Oridonin induces ferroptosis by inhibiting gamma-glutamyl cycle in TE1 cells

Oridonin promotes RSL3-induced ferroptosis in breast cancer cells by regulating the oxidative stress signaling pathway JNK/Nrf2/HO-1

The incidence and mortality of breast cancer, the most common malignant tumor among women in the world, are increasing year by year, which greatly threatens women's health. Ferroptosis is an iron and lipid reactive oxygen species (ROS)-dependent process, a novel form of cell death that is distinct from apoptosis and is closely related to the progression of breast cancer. Inducing the occurrence of ferroptosis in tumor cells can effectively block its malignant progress in vivo. Oridonin (ORI), the primary active ingredient extracted from the Chinese herbal medicine Rabdosia rubescens, has been shown to cause glutathione depletion and directly inhibit glutathione peroxidase 4 induced cell death by ferroptosis, but its mechanism of action in breast cancer remains inadequately elucidated. Therefore, we further investigated whether ORI could promote RSL3-induced ferroptosis in breast cancer cells by regulating the oxidative stress pathway JNK/Nrf2/HO-1. In our study, we assessed cell survival of RSL3 and ORI treatment by MTT assay, and found that co-treatment with RSL3 and ORI inhibited cell proliferation, as evidenced by the cloning assay. To investigate the ability of ORI to promote RSL3-induced ferroptosis in breast cancer cells, we measured levels of ROS, malondialdehyde, glutathione, superoxide dismutase, and Fe2+ content. Lipid peroxidation, ROS, and mitochondrial membrane potential levels induced by co-treatment of ORI with RSL3 were reversed by ferrostatin-1, further confirming that the cell death induced by RSL3 and ORI was ferroptosis rather than other programmed cell death modes. Moreover, RSL3 and ORI co-treatment regulated the JNK/Nrf2/HO-1 axis, as demonstrated by western blotting and target activator validation. Our results showed that ORI could enhance the inhibitory effect of RSL3 on breast cancer cells viability via the induction of ferroptosis. Mechanistically, it potentiated RSL3-induced ferroptosis in breast cancer cells by activating the JNK/Nrf2/HO-1 axis. This study provides a theoretical basis for the application of ORI based on the mechanism of ferroptosis, and provides potential natural drug candidates for cancer prevention and treatment.

Oridonin from Rabdosia rubescens: An emerging potential in cancer therapy - A comprehensive review

Cancer incidences are rising each year. In 2020, approximately 20 million new cancer cases and 10 million cancer-related deaths were recorded. The World Health Organization (WHO) predicts that by 2024 the incidence of cancer will increase to 30.2 million individuals annually. Considering the invasive characteristics of its diagnostic procedures and therapeutic methods side effects, scientists are searching for different solutions, including using plant-derived bioactive compounds, that could reduce the probability of cancer occurrence and make its treatment more comfortable. In this regard, oridonin (ORI), an ent-kaurane diterpenoid, naturally found in the leaves of Rabdosia rubescens species, has been found to have antitumor, antiangiogenesis, antiasthmatic, antiinflammatory, and apoptosis induction properties. Extensive research has been performed on ORI to find various mechanisms involved in its anticancer activities. This review article provides an overview of ORI's effectiveness on murine and human cancer populations from 1976 to 2022 and provides insight into the future application of ORI in different cancer therapies.

Emerging trends of phytochemicals as ferroptosis modulators in cancer therapy

Ferroptosis, a novel form of regulated cell death characterized by dependence on iron and lipid peroxidation, has been implicated in a wide range of clinical conditions including neurological diseases, cardiovascular disorders, acute kidney failure, and various types of cancer. Therefore, it is critical to suppress cancer progression and proliferation. Ferroptosis can be triggered in cancer cells and some normal cells by synthetic substances, such as erastin, Ras-selective lethal small molecule-3, or clinical pharmaceuticals. Natural bioactive compounds are traditional drug discovery tools, and some have been therapeutically used as dietary additives or pharmaceutical agents against various malignancies. The fact that natural products have multiple targets and minimal side effects has led to notable advances in anticancer research. Research has indicated that ferroptosis can also be induced by natural compounds during cancer treatment. In this review, we focused on the most recent developments in emerging molecular processes and the significance of ferroptosis in cancer. To provide new perspectives on the future development of ferroptosis-related anticancer medications, we also provide a summary of the implications of natural phytochemicals in triggering ferroptosis through ROS production and ferritinophagy induction in a variety of malignancies.

The causal relationship between serum metabolites and the risk of psoriasis: a Mendelian randomization and meta-analysis study

Objective

To explore the influence of serum metabolites on the risk of psoriasis.

Methods

In the initial stage, we applied Mendelian randomization to evaluate the association between 1,400 serum metabolites and the risk of psoriasis. Causal effects were primarily assessed through the Inverse-Variance Weighted method and Wald Ratio's odds ratios, and 95% confidence intervals. False Discovery Rate was used for multiple comparison corrections. Sensitivity analyses were conducted using Cochran's Q Test, MR-PRESSO. MR-Steiger Test was employed to check for reverse causality. In the validation stage, we sought other sources of psoriasis GWAS data to verify the initial results and used meta-analysis to combine the effect sizes to obtain robust causal relationships. In addition, we also conducted metabolic pathway enrichment analysis on known metabolites that have a causal relationship with the risk of psoriasis in both stages.

Results

In the initial stage, we identified 112 metabolites causally associated with psoriasis, including 32 metabolite ratios and 80 metabolites (69 known and 11 unknown). In the validation stage, 24 metabolites (16 known, 1 unknown, and 7 metabolite ratios) were confirmed to have a causal relationship with psoriasis onset. Meta-analysis results showed that the overall effect of combined metabolites was consistent with the main analysis in direction and robust in the causal relationship with psoriasis onset. Of the 16 known metabolites, most were attributed to lipid metabolism, with 5 as risk factors and 8 as protective factors for psoriasis. Peptidic metabolite Gamma-glutamylvaline levels had a negative causal relationship with psoriasis, while exogenous metabolite Catechol sulfate levels and amino acid 3-methylglutaconate levels had a positive causal relationship with the disease onset. The metabolites associated with psoriasis risk in the two stages are mainly enriched in the following metabolic pathways: Glutathione metabolism, Alpha Linolenic Acid and Linoleic Acid Metabolism, Biosynthesis of unsaturated fatty acids, Arachidonic acid metabolism, Glycerophospholipid metabolism.

Conclusion

Circulating metabolites may have a potential causal relationship with psoriasis risk, and targeting specific metabolites may benefit psoriasis diagnosis, disease assessment, and treatment.

Natural product-derived ferroptosis mediators

It has been 11 years since ferroptosis, a new mode of programmed cell death, was first proposed. Natural products are an important source of drug discovery. In the past five years, natural product-derived ferroptosis regulators have been discovered in an endless stream. Herein, 178 natural products discovered so far to trigger or resist ferroptosis are classified into 6 structural classes based on skeleton type, and the mechanisms of action that have been reported are elaborated upon. If pharmacodynamic data are sufficient, the structure and bioactivity relationship is also presented. This review will provide medicinal chemists with some effective ferroptosis regulators, which will promote the research of natural product-based treatment of ferroptosis-related diseases in the future.

Oridonin-induced ferroptosis and apoptosis: a dual approach to suppress the growth of osteosarcoma cells

BACKGROUND

Osteosarcoma (OS) is one of the most common aggressive bone malignancy tumors in adolescents. With the application of new chemotherapy regimens, finding new and effective anti-OS drugs to coordinate program implementation is urgent for the patients of OS. Oridonin had been proved to mediate anti-tumor effect on OS cells, but its mechanism has not been fully elucidated.

METHODS

The effects of oridonin on the viability, clonal formation and migration of 143B and U2OS cells were detected by CCK-8, colony formation assays and wound-healing test. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was used to explore the mechanism of oridonin on OS. Western blot (WB), real-time quantitative PCR (qRT-PCR) were used to detect the expression levels of apoptosis and ferroptosis-relative proteins and genes. Annexin V-FITC apoptosis detection kit and flow cytometry examination were used to detect the level of apoptosis. Iron assay kit was used to evaluate the relative Fe2+ content. The levels of mitochondrial membrane potential and lipid peroxidation production was determined by mitochondrial membrane potential detection kit and ROS assay kit.

RESULTS

Oridonin could effectively inhibit the survival, clonal formation and metastasis of OS cells. The KEGG results indicated that oridonin is associated with the malignant phenotypic signaling pathways of proliferation, migration, and drug resistance in OS. Oridonin was capable of inhibiting expressions of BAX, cl-caspase3, SLC7A11, GPX4 and FTH1 proteins and mRNA, while promoting the expressions of Bcl-2 and ACSL4 in 143B and U2OS cells. Additionally, we found that oridonin could promote the accumulation of reactive oxygen species (ROS) and Fe2+ in OS cells, as well as reduce mitochondrial membrane potential, and these effects could be significantly reversed by the ferroptosis inhibitor ferrostatin-1 (Fer-1).

CONCLUSION

Oridonin can trigger apoptosis and ferroptosis collaboratively in OS cells, making it a promising and effective agent for OS therapy.

Ferroptosis: A New Research Direction of Artemisinin and Its Derivatives in Anti-Cancer Treatment

Ferroptosis, an iron-dependent cell death mechanism driven by an accumulation of lipid peroxides on cellular membranes, has emerged as a promising strategy to treat various diseases, including cancer. Ferroptosis inducers not only exhibit cytotoxic effects on multiple cancer cells, including drug-resistant cancer variants, but also hold potential as adjuncts to enhance the efficacy of other anti-cancer therapies, such as immunotherapy. In addition to synthetic inducers, natural compounds, such as artemisinin, can be considered ferroptosis inducers. Artemisinin, extracted from Artemisia annua L., is a poorly water-soluble antimalarial drug. For clinical applications, researchers have synthesized various water-soluble artemisinin derivatives such as dihydroartemisinin, artesunate, and artemether. Artemisinin and artemisinin derivatives (ARTEs) upregulate intracellular free iron levels and promote the accumulation of intracellular lipid peroxides to induce cancer cell ferroptosis, alleviating cancer development and resulting in strong anti-cancer effects in vitro and in vivo. In this review, we introduce the mechanisms of ferroptosis, summarize the research on ARTEs-induced ferroptosis in cancer cells, and discuss the clinical research progress and current challenges of ARTEs in anti-cancer treatment. This review deepens the current understanding of the relationship between ARTEs and ferroptosis and provides a theoretical basis for the clinical anti-cancer application of ARTEs in the future.

Ferroptosis: a new mechanism of traditional Chinese medicine for cancer treatment

Ferroptosis, distinct from apoptosis, is a novel cellular death pathway characterized by the build-up of lipid peroxidation and reactive oxygen species (ROS) derived from lipids within cells. Recent studies demonstrated the efficacy of ferroptosis inducers in targeting malignant cells, thereby establishing a promising avenue for combating cancer. Traditional Chinese medicine (TCM) has a long history of use and is widely used in cancer treatment. TCM takes a holistic approach, viewing the patient as a system and utilizing herbal formulas to address complex diseases such as cancer. Recent TCM studies have elucidated the molecular mechanisms underlying ferroptosis induction during cancer treatment. These studies have identified numerous plant metabolites and derivatives that target multiple pathways and molecular targets. TCM can induce ferroptosis in tumor cells through various regulatory mechanisms, such as amino acid, iron, and lipid metabolism pathways, which may provide novel therapeutic strategies for apoptosis-resistant cancer treatment. TCM also influence anticancer immunotherapy via ferroptosis. This review comprehensively elucidates the molecular mechanisms underlying ferroptosis, highlights the pivotal regulatory genes involved in orchestrating this process, evaluates the advancements made in TCM research pertaining to ferroptosis, and provides theoretical insights into the induction of ferroptosis in tumors using botanical drugs.

Novel Insights on Ferroptosis Modulation as Potential Strategy for Cancer Treatment: When Nature Kills

Significance: The multifactorial nature of the mechanisms implicated in cancer development still represents a major issue for the success of established antitumor therapies. The discovery of ferroptosis, a novel form of programmed cell death distinct from apoptosis, along with the identification of the molecular pathways activated during its execution, has led to the uncovering of novel molecules characterized by ferroptosis-inducing properties. Recent advances: As of today, the ferroptosis-inducing properties of compounds derived from natural sources have been investigated and interesting findings have been reported both in vitro and in vivo. Critical Issues: Despite the efforts made so far, only a limited number of synthetic compounds have been identified as ferroptosis inducers, and their utilization is still limited to basic research. In this review, we analyzed the most important biochemical pathways involved in ferroptosis execution, with particular attention to the newest literature findings on canonical and non-canonical hallmarks, together with mechanisms of action of natural compounds identified as novel ferroptosis inducers. Compounds have been classified based on their chemical structure, and modulation of ferroptosis-related biochemical pathways has been reported. Future Directions: The outcomes herein collected represent a fascinating starting point from which to take hints for future drug discovery studies aimed at identifying ferroptosis-inducing natural compounds for anticancer therapies. Antioxid. Redox Signal. 40, 40-85.

Effects of Natural Products on Enzymes Involved in Ferroptosis: Regulation and Implications

Ferroptosis is a form of regulated cell death that is characterized by the accumulation of iron-dependent lipid peroxides. The regulation of ferroptosis involves both non-enzymatic reactions and enzymatic mechanisms. Natural products have demonstrated potential effects on various enzymes, including GPX4, HO-1, NQO1, NOX4, GCLC, and GCLM, which are mainly involved in glutathione metabolic pathway or oxidative stress regulation, and ACSL3 and ACSL4, which mainly participate in lipid metabolism, thereby influencing the regulation of ferroptosis. In this review, we have provided a comprehensive overview of the existing literature pertaining to the effects of natural products on enzymes involved in ferroptosis and discussed their potential implications for the prevention and treatment of ferroptosis-related diseases. We also highlight the potential challenge that the majority of research has concentrated on investigating the impact of natural products on the expression of enzymes involving ferroptosis while limited attention is given to the regulation of enzyme activity. This observation underscores the considerable potential and scope for exploring the influence of natural products on enzyme activity.

GGT1 Suppresses the Development of Ferroptosis and Autophagy in Mouse Retinal Ganglion Cell Through Targeting GCLC

Background

Glaucoma is a neurodegenerative disorder characterized with optic nerve injury and the loss of retinal ganglion cells (RGCs). Ferroptosis has been proved to be associated with the degradation of RGCs. The aim of this study is to elucidate the relationship between ferroptosis and glaucoma pathogenesis, and unveil the underlying mechanism.

Methods

Methyl thiazolyl tetrazolium (MTT) assay was used to evaluate the proliferation of RGCs. The accumulation of cellular iron was measured by Iron assay kit, and the level of reactive oxygen species (ROS) was detected by fluorescence probe. The mitochondrial morphology and autophagosomes were analysed by using transmission electron microscopy (TEM). The contents of glutathione (GSH) and malondialdehyde (MDA) were tested by a GSH assay kit and an MDA detection kit, respectively. The expression of autophagy-related proteins was detected by Western blotting.

Results

A serious cell damage, aberrant iron homeostasis, and oxidative stress was shown in RGC-5 after oxygen-glucose deprivation/reoxygenation (OGD/R) treatment and gamma-Glutamyl transpeptidase 1 (GGT1) knockdown, but these effects were significantly alleviated by overexpression of GGT1 or ferroptosis inhibitors. The TEM and immunofluorescent results indicated that mitochondria impairment and autophagosome accumulation in OGD/R-treated cells was improved after GGT1 overexpression, while the phenomenon in GGT1-silenced cells was aggravated. Furthermore, we found that GGT1 can interact with glutamate cysteine ligase catalytic subunit (GCLC) to inhibit autophagy and ferroptosis in RGC-5 cells.

Conclusion

GGT1 represses autophagy in RGC-5 cells by targeting GCLC, which further restrains the development of ferroptosis in cells.

Natural Compounds and Glutathione: Beyond Mere Antioxidants

The tripeptide glutathione plays important roles in many cell processes, including differentiation, proliferation, and apoptosis; in fact, disorders in glutathione homeostasis are involved both in the etiology and in the progression of several human diseases, including cancer. Natural compounds have been found to modulate glutathione levels and function beyond their role as mere antioxidants. For example, certain compounds can upregulate the expression of glutathione-related enzymes, increase the availability of cysteine, the limiting amino acid for glutathione synthesis, or directly interact with glutathione and modulate its function. These compounds may have therapeutic potential in a variety of disease states where glutathione dysregulation is a contributing factor. On the other hand, flavonoids' potential to deplete glutathione levels could be significant for cancer treatment. Overall, while natural compounds may have potential therapeutic and/or preventive properties and may be able to increase glutathione levels, more research is needed to fully understand their mechanisms of action and their potential benefits for the prevention and treatment of several diseases. In this review, particular emphasis will be placed on phytochemical compounds belonging to the class of polyphenols, terpenoids, and glucosinolates that have an impact on glutathione-related processes, both in physiological and pathological conditions. These classes of secondary metabolites represent the most food-derived bioactive compounds that have been intensively explored and studied in the last few decades.

Role of ferroptosis in esophageal cancer and corresponding immunotherapy

Esophageal cancer (EC) is one of the most common digestive system malignancies in the world. The combined modality treatment of EC is usually surgery and radiation therapy, however, its clinical efficacy for advanced patients is relatively limited. Ferroptosis, a new type of iron-dependent programmed cell death, is different from apoptosis, necrosis and autophagy. In recent years, many studies have further enlightened that ferroptosis plays an essential role in the occurrence, development and metastasis of tumors. Targeting ferroptosis stimulates a new direction for further exploration of oncologic treatment regimens. Furthermore, ferroptosis has a critical role in the immune microenvironment of tumors. This paper reviews the mechanism of ferroptosis and the ferroptosis research progress in the treatment of EC. We further elaborate the interaction between ferroptosis and immunotherapy, and the related mechanisms of ferroptosis participation in the immunotherapy of EC, so as to provide new directions and ideas for the treatment of EC.

Molecular mechanisms of ferroptosis and its antitumor applications in natural products

Ferroptosis, an iron-dependent form of regulated cell death, results in lipid peroxidation of polyunsaturated fatty acids in the cell membrane, which is catalyzed by iron ions and accumulated to lethal levels. It is mechanistically distinct from other forms of cell death, such as apoptosis, pyroptosis, and necroptosis, so it may address the problem of cancer resistance to apoptosis and provide new therapeutic strategies for cancer treatment, which has been intensively studied over the past few years. Notably, considerable advances have been made in the antitumor research of natural products due to their multitargets and few side effects. According to research, natural products can also induce ferroptosis in cancer therapies. In this review we summarize the molecular mechanisms of ferroptosis, introduce the key regulatory genes of ferroptosis, and discuss the progress of natural product research in the field of ferroptosis to provide theoretical guidance for research on natural product-induced ferroptosis in tumors.

Oridonin impedes breast cancer growth by blocking cells in S phase and inhibiting the PI3K/AKT/mTOR signaling pathway

Breast cancer is one of the most common cancers. Oridonin, a traditional Chinese medicine, is believed to inhibit tumor growth, but its particular effects on breast cancer remain unknown. In this study, we examined oridonin's effects on 4T1, MCF-7, and MDAMB-231 cellular activity using CCK8. Scratch assays were used to detect oridonin's effects on cellular migration. Oridonin's effects on the breast cancer cell cycle were studied using flow cytometry, and expression of cell cycle related proteins p53, CDK2, and p21 was detected using Western blot assays. Metabolomics assays were used to detect changes in small molecule metabolites and metabolic pathways in breast cancer cells after treatment with oridonin. Oridonin's effects on breast cancer growth were also studied using xenograft mice. Metabolomics assays were used to detect changes in metabolites and metabolic pathways in xenograft mouse plasma in a control group, model group, and drug administration group. Experimental results showed that oridonin could significantly inhibit breast cancer growth both in vivo and in vitro. Scratch experiments showed that oridonin could inhibit breast cancer cell migration. Oridonin was also able to arrest cells in S phase by affecting several cell cycle-related proteins, including p53, CDK2, and p21. Metabolomic analysis of 4T1 cells identified a total of 33 differential metabolites, including multiple amino acids (such as l-Glutamic acid, l-Asparagine, l-Histidine, l-Valine, and l-Isoleucine). KEGG pathway enrichment analysis showed significant changes in aminoacyl-tRNA biosynthesis, and in multiple amino acid metabolic pathways. Plasma metabolomic analyses of xenograft mice revealed 28 differentially-expressed metabolites between the different animal model groups, including multiple amino acids. KEGG pathway analysis showed significant alterations in multiple amino acid metabolic pathways in oridonin-treated mice. Additionally, changes in the expression of PI3K, AKT and mTOR proteins, as well as in branched amino acids, suggest that oridonin affects the PI3K/AKT/mTOR signaling pathway by inhibiting the biosynthesis of valine, leucine and isoleucine. Taken together, our results suggest that oridonin has strong anti-tumor activity in vitro and in vivo, and has potential as an adjuvant to breast cancer treatment regimens.

Ferroptosis-modulating small molecules for targeting drug-resistant cancer: Challenges and opportunities in manipulating redox signaling

Ferroptosis is an iron-dependent cell death program that is characterized by excessive lipid peroxidation. Triggering ferroptosis has been proposed as a promising strategy to fight cancer and overcome drug resistance in antitumor therapy. Understanding the molecular interactions and structural features of ferroptosis-inducing compounds might therefore open the door to efficient pharmacological strategies against aggressive, metastatic, and therapy-resistant cancer. We here summarize the molecular mechanisms and structural requirements of ferroptosis-inducing small molecules that target central players in ferroptosis. Focus is placed on (i) glutathione peroxidase (GPX) 4, the only GPX isoenzyme that detoxifies complex membrane-bound lipid hydroperoxides, (ii) the cystine/glutamate antiporter system Xc - that is central for glutathione regeneration, (iii) the redox-protective transcription factor nuclear factor erythroid 2-related factor (NRF2), and (iv) GPX4 repression in combination with induced heme degradation via heme oxygenase-1. We deduce common features for efficient ferroptotic activity and highlight challenges in drug development. Moreover, we critically discuss the potential of natural products as ferroptosis-inducing lead structures and provide a comprehensive overview of structurally diverse biogenic and bioinspired small molecules that trigger ferroptosis via iron oxidation, inhibition of the thioredoxin/thioredoxin reductase system or less defined modes of action.

Single-cell transcriptomes reveal heterogeneity of chlorine-induced mice acute lung injury and the inhibitory effect of pentoxifylline on ferroptosis

To investigate the effect of pentoxifylline (PTX) on Chlorine (Cl₂)-induced acute lung injury (ALI) by single-cell RNA sequencing (scRNA-seq). Female BALB/c mice were exposed to Cl₂ at 400 ppm for 15 min. H&E staining was used to observe the degree of lung injury. scRNA-seq was conducted to analysis of normal and Cl₂-exposed mice lung tissues. Immunofluorescence was used to observe genes of interest. Thirty-two mice were randomly divided into four groups: Control, Cl₂, Cl₂+Fer-1, Cl₂+PTX. TEM, WB and ELISA were used to detect ferroptosis-related indicators. The 5, 8, 10, 12, 16, 20 clusters were epithelial cells and 4, 15, 18, 19, 21 clusters were endothelial cells. Pseudo-time analysis revealed the differentiation trajectory of epithelial cells and key regulatory genes (Gclc, Bpifa1, Dnah5 and Dnah9) during the process of injury. Cell-cell communication analysis identified several important receptor-ligand complexes (Nrp1-Vegfa, Nrp2-Vegfa, Flt1-Vegfa and Flt4-Vegfa). Ferroptosis were found up-regulated in epithelial and endothelial cells by GSVA analysis. Highly expressed genes to which closely related ferroptosis were found by SCENIC analysis. PTX could significantly decrease the levels of MDA and abnormal high expression of solute carrier family 7 member 11 (SLC7A11, the key transporter of cystine) as well as increase the expression of GSH/GSSG and glutathione peroxidase 4 (GPX4) (p < 0.05). This study revealed novel molecular features of Cl₂-induced ALI. PTX may be a potential specific drug by inhibiting the process of ferroptosis in epithelial and endothelial cells.

Oridonin inhibits Hela cell proliferation via downregulation of glutathione metabolism: a new insight from metabolomics

Objectives

This study aims to elucidate Oridonin' s inhibitory mechanism to cervical cancer using metabolomics methods and pharmacological assays.

Methods

Network pharmacology and KEGG pathway analysis are used to identify overlapped targets and involved metabolic pathways. UPLC-MS/MS metabolomics analysis is used to determine altered metabolites after Oridonin treatment. Other bioassays are also employed to uncover the changes in critical molecules that are highly related to altered metabolites.

Key findings

Seventy-five overlapped targets are identified between Oridonin and cervical cancer. Twenty-one metabolites involved in tricarboxylic acid cycle glutathione metabolism, branched-chain amino acid metabolism and so on changes significantly after Oridonin treatment. Oridonin treatment significantly reduces the content of cysteine and inhibit the catalytic activity of glutamine–cysteine ligase subunit, a rate-limiting enzyme for the synthesis of glutathione. As a result, the content of glutathione is also reduced. The antioxidant enzyme glutathione peroxidase 4 which uses glutathione as a cofactor, is inactivated, resulting in a burst release of reactive oxygen species. The ATP content is also significantly reduced in Hela cells after Oridonin treatment.

Conclusions

This study finds that Oridonin treatment induces Hela cell apoptosis possibly via inhibition of the glutathione metabolism.

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.

Oridonin Induces Apoptosis in Esophageal Squamous Cell Carcinoma by Inhibiting Cytoskeletal Protein LASP1 and PDLIM1

Esophageal squamous cell carcinoma is a severe malignancy for its high mortality and poor prognosis. Mainstay chemotherapies cause serious side effects for their ways of inducing cell death. Oridonin is the main bioactive constituent from natural plants that has anticancer ability and weak side effects. The proteomics method is efficient to understand the anticancer mechanism. However, proteins identified by proteomics aimed at understanding oridonin's anticancer mechanism is seldom overlapped by different groups. This study used proteomics based on two-dimensional electrophoresis sodium dodecyl sulfate-polyacrylamide gel electrophoresis (2-DE SDS-PAGE) integrated with mass spectrometry and Gene Set Enrichment Analysis (GSEA) to understand the anticancer mechanism of oridonin on esophageal squamous cell carcinoma (ESCC). The results showed that oridonin induced ESCC cell death via apoptosis by decreasing the protein expression of LASP1 and PDLIM1.

Identification of the γ-glutamyl cycle as a novel therapeutic target and 5-oxoproline as a new biomarker for diagnosing pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant solid tumours, and abnormal metabolic reprogramming in the tumour microenvironment is regarded as an important contributor to its pathogenesis.

OBJECTIVES

As there is an urgency to identify new targets based on the metabolic features that are highly refractory to PDAC treatment, this study aimed to identify suitable therapeutic targets for PDAC.

METHODS

In this study, gene set enrichment and Kyoto Encyclopedia of Genes and Genomes analyses were performed on 163 PDAC tissue samples and 165 normal pancreatic tissue samples from The Cancer Genome Atlas and Genotype-Tissue Expression databases to identify alterations in critical metabolites that may contribute to PDAC pathogenesis. Furthermore, ultra-performance liquid chromatography-tandem mass spectrometry was performed to identify significant metabolic pathways between 24 pairs of tumour and adjacent non-tumour tissues and between serum samples from PDAC patients and healthy donors.

RESULTS

Fifty-one tissue metabolites and 26 serum metabolites were altered in PDAC. Among them, those in the γ-glutamyl cycle were the most substantially changed, and 5-oxoproline was the biomarker of PDAC with the most significantly decreased levels.

CONCLUSIONS

The γ-glutamyl cycle and 5-oxoproline might be potential biomarkers and therapeutic targets to improve the diagnosis, therapy, and prognosis of PDAC.

Ferulic Acid Mitigates Growth and Invasion of Esophageal Squamous Cell Carcinoma through Inducing Ferroptotic Cell Death

Objective

Ferroptosis is an iron- and ROS-dependent form of cell death initiated by lipid peroxidation. The rapidly developing study of ferroptosis has facilitated its application in cancer therapeutics. The current study is aimed at investigating the functional property of ferulic acid (FA, a phenolic acid substance) on inducing ferroptosis in antiesophageal squamous cell carcinoma (ESCC).

Methods

ESCC cells were administrated with gradient doses of FA or with ferroptosis inhibitor deferoxamine. Cellular growth was measured with CCK-8 and colony formation experiments. LDH, caspase-3, MDA, SOD, GSH, and iron were assayed with corresponding kits. Apoptotic level was evaluated through Annexin V-FITC apoptosis staining, with migration and invasion utilizing Transwell assays. Through quantitative RT-PCR, angiogenesis-relevant genes VEGFA and PDGFB were detected. ROS generation was measured via DCFH-DA probe. Immunoblotting was conducted for monitoring ACSL4, SLC7A11, HO-1, and GPX4.

Results

FA administration observably mitigated cellular viability and colony formation capacity and motivated LDH release, caspase-3 activity, and apoptosis in EC-1 and TE-4 cells. In addition, migration and invasion together with angiogenesis of ESCC cells were restraint by FA. FA exposure led to the increase of MDA content, ROS production, and iron load as well as the reduction of SOD activity and GSH content. Also, FA augmented the activities of ACSL4 and HO-1, with lessening SLC7A11 and GPX4. Nonetheless, deferoxamine restrained the effect of FA on ESCC ferroptosis.

Conclusion

Altogether, FA may act as a ferroptosis inducer and thus attenuates cell growth and invasion of ESCC, which boosts the clinical application of FA in ESCC therapeutics.

Ferroptosis and its emerging role in esophageal cancer

The occurrence and development of tumors involve a series of life activities of cells, among which cell death has always been a crucial part in the research of tumor mechanisms and treatment methods. Ferroptosis is a non-apoptotic form of cell death, which is characterized by lipid peroxidation accumulation and further cell membrane rupture caused by excessive production of intracellular oxygen free radicals dependent on iron ions. Esophageal cancer is one of the common digestive tract tumors. Patients in the early stage are mainly treated with surgery, and the curative effect is awe-inspiring. However, surgery is far from enough for terminal patients, and it is the best choice to combine radiotherapy and chemotherapy before the operation or during the perioperative period. Although the treatment plan for patients with advanced esophageal cancer is constantly being optimized, we are disappointed at the still meager 5-year survival rate of patients and the poor quality of life. A series of complex problems, such as increased chemotherapy drug resistance and decreased radiotherapy sensitivity of esophageal cancer cells, are waiting for us to tackle. Perhaps ferroptosis can provide practical and feasible solutions and bring new hope to patients with advanced esophageal cancer. The occurrence of ferroptosis is related to the dysregulation of iron metabolism, lipid metabolism, and glutamate metabolism. Therefore, these dysregulated metabolic participant proteins and signaling pathways are essential entry points for using cellular ferroptosis to resist the occurrence and development of cancer cells. This review first introduced the main regulatory mechanisms of ferroptosis. It then summarized the current research status of ferroptosis in esophageal cancer, expecting to provide ideas for the research related to ferroptosis in esophageal cancer.

Exploring the Mechanism of Realgar against Esophageal Cancer Based on Ferroptosis Induced by ROS-ASK1-p38 MAPK Signaling Pathway

Background. Realgar (REA), a Chinese herbal decoction, has been used to treat various tumors and has produced positive outcomes; however, there is a lack of convincing evidence for the treatment of esophageal cancer. The present study aimed to investigate the effects of REA on esophageal cancer (EC) and explore its mechanism. Methods. EC cells Eca109 and KYSE150 were selected for this study, and different groups of treated cells were set up. We studied the inhibition rate and half inhibition concentration (IC50) by CCK-8 method, the clone formation assay was used to detect the clone formation ability, the scratch assay is used to determine the cell migration ability, the Transwell assay was used to detect the cell invasion ability, the protein expressions of E-cadherin, Slug, N-cadherin, ASK1, p38 MAPK, p-p38 MAPK, and GPX4 were determined using Western blot, the mRNA expressions of ASK1 and p38 MAPK were assessed using qRT-PCR, transmission electron microscopy was used to observe the cellular ultrastructure, Prussian blue staining was used to observe the intracellular iron particle distribution, and biochemical analysis of cellular MDA, SOD, GSH, and GPXS activities, flow cytometric analysis of cellular ROS levels, immunofluorescence staining to detect cellular GPX4 expression, and JC-1 method to detect mitochondrial membrane potential were used. Results. REA inhibited the proliferation of Eca109 and KYSE150 cells in a time- and concentration-dependent manner, and REA significantly inhibited the migration and invasion of Eca109 and KYSE150 cells and activated the cellular ferroptosis and ROS-ASK1-p38 MAPK signaling pathways ( $P<0.05$ ). Inhibition of activation of the ROS-ASK1-p38 MAPK signaling pathway promoted the inhibition of proliferation, migration, and invasion of Eca109 and KYSE150 cells and the induction of ferroptosis by REA. Conclusion. REA induced ferroptosis and inhibited the migration of EC cells by activating the ROS-ASK1-p38 MAPK signaling pathway.

Cancer suppression by ferroptosis and its role in digestive system tumors

Cancer is the second leading cause of death worldwide, and digestive system tumors remain the leading malignancy in China, seriously endangering national health and imposing a huge economic burden. Ferroptosis is a form of cell death characterized by increased intracellular reduced iron and accumulated lipid peroxide. Recent studies have revealed that ferroptosis is closely related to the occurrence and treatment of cancer. Therefore, this paper reviews the studies on ferroptosis and cancer to explore the potential of ferroptosis in the treatment of malignant tumors, especially digestive system tumors, and to provide a new direction for developing treatment options.

The role of ferroptosis in esophageal cancer

Esophageal cancer is one of the most common cancers with high mortality rate around the world. Although the treatment strategy of this disease has made great progress, the prognosis of advanced patients is not ideal. Ferroptosis, a novel regulatory cell death model, that is different from traditional apoptosis and characterized by increased Fenton reaction mediated by intracellular free iron and lipid peroxidation of cell membrane. Ferroptosis has been proved to be closely linked to a variety of diseases, especially cancer. This review aims to summarize the core mechanism of ferroptosis in esophageal cancer, the regulation of ferroptosis signaling pathway and its current application. At the same time, we emphasize the potential and prospect of ferroptosis in the treatment of esophageal cancer. Collectively, targeting ferroptosis pathway may provide new insights into the diagnosis, treatment and prognosis of esophageal cancer.

Hypersensitivity to ferroptosis in chromophobe RCC is mediated by a glutathione metabolic dependency and cystine import via solute carrier family 7 member 11

Chromophobe (Ch) renal cell carcinoma (RCC) arises from the intercalated cell in the distal nephron. There are no proven treatments for metastatic ChRCC. A distinguishing characteristic of ChRCC is strikingly high levels of reduced (GSH) and oxidized (GSSG) glutathione. Here, we demonstrate that ChRCC-derived cells exhibit higher sensitivity to ferroptotic inducers compared with clear-cell RCC. ChRCC-derived cells are critically dependent on cystine via the cystine/glutamate antiporter xCT to maintain high levels of glutathione, making them sensitive to inhibitors of cystine uptake and cyst(e)inase. Gamma-glutamyl transferase 1 (GGT1), a key enzyme in glutathione homeostasis, is markedly suppressed in ChRCC relative to normal kidney. Importantly, GGT1 overexpression inhibits the proliferation of ChRCC cells in vitro and in vivo, suppresses cystine uptake, and decreases levels of GSH and GSSG. Collectively, these data identify ferroptosis as a metabolic vulnerability in ChRCC, providing a potential avenue for targeted therapy for these distinctive tumors.

Medicinal Plants for the Treatment of Gastrointestinal Cancers From the Metabolomics Perspective

Gastrointestinal cancer (GIC), primarily including colorectal cancer, gastric cancer, liver cancer, pancreatic cancer, and esophageal cancer, is one of the most common causes of cancer-related deaths with increasing prevalence and poor prognosis. Medicinal plants have been shown to be a great resource for the treatment of GIC. Due to their complex manifestations of multi-component and multi-target, the underlying mechanisms how they function against GIC remain to be completely deciphered. Cell metabolism is of primary importance in the initialization and development of GIC, which is reported to be a potential target. As an essential supplement to the newest “omics” sciences, metabolomics focuses on the systematic study of the small exogenous and endogenous metabolites involved in extensive biochemical metabolic pathways of living system. In good agreement with the systemic perspective of medicinal plants, metabolomics offers a new insight into the efficacy assessment and action mechanism investigation of medicinal plants as adjuvant therapeutics for GIC therapy. In this review, the metabolomics investigations on metabolism-targeting therapies for GIC in the recent 10 years were systematically reviewed from five aspects of carbohydrate, lipid, amino acid, and nucleotide metabolisms, as well as other altered metabolisms (microbial metabolism, inflammation, and oxidation), with particular attention to the potential of active compounds, extracts, and formulae from medicinal plants. Meanwhile, the current perspectives and future challenges of metabolism-targeting therapies of medicinal plants for GIC were also discussed. In conclusion, the understanding of the action mechanisms of medicinal plants in GIC from the metabolomics perspective will contribute to the clinical application of potential candidates from the resourceful medicinal plants as novel and efficient adjuvant therapeutics for GIC therapy.

Ponicidin suppresses pancreatic cancer growth by inducing ferroptosis: Insight gained by mass spectrometry-based metabolomics

BACKGROUND

Pancreatic cancer is one of the most common malignant tumors of the digestive tract. Ponicidin, a tetracyclic diterpenoid active ingredient extracted from the traditional phytomedicine Rubescens, has high safety and great inhibitory effect on the proliferation of a variety of cancer cells, especially malignant tumor cells of the digestive tract. However, the inhibitory effect and mechanism of ponicidin on pancreatic cancer cells is still unclear. Our study aimed to use metabonomics technology to analyze and explore the suppressive effect of ponidicin against pancreatic cancer cells.

METHODS

MTT and flow cytometry were conducted to study the potential effect of ponicidin on SW1990 cells. Secondly, UPLC-MS/MS was used to analyze the small molecule metabolites and relevant differential metabolic pathways induced by ponicidin treatment. Furthermore, through the determination of glutathione peroxidase 4 (GPX4) activity and molecular docking simulation experiments, the effects of intracellular GPX4 activity and GSH/GSSG ratio after ponicidin were evaluated. Finally, the determination of the content of iron ions and malondialdehyde in cells, and the experiment of the effect of ferroptosis inhibitors on cell viability, the effect of ponicidin on the induction of ferroptosis in SW1990 cells was also detected.

RESULTS

The IC50 of ponicidin on SW1990 cells was 20 μM, which could significantly induce cell apoptosis and arrest the cells in G2/M phase. Metabolomics results showed that the contents of endogenous small molecules such as gamma-glutamylcysteine, 5-oxoproline, glutamic acid, reduced glutathione (GSH), oxidized glutathione (GSSG) and arachidonic acid have changed significantly. Main differential compounds were involved in the gamma-glutamyl cycle and polyunsaturated fatty acid metabolism of pancreatic cancer cell lines. Additionally, ponicidin could covalently bind to GSH in SW1990 cells to form a conjugate Pon-GSH, which further reduced the content of free GSH and GPX4 activity in cells. Notably, ponicidin dose-dependently increased levels of iron ions, malondialdehyde and reactive oxygen species in SW1990 cells, and the ferroptosis inhibitors could significantly block the effects of ponicidin on the proliferation of SW1990 cells.

CONCLUSION

Ponicidin could suppress the pancreatic cancer cell proliferation via inducing ferroptosis by inhibiting the gamma-glutamyl cycle and regulating the polyunsaturated fatty acid metabolism in SW1990 cells.

Cysteine as a Multifaceted Player in Kidney, the Cysteine-Related Thiolome and Its Implications for Precision Medicine

In this review encouraged by original data, we first provided in vivo evidence that the kidney, comparative to the liver or brain, is an organ particularly rich in cysteine. In the kidney, the total availability of cysteine was higher in cortex tissue than in the medulla and distributed in free reduced, free oxidized and protein-bound fractions (in descending order). Next, we provided a comprehensive integrated review on the evidence that supports the reliance on cysteine of the kidney beyond cysteine antioxidant properties, highlighting the relevance of cysteine and its renal metabolism in the control of cysteine excess in the body as a pivotal source of metabolites to kidney biomass and bioenergetics and a promoter of adaptive responses to stressors. This view might translate into novel perspectives on the mechanisms of kidney function and blood pressure regulation and on clinical implications of the cysteine-related thiolome as a tool in precision medicine.

Ferroptosis triggered by dihydroartemisinin facilitates chlorin e6 induced photodynamic therapy by inhibiting GPX4 and enhancing ROS

Photodynamic therapy (PDT) is noninvasive, low toxicity, and photo-selective, but may be resisted by malignant cells. A previous study found chlorin e6 (Ce6) mediated PDT showed drug resistance in lung cancer cells (LLC), which may be associated with PDT-induced DNA damage response (DDR). DDR may up-regulate glutathione peroxidase 4 (GPX4), which in turn degrade ROS induced by PDT. However, dihydroartemisinin (DHA) was found to down-regulate GPX4. Accordingly, the DHA was hypothesized to improve the resistance to PDT. The present work explores the mechanism of Ce6 mediated drug resistance and reveals whether DHA can enhance the efficacy of PDT by suppressing GPX4. The in vitro experiments found Ce6 treatment did not inhibit the viability of LLC within 6 hr without inducing significant apoptosis, suggesting LLC were resistant to PDT. Further investigation demonstrated PDT could damage DNA and up-regulate GPX4, thus degrading the generated ROS. DHA effectively inhibited the viability of LLC and induced apoptosis. Importantly, DHA displayed a prominent inhibitory effect on the GPX4 expression and thereby triggered ferroptosis. Combining DHA with Ce6 for treatment of LLC resulted in the suppressed GPX4 and elevated ROS. Finally, the findings showed DHA combined with Ce6 exhibited superb anti-lung cancer efficacy. In summary, Ce6 PDT damages DNA, up-regulates GPX4 to degrade ROS, thereby inducing drug resistance. Down-regulation of GPX4 by DHA-triggered ferroptosis significantly enhances the efficacy of PDT. This study provides an outstanding theoretical basis for the regulation of the intratumoral redox system and improving PDT efficacy against lung cancer by herbal monomer DHA.

Understanding the role of cysteine in ferroptosis: progress & paradoxes

Cysteine is a conditionally essential amino acid required for the synthesis of proteins and many important intracellular metabolites. Cysteine depletion can trigger iron-dependent nonapoptotic cell death-ferroptosis. Despite this, cysteine itself is normally maintained at relatively low levels within the cell, and many mechanisms that could act to buffer cysteine depletion do not appear to be especially effective or active, at least in cancer cells. How do we reconcile these seemingly paradoxical features? Here, we describe the regulation of cysteine and its contribution to ferroptosis and speculate about how the levels of this amino acid are controlled to govern nonapoptotic cell death.

The Regulatory Effects and the Signaling Pathways of Natural Bioactive Compounds on Ferroptosis

Natural bioactive compounds abundantly presented in foods and medicinal plants have recently received a remarkable attention because of their various biological activities and minimal toxicity. In recent years, many natural compounds appear to offer significant effects in the regulation of ferroptosis. Ferroptosis is the forefront of international scientific research which has been exponential growth since the term was coined. This type of regulated cell death is driven by iron-dependent phospholipid peroxidation. Recent studies have shown that numerous organ injuries and pathophysiological processes of many diseases are driven by ferroptosis, such as cancer, arteriosclerosis, neurodegenerative disease, diabetes, ischemia-reperfusion injury and acute renal failure. It is reported that the initiation and inhibition of ferroptosis plays a pivotal role in lipid peroxidation, organ damage, neurodegeneration and cancer growth and progression. Recently, many natural phytochemicals extracted from edible plants have been demonstrated to be novel ferroptosis regulators and have the potential to treat ferroptosis-related diseases. This review provides an updated overview on the role of natural bioactive compounds and the potential signaling pathways in the regulation of ferroptosis.

Terpenoids' anti-cancer effects: focus on autophagy

Terpenoids are the largest class of natural products, most of which are derived from plants. Amongst their numerous biological properties, their anti-tumor effects are of interest for they are extremely diverse which include anti-proliferative, apoptotic, anti-angiogenic, and anti-metastatic activities. Recently, several in vitro and in vivo studies have been dedicated to understanding the 'terpenoid induced autophagy' phenomenon in cancer cells. Light has already been shed on the intricacy of apoptosis and autophagy relationship. This latter crosstalk is driven by the delicate balance between activating or silencing of certain proteins whereby the outcome is expressed via interrelated signaling pathways. In this review, we focus on nine of the most studied terpenoids and on their cell death and autophagic activity. These terpenoids are grouped in three classes: sesquiterpenoid (artemisinin, parthenolide), diterpenoids (oridonin, triptolide), and triterpenoids (alisol, betulinic acid, oleanolic acid, platycodin D, and ursolic acid). We have selected these nine terpenoids among others as they belong to the different major classes of terpenoids and our extensive search of the literature indicated that they were the most studied in terms of autophagy in cancer. These terpenoids alone demonstrate the complexity by which these secondary metabolites induce autophagy via complex signaling pathways such as MAPK/ERK/JNK, PI3K/AKT/mTOR, AMPK, NF-kB, and reactive oxygen species. Moreover, induction of autophagy can be either destructive or protective in tumor cells. Nevertheless, should this phenomenon be well understood, we ought to be able to exploit it to create novel therapies and design more effective regimens in the management and treatment of cancer.

A ferroptosis-related gene signature predicts overall survival in patients with lung adenocarcinoma

Aims: To elucidate the association between ferroptosis-related genes and prognosis in patients with lung adenocarcinoma (LUAD). Materials & methods: A ferroptosis-related gene signature was made by lasso regression analysis through the LUAD datasets of the Cancer Genome Atlas. The prognostic value of the multigene signature was externally validated in the GSE72094 dataset from the Gene Expression Omnibus database. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analysis were used to explore underlying mechanisms. Results & conclusion: We established a novel ferroptosis-related gene signature for overall survival in LUAD that was predictive in both the training and validation cohorts. Immune-related pathways were significantly enriched, and immune status differed between the high- and low-risk groups. Targeting ferroptosis is a potential therapeutic option in LUAD. These results still need to be confirmed by more studies.

Role of Phytochemicals in Perturbation of Redox Homeostasis in Cancer

Over the past few decades, research on reactive oxygen species (ROS) has revealed their critical role in the initiation and progression of cancer by virtue of various transcription factors. At certain threshold values, ROS act as signaling molecules leading to activation of oncogenic pathways. However, if perturbated beyond the threshold values, ROS act in an anti-tumor manner leading to cellular death. ROS mediate cellular death through various programmed cell death (PCD) approaches such as apoptosis, autophagy, ferroptosis, etc. Thus, external stimulation of ROS beyond a threshold is considered a promising therapeutic strategy. Phytochemicals have been widely regarded as favorable therapeutic options in many diseased conditions. Over the past few decades, mechanistic studies on phytochemicals have revealed their effect on ROS homeostasis in cancer. Considering their favorable side effect profile, phytochemicals remain attractive treatment options in cancer. Herein, we review some of the most recent studies performed using phytochemicals and, we further delve into the mechanism of action enacted by individual phytochemicals for PCD in cancer.