroptosis, the similarities and differences with traditional modes of programmed cell death (e.g., apoptosis, autophagy, and necrosis), as well as the core regulatory mechanisms of ferroptosis (including cystine/glutamate transporter blockade, imbalance of iron metabolism, and lipid peroxidation). In addition, it provides not only a detailed review of the role of ferroptosis and its therapeutic potential in widely studied CVDs such as coronary atherosclerotic heart disease, myocardial infarction, myocardial ischemia/reperfusion injury, heart failure, cardiomyopathy, and aortic aneurysm but also an overview of the phenomenon and therapeutic perspectives of ferroptosis in lesser-addressed CVDs such as cardiac valvulopathy, pulmonary hypertension, and sickle cell disease. This article aims to integrate this knowledge to provide a comprehensive view of ferroptosis in a wide range of CVDs and to drive innovation and progress in therapeutic strategies in this field.

Molecular mechanisms of secretory autophagy and its potential role in diseases

Autophagy is a cellular degradation system that recycles or degrades damaged organelles, viral particles, and aggregated proteins through the lysosomal pathway. Autophagy plays an indispensable role in cellular homeostasis and communication processes. An interesting aspect is that autophagy also mediates the secretion of cellular contents, a process known as secretory autophagy. Secretory autophagy differs from macroautophagy, which sequesters recruited proteins, organelles, or viral particles into autophagosomes and degrades these sequesters in lysosomes, while the secretory autophagy pathway participates in the extracellular export of cellular contents sequestered by autophagosomes through autophagy and endosomal modulators. Recent evidence reveals that secretory autophagy is pivotal in the occurrence and progression of diseases. In this review, we summarize the molecular mechanisms of secretory autophagy. Furthermore, we review the impact of secretory autophagy on diseases, including cancer, viral infectious diseases, neurodegenerative diseases, and cardiovascular diseases. Considering the pleiotropic actions of secretory autophagy on diseases, studying the mechanism of secretory autophagy may help to understand the relevant pathophysiological processes.

Ciprofloxacin is a novel anti-ferroptotic antibiotic

Cancer patients undergoing chemotherapy are susceptible to various bacterial infections, necessitating prompt and precise antimicrobial treatment with antibiotics. Ciprofloxacin is a clinically utilized broad-spectrum antimicrobial agent known for its robust antiseptic activity. While ferroptosis, an oxidative form of cell death, has garnered attention as a promising avenue in cancer therapy, the potential impact of ciprofloxacin on the anticancer effects of ferroptosis remains unclear. This study seeks to investigate the potential influence of antibiotics on ferroptosis in human pancreatic ductal adenocarcinoma (PDAC) cells. Here, we report a previously unrecognized role of ciprofloxacin in inhibiting ferroptosis in human PDAC cells. Mechanistically, ciprofloxacin suppresses erastin-induced endoplasmic reticulum (ER) stress through the activating transcription factor 6 (ATF6) and ER to nucleus signaling 1 (ERN1) pathway. Excessive ER stress activation can trigger glutathione peroxidase 4 (GPX4) degradation through autophagic mechanisms. In contrast, ciprofloxacin enhances the protein stability of GPX4, a crucial regulator that suppresses ferroptosis by inhibiting lipid peroxidation. Thus, our study demonstrates the anti-ferroptotic role of ciprofloxacin, highlighting the importance of careful consideration when contemplating the combination of ciprofloxacin with specific ferroptosis inducers in PDAC patients.

Ferroptosis: principles and significance in health and disease

Ferroptosis, an iron-dependent form of cell death characterized by uncontrolled lipid peroxidation, is governed by molecular networks involving diverse molecules and organelles. Since its recognition as a non-apoptotic cell death pathway in 2012, ferroptosis has emerged as a crucial mechanism in numerous physiological and pathological contexts, leading to significant therapeutic advancements across a wide range of diseases. This review summarizes the fundamental molecular mechanisms and regulatory pathways underlying ferroptosis, including both GPX4-dependent and -independent antioxidant mechanisms. Additionally, we examine the involvement of ferroptosis in various pathological conditions, including cancer, neurodegenerative diseases, sepsis, ischemia-reperfusion injury, autoimmune disorders, and metabolic disorders. Specifically, we explore the role of ferroptosis in response to chemotherapy, radiotherapy, immunotherapy, nanotherapy, and targeted therapy. Furthermore, we discuss pharmacological strategies for modulating ferroptosis and potential biomarkers for monitoring this process. Lastly, we elucidate the interplay between ferroptosis and other forms of regulated cell death. Such insights hold promise for advancing our understanding of ferroptosis in the context of human health and disease.

International consensus guidelines for the definition, detection, and interpretation of autophagy-dependent ferroptosis

Macroautophagy/autophagy is a complex degradation process with a dual role in cell death that is influenced by the cell types that are involved and the stressors they are exposed to. Ferroptosis is an iron-dependent oxidative form of cell death characterized by unrestricted lipid peroxidation in the context of heterogeneous and plastic mechanisms. Recent studies have shed light on the involvement of specific types of autophagy (e.g. ferritinophagy, lipophagy, and clockophagy) in initiating or executing ferroptotic cell death through the selective degradation of anti-injury proteins or organelles. Conversely, other forms of selective autophagy (e.g. reticulophagy and lysophagy) enhance the cellular defense against ferroptotic damage. Dysregulated autophagy-dependent ferroptosis has implications for a diverse range of pathological conditions. This review aims to present an updated definition of autophagy-dependent ferroptosis, discuss influential substrates and receptors, outline experimental methods, and propose guidelines for interpreting the results.Abbreviation: 3-MA:3-methyladenine; 4HNE: 4-hydroxynonenal; ACD: accidentalcell death; ADF: autophagy-dependentferroptosis; ARE: antioxidant response element; BH2:dihydrobiopterin; BH4: tetrahydrobiopterin; BMDMs: bonemarrow-derived macrophages; CMA: chaperone-mediated autophagy; CQ:chloroquine; DAMPs: danger/damage-associated molecular patterns; EMT,epithelial-mesenchymal transition; EPR: electronparamagnetic resonance; ER, endoplasmic reticulum; FRET: Försterresonance energy transfer; GFP: green fluorescent protein;GSH: glutathione;IF: immunofluorescence; IHC: immunohistochemistry; IOP, intraocularpressure; IRI: ischemia-reperfusion injury; LAA: linoleamide alkyne;MDA: malondialdehyde; PGSK: Phen Green™ SK;RCD: regulatedcell death; PUFAs: polyunsaturated fatty acids; RFP: red fluorescentprotein;ROS: reactive oxygen species; TBA: thiobarbituricacid; TBARS: thiobarbituric acid reactive substances; TEM:transmission electron microscopy.

Cadmium toxicity and autophagy: a review

Cadmium (Cd) is an important environmental pollutant that poses a threat to human health and represents a critical component of air pollutants, food sources, and cigarette smoke. Cd is a known carcinogen and has toxic effects on the environment and various organs in humans. Heavy metals within an organism are difficult to biodegrade, and those that enter the respiratory tract are difficult to remove. Autophagy is a key mechanism for counteracting extracellular (microorganisms and foreign bodies) or intracellular (damaged organelles and proteins that cannot be degraded by the proteasome) stress and represents a self-protective mechanism for eukaryotes against heavy metal toxicity. Autophagy maintains cellular homeostasis by isolating and gathering information about foreign chemicals associated with other molecular events. However, autophagy may trigger cell death under certain pathological conditions, including cancer. Autophagy dysfunction is one of the main mechanisms underlying Cd-induced cytotoxicity. In this review, the toxic effects of Cd-induced autophagy on different human organ systems were evaluated, with a focus on hepatotoxicity, nephrotoxicity, respiratory toxicity, and neurotoxicity. This review also highlighted the classical molecular pathways of Cd-induced autophagy, including the ROS-dependent signaling pathways, endoplasmic reticulum (ER) stress pathway, Mammalian target of rapamycin (mTOR) pathway, Beclin-1 and Bcl-2 family, and recently identified molecules associated with Cd. Moreover, research directions for Cd toxicity regarding autophagic function were proposed. This review presents the latest theories to comprehensively reveal autophagy behavior in response to Cd toxicity and proposes novel potential autophagy-targeted prevention and treatment strategies for Cd toxicity and Cd-associated diseases in humans.

Up-regulated ORC1 promotes lung adenocarcinoma by inhibiting ferroptosis via SLC7A11 dependent pathway

Background

Lung adenocarcinoma (LUAD) is a pulmonary malignant disease that poses a high risk of mortality and morbidity. Previous study indicated that ORC1 plays an oncogenic function. However, the precise regulatory function that ORC1 serves in the progression of LUAD is still not clearly known.

Methods

Bioinformatics analyses were performed using TCGA and GEO datasets. The human LUAD cell line NCIH1355, NCIH1568 as well as BEAS-2B cell line (human normal lung epithelial cell) were utilized for in vitro study. LUAD cell proliferation were determined via CCK-8 assays and RT-qPCR for ki-67. The relation of ORC1 and SLC7A11 was detected by Western blot and qPCR with or without sh-RNA. The expression level ACSL4, the biomarker of ferroptosis, were detected using RT-qPCR.

Results

ORC1 and SLC7A11 exhibit high expression levels in both LUAD patients and cell lines, and are strongly associated with poor prognosis. In vitro experiments demonstrate that ORC1 and SLC7A11 promote proliferation of LUAD cell lines while inhibiting gefitinib-induced ferroptosis. Additionally, the function of ORC1 in LUAD cells is dependent on SLC7A11.

Conclusion

ORC1 promotes LUAD cell proliferation and inhibits ferroptosis in a SLC7A11-dependent manner. This implies that ORC1 could potentially serve as a useful diagnosis biomarker and treatment target.

Ferroptotic therapy in cancer: benefits, side effects, and risks

Ferroptosis is a type of regulated cell death characterized by iron accumulation and uncontrolled lipid peroxidation, leading to plasma membrane rupture and intracellular content release. Originally investigated as a targeted therapy for cancer cells carrying oncogenic RAS mutations, ferroptosis induction now exhibits potential to complement chemotherapy, immunotherapy, and radiotherapy in various cancer types. However, it can lead to side effects, including immune cell death, bone marrow impairment, liver and kidney damage, cachexia (severe weight loss and muscle wasting), and secondary tumorigenesis. In this review, we discuss the advantages and offer an overview of the diverse range of documented side effects. Furthermore, we examine the underlying mechanisms and explore potential strategies for side effect mitigation.

USP24-i-101 targeting of USP24 activates autophagy to inhibit drug resistance acquired during cancer therapy

Drug resistance in cancer therapy is the major reason for poor prognosis. Addressing this clinically unmet issue is important and urgent. In this study, we found that targeting USP24 by the specific USP24 inhibitors, USP24-i and its analogues, dramatically activated autophagy in the interphase and mitotic periods of lung cancer cells by inhibiting E2F4 and TRAF6, respectively. USP24 functional knockout, USP24C1695A, or targeting USP24 by USP24-i-101 inhibited drug resistance and activated autophagy in gefitinib-induced drug-resistant mice with doxycycline-induced EGFRL858R lung cancer, but this effect was abolished after inhibition of autophagy, indicating that targeting USP24-mediated induction of autophagy is required for inhibition of drug resistance. Genomic instability and PD-L1 levels were increased in drug resistant lung cancer cells and were inhibited by USP24-i-101 treatment or knockdown of USP24. In addition, inhibition of autophagy by bafilomycin-A1 significantly abolished the effect of USP24-i-101 on maintaining genomic integrity, decreasing PD-L1 and inhibiting drug resistance acquired in chemotherapy or targeted therapy. In summary, an increase in the expression of USP24 in cancer cells is beneficial for the induction of drug resistance and targeting USP24 by USP24-i-101 optimized from USP24-i inhibits drug resistance acquired during cancer therapy by increasing PD-L1 protein degradation and genomic stability in an autophagy induction-dependent manner.

N6-methyladenosine-associated genetic variants in NECTIN2 and HPCAL1 are risk factors for abdominal aortic aneurysm

Although N6-methyladenosine (m6A) modification has been implicated in the pathogenesis of abdominal aortic aneurysm (AAA), the relationship between m6A-associated single nucleotide polymorphisms (m6A-SNPs) and AAA remains unknown. This study used integrative multi-omics analysis and clinical validation approaches to systematically identify potential m6A-SNPs connected with AAA risk. We found that rs6859 and rs10198139 could modulate the expression of local genes, NECTIN2 and HPCAL1, respectively, which exhibited upregulation in AAA tissues, and their risk variants were significantly correlated with an increased susceptibility to AAA. Incorporating rs6859 and rs10198139 improved the efficiency of AAA risk prediction compared to the model considering only conventional risk factors. Additionally, these two SNPs were predicted to be located within the regulatory sequences, and rs6859 showed a substantial impact on m6A modification levels. Our findings suggest that m6A-SNPs rs6859 and rs10198139 confer an elevated risk of AAA, possibly by promoting local gene expression through an m6A-mediated manner.

Nicotinamide mononucleotide induces autophagy and ferroptosis via AMPK/mTOR pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common malignancy worldwide. Herein, we investigated the role of nicotinamide mononucleotide (NMN) in HCC progression. HCC cells were treated with NMN (125, 250, and 500 μM), and then nicotinamide adenine dinucleotide (NAD+ ) and NADH levels in HCC cells were measured to calculate NAD+ /NADH ratio. Cell proliferation, apoptosis, autophagy and ferroptosis were determined. AMPK was knocked down to confirm the involvement of AMPK/mTOR signaling. Furthermore, tumor-inhibitory effect of NMN was investigated in xenograft models. Exposure to NMN dose-dependently increased NAD+ level and NAD+ /NADH ratio in HCC cells. After NMN treatment, cell proliferation was inhibited, whereas apoptosis was enhanced in both cell lines. Additionally, NMN dose-dependently enhanced autophagy/ferroptosis and activated AMPK/mTOR pathway in HCC cells. AMPK knockdown partially rescued the effects of NMN in vitro. Furthermore, NMN treatment restrained tumor growth in nude mice, activated autophagy/ferroptosis, and promoted apoptosis and necrosis in tumor tissues. The results indicate that NMN inhibits HCC progression by inducing autophagy and ferroptosis via AMPK/mTOR signaling. NMN may serve as a promising agent for HCC treatment.

ATF4 in cellular stress, ferroptosis, and cancer

Activating transcription factor 4 (ATF4), a member of the ATF/cAMP response element-binding (CREB) family, plays a critical role as a stress-induced transcription factor. It orchestrates cellular responses, particularly in the management of endoplasmic reticulum stress, amino acid deprivation, and oxidative challenges. ATF4's primary function lies in regulating gene expression to ensure cell survival during stressful conditions. However, when considering its involvement in ferroptosis, characterized by severe lipid peroxidation and pronounced endoplasmic reticulum stress, the ATF4 pathway can either inhibit or promote ferroptosis. This intricate relationship underscores the complexity of cellular responses to varying stress levels. Understanding the connections between ATF4, ferroptosis, and endoplasmic reticulum stress holds promise for innovative cancer therapies, especially in addressing apoptosis-resistant cells. In this review, we provide an overview of ATF4, including its structure, modifications, and functions, and delve into its dual role in both ferroptosis and cancer.

Targeting paraptosis in cancer: opportunities and challenges

Cell death can be classified into two primary categories: accidental cell death and regulated cell death (RCD). Within RCD, there are distinct apoptotic and non-apoptotic cell death pathways. Among the various forms of non-apoptotic RCD, paraptosis stands out as a unique mechanism characterized by distinct morphological changes within cells. These alterations encompass cytoplasmic vacuolization, organelle swelling, notably in the endoplasmic reticulum and mitochondria, and the absence of typical apoptotic features, such as cell shrinkage and DNA fragmentation. Biochemically, paraptosis distinguishes itself by its independence from caspases, which are conventionally associated with apoptotic death. This intriguing cell death pathway can be initiated by various cellular stressors, including oxidative stress, protein misfolding, and specific chemical compounds. Dysregulated paraptosis plays a pivotal role in several critical cancer-related processes, such as autophagic degradation, drug resistance, and angiogenesis. This review provides a comprehensive overview of recent advancements in our understanding of the mechanisms and regulation of paraptosis. Additionally, it delves into the potential of paraptosis-related compounds for targeted cancer treatment, with the aim of enhancing treatment efficacy while minimizing harm to healthy cells.

Antioxidant Systems as Modulators of Ferroptosis: Focus on Transcription Factors

Ferroptosis is a type of programmed cell death that differs from apoptosis, autophagy, and necrosis and is related to several physio-pathological processes, including tumorigenesis, neurodegeneration, senescence, blood diseases, kidney disorders, and ischemia-reperfusion injuries. Ferroptosis is linked to iron accumulation, eliciting dysfunction of antioxidant systems, which favor the production of lipid peroxides, cell membrane damage, and ultimately, cell death. Thus, signaling pathways evoking ferroptosis are strongly associated with those protecting cells against iron excess and/or lipid-derived ROS. Here, we discuss the interaction between the metabolic pathways of ferroptosis and antioxidant systems, with a particular focus on transcription factors implicated in the regulation of ferroptosis, either as triggers of lipid peroxidation or as ferroptosis antioxidant defense pathways.

Autophagy Genes and Otitis Media Outcomes

Otitis media (OM) is a common cause of hearing loss in children that requires corrective surgery. Various studies have investigated the pathomechanisms and treatment of OM. Autophagy, an essential cellular recycling and elimination mechanism implicated in various diseases, is known to play an important role in the pathogenesis of OM. Here, we conducted a literature review on autophagy in OM, highlighting the relationship between expression patterns of autophagy-related factors and pathophysiological and clinical aspects of OM. We summarized the existing research results on the expression of autophagy-related factors in acute OM (AOM), OM with effusion (OME), chronic OM (COM) with cholesteatoma, and COM without cholesteatoma (CholeOM) in animals and humans. Autophagy-related factors are expressed in the middle ear mucosa or fluid of AOM, effusion of OME, granulation tissue of COM, and cholesteatoma of CholeOM. Among ATGs and other autophagy-related factors, the most extensively studied in relation to the pathogenesis of OM are mTOR, LC3II/I, PI3K, Beclin-1, FLIP, Akt, and Rubicon. Expression of autophagy-related factors is associated with AOM, OME, COM, and CholeOM. Inadequate expression of these factors or a decrease/increase in autophagy responses can result in OM, underscoring the critical role of ATGs and related factors in the pathogenesis of OM.

Ferroptosis at the crossroads of manganese-induced neurotoxicity: A retrospective study

Manganese is an essential trace element, but overexposure can cause neurotoxicity and subsequent neurodegenerative diseases. Ferroptosis is a form of cell death characterized by lipid peroxidation and iron overload inside cells, which is closely related to manganese neurotoxicity. Manganese can induce ferroptosis through multiple pathways: causing oxidative stress and increased cellular reactive oxygen species (ROS), resulting in lipid peroxidation; depleting glutathione (GSH) and weakening the antioxidant capacity of cells; disrupting iron metabolism and increasing iron-dependent lipid peroxidation; damaging mitochondrial function and disrupting the electron transport chain, leading to increased ROS production. Oxidative stress, iron metabolism disorders, lipid peroxidation, GSH depletion, and mitochondrial dysfunction, typical features of ferroptosis, have been observed in animal and cell models after manganese exposure. In summary, manganese can participate in the pathogenesis of neurodegenerative diseases by inducing events related to ferroptosis. This provides new insights into studying the mechanism of manganese neurotoxicity and developing therapeutic drugs.

Deciphering the link: ferroptosis and its role in glioma

Glioma, as the most frequently occurring primary malignancy in the central nervous system, significantly impacts patients' quality of life and cognitive abilities. Ferroptosis, a newly discovered form of cell death, is characterized by significant iron accumulation and lipid peroxidation. This process is fundamentally dependent on iron. Various factors inducing ferroptosis can either directly or indirectly influence glutathione peroxidase, leading to reduced antioxidant capabilities and an increase in lipid reactive oxygen species (ROS) within cells, culminating in oxidative cell death. Recent research indicates a strong connection between ferroptosis and a range of pathophysiological conditions, including tumors, neurological disorders, ischemia-reperfusion injuries, kidney damage, and hematological diseases. The regulation of ferroptosis to intervene in the progression of these diseases has emerged as a major area of interest in etiological research and therapy. However, the exact functional alterations and molecular mechanisms underlying ferroptosis remain to be extensively studied. The review firstly explores the intricate relationship between ferroptosis and glioma, highlighting how ferroptosis contributes to glioma pathogenesis and how glioma cells may resist this form of cell death. Then, we discuss recent studies that have identified potential ferroptosis inducers and inhibitors, which could serve as novel therapeutic strategies for glioma. We also examine the current challenges in targeting ferroptosis in glioma treatment, including the complexity of its regulation and the need for precise delivery methods. This review aims to provide a comprehensive overview of the current state of research on ferroptosis in glioma, offering insights into future therapeutic strategies and the broader implications of this novel cell death pathway in cancer biology.

Ferroptosis in immunostimulation and immunosuppression

Ferroptosis is a form of iron-dependent regulated cell death characterized by the accumulation of toxic lipid peroxides, particularly in the plasma membrane, leading to lytic cell death. While it plays a crucial role in maintaining the overall health and proper functioning of multicellular organisms, it can also contribute to tissue damage and pathological conditions. Although ferroptotic damage is generally recognized as an immunostimulatory process associated with the release of damage-associated molecular patterns (DAMPs), the occurrence of ferroptosis in immune cells or the release of immunosuppressive molecules can result in immune tolerance. Consequently, there is ongoing exploration of targeting the upstream signals or the machinery of ferroptosis to therapeutically enhance or inhibit the immune response. In addition to introducing the core molecular mechanisms of ferroptosis, we will focus on the immune characteristics of ferroptosis in pathological conditions, particularly in the context of infection, sterile inflammation, and tumor immunity.

Tumor-specific GPX4 degradation enhances ferroptosis-initiated antitumor immune response in mouse models of pancreatic cancer

Lipid peroxidation-dependent ferroptosis has become an emerging strategy for tumor therapy. However, current strategies not only selectively induce ferroptosis in malignant cells but also trigger ferroptosis in immune cells simultaneously, which can compromise anti-tumor immunity. Here, we used In-Cell Western assays combined with an unbiased drug screening to identify the compound N6F11 as a ferroptosis inducer that triggered the degradation of glutathione peroxidase 4 (GPX4), a key ferroptosis repressor, specifically in cancer cells. N6F11 did not cause the degradation of GPX4 in immune cells, including dendritic, T, natural killer, and neutrophil cells. Mechanistically, N6F11 bound to the RING domain of E3 ubiquitin ligase tripartite motif containing 25 (TRIM25) in cancer cells to trigger TRIM25-mediated K48-linked ubiquitination of GPX4, resulting in its proteasomal degradation. Functionally, N6F11 treatment caused ferroptotic cancer cell death that initiated HMGB1-dependent antitumor immunity mediated by CD8+ T cells. N6F11 also sensitized immune checkpoint blockade that targeted CD274/PD-L1 in advanced cancer models, including genetically engineered mouse models of pancreatic cancer driven by KRAS and TP53 mutations. These findings may establish a safe and efficient strategy to boost ferroptosis-driven antitumor immunity.

IR-820@NBs Combined with MG-132 Enhances the Anti-Hepatocellular Carcinoma Effect of Sonodynamic Therapy

Purpose

Sonodynamic therapy (SDT) is a promising and significant measure for the treatment of tumors. However, the internal situation of hepatocellular carcinoma (HCC) is complex, separate SDT treatment is difficult to play a good therapeutic effect. Here, we used SDT combined with MG-132 to mediate apoptosis and autophagy of HCC cells to achieve the purpose of treatment of cancer.

Methods

To determine the generated reactive oxygen species (ROS) and the change of mitochondrial membrane potential (ΔΨm), HepG2 cells were stained by 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) and 5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide (JC-1) staining to determine the IR-820@NBs-mediated SDT to achieve HCC therapy through the mitochondrial pathway. Cell counting kit 8 (CCK-8) assay and flow cytometry were used to detect cell viability and apoptosis rate of HepG2 cells. Autophagy was detected by mCherry-GFP-LC3B fluorescence labeling. Chloroquine (Cq) pretreatment was used to explore the relationship between autophagy and apoptosis. To detect the ability of HepG2 cells migration and invasion, cell scratch assay and transwell assay were used.

Results

The successfully prepared IR-820@NBs could effectively overcome the shortcomings of IR-820 and induce lethal levels of ROS by ultrasound irradiation. As a dual agonist of apoptosis and autophagy, MG-132 could effectively enhance the efficacy of SDT in the process of treating HCC. After pre-treatment with Cq, the cell activity increased and the level of apoptosis decreased, which proved that apoptosis and autophagy were induced by combined therapy, autophagy, and apoptosis have the synergistic anti-tumor effect, and part of apoptosis was autophagy-dependent. After combined therapy, the activity and invasive ability of HCC cells decreased significantly.

Conclusion

SDT combined with MG-132 in the process of treating liver cancer could effectively induce apoptosis and autophagy anti-tumor therapy, which is helpful to the research of new methods to treat liver cancer.

Interaction mechanisms between autophagy and ferroptosis: Potential role in colorectal cancer

Colorectal cancer (CRC) is a common malignancy that has the second highest incidence and mortality rate. Although there are many personalized treatment options for CRC, the therapeutic effects are ultimately limited by drug resistance. Studies have aimed to block the initiation and progression of CRC by inducing cell death to overcome this obstacle. Substantial evidence has indicated that both autophagy and ferroptosis play important regulatory roles in CRC. Autophagy, a lysosome-dependent process by which cellular proteins and organelles are degraded, is the basic mechanism for maintaining cell homeostasis. The duality and complexity of autophagy in cancer therapy is a hot topic of discussion. Ferroptosis, a regulated cell death pathway, is associated with iron accumulation-induced lipid peroxidation. The activation of ferroptosis can suppress CRC proliferation, invasion and drug resistance. Furthermore, recent studies have suggested an interaction between autophagy and ferroptosis. Autophagy can selectively degrade certain cellular contents to provide raw materials for ferroptosis, ultimately achieving antitumor and anti-drug resistance. Therefore, exploring the interaction between autophagy and ferroptosis could reveal novel ideas for the treatment of CRC. In this review, we describe the mechanisms of autophagy and ferroptosis, focusing on their roles in CRC and the crosstalk between them.

From Oxytosis to Ferroptosis: 10 Years of Research on Oxidative Cell Death

Over the past decade, extensive research has been dedicated to understanding oxidative cell death, specifically the transition from oxytosis to ferroptosis. Oxytosis was initially characterized in 1989 as a calcium-dependent form of nerve cell death induced by glutamate. It was associated with intracellular glutathione depletion and the inhibition of cystine uptake through system xc-, a cystine-glutamate antiporter. In 2012, the term "ferroptosis" was coined during a compound screening that aimed to selectively induce cell death in RAS-mutated cancer cells. This screening identified erastin and RSL3 as inhibitors of system xc- and glutathione peroxidase 4 (GPX4), respectively, triggering oxidative cell death. Subsequently, the term oxytosis gradually fell out of frequent usage, being replaced by ferroptosis. This editorial provides a narrative review of the significant findings, experimental models, and molecular players involved in ferroptosis, shedding light on its intricate mechanisms. Moreover, it discusses the implications of these findings in various pathological conditions, including neurodegenerative disorders, cancer, and ischemia-reperfusion disease. By summarizing the decade-long progress made in this field, the present Forum serves as a valuable resource for researchers aiming to unravel the complex mechanisms underlying oxidative cell death and explore potential therapeutic interventions. Antioxid. Redox Signal. 39, 162-165.

Hyperforin Enhances Heme Oxygenase-1 Expression Triggering Lipid Peroxidation in BRAF-Mutated Melanoma Cells and Hampers the Expression of Pro-Metastatic Markers

Hyperforin (HPF) is an acylphloroglucinol compound found abundantly in Hypericum perforatum extract which exhibits antidepressant, anti-inflammatory, antimicrobial, and antitumor activities. Our recent study revealed a potent antimelanoma effect of HPF, which hinders melanoma cell proliferation, motility, colony formation, and induces apoptosis. Furthermore, we have identified glutathione peroxidase-4 (GPX-4), a key enzyme involved in cellular protection against iron-induced lipid peroxidation, as one of the molecular targets of HPF. Thus, in three BRAF-mutated melanoma cell lines, we investigated whether iron unbalance and lipid peroxidation may be a part of the molecular mechanisms underlying the antimelanoma activity of HPF. Initially, we focused on heme oxygenase-1 (HO-1), which catalyzes the heme group into CO, biliverdin, and free iron, and observed that HPF treatment triggered the expression of this inducible enzyme. In order to investigate the mechanism involved in HO-1 induction, we verified that HPF downregulates the BTB and CNC homology 1 (BACH-1) transcription factor, an inhibitor of the heme oxygenase 1 (HMOX-1) gene transcription. Remarkably, we observed a partial recovery of cell viability and an increase in the expression of the phosphorylated and active form of retinoblastoma protein when we suppressed the HMOX-1 gene using HMOX-1 siRNA while HPF was present. This suggests that the HO-1 pathway is involved in the cytostatic effect of HPF in melanoma cells. To explore whether lipid peroxidation is induced, we conducted cytofluorimetric analysis and observed a significant increase in the fluorescence of the BODIPY C-11 probe 48 h after HPF administration in all tested melanoma cell lines. To discover the mechanism by which HPF triggers lipid peroxidation, along with the induction of HO-1, we examined the expression of additional proteins associated with iron homeostasis and lipid peroxidation. After HPF administration, we confirmed the downregulation of GPX-4 and observed low expression levels of SLC7A11, a cystine transporter crucial for the glutathione production, and ferritin, able to sequester free iron. A decreased expression level of these proteins can sensitize cells to lipid peroxidation. On the other hand, HPF treatment resulted in increased expression levels of transferrin, which facilitates iron uptake, and LC3B proteins, a molecular marker of autophagy induction. Indeed, ferritin and GPX-4 have been reported to be digested during autophagy. Altogether, these findings suggest that HPF induced lipid peroxidation likely through iron overloading and decreasing the expression of proteins that protect cells from lipid peroxidation. Finally, we examined the expression levels of proteins associated with melanoma cell invasion and metastatic potential. We observed the decreased expression of CD133, octamer-4, tyrosine-kinase receptor AXL, urokinase plasminogen activator receptor, and metalloproteinase-2 following HPF treatment. These findings provide further support for our previous observations, demonstrating the inhibitory effects of HPF on cell motility and colony formation in soft agar, which are both metastasis-related processes in tumor cells.

Autophagy Regulators in Cancer

Autophagy plays a complex impact role in tumor initiation and development. It serves as a double-edged sword by supporting cell survival in certain situations while also triggering autophagic cell death in specific cellular contexts. Understanding the intricate functions and mechanisms of autophagy in tumors is crucial for guiding clinical approaches to cancer treatment. Recent studies highlight its significance in various aspects of cancer biology. Autophagy enables cancer cells to adapt to and survive unfavorable conditions by recycling cellular components. However, excessive or prolonged autophagy can lead to the self-destruction of cancer cells via a process known as autophagic cell death. Unraveling the molecular mechanisms underlying autophagy regulation in cancer is crucial for the development of targeted therapeutic interventions. In this review, we seek to present a comprehensive summary of current knowledge regarding autophagy, its impact on cancer cell survival and death, and the molecular mechanisms involved in the modulation of autophagy for cancer therapy.

The ACSL4 Network Regulates Cell Death and Autophagy in Diseases

Lipid metabolism, cell death, and autophagy are interconnected processes in cells. Dysregulation of lipid metabolism can lead to cell death, such as via ferroptosis and apoptosis, while lipids also play a crucial role in the regulation of autophagosome formation. An increased autophagic response not only promotes cell survival but also causes cell death depending on the context, especially when selectively degrading antioxidant proteins or organelles that promote ferroptosis. ACSL4 is an enzyme that catalyzes the formation of long-chain acyl-CoA molecules, which are important intermediates in the biosynthesis of various types of lipids. ACSL4 is found in many tissues and is particularly abundant in the brain, liver, and adipose tissue. Dysregulation of ACSL4 is linked to a variety of diseases, including cancer, neurodegenerative disorders, cardiovascular disease, acute kidney injury, and metabolic disorders (such as obesity and non-alcoholic fatty liver disease). In this review, we introduce the structure, function, and regulation of ACSL4; discuss its role in apoptosis, ferroptosis, and autophagy; summarize its pathological function; and explore the potential implications of targeting ACSL4 in the treatment of various diseases.

Ferroptosis in gastrointestinal cancer: From mechanisms to implications

Ferroptosis is a form of regulated cell death that is initiated by excessive lipid peroxidation that results in plasma membrane damage and the release of damage-associated molecular patterns. In recent years, ferroptosis has gained significant attention in cancer research due to its unique mechanism compared to other forms of regulated cell death, especially caspase-dependent apoptotic cell death. Gastrointestinal (GI) cancer encompasses malignancies that arise in the digestive tract, including the stomach, intestines, pancreas, colon, liver, rectum, anus, and biliary system. These cancers are a global health concern, with high incidence and mortality rates. Despite advances in medical treatments, drug resistance caused by defects in apoptotic pathways remains a persistent challenge in the management of GI cancer. Hence, exploring the role of ferroptosis in GI cancers may lead to more efficacious treatment strategies. In this review, we provide a comprehensive overview of the core mechanism of ferroptosis and discuss its function, regulation, and implications in the context of GI cancers.

Detection of Ferroptosis by Immunohistochemistry and Immunofluorescence

Ferroptosis is a type of regulated cell death driven by oxidative damage, characterized by iron overload and lipid peroxidation, and regulated by a network of distinct molecules and organelles. Impaired ferroptotic response is implicated in multiple physiological and pathological processes, including tumorigenesis, neurodegeneration, and ischemia-reperfusion damage. Classical techniques of immunohistochemistry (IHC) and immunofluorescence (IF) can be employed to exhibit antigen expression and location in tissues observed with microscopy, making them powerful tools in studying the ferroptosis process. In this chapter, we introduce commonly used protocols and summarize typical markers used in IHC and IF to monitor ferroptosis.

Generation of Organoids and Analysis of Ferroptosis in Organoids

Ferroptosis is a unique form of iron-dependent cell death induced by lipid peroxidation and subsequent plasma membrane rupture, which sets it apart from other types of regulated cell death. Ferroptosis has been linked to a diverse range of biological processes, such as aging, immunity, and cancer. Organoids, on the other hand, are three-dimensional (3D) miniaturized model systems of different organs in vitro cultures, which have gained widespread interest for modeling tissue development and disease, drug screening, and cell therapy. Organoids offer tremendous potential for improving our understanding of human diseases, particularly in the search for the field of ferroptosis in pathological processes of organs. Furthermore, cancer organoids are utilized to investigate molecular mechanisms and drug screening in vitro due to the anti-tumor effect of ferroptosis. Currently, the development of liver organoids has reached a relatively mature stage. Here, we present the protocols for the generation of liver organoids and liver cancer organoids, along with the methods for detecting ferroptosis in organoids.

Monitoring Mitochondria Function in Ferroptosis

Ferroptosis is a type of regulated necrosis driven by uncontrolled membrane lipid peroxidation. Mitochondria, which are membrane-bound organelles present in almost all eukaryotic cells and play a central role in energy metabolism and various types of cell death, have a complicated role in ferroptosis. On one hand, mitochondrial-derived iron metabolism and reactive oxygen species (ROS) production may promote ferroptosis. On the other hand, mitochondria also possess a dihydroorotate dehydrogenase (DHODH)-dependent antioxidant system that detoxifies lipid peroxides. This chapter summarizes several methods, such as western blotting, immunofluorescence, cell viability assays, mitochondrial fluorescent probes, adenosine 5'-triphosphate (ATP) assay kits, mitochondrial respiration, and mitophagy tests, that may enable researchers to gain a deeper understanding of the dual role of mitochondria in ferroptosis.

In-Cell Western Assay in Ferroptosis

Ferroptosis is a regulated form of cell death caused by the excessive accumulation of iron-dependent lipid peroxidation. It has been implicated in various pathological processes and diseases, and its modulation involves multiple proteins associated with iron and lipid metabolism. To better understand these mechanisms and monitor the ferroptosis process, there is a need for reliable and high-throughput methods to evaluate variations in protein expression levels. In-Cell Western assays provide a simple and rapid assay method for detecting biomarkers and signaling proteins in whole cells using antibodies. This assay involves seeding cells in microtiter plates, followed by fixation/permeabilization and subsequent labeling with primary antibodies and infrared-conjugated secondary antibodies. In this chapter, we introduce the protocol for the In-Cell Western assay for detecting intracellular proteins during ferroptosis.

Monitoring Lysosome Function in Ferroptosis

Ferroptosis is a type of regulated cell death that occurs due to iron-induced membrane lipid peroxidation. Lysosomes, which are acidic, membrane-bound organelles containing various hydrolases, play a vital role in ferroptosis. They not only aid in the degradation of autophagic substrates, but also serve as signaling hubs in cell death. Specifically, lysosomes are involved in the induction and execution of ferroptosis through autophagy-mediated degradation of anti-ferroptotic proteins, lysosomal membrane permeability-mediated release of cathepsins, and iron-induced lysosomal membrane lipid peroxidation. Therefore, it is essential to have reliable methods for monitoring lysosomal functions, including lysosomal activity, pH, and membrane integrity, as well as iron accumulation and lipid peroxidation, to understand ferroptosis. This chapter introduces several protocols, such as western blotting, immunofluorescence, lysosomal probes, and lipid peroxidation assay kits, for monitoring the process of lysosome-related ferroptosis.