The Lipogenic Regulator SREBP2 Induces Transferrin in Circulating Melanoma Cells and Suppresses Ferroptosis

The Regulators of Peroxisomal Acyl-Carnitine Shuttle CROT and CRAT Promote Metastasis in Melanoma

Circulating tumor cells are the key link between a primary tumor and distant metastases, but once in the bloodstream, loss of adhesion induces cell death. To identify the mechanisms relevant for melanoma circulating tumor cell survival, we performed RNA sequencing and discovered that detached melanoma cells and isolated melanoma circulating tumor cells rewire lipid metabolism by upregulating fatty acid (FA) transport and FA beta-oxidation‒related genes. In patients with melanoma, high expression of FA transporters and FA beta-oxidation enzymes significantly correlates with reduced progression-free and overall survival. Among the highest expressed regulators in melanoma circulating tumor cells were the carnitine transferases carnitine O-octanoyltransferase and carnitine acetyltransferase, which control the shuttle of peroxisome-derived medium-chain FAs toward mitochondria to fuel mitochondrial FA beta-oxidation. Knockdown of carnitine O-octanoyltransferase or carnitine acetyltransferase and short-term treatment with peroxisomal or mitochondrial FA beta-oxidation inhibitors thioridazine or ranolazine suppressed melanoma metastasis in mice. Carnitine O-octanoyltransferase and carnitine acetyltransferase depletion could be rescued by medium-chain FA supplementation, indicating that the peroxisomal supply of FAs is crucial for the survival of nonadherent melanoma cells. Our study identifies targeting the FA-based cross-talk between peroxisomes and mitochondria as a potential therapeutic opportunity to challenge melanoma progression. Moreover, the discovery of the antimetastatic activity of the Food and Drug Administration‒approved drug ranolazine carries translational potential.

Targeting lipid metabolism for ferroptotic cancer therapy

It has been 10 years since the concept of ferroptosis was put forward and research focusing on ferroptosis has been increasing continuously. Ferroptosis is driven by iron-dependent lipid peroxidation, which can be antagonized by glutathione peroxidase 4 (GPX4), ferroptosis inhibitory protein 1 (FSP1), dihydroorotate dehydrogenase (DHODH) and Fas-associated factor 1 (FAF1). Various cellular metabolic events, including lipid metabolism, can modulate ferroptosis sensitivity. It is worth noting that the reprogramming of lipid metabolism in cancer cells can promote the occurrence and development of tumors. The metabolic flexibility of cancer cells opens the possibility for the coordinated targeting of multiple lipid metabolic pathways to trigger cancer cells ferroptosis. In addition, cancer cells must obtain immortality, escape from programmed cell death including ferroptosis, to promote cancer progression, which provides new perspectives for improving cancer therapy. Targeting the vulnerability of ferroptosis has received attention as one of the significant possible strategies to treat cancer given its role in regulating tumor cell survival. We review the impact of iron and lipid metabolism on ferroptosis and the potential role of the crosstalk of lipid metabolism reprogramming and ferroptosis in antitumor immunity and sum up agents targeting lipid metabolism and ferroptosis for cancer therapy.

A mechanistic investigation about hepatoxic effects of borneol using zebrafish

Except for clinical value, borneol is routinely used in food and cosmetics with seldom safety evaluation. To investigate its hepatoxicity, we exposed 3 dpf (days post fertilization) larval zebrafish to borneol at a gradient of concentrations (200-500 μM) for 3 days. Herein, our results revealed that high doses of borneol (300-500 μM) caused liver size decrease or lateral lobe absence. Borneol also seriously disturbed the hepatic protein metabolism presented with the increased activity of alanine aminotransferase (ALT) and lipid metabolism shown with the increased level of triglycerides (TG) and total cholesterol (TC). The lipid accumulation (oil red staining) was detected as well. Additionally, significant upregulation of genes was detected that related to oxidative stress, lipid anabolism, endoplasmic reticulum stress (ERS), and autophagy. Conversely, the lipid metabolism-related genes were markedly downregulated. Moreover, the changes in the superoxide dismutase activity and the level of glutathione and malondialdehyde raised the likelihood of lipid peroxidation. The outcomes indicated the involvement of oxidative stress, ERS, lipid metabolism, and autophagy in borneol-induced lipid metabolic disorder and hepatic injury. This study will provide a more comprehensive understanding of borneol hepatoxicity and the theoretical basis for the safe use of this compound.

Ferrostatin-1 attenuates pathological angiogenesis in oxygen-induced retinopathy via inhibition of ferroptosis

Retinopathy of prematurity (ROP) is a vision-threatening ocular disease that occurs in premature infants, but the underlying mechanism is still unclear. Since oxidative stress has been well documented in the ROP development, we aimed to investigate whether ferroptosis, a new type of cell death characterized by lipid peroxidation and iron overload, is also involved in ROP. We detected the lipid peroxidation, oxidative stress and the expression of ferroptosis markers in the retina of mouse model of oxygen-induced retinopathy. After ferroptosis inhibitor, ferrostatin-1, was administered by intravitreal injection, ferroptosis marker, lipid peroxidation, retinal vasculature and glial cell activation were examined. We found decreased expression of SLC7A11 and GPX4, increased expression of FTH1 and TFRC, as well as increase of lipid peroxidation in the retina of OIR mice. Ferrostatin-1 administration significantly reduced lipid peroxidation, and also reversed the change of ferroptosis marker. Neovascular area and avascular area were suppressed and the pathological vasculature changes including acellular vessels and ghost pericytes were decreased. Microglial cell and Müller cell activation was not evidently influenced by ferrostatin-1 treatment. Our findings suggest that ferroptosis is involved in the pathological angiogenesis and might be a promising target for ROP therapy.

Gut flora disequilibrium promotes the initiation of liver cancer by modulating tryptophan metabolism and up-regulating SREBP2

The gut microbiota and liver cancer have a complex interaction. However, the role of gut microbiome in liver tumor initiation remains unknown. Herein, liver cancer was induced using hydrodynamic transfection of oncogenes to explore liver tumorigenesis in mice. Gut microbiota depletion promoted liver tumorigenesis but not progression. Elevated sterol regulatory element-binding protein 2 (SREBP2) was observed in mice with gut flora disequilibrium. Pharmacological inhibition of SREBP2 or Srebf2 RNA interference attenuated mouse liver cancer initiation under gut flora disequilibrium. Furthermore, gut microbiota depletion impaired gut tryptophan metabolism to activate aryl hydrocarbon receptor (AhR). AhR agonist Ficz inhibited SREBP2 posttranslationally and reversed the tumorigenesis in mice. And, AhR knockout mice recapitulated the accelerated liver tumorigenesis. Supplementation with Lactobacillus reuteri, which produces tryptophan metabolites, inhibited SREBP2 expression and tumorigenesis in mice with gut flora disequilibrium. Thus, gut flora disequilibrium promotes liver cancer initiation by modulating tryptophan metabolism and up-regulating SREBP2.

Deciphering functional tumor states at single-cell resolution

Within a tumor, cancer cells exist in different states that are associated with distinct tumor functions, including proliferation, differentiation, invasion, metastasis, and resistance to anti-cancer therapy. The identification of the gene regulatory networks underpinning each state is essential for better understanding functional tumor heterogeneity and revealing tumor vulnerabilities. Here, we review the different studies identifying tumor states by single-cell sequencing approaches and the mechanisms that promote and sustain these functional states and regulate their transitions. We also describe how different tumor states are spatially distributed and interact with the specific stromal cells that compose the tumor microenvironment. Finally, we discuss how the understanding of tumor plasticity and transition states can be used to develop new strategies to improve cancer therapy.

Ferroptosis: a potential therapeutic target for Alzheimer's disease

The most prevalent dementia-causing neurodegenerative condition is Alzheimer's disease (AD). The aberrant buildup of amyloid β and tau hyperphosphorylation are the two most well-known theories about the mechanisms underlying AD development. However, a significant number of pharmacological clinical studies conducted around the world based on the two aforementioned theories have not shown promising outcomes, and AD is still not effectively treated. Ferroptosis, a non-apoptotic programmed cell death defined by the buildup of deadly amounts of iron-dependent lipid peroxides, has received more attention in recent years. A wealth of data is emerging to support the role of iron in the pathophysiology of AD. Cell line and animal studies applying ferroptosis modulators to the treatment of AD have shown encouraging results. Based on these studies, we describe in this review the underlying mechanisms of ferroptosis; the role that ferroptosis plays in AD pathology; and summarise some of the research advances in the treatment of AD with ferroptosis modulators. We hope to contribute to the clinical management of AD.

Ferroptosis and triple-negative breast cancer: Potential therapeutic targets

PURPOSE

Triple-negative breast cancer (TNBC) is an aggressive tumor with poor prognosis, it has higher recurrence and metastatic rates than other breast cancer subtypes. This study aims to investigate biomarkers and potential targets for TNBC related to ferroptosis through data mining and bioinformatics analysis. The findings may provide new insights for treating TNBC.

METHODS

The TNBC patients' data from the Cancer Genome Atlas (TCGA) database were extracted for differential expression and prognosis analysis. Consensus genes obtained by intersecting differential expressed and ferroptosis-related genes was used to establish the prognostic model by the univariate and multivariate Cox analyses. Besides, TNBC data from the Gene Expression Omnibus (GEO) database was used to confirm the reliability of the prognosis model. Moreover, clinical information was analyzed by multifactorial independent analysis to identify independent prognostic factors. The expression of genes constituting the prognostic model was further validated using the Human Protein Atlas (HPA) database. Finally, the Comparative Toxicogenomic Data (CTD) database was used to explore possible treatment drugs for TNBC.

RESULTS

We obtained 13,245 differential expressed genes, and 177 consensus genes. 98 genes with prognostic implication were obtained by univariable Cox. Then, a prognostic model including 12 ferroptosis-related genes was constructed by multivariable Cox. The area under curve (AUC) value of the prognostic model for TNBC was 0.82. The GEO database validated that the model (AUC = 0.77) could predict the patient outcomes. The staining results of 10 out of 12 prognostic model genes in HPA database showed that their expression was consistent with our predictions. Clinical risk analysis indicated that risk score of patients could act as an independent prognostic factor. Finally, six drugs that may have interaction with 12 ferroptosis-related genes were obtained using the CTD database.

CONCLUSION

The prognostic model composed of 12 ferroptosis-related genes could predict the prognosis of TNBC patients, and seven genes (ASNS, LAMP2, CAV1, DPP4, HELLS, TF, ZFP69B) could be potential new therapeutic targets for TNBC, and two drugs (1-methyl-3-isobutylxanthine, rosiglitazone) could act as potential therapeutic drugs for the treatment of TNBC.

Molecular mechanisms of ferroptosis and the potential therapeutic targets of ferroptosis signaling pathways for glioblastoma

Ferroptosis is a newly identified form of cell death that differs from autophagy, apoptosis and necrosis, and its molecular characteristics include iron-dependent lipid reactive oxygen species accumulation, mitochondrial morphology changes, and membrane permeability damage. These characteristics are closely related to various human diseases, especially tumors of the nervous system. Glioblastoma is the most common primary malignant tumor of the adult central nervous system, and the 5-year survival rate is only 4%-5%. This study reviewed the role and mechanism of ferroptosis in glioblastoma and the research status and progress on ferroptosis as a potential therapeutic target. The mechanism of ferroptosis is related to the intracellular iron metabolism level, lipid peroxide content and glutathione peroxidase 4 activity. It is worth exploring how ferroptosis can be applied in disease treatment; however, the relation between ferroptosis and other apoptosis methods is poorly understood and methods of applying ferroptosis to drug-resistant tumors are insufficient. Ferroptosis is a promising therapeutic target for glioblastoma. In-depth studies of its mechanism of action in glioblastoma and applications for clinical treatment are expected to provide insights for glioblastoma patients.

Targeting Wnt/β-Catenin Signaling Exacerbates Ferroptosis and Increases the Efficacy of Melanoma Immunotherapy via the Regulation of MITF

Melanoma is the most lethal form of skin cancer, resulting from the malignant transformation of epidermal melanocytes. Recent revolutionary progress in targeted therapy and immunotherapy has prominently improved the treatment outcome, but the survival of melanoma patients remains suboptimal. Ferroptosis is greatly involved in cancer pathogenesis and can execute the outcome of immunotherapy. However, the detailed regulatory mechanisms of melanoma cell ferroptosis remain elusive. Herein, we report that Wnt/β-catenin signaling regulates ferroptosis and melanoma immunotherapy efficacy via the regulation of MITF. First of all, we found that Wnt/β-catenin signaling was prominently suppressed in melanoma cell ferroptosis. Then, we proved that targeting β-catenin exacerbated melanoma cell ferroptosis by promoting the generation of lipid peroxidation both in vitro and in vivo. Subsequent mechanistic studies revealed that MITF mediated the effect of Wnt/β-catenin signaling on melanoma cell ferroptosis, and PGC1α and SCD1 were documented as two main effectors downstream of Wnt/β-catenin-MITF pathway. Ultimately, pharmacological inhibition of β-catenin or MITF increased the efficacy of anti-PD-1 immunotherapy in preclinical xenograft tumor model by promoting ferroptosis. Taken together, Wnt/β-catenin signaling deficiency exacerbates ferroptosis in melanoma via the regulation of MITF. Targeting Wnt/β-catenin-MITF pathway could be a promising strategy to potentiate ferroptosis and increase the efficacy of anti-PD-1 immunotherapy.

Deubiquitinase USP35 stabilizes BRPF1 to activate mevalonate (MVA) metabolism during prostate tumorigenesis

The mutual interplay between epigenetic modifications and metabolic rewiring contributes to malignant features of prostate adenocarcinoma (PRAD). This study aimed to uncover the biological roles of deubiquitylase USP35 in PRAD and find effective epigenetic or metabolic targets. Bioinformatic tools or methods revealed that USP35 is upregulated in PRAD samples and correlates with inferior prognosis. The in vitro and in vivo assays suggested that USP35 could enhance malignant features of PRAD cells. Mechanistically, we found that USP35 could directly deubiquitinate and stabilize BRPF1 proteins. USP35 depends on accumulated BRPF1 proteins to accelerate cell growth, stem-like properties, and migration in vitro and in vivo. Interestingly, high BRPF1 could bind to promoter of SREBP2 and activate the SREBP2 transcriptional capacity. Therefore, USP35/BRPF1 aixs could promote expressions of mevalonate (MVA) metabolism signature in a SREBP2-dependent manner. USP35 depends on BRPF1 to maintain the activity of mevalonate metabolism in PRAD cells. Last of all, we observed that targeting BRPF1 or using MVA inhibitor (atorvastatin) are effective to suppress USP35high PRAD in vivo tumor growth. USP35 is an indicator of MVA metabolic signature in PRAD. Collectively, our study highlighted the USP35/BRPF1/SREBP2 axis in modulating MVA metabolism in PRAD, suggesting the significance of BRPF1 or MVA as the potential therapeutic targets for PRAD treatment.

Integrative insights and clinical applications of single-cell sequencing in cancer immunotherapy

Recently, immunotherapy has gained increasing popularity in oncology. Several immunotherapies obtained remarkable clinical effects, but the efficacy varied, and only subsets of cancer patients benefited. Breaking the constraints and improving immunotherapy efficacy is extremely important in precision medicine. Whereas traditional sequencing approaches mask the characteristics of individual cells, single-cell sequencing provides multiple dimensions of cellular characterization at the single-cell level, including genomic, transcriptomic, epigenomic, proteomic, and multi-omics. Hence, the complexity of the tumor microenvironment, the universality of tumor heterogeneity, cell composition and cell-cell interactions, cell lineage tracking, and tumor drug resistance mechanisms are revealed in-depth. However, the clinical transformation of single-cell technology is not to the point of in-depth study, especially in the application of immunotherapy. The newly discovered vital cells and tremendous biomarkers facilitate the development of more efficient individualized therapeutic regimens to guide clinical treatment and predict prognosis. This review provided an overview of the progress in distinct single-cell sequencing methods and emerging strategies. For perspective, the expanding utility of combining single-cell sequencing and other technologies was discussed.

Role of ferroptosis on tumor progression and immunotherapy

Ferroptosis is triggered by intracellular iron leading to accumulation of lipid peroxidation consequent promotion of cell death. Cancer cell exhibits ability to evade ferroptosis by activation of antioxidant signaling pathways such as SLC7A11/GPX4 axis. In addition to transcriptional regulation on ferroptosis by NRF2, SREBP1, YAP, and p53, ferroptosis is modulated by ubiquitination or autophagic degradation. Moreover, zinc or Ca²⁺ could modulate ferroptosis by inducing lipid peroxidation and ferroptosis. Induction of ferroptosis enhances immune cell activity such as T cells or macrophages, which is associated with the release of DAMPs (damage-associated molecular patterns) and IFNγ. Therefore, combined immune checkpoint inhibitors with ferroptosis inducers effectively enhance antitumor immunotherapy, whereas induction of ferroptosis could impair T cell activity or survival, suggesting that rational combined therapy for cancer is essential. In this review, we discussed the regulatory role of ferroptosis on tumor progression and immunotherapy.

Targeting breast and pancreatic cancer metastasis using a dual-cadherin antibody

The successful application of antibody-based therapeutics in either primary or metastatic cancer depends upon the selection of rare cell surface epitopes that distinguish cancer cells from surrounding normal epithelial cells. By contrast, as circulating tumor cells (CTCs) transit through the bloodstream, they are surrounded by hematopoietic cells with dramatically distinct cell surface proteins, greatly expanding the number of targetable epitopes. Here, we show that an antibody (23C6) against cadherin proteins effectively suppresses blood-borne metastasis in mouse isogenic and xenograft models of triple negative breast and pancreatic cancers. The 23C6 antibody is remarkable in that it recognizes both the epithelial E-cadherin (CDH1) and mesenchymal OB-cadherin (CDH11), thus overcoming considerable heterogeneity across tumor cells. Despite its efficacy against single cells in circulation, the antibody does not suppress primary tumor formation, nor does it elicit detectable toxicity in normal epithelial organs, where cadherins may be engaged within intercellular junctions and hence inaccessible for antibody binding. Antibody-mediated suppression of metastasis is comparable in matched immunocompetent and immunodeficient mouse models. Together, these studies raise the possibility of antibody targeting CTCs within the vasculature, thereby suppressing blood-borne metastasis.

Ferroptotic MSCs protect mice against sepsis via promoting macrophage efferocytosis

The therapeutic effect of mesenchymal stem cells (MSCs) on sepsis has been well-known. However, a comprehensive understanding of the relationship between MSCs and macrophages remains elusive. Superparamagnetic iron oxide (SPIO) is one of the most commonly used tracers for MSCs. Our previous study has shown that SPIO enhanced the therapeutic effect of MSCs in a macrophage-dependent manner. However, the fate of SPIO-labeled MSCs (MSC^SPIO) after infusion remains unknown and the direct interaction between MSC^SPIO and macrophages remains unclear. Mice were injected intravenously with MSC^SPIO at 2 h after Escherichia coli infection and sacrificed at different times to investigate their distribution and therapeutic effect. We found that MSC^SPIO homed to lungs rapidly after infusion and then trapped in livers for more than 10 days. Only a few MSC^SPIO homed to the spleen and there was no MSC^SPIO detectable in the brain, heart, kidney, colon, and uterus. MSC^SPIO tended to stay longer in injured organs compared with healthy organs and played a long-term protective role in sepsis. The mRNA expression profiles between MSCs and MSC^SPIO were rather different, genes related to lipid metabolism, inflammation, and oxidative stress were changed. The levels of ROS and lipid peroxide were elevated in MSC^SPIO, which confirmed that SPIO-induced ferroptosis in MSC^SPIO. Ferroptosis of MSC^SPIO induced by SPIO enhanced the efferocytosis of macrophages and thus enhanced the protective effect on septic mice, while the benefits were impaired after MSC^SPIO were treated with Ferrostatin-1 (Fer-1) or Liproxtatin-1 (Lip-1), the inhibitors of ferroptosis. SPIO-induced ferroptosis in MSCs contributes to better therapeutic effects in sepsis by enhancing the efferocytosis of macrophages. Our data showed the efficacy and advantage of MSC^SPIO as a therapeutic tool and the cell states exert different curative effects on sepsis.

Crosstalk between regulated necrosis and micronutrition, bridged by reactive oxygen species

The discovery of regulated necrosis revitalizes the understanding of necrosis from a passive and accidental cell death to a highly coordinated and genetically regulated cell death routine. Since the emergence of RIPK1 (receptor-interacting protein kinase 1)-RIPK3-MLKL (mixed lineage kinase domain-like) axis-mediated necroptosis, various other forms of regulated necrosis, including ferroptosis and pyroptosis, have been described, which enrich the understanding of pathophysiological nature of diseases and provide novel therapeutics. Micronutrients, vitamins, and minerals, position centrally in metabolism, which are required to maintain cellular homeostasis and functions. A steady supply of micronutrients benefits health, whereas either deficiency or excessive amounts of micronutrients are considered harmful and clinically associated with certain diseases, such as cardiovascular disease and neurodegenerative disease. Recent advance reveals that micronutrients are actively involved in the signaling pathways of regulated necrosis. For example, iron-mediated oxidative stress leads to lipid peroxidation, which triggers ferroptotic cell death in cancer cells. In this review, we illustrate the crosstalk between micronutrients and regulated necrosis, and unravel the important roles of micronutrients in the process of regulated necrosis. Meanwhile, we analyze the perspective mechanism of each micronutrient in regulated necrosis, with a particular focus on reactive oxygen species (ROS).

Ferroptosis in sepsis: The mechanism, the role and the therapeutic potential

Sepsis is a common critical illness in the Intensive care unit(ICU) and its management and treatment has always been a major challenge in critical care medicine. The dysregulated host response to infection, causing systemic multi-organ and multi-system damage is the main pathogenesis. Notably, intense stress during sepsis can lead to metabolic disturbances of ions, lipids and energy in the organism. Ferroptosis is an iron-dependent, non-apoptotic cell death distinguished by a disruption of iron metabolism and iron-dependent accumulation of lipid peroxides. Mounting researches have established that ferroptosis has an essential part in anti-inflammatory and sepsis, and drugs targeting ferroptosis-related molecules, such as ferroptosis inhibitors, are gradually proving their effectiveness in sepsis. This paper summarizes and reviews the pathogenesis of ferroptosis, its regulatory network, and its vital involvement in the initiation of sepsis and related organ damage, and finally discusses the possible target drugs provided by the above mechanisms, describes the dilemmas as well as the outlook, in the hope of finding more links between ferroptosis and sepsis and providing new perspectives for the future treatment of sepsis.

Non-coding RNAs in necroptosis, pyroptosis, and ferroptosis in cardiovascular diseases

Accumulating evidence has proved that non-coding RNAs (ncRNAs) play a critical role in the genetic programming and gene regulation of cardiovascular diseases (CVDs). Cardiovascular disease morbidity and mortality are rising and have become a primary public health issue that requires immediate resolution through effective intervention. Numerous studies have revealed that new types of cell death, such as pyroptosis, necroptosis, and ferroptosis, play critical cellular roles in CVD progression. It is worth noting that ncRNAs are critical novel regulators of cardiovascular risk factors and cell functions by mediating pyroptosis, necroptosis, and ferroptosis. Thus, ncRNAs can be regarded as promising therapeutic targets for treating and diagnosing cardiovascular diseases. Recently, there has been a surge of interest in the mediation of ncRNAs on three types of cell death in regulating tissue homeostasis and pathophysiological conditions in CVDs. Although our understanding of ncRNAs remains in its infancy, the studies reviewed here may provide important new insights into how ncRNAs interact with CVDs. This review summarizes what is known about the functions of ncRNAs in modulating cell death-associated CVDs and their role in CVDs, as well as their current limitations and future prospects.

Mutant p53, the Mevalonate Pathway and the Tumor Microenvironment Regulate Tumor Response to Statin Therapy

Tumor cells have the ability to co-opt multiple metabolic pathways, enhance glucose uptake and utilize aerobic glycolysis to promote tumorigenesis, which are characteristics constituting an emerging hallmark of cancer. Mutated tumor suppressor and proto-oncogenes are frequently responsible for enhanced metabolic pathway signaling. The link between mutant p53 and the mevalonate (MVA) pathway has been implicated in the advancement of various malignancies, with tumor cells relying heavily on increased MVA signaling to fuel their rapid growth, metastatic spread and development of therapy resistance. Statin drugs inhibit HMG-CoA reductase, the pathway’s rate-limiting enzyme, and as such, have long been studied as a potential anti-cancer therapy. However, whether statins provide additional anti-cancer properties is worthy of debate. Here, we examine retrospective, prospective and pre-clinical studies involving the use of statins in various cancer types, as well as potential issues with statins’ lack of efficacy observed in clinical trials and future considerations for upcoming clinical trials.

Targeting of the Lipid Metabolism Impairs Resistance to BRAF Kinase Inhibitor in Melanoma

Drug resistance limits the achievement of persistent cures for the treatment of melanoma, in spite of the efficacy of the available drugs. The aim of the present study was to explore the involvement of lipid metabolism in melanoma resistance and assess the effects of its targeting in cellular models of melanoma with acquired resistance to the BRAF-inhibitor PLX4032/Vemurafenib. Since transcriptional profiles pointed to decreased cholesterol and fatty acids synthesis in resistant cells as compared to their parental counterparts, we examined lipid composition profiles of resistant cells, studied cell growth dependence on extracellular lipids, assessed the modulation of enzymes controlling the main nodes in lipid biosynthesis, and evaluated the effects of targeting Acetyl-CoA Acetyltransferase 2 (ACAT2), the first enzyme in the cholesterol synthesis pathway, and Acyl-CoA Cholesterol Acyl Transferase (ACAT/SOAT), which catalyzes the intracellular esterification of cholesterol and the formation of cholesteryl esters. We found a different lipid composition in the resistant cells, which displayed reduced saturated fatty acids (SFA), increased monounsaturated (MUFA) and polyunsaturated (PUFA), and reduced cholesteryl esters (CE) and triglycerides (TG), along with modulated expression of enzymes regulating biosynthetic nodes of the lipid metabolism. The effect of tackling lipid metabolism pathways in resistant cells was evidenced by lipid starvation, which reduced cell growth, increased sensitivity to the BRAF-inhibitor PLX4032, and induced the expression of enzymes involved in fatty acid and cholesterol metabolism. Molecular targeting of ACAT2 or pharmacological inhibition of SOAT by avasimibe showed antiproliferative effects in melanoma cell lines and a synergistic drug interaction with PLX4032, an effect associated to increased ferroptosis. Overall, our findings reveal that lipid metabolism affects melanoma sensitivity to BRAF inhibitors and that extracellular lipid availability may influence tumor cell response to treatment, a relevant finding in the frame of personalized therapy. In addition, our results indicate new candidate targets for drug combination treatments.

An overview of ferroptosis in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a public health problem associated with high mortality and high morbidity rates worldwide. Presently, its complex pathophysiology is still unclear, and there is no specific drug to reverse NAFLD. Ferroptosis is an iron-dependent and non-apoptotic form of cell death characterized by the iron-induced accumulation of lipid reactive oxygen species (ROS), which damage nucleic acids, proteins, and lipids; generate intracellular oxidative stress; and ultimately cause cell death. Emerging evidence indicates that ferroptosis is involved in the progression of NAFLD, although the mechanism of action of ferroptosis in NAFLD is still poorly understood. Herein, we summarize the mechanism of action of ferroptosis in certain diseases, especially in the pathogenesis of NAFLD, and discuss the potential therapeutic approaches currently used to treat NAFLD. This review also highlights further directions for the treatment and prevention of NAFLD and related diseases.

Targeting Ferroptosis Pathway to Combat Therapy Resistance and Metastasis of Cancer

Ferroptosis is an iron-dependent regulated form of cell death caused by excessive lipid peroxidation. This form of cell death differed from known forms of cell death in morphological and biochemical features such as apoptosis, necrosis, and autophagy. Cancer cells require higher levels of iron to survive, which makes them highly susceptible to ferroptosis. Therefore, it was found to be closely related to the progression, treatment response, and metastasis of various cancer types. Numerous studies have found that the ferroptosis pathway is closely related to drug resistance and metastasis of cancer. Some cancer cells reduce their susceptibility to ferroptosis by downregulating the ferroptosis pathway, resulting in resistance to anticancer therapy. Induction of ferroptosis restores the sensitivity of drug-resistant cancer cells to standard treatments. Cancer cells that are resistant to conventional therapies or have a high propensity to metastasize might be particularly susceptible to ferroptosis. Some biological processes and cellular components, such as epithelial–mesenchymal transition (EMT) and noncoding RNAs, can influence cancer metastasis by regulating ferroptosis. Therefore, targeting ferroptosis may help suppress cancer metastasis. Those progresses revealed the importance of ferroptosis in cancer, In order to provide the detailed molecular mechanisms of ferroptosis in regulating therapy resistance and metastasis and strategies to overcome these barriers are not fully understood, we described the key molecular mechanisms of ferroptosis and its interaction with signaling pathways related to therapy resistance and metastasis. Furthermore, we summarized strategies for reversing resistance to targeted therapy, chemotherapy, radiotherapy, and immunotherapy and inhibiting cancer metastasis by modulating ferroptosis. Understanding the comprehensive regulatory mechanisms and signaling pathways of ferroptosis in cancer can provide new insights to enhance the efficacy of anticancer drugs, overcome drug resistance, and inhibit cancer metastasis.

Caspase-3-induced activation of SREBP2 drives drug resistance via promotion of cholesterol biosynthesis in hepatocellular carcinoma

Accumulating evidence has demonstrated that drug resistance can be acquired in cancer through the repopulation of tumors by cancer stem cell (CSC) expansion. Here, we investigated mechanisms driving resistance and CSC repopulation in hepatocellular carcinoma (HCC) as a cancer model using two drug-resistant, patient-derived tumor xenografts that mimicked the development of acquired resistance to sorafenib or lenvatinib treatment observed in HCC patients. RNA sequencing analysis revealed that cholesterol biosynthesis was most commonly enriched in the drug-resistant xenografts. Comparison of the genetic profiles of CD133+ stem cells and CD133- bulk cells from liver regeneration and HCC mouse models showed that the cholesterol pathway was preferentially upregulated in liver CSCs compared to normal liver stem cells. Consistently, SREBP2-mediated cholesterol biosynthesis was crucial for the augmentation of liver CSCs, and loss of SREBP2 conferred sensitivity to tyrosine kinase inhibitors, suggesting a role in regulation of acquired drug resistance in HCC. Similarly, exogenous cholesterol-treated HCC cells showed enhanced cancer stemness abilities and drug resistance. Mechanistically, caspase-3 (CASP3)-mediated cleavage of SREBP2 from the endoplasmic reticulum to promote cholesterol biosynthesis, which consequently caused resistance to sorafenib/lenvatinib treatment by driving activation of the sonic hedgehog signaling pathway. Simvastatin, an FDA-approved cholesterol-lowering drug, not only suppressed HCC tumor growth but also sensitized HCC cells to sorafenib. These findings demonstrate that CSC populations in HCC expand via CASP3-dependent, SREBP2-mediated cholesterol biosynthesis in response to tyrosine kinase inhibitor therapy and that targeting cholesterol biosynthesis can overcome acquired drug resistance.

Dyslipidemia in Children Treated with a BRAF Inhibitor for Low-Grade Gliomas: A New Side Effect?

BRAF inhibitors, in recent years, have played a central role in the disease control of unresectable BRAF-mutated pediatric low-grade gliomas (LGGs). The aim of the study was to investigate the acute and long-term effects of vemurafenib on the lipid metabolism in children treated for an LGG. In our cohort, children treated with vemurafenib (n = 6) exhibited alterations in lipid metabolism a few weeks after starting, as was demonstrated after 1 month (n = 4) by the high plasma levels of the total cholesterol (TC = 221.5 ± 42.1 mg/dL), triglycerides (TG = 107.8 ± 44.4 mg/dL), and low-density lipoprotein (LDL = 139.5 ± 51.5 mg/dL). Despite dietary recommendations, the dyslipidemia persisted over time. The mean lipid levels of the TC (222.3 ± 34.7 mg/dL), TG (134.8 ± 83.6 mg/dL), and LDL (139.8 ± 46.9 mg/dL) were confirmed abnormal at the last follow-up (45 ± 27 months, n = 6). Vemurafenib could be associated with an increased risk of dyslipidemia. An accurate screening strategy in new clinical trials, and a multidisciplinary team, are required for the optimal management of unexpected adverse events, including dyslipidemia.

Wnt/beta-catenin signaling confers ferroptosis resistance by targeting GPX4 in gastric cancer

The development of chemotherapy resistance is the most vital obstacle to clinical efficacy in gastric cancer (GC). The dysregulation of the Wnt/beta-catenin signaling pathway is critically associated with GC development and chemotherapy resistance. Ferroptosis is a form of regulated cell death, induced by an iron-dependent accumulation of lipid peroxides during chemotherapy. However, whether the Wnt/beta-catenin signaling directly controls resistance to cell death, remains unclear. Here, we show that the activation of the Wnt/beta-catenin signaling attenuates cellular lipid ROS production and subsequently inhibits ferroptosis in GC cells. The beta-catenin/TCF4 transcription complex directly binds to the promoter region of GPX4 and induces its expression, resulting in the suppression of ferroptotic cell death. Concordantly, TCF4 deficiency promotes cisplatin-induced ferroptosis in vitro and in vivo. Thus, we demonstrate that the aberrant activation of the Wnt/beta-catenin signaling confers ferroptosis resistance and suggests a potential therapeutic strategy to enhance chemo-sensitivity for advanced GC patients.

The Relationship of Redox With Hallmarks of Cancer: The Importance of Homeostasis and Context

Redox homeostasis is a lifelong pursuit of cancer cells. Depending on the context, reactive oxygen species (ROS) exert paradoxical effects on cancers; an appropriate concentration stimulates tumorigenesis and supports the progression of cancer cells, while an excessive concentration leads to cell death. The upregulated antioxidant system in cancer cells limits ROS to a tumor-promoting level. In cancers, redox regulation interacts with tumor initiation, proliferation, metastasis, programmed cell death, autophagy, metabolic reprogramming, the tumor microenvironment, therapies, and therapeutic resistance to facilitate cancer development. This review discusses redox control and the major hallmarks of cancer.

Cell Lines of Circulating Tumor Cells: What Is Known and What Needs to Be Resolved

The importance of circulating tumor cells (CTC) is well recognized. However, the biological characteristics of CTC in the bloodstream have not yet been examined in detail, due to the limited number of CTC cell lines currently available. Thirty-nine CTC cell lines were reported by 2021. For successful cell culturing, these CTC cell lines were reviewed. Previous studies on short-term cultures of CTC also analyzed approaches for establishing the long-term culture of CTC. Negative selection, hypoxic conditions, three-dimensional conditions, and careful management are preferable for the long-term culture of CTC. However, the establishment of CTC cell lines is dependent on the specific characteristics of each cell type. Therefore, a method to establish CTC cell lines has not yet been developed. Further efforts are needed to resolve this issue.

Targeting Cancer Cell Ferroptosis to Reverse Immune Checkpoint Inhibitor Therapy Resistance

In recent years, cancer therapies using immune checkpoint inhibitors (ICIs) have achieved meaningful success, with patients with advanced tumors presenting longer survival times and better quality of life. However, several patients still do not exhibit good clinical outcomes for ICI therapy due to low sensitivity. To solve this, researchers have focused on identifying the cellular and molecular mechanisms underlying resistance to ICI therapy. ICI therapy induces apoptosis, which is the most frequent regulated cell death (RCD) but lacks immunogenicity and is regarded as an “immune silent” cell death. Ferroptosis, a unique type of non-apoptotic-RCD, has been preliminarily identified as an immunogenic cell death (ICD), stimulating tumor-antigen-specific immune responses and augmenting anti-tumor immune effects. However, ferroptosis has rarely been used in clinical practice. Present evidence strongly supports that the interferon-γ signaling pathway is at the crossroads of ICI therapy and ferroptosis. TYRO3, a receptor tyrosine kinase, is highly expressed in tumors and can induce anti-programmed cell death (PD)-ligand 1/PD-1 therapy resistance by limiting tumoral ferroptosis. Therefore, in this review, we summarize the clinical practice and effects of ICI therapy in various cancers. We also provide an overview of ferroptosis and report the molecular connections between cancer cell ferroptosis and ICI therapy, and discuss the possibility to reverse ICI therapy resistance by inducing cancer cell ferroptosis.

Intracellular Cholesterol Synthesis and Transport

Cholesterol homeostasis is related to multiple diseases in humans, including cardiovascular disease, cancer, and neurodegenerative and hepatic diseases. The cholesterol levels in cells are balanced dynamically by uptake, biosynthesis, transport, distribution, esterification, and export. In this review, we focus on de novo cholesterol synthesis, cholesterol synthesis regulation, and intracellular cholesterol trafficking. In addition, the progression of lipid transfer proteins (LTPs) at multiple contact sites between organelles is considered.

Construction and Validation of a Ferroptosis-Related Prognostic Signature for Melanoma Based on Single-Cell RNA Sequencing

Melanoma, the deadliest type of skin cancer, is on the rise globally. The generally poor prognosis makes melanoma still an enormous public health problem. Ferroptosis is a newly emerging form of iron-dependent regulated cell death, which has been implicated in the development and treatment of several tumors. However, whether there is a connection between ferroptosis-related genes and the prognosis of melanoma patients remains an enigma. In the present study, we identified a ferroptosis-related genes signature to predict the prognosis of melanoma patients by analyzing single-cell RNA-sequencing data from the Gene Expression Omnibus (GEO). Single-cell trajectory analysis was performed to explore malignant differentiation. CellChat was used to investigate intercellular communications in melanoma. Collectively, a novel four-gene signature (CP, MAP1LC3A, transferrin, and TP53) was constructed for prognosis prediction. COX proportional hazards regression analysis showed that the established ferroptosis-associated risk model was an independent prognostic predictor for melanoma patients (HR = 2.3293; 95%CI 1.1528–4.706) (p < 0.018). Patients with low-risk scores had significantly better overall survival (OS) than those with high-risk scores in The Cancer Genome Atlas, GSE59455, and GSE22153 dataset (p = 0.0015, p = 0.031, p = 0.077). Furthermore, the gene expression level of the four genes were verified in multistrain melanoma cell lines and normal human epidermal melanocytes (NHEM). The protein expression level of the four genes in clinical samples were further verified in the Human Protein Atlas (HPA) databases. Taken together, our study identified the prognostic significance of the ferroptosis-related genes in melanoma and developed a novel four-gene prognostic signature, which may shed light on the prognostic assessment and clinical decision making for melanoma patients.

The critical function of metabolic reprogramming in cancer metastasis

Cancer metastasis is the leading cause of cancer‐related death. It is a complex, inefficient, and multistep process related to poor prognosis and high mortality of patients. Increasing evidence has shown that metabolic programming is a recognized hallmarker of cancer, plays a critical role in cancer metastasis. Metabolism alterations of glucose, lipid, and amino acid provide cancer cells with energy and substances for biosynthesis, maintain biofunctions and significantly affect proliferation, invasion, and metastasis of cancer cells. Tumor microenvironment (TME) is a complex system formed by varieties of cellular and noncellular elements. Nontumor cells in TME also undergo metabolic reprogramming or respond to metabolites to promote migration and invasion of cancer cells. A comprehensive understanding of the regulatory mechanism in metastasis from the metabolic reprogramming aspect is required to develop new therapeutic strategies combatting cancer metastasis. This review illustrates the metabolic reprogramming and interaction of cancer cells and nontumor cells in the TME, and the development of treatment strategies targeting metabolism alterations.

YAP regulates an SGK1/mTORC1/SREBP-dependent lipogenic program to support proliferation and tissue growth

The coordinated regulation of growth control and metabolic pathways is required to meet the energetic and biosynthetic demands associated with proliferation. Emerging evidence suggests that the Hippo pathway effector Yes-associated protein 1 (YAP) reprograms cellular metabolism to meet the anabolic demands of growth, although the mechanisms involved are poorly understood. Here, we demonstrate that YAP co-opts the sterol regulatory element-binding protein (SREBP)-dependent lipogenic program to facilitate proliferation and tissue growth. Mechanistically, YAP stimulates de novo lipogenesis via mechanistic target of rapamcyin (mTOR) complex 1 (mTORC1) signaling and subsequent activation of SREBP. Importantly, YAP-dependent regulation of serum- and glucocorticoid-regulated kinase 1 (SGK1) is required to activate mTORC1/SREBP and stimulate de novo lipogenesis. We also find that the SREBP target genes fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD) are conditionally required to support YAP-dependent proliferation and tissue growth. These studies reveal that de novo lipogenesis is a metabolic vulnerability that can be targeted to disrupt YAP-dependent proliferation and tissue growth.

Loss of glucose 6-phosphate dehydrogenase function increases oxidative stress and glutaminolysis in metastasizing melanoma cells

Melanoma metastasis is limited by oxidative stress. Cells that enter the blood experience high levels of reactive oxygen species and usually die of ferroptosis. We found that melanoma cells become more dependent upon the oxidative pentose phosphate pathway to manage oxidative stress during metastasis. When pentose phosphate pathway function was impaired by reduced glucose 6-phosphate dehydrogenase (G6PD) function, melanoma cells increased malic enzyme activity and glutamine consumption. Melanoma cells thus have redundant and layered protection against oxidative stress.

The pentose phosphate pathway is a major source of NADPH for oxidative stress resistance in cancer cells but there is limited insight into its role in metastasis, when some cancer cells experience high levels of oxidative stress. To address this, we mutated the substrate binding site of glucose 6-phosphate dehydrogenase (G6PD), which catalyzes the first step of the pentose phosphate pathway, in patient-derived melanomas. G6PD mutant melanomas had significantly decreased G6PD enzymatic activity and depletion of intermediates in the oxidative pentose phosphate pathway. Reduced G6PD function had little effect on the formation of primary subcutaneous tumors, but when these tumors spontaneously metastasized, the frequency of circulating melanoma cells in the blood and metastatic disease burden were significantly reduced. G6PD mutant melanomas exhibited increased levels of reactive oxygen species, decreased NADPH levels, and depleted glutathione as compared to control melanomas. G6PD mutant melanomas compensated for this increase in oxidative stress by increasing malic enzyme activity and glutamine consumption. This generated a new metabolic vulnerability as G6PD mutant melanomas were more dependent upon glutaminase than control melanomas, both for oxidative stress management and anaplerosis. The oxidative pentose phosphate pathway, malic enzyme, and glutaminolysis thus confer layered protection against oxidative stress during metastasis.

Ferroptosis in cancer and cancer immunotherapy

The hallmark of tumorigenesis is the successful circumvention of cell death regulation for achieving unlimited replication and immortality. Ferroptosis is a newly identified type of cell death dependent on lipid peroxidation which differs from classical programmed cell death in terms of morphology, physiology and biochemistry. The broad spectrum of injury and tumor tolerance are the main reasons for radiotherapy and chemotherapy failure. The effective rate of tumor immunotherapy as a new treatment method is less than 30%. Ferroptosis can be seen in radiotherapy, chemotherapy, and tumor immunotherapy; therefore, ferroptosis activation may be a potential strategy to overcome the drug resistance mechanism of traditional cancer treatments. In this review, the characteristics and causes of cell death by lipid peroxidation in ferroptosis are briefly described. In addition, the three metabolic regulations of ferroptosis and its crosstalk with classical signaling pathways are summarized. Collectively, these findings suggest the vital role of ferroptosis in immunotherapy based on the interaction of ferroptosis with tumor immunotherapy, chemotherapy and radiotherapy, thus, indicating the remarkable potential of ferroptosis in cancer treatment.

Ferroptosis: A Potential Target in Cardiovascular Disease

Ferroptosis is a new form of regulatory cell death characterized by iron-dependent and intracellular lipid peroxidation. Ferroptosis can be divided into two stages. The first stage is iron overload in the cell, which generates a large amount of reactive oxygen species through the Fenton reaction, and the second stage results from an imbalance of the intracellular antioxidant system. Excessive phospholipid hydroperoxides cannot be removed by reduction reactions, as this could destroy the cell membrane structure and interfere with mitochondrial function, eventually leading to ferroptosis of the cell. Cardiovascular diseases have gradually become the leading cause of death in modern society. The relationship between ferroptosis and the occurrence and progression of cardiovascular disease has become a research hotspot in recent years. In this review, we summarize the mechanism of ferroptosis and its specific role in cardiovascular disease.

Signal pathways of melanoma and targeted therapy

Melanoma is the most lethal skin cancer that originates from the malignant transformation of melanocytes. Although melanoma has long been regarded as a cancerous malignancy with few therapeutic options, increased biological understanding and unprecedented innovations in therapies targeting mutated driver genes and immune checkpoints have substantially improved the prognosis of patients. However, the low response rate and inevitable occurrence of resistance to currently available targeted therapies have posed the obstacle in the path of melanoma management to obtain further amelioration. Therefore, it is necessary to understand the mechanisms underlying melanoma pathogenesis more comprehensively, which might lead to more substantial progress in therapeutic approaches and expand clinical options for melanoma therapy. In this review, we firstly make a brief introduction to melanoma epidemiology, clinical subtypes, risk factors, and current therapies. Then, the signal pathways orchestrating melanoma pathogenesis, including genetic mutations, key transcriptional regulators, epigenetic dysregulations, metabolic reprogramming, crucial metastasis-related signals, tumor-promoting inflammatory pathways, and pro-angiogenic factors, have been systemically reviewed and discussed. Subsequently, we outline current progresses in therapies targeting mutated driver genes and immune checkpoints, as well as the mechanisms underlying the treatment resistance. Finally, the prospects and challenges in the development of melanoma therapy, especially immunotherapy and related ongoing clinical trials, are summarized and discussed.

Advancements in 3D Cell Culture Systems for Personalizing Anti-Cancer Therapies

Over 90% of potential anti-cancer drug candidates results in translational failures in clinical trials. The main reason for this failure can be attributed to the non-accurate pre-clinical models that are being currently used for drug development and in personalised therapies. To ensure that the assessment of drug efficacy and their mechanism of action have clinical translatability, the complexity of the tumor microenvironment needs to be properly modelled. 3D culture models are emerging as a powerful research tool that recapitulates in vivo characteristics. Technological advancements in this field show promising application in improving drug discovery, pre-clinical validation, and precision medicine. In this review, we discuss the significance of the tumor microenvironment and its impact on therapy success, the current developments of 3D culture, and the opportunities that advancements that in vitro technologies can provide to improve cancer therapeutics.

Stigmasterol alleviates interleukin-1beta-induced chondrocyte injury by down-regulatingsterol regulatory element binding transcription factor 2 to regulateferroptosis

Stigmasterol (STM), one of the main active components of Achyranthes bidentata, has been shown to effectively inhibit proinflammatory factors and matrix degradation in chondrocytes. However, the effect of STM on interleukin (IL)-1β-induced chondrocytes and its specific mechanism remain unclear. The purpose of the present study was to explore the effect and mechanism of sterol regulatory element binding transcription factor 2 (SREBF2) on IL-1β induced chondrocytes in the presence of STM. CCK-8 was used to detect the effect of STM on the cell viability of mouse chondrogenic cells (ATDC5). After ATDC5 cells were induced by IL-1β, the expression of SREBF2 in osteoarthritis cells was detected by RT-qPCR. The content of iron ion in the cells was detected by using an iron colorimetric assay kit. After further transfection of a SREBF2 overexpressing vector (Oe-SREBF2) or addition of a ferroptosis inhibitor, the expression levels of inflammation and matrix degradation-related proteins were detected via Western blotting. The levels of oxidative stress in cells were determined by using an ELISA kit. The results revealed that STM had no significant effect on the viability of ATDC5 cells. STM reduced IL-1β-induced ATDC5 cell damage and ferroptosis through SREBF2 and enhanced the inhibitory effect of ferroptosis inhibitors on IL-1β-induced ATDC5 cell injury. The present data suggest that STM attenuated chondrocyte injury induced by IL-1β by regulating ferroptosis via down-regulation of SREBF2, and may have potential as a novel therapeutic method for knee osteoarthritis.

The mechanisms and therapeutic targets of ferroptosis in cancer

INTRODUCTION

Ferroptosis, a form of programmed cell death, is mediated primarily by lipid peroxidation via a unique iron-dependent process. The mechanisms of ferroptosis involve the metabolisms of amino acids, irons, and lipids, and the regulation of antioxidant systems. Evidence supports the roles of ferroptosis in cancer, while metabolic reprogramming (a hallmark of cancer) renders tumor cells highly vulnerable to ferroptosis and thus provides a rationale for ferroptosis-targeted therapy for cancer.

AREA COVERED

This article examines the current understanding of the mechanisms and related signaling pathways involving ferroptosis; it focuses on novel targets in cancer and its treatment and drug resistance. The development of ferroptosis-targeted therapy, especially in combination with conventional or non-conventional therapies, are considered with dilemmas and key questions in this research area.

EXPERT OPINION

An increasing number of potential targets and ferroptosis inducers (FINs) have been identified to treat cancer. However, no specific FIN has entered clinical trials thus far, likely due to poor efficacy and high toxicity in vivo. Thus, new FINs with high selectivity and bioavailability are required to target tumor cells more specifically and potently. Particularly, the combination of FINs with chemotherapy, radiotherapy, targeted therapy, and immunotherapy warrants clinical investigation in the future.

Metabolic requirements of the metastatic cascade

Metastases represent a major cause of cancer-associated deaths. Despite extensive research, targeting metastasis remains the main obstacle in cancer therapy. Therefore, it is of tremendous importance to elucidate the mechanisms that impinge on the different steps of the metastatic cascade. Metabolic plasticity is a cornerstone of the tumorigenic process that not only enables cancer cells to rapidly proliferate but also thrive and retain vitality. Plasticity of the metabolic networks that wire cancer cells is of utmost importance during the metastatic cascade when cancer cells are at their most vulnerable and have to survive in a panoply of inhospitable environments as they make their journey to form metastatic lesions. Here, we highlight which metabolic processes are known to power metastasis formation and lay the foundation for additional work aimed at discovering regulatory nodes of metabolic plasticity that can be used to target metastatic disease.

Redox Regulation in Cancer Cells during Metastasis

Metastasis is an inefficient process in which the vast majority of cancer cells are fated to die, partly because they experience oxidative stress. Metastasizing cancer cells migrate through diverse environments that differ dramatically from their tumor of origin, leading to redox imbalances. The rare metastasizing cells that survive undergo reversible metabolic changes that confer oxidative stress resistance. We review the changes in redox regulation that cancer cells undergo during metastasis. By better understanding these mechanisms, it may be possible to develop pro-oxidant therapies that block disease progression by exacerbating oxidative stress in cancer cells. SIGNIFICANCE: Oxidative stress often limits cancer cell survival during metastasis, raising the possibility of inhibiting cancer progression with pro-oxidant therapies. This is the opposite strategy of treating patients with antioxidants, an approach that worsened outcomes in large clinical trials.

Cross-link between ferroptosis and nasopharyngeal carcinoma: New approach to radiotherapy sensitization

Ferroptosis is a recently discovered special type of regulated cell death that is strongly associated with both homeostasis maintenance and cancer development. Previous studies have indicated that a number of small-molecular agents inducing ferroptosis have great potential in the treatment of different types of cancer, including breast, pancreatic, prostate and head and neck cancer. However, the role of ferroptosis in nasopharyngeal carcinoma (NPC) has remained to be fully determined. To the best of our knowledge, no review of the currently available studies on this subject has been published to date. The metabolism and expression of specific genes that regulate ferroptosis may represent a promising radiosensitization target in cancer treatment. The aim of the present review was to describe the cross-link between ferroptosis and NPC and to discuss the potential value of regulators and the possible mechanism underlying the role of ferroptosis in the radiosensitization of NPC, in the hope that linking the mechanism of ferroptosis with the development of NPC will accelerate the development of novel ferroptosis-based targets and radiotherapy strategies in NPC.

Ironing-Out the Details: New Strategies for Combining Ferroptosis Inhibitors with Immunotherapy in Melanoma

Escape from ferroptosis is an important determinant of metastasis and immune evasion in melanoma. In a new article of the Journal of Investigative Dermatology, Wang et al. (2021) identify the CAMKK2‒adenosine monophosphate-activated protein kinase‒NRF2 signaling axis as a negative regulator of ferroptosis and showed that inhibiting CAMKK2 increases the efficacy of anti-PD-1 therapy. These findings offer new opportunities for the development of ferroptosis-inducing therapies to use in combination with immune checkpoint agents.

Circulating Tumor Cells (CTCs): A Unique Model of Cancer Metastases and Non-invasive Biomarkers of Therapeutic Response

Late-stage cancer metastasis remains incurable in the clinic and is the major cause death in patients. Circulating tumor cells (CTCs) are thought to be metastatic precursors shed from the primary tumor or metastatic deposits and circulate in the blood. The molecular network regulating CTC survival, extravasation, and colonization in distant metastatic sites is poorly defined, largely due to challenges in isolating rare CTCs. Recent advances in CTC isolation and ex vivo culture techniques facilitates single-cell omics and the development of related animal models to study CTC-mediated metastatic progression. With these powerful tools, CTCs can potentially be used as non-invasive biomarkers predicting therapeutic response. These studies may open a new avenue for CTC-specific drug discoveries. In this short review, we aim to summarize recent progress in the characterization of CTCs and their clinical relevance in various cancers, setting the stage for realizing personalized therapies against metastases.

Regulation of Ferroptosis Pathway by Ubiquitination

Ferroptosis is an iron-dependent form of programmed cell death, which plays crucial roles in tumorigenesis, ischemia–reperfusion injury and various human degenerative diseases. Ferroptosis is characterized by aberrant iron and lipid metabolisms. Mechanistically, excess of catalytic iron is capable of triggering lipid peroxidation followed by Fenton reaction to induce ferroptosis. The induction of ferroptosis can be inhibited by sufficient glutathione (GSH) synthesis via system Xc^– transporter-mediated cystine uptake. Therefore, induction of ferroptosis by inhibition of cystine uptake or dampening of GSH synthesis has been considered as a novel strategy for cancer therapy, while reversal of ferroptotic effect is able to delay progression of diverse disorders, such as cardiopathy, steatohepatitis, and acute kidney injury. The ubiquitin (Ub)–proteasome pathway (UPP) dominates the majority of intracellular protein degradation by coupling Ub molecules to the lysine residues of protein substrate, which is subsequently recognized by the 26S proteasome for degradation. Ubiquitination is crucially involved in a variety of physiological and pathological processes. Modulation of ubiquitination system has been exhibited to be a potential strategy for cancer treatment. Currently, more and more emerged evidence has demonstrated that ubiquitous modification is involved in ferroptosis and dominates the vulnerability to ferroptosis in multiple types of cancer. In this review, we will summarize the current findings of ferroptosis surrounding the viewpoint of ubiquitination regulation. Furthermore, we also highlight the potential effect of ubiquitination modulation on the perspective of ferroptosis-targeted cancer therapy.

Non-coding RNAs in necroptosis, pyroptosis and ferroptosis in cancer metastasis

Distant metastasis is the main cause of death for cancer patients. Recently, the newly discovered programmed cell death includes necroptosis, pyroptosis, and ferroptosis, which possesses an important role in the process of tumor metastasis. At the same time, it is widely reported that non-coding RNA precisely regulates programmed death and tumor metastasis. In the present review, we summarize the function and role of necroptosis, pyrolysis, and ferroptosis involving in cancer metastasis, as well as the regulatory factors, including non-coding RNAs, of necroptosis, pyroptosis, and ferroptosis in the process of tumor metastasis.

Statins: a repurposed drug to fight cancer

As competitive HMG-CoA reductase (HMGCR) inhibitors, statins not only reduce cholesterol and improve cardiovascular risk, but also exhibit pleiotropic effects that are independent of their lipid-lowering effects. Among them, the anti-cancer properties of statins have attracted much attention and indicated the potential of statins as repurposed drugs for the treatment of cancer. A large number of clinical and epidemiological studies have described the anticancer properties of statins, but the evidence for anticancer effectiveness of statins is inconsistent. It may be that certain molecular subtypes of cancer are more vulnerable to statin therapy than others. Whether statins have clinical anticancer effects is still an active area of research. Statins appear to enhance the efficacy and address the shortcomings associated with conventional cancer treatments, suggesting that statins should be considered in the context of combined therapies for cancer. Here, we present a comprehensive review of the potential of statins in anti-cancer treatments. We discuss the current understanding of the mechanisms underlying the anti-cancer properties of statins and their effects on different malignancies. We also provide recommendations for the design of future well-designed clinical trials of the anti-cancer efficacy of statins.