Iron-responsive element-binding protein 2 plays an essential role in regulating prostate cancer cell growth

Unlocking ferroptosis in prostate cancer - the road to novel therapies and imaging markers

Ferroptosis is a distinct form of regulated cell death that is predominantly driven by the build-up of intracellular iron and lipid peroxides. Ferroptosis suppression is widely accepted to contribute to the pathogenesis of several tumours including prostate cancer. Results from some studies reported that prostate cancer cells can be highly susceptible to ferroptosis inducers, providing potential for an interesting new avenue of therapeutic intervention for advanced prostate cancer. In this Perspective, we describe novel molecular underpinnings and metabolic drivers of ferroptosis, analyse the functions and mechanisms of ferroptosis in tumours, and highlight prostate cancer-specific susceptibilities to ferroptosis by connecting ferroptosis pathways to the distinctive metabolic reprogramming of prostate cancer cells. Leveraging these novel mechanistic insights could provide innovative therapeutic opportunities in which ferroptosis induction augments the efficacy of currently available prostate cancer treatment regimens, pending the elimination of major bottlenecks for the clinical translation of these treatment combinations, such as the development of clinical-grade inhibitors of the anti-ferroptotic enzymes as well as non-invasive biomarkers of ferroptosis. These biomarkers could be exploited for diagnostic imaging and treatment decision-making.

Static Magnetic Field Reduces the Anticancer Effect of Hinokitiol on Melanoma Malignant Cells-Gene Expression and Redox Homeostasis Studies

BACKGROUND

Melanoma malignant is characterized by a high mortality rate, accounting for as much as 65% of deaths caused by skin cancer. A potential strategy in cancer treatment may be the use of natural compounds, which include hinokitiol (β-Thujaplicin), a phenolic component of essential oils extracted from cypress trees. Many studies confirm that a high-induction SMF (static magnetic field) has anticancer effects and can be used as a non-invasive anticancer therapy in combination with or without drugs.

AIM

The aim of this experiment was to evaluate the effect of a static magnetic field on melanoma cell cultures (C32 and COLO 829) treated with hinokitiol.

METHODS AND RESULTS

Melanoma cells were exposed to a static magnetic field of moderate induction and hinokitiol. The research included determining the activity of the antioxidant enzymes (SOD, GPx, and CAT) and MDA concentration as well as the gene expression profile.

CONCLUSION

Hinokitiol disturbs the redox homeostasis of C32 and COLO 829 melanoma malignant cells. Moreover, a static magnetic field has a protective effect on melanoma malignant cells and abolishes the anticancer effect of hinokitiol.

Transferrin-Bearing, Zein-Based Hybrid Lipid Nanoparticles for Drug and Gene Delivery to Prostate Cancer Cells

Gene therapy holds great promise for treating prostate cancer unresponsive to conventional therapies. However, the lack of delivery systems that can transport therapeutic DNA and drugs while targeting tumors without harming healthy tissues presents a significant challenge. This study aimed to explore the potential of novel hybrid lipid nanoparticles, composed of biocompatible zein and conjugated to the cancer-targeting ligand transferrin. These nanoparticles were designed to entrap the anti-cancer drug docetaxel and carry plasmid DNA, with the objective of improving the delivery of therapeutic payloads to prostate cancer cells, thereby enhancing their anti-proliferative efficacy and gene expression levels. These transferrin-bearing, zein-based hybrid lipid nanoparticles efficiently entrapped docetaxel, leading to increased uptake by PC-3 and LNCaP cancer cells and significantly enhancing anti-proliferative efficacy at docetaxel concentrations exceeding 1 µg/mL. Furthermore, they demonstrated proficient DNA condensation, exceeding 80% at polymer-DNA weight ratios of 1500:1 and 2000:1. This resulted in increased gene expression across all tested cell lines, with the highest transfection levels up to 11-fold higher than those observed with controls, in LNCaP cells. These novel transferrin-bearing, zein-based hybrid lipid nanoparticles therefore exhibit promising potential as drug and gene delivery systems for prostate cancer therapy.

Assessing the Potential of Small Peptides for Altering Expression Levels of the Iron-Regulatory Genes FTH1 and TFRC and Enhancing Androgen Receptor Inhibitor Activity in In Vitro Prostate Cancer Models

Recent research highlights the key role of iron dyshomeostasis in the pathogenesis of prostate cancer (PCa). PCa cells are heavily dependent on bioavailable iron, which frequently results in the reprogramming of iron uptake and storage pathways. Although advanced-stage PCa is currently incurable, bioactive peptides capable of modulating key iron-regulatory genes may constitute a means of exploiting a metabolic adaptation necessary for tumor growth. Recent annual increases in PCa incidence have been reported, highlighting the urgent need for novel treatments. We examined the ability of LNCaP, PC3, VCaP, and VCaP-EnzR cells to form colonies in the presence of androgen receptor inhibitors (ARI) and a series of iron-gene modulating oligopeptides (FT-001-FT-008). The viability of colonies following treatment was determined with clonogenic assays, and the expression levels of FTH1 (ferritin heavy chain 1) and TFRC (transferrin receptor) were determined with quantitative polymerase chain reaction (PCR). Peptides and ARIs combined significantly reduced PCa cell growth across all phenotypes, of which two peptides were the most effective. Colony growth suppression generally correlated with the magnitude of concurrent increases in FTH1 and decreases in TFRC expression for all cells. The results of this study provide preliminary insight into a novel approach at targeting iron dysmetabolism and sensitizing PCa cells to established cancer treatments.

A novel view of ferritin in cancer

Since its discovery more than 85 years ago, ferritin has principally been known as an iron storage protein. However, new roles, beyond iron storage, are being uncovered. Novel processes involving ferritin such as ferritinophagy and ferroptosis and as a cellular iron delivery protein not only expand our thinking on the range of contributions of this protein but present an opportunity to target these pathways in cancers. The key question we focus on within this review is whether ferritin modulation represents a useful approach for treating cancers. We discussed novel functions and processes of this protein in cancers. We are not limiting this review to cell intrinsic modulation of ferritin in cancers, but also focus on its utility in the trojan horse approach in cancer therapeutics. The novel functions of ferritin as discussed herein realize the multiple roles of ferritin in cell biology that can be probed for therapeutic opportunities and further research.

Expression of genes related to iron homeostasis in breast cancer

BACKGROUND

The dysfunctions in the metabolism of iron have an important role in many pathological conditions, ranging from disease with iron deposition to cancer. Studies on malignant diseases of the breast reported irregular expression in genes associated with iron metabolism. The variations are related to findings that have prognostic significance. This study evaluated the relationship of the expression levels of transferrin receptor 1 (TFRC), iron regulatory protein 1 (IRP1), hepcidin (HAMP), ferroportin 1 (FPN1), hemojuvelin (HFE2), matriptase 2 (TMPRSS6), and miR-122 genes in the normal and malignant tissues of breast cancer patients.

METHODS & RESULTS

The normal and malignant tissues from 75 women with breast malignancies were used in this study. The patients did not receive any treatment previously. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used in figuring the levels of gene expression associated with iron metabolism. When the malignant and normal tissues gene expression levels were analyzed, expression of TFRC increased (1.586-fold); IRP1 (0.594 fold) and miR-122 (0.320 fold) expression decreased; HAMP, FPN1, HFE2, and TMPRSS6 expressions did not change. FPN1 and IRP1 had a positive association, and this association was statistically significant (r = 0.266; p = 0.022). IRP1 and miR-122 had a positive association, and this association had statistical significance (r = 0.231; p = 0.048).

CONCLUSIONS

Our study portrayed the important association between genes involved in iron hemostasis and breast malignancy. The results could be used to establish new diagnostic techniques in the management of breast malignancies. The alterations in the metabolism of malignant breast cells with normal breast cells could be utilized to achieve advantages in treatment.

Ferroptosis landscape in prostate cancer from molecular and metabolic perspective

Prostate cancer is a major disease that threatens men's health. Its rapid progression, easy metastasis, and late castration resistance have brought obstacles to treatment. It is necessary to find new effective anticancer methods. Ferroptosis is a novel iron-dependent programmed cell death that plays a role in various cancers. Understanding how ferroptosis is regulated in prostate cancer will help us to use it as a new way to kill cancer cells. In this review, we summarize the regulation and role of ferroptosis in prostate cancer and the relationship with AR from the perspective of metabolism and molecular pathways. We also discuss the feasibility of ferroptosis in prostate cancer treatment and describe current limitations and prospects, providing a reference for future research and clinical application of ferroptosis.

Ferroportin depletes iron needed for cell cycle progression in head and neck squamous cell carcinoma

Introduction

Ferroportin (FPN), the only identified eukaryotic iron efflux channel, plays an important role in iron homeostasis and is downregulated in many cancers. To determine if iron related pathways are important for Head and Neck Squamous Cell Carcinoma (HNSCC) progression and proliferation, we utilize a model of FPN over-expression to simulate iron depletion and probe associated molecular pathways.

Methods

The state of iron related proteins and ferroptosis sensitivity was assessed in a panel of metastatic HNSCC cell lines. Stable, inducible expression of FPN was confirmed in the metastatic HNSCC lines HN12 and JHU-022 as well as the non-transformed normal oral keratinocyte (NOK) cell line and the effect of FPN mediated iron depletion was assessed in these cell lines.

Results

HNSCC cells are sensitive to iron chelation and ferroptosis, but the non-transformed NOK cell line is not. We found that FPN expression inhibits HNSCC cell proliferation and colony formation but NOK cells are unaffected. Inhibition of cell proliferation is rescued by the addition of hepcidin. Decreases in proliferation are due to the disruption of iron homeostasis via loss of labile iron caused by elevated FPN levels. This in turn protects HNSCC cells from ferroptotic cell death. Expression of FPN induces DNA damage, activates p21, and reduces levels of cyclin proteins thereby inhibiting cell cycle progression of HNSCC cells, arresting cells in the S-phase. Induction of FPN severely inhibits Edu incorporation and increased β-galactosidase activity, indicating cells have entered senescence. Finally, in an oral orthotopic mouse xenograft model, FPN induction yields a significant decrease in tumor growth.

Conclusions

Our results indicate that iron plays a role in HNSCC cell proliferation and growth and is important for cell cycle progression. Iron based interventional strategies such as ferroptosis or iron chelation may have potential therapeutic benefits in advanced HNSCC.

Molecular mechanism of the unusual biphasic effects of the natural compound hinokitiol on iron-induced cellular DNA damage

Hinokitiol is a natural monoterpene compound found in the heartwood of cupressaceous plants that have anticancer and anti-inflammatory properties. However, few studies have focused on its effect on iron-mediated cellular DNA damage. Here we show that hinokitiol exhibited unusual biphasic effects on iron-induced DNA damage in a molar ratio (hinokitiol/iron) dependent manner in HeLa cells. Under low ratios (<3:1), hinokitiol markedly enhanced DNA damage induced by Fe(II) or Fe(II)-H₂O₂; However, when the ratios increased over 3:1, the DNA damage was progressively inhibited. We found that the total cytoplasmic and nuclear iron concentration increased as the ratios of hinokitiol/iron increased. However, the cellular level of labile iron pool (LIP) only increased at ratios lower than 3, and the ROS generation is consistent with LIP change. Hinokitiol was found to interact with iron to form lipophilic hinokitiol-iron complexes with different stoichiometry and redox-activity by complementary applications of various analytical methods. Taken together, we propose that the enhancement of iron-induced cellular DNA damage by hinokitiol at low ratios (<3:1) was due to formation of lipophilic and redox-active iron complexes which facilitated cellular iron uptake and •OH production, while the inhibition at ratios higher than 3 was due to formation of redox-inactive iron complexes. These new findings will help us to design more effective drugs for the prevention and treatment of a series of iron-related diseases via regulating the two critical physicochemical factors (lipophilicity and redox activity of iron complexes) by simple natural compounds with iron-chelating properties.

Cell Size as a Primary Determinant in Targeted Nanoparticle Uptake

Nanoparticle (NP) internalization by cells is complex, highly heterogeneous, and fundamentally important for nanomedicine. We report powerful probabilistic statistics from single-cell data on quantitative NP uptake of PEG-coated transferrin receptor-targeted gold NPs for cancer-derived and fibroblast cells according to their cell size, receptor expression, and receptor density. The smaller cancer cells had a greater receptor density and more efficient uptake of targeted NPs. However, simply due to fibroblasts being larger with more receptors, they exhibited greater NP uptake. While highly heterogeneous, targeted NP uptake strongly correlated with receptor expression. When uptake was normalized to cell size, no correlation existed. Consequently, skewed population distributions in cell sizes explain the distribution in NP uptake. Furthermore, exposure to the transferrin receptor-targeted NPs alters the fibroblast size and receptor expression, suggesting that the receptor-targeted NPs may interfere with the metabolic flux and nutrient exchange, which could assist in explaining the altered regulation of cells exposed to nanoparticles.

ACO1 and IREB2 downregulation confer poor prognosis and correlate with autophagy-related ferroptosis and immune infiltration in KIRC

Background

ACO1 and IREB2 are two homologous cytosolic regulatory proteins, which sense iron levels and change iron metabolism–linked molecules. These two genes were noticeably decreased in kidney renal clear cell carcinoma (KIRC), which confer poor survival. Meanwhile, there is a paucity of information about the mechanisms and clinical significance of ACO1 and IREB2 downregulation in renal cancers.

Methods

The expression profiles of ACO1 and IREB2 were assessed using multiple public data sets via several bioinformatics platforms. Clinical and pathological information was utilized to stratify cohorts for comparison. Patient survival outcomes were evaluated using the Kaplan–Meier plotter, a meta-analysis tool. The correlations of ACO1 and IREB2 with ferroptosis were further evaluated in The Cancer Genome Atlas (TCGA)–KIRC database. Tumor immune infiltration was analyzed using the CIBERSORT, TIMER, and GEPIA data resources. ACO1 antagonist sodium oxalomalate (OMA) and IREB2 inhibitor sodium nitroprusside (SNP) was used to treat renal cancer ACHN cells together with sorafenib.

Results

KIRC patients with low ACO1 or IREB2 contents exhibited a remarkably worse survival rate in contrast with those with high expression in Kaplan–Meier survival analyses. Meanwhile, ACO1 and IREB2 regulate autophagy-linked ferroptosis along with immune cell invasion in the tumor microenvironment in KIRC patients. Blocking the activation of these two genes by their inhibitors OMA and SNP ameliorated sorafenib-triggered cell death, supporting that ACO1 and IREB2 could be participated in its cytotoxic influence on renal cancer cells.

Conclusion

ACO1 and IREB2 downregulation in renal cancers were correlated with cancer aggressiveness, cellular iron homeostasis, cytotoxic immune cell infiltration, and patient survival outcomes. Our research is integral to verify the possible significance of ACO1 and IREB2 contents as a powerful signature for targeted treatment or novel immunotherapy in clinical settings.

Effect of Cisplatin on Renal Iron Homeostasis Components: Implication in Nephropathy

Cisplatin is an important chemotherapeutic drug for the treatment of solid tumors but often causes nephropathy as part of the off-target toxicity. Iron accumulation and related damage were implicated in cisplatin-induced kidney injury. However, the role of cisplatin in the renal iron sensing mechanism and its target genes responsible for iron uptake, storage, and release have not been investigated. Cellular iron homeostasis is controlled by the interaction of iron regulatory proteins (IRP1 and IRP2) and iron-responsive elements (IREs) present in the untranslated regions of iron transport and storage components. Here, we report that cisplatin does not influence the expressions of IRP targets such as transferrin receptor-1 (TfR1), divalent metal transporter-1 (DMT1), and ferroportin in renal cells despite the increased heme oxygenase-1 (HO-1) level. Ferritin subunits (Ft-H and Ft-L) are elevated in different magnitudes due to the increased mRNA expression. Intriguingly, a higher expression of Ft-L mRNA is detected than that of Ft-H mRNA. The inability of cisplatin in altering the IRE-IRP interaction is confirmed by examining IRE-containing luciferase activity, RNA electrophoretic mobility shift assay, and activation of IRPs. The labile iron pool is depleted but reversed by silencing of either Ft-H or Ft-L, suggesting increased iron storage by ferritin. Silencing of Ft-H or Ft-L promotes cell death, suggesting that ferritin acts to protect the renal cells from cisplatin-mediated toxicity. A differential increase of transcripts and equivalent increase of proteins of Ft-H and Ft-L and unaltered TfR1 and DMT1 transcripts are found in the kidneys of cisplatin-treated rats along with iron accumulation. Our results reveal that cisplatin does not influence the IRE-IRP interaction despite alteration of the cellular iron pool in renal cells. This insensitivity of the IRE-IRP system may be implicated in the accumulation of iron to contribute to cisplatin-induced nephropathy.

Puzzling Out Iron Complications in Cancer Drug Resistance

Iron metabolism are frequently disrupted in cancer. Patients with cancer are prone to anemia and receive transfusions frequently; the condition which results in iron overload, contributing to serious therapeutic complications. Iron is introduced as a carcinogen that may increase tumor growth. However, investigations regarding its impact on response to chemotherapy, particularly the induction of drug resistance are still limited. Here, iron contribution to cell signaling and various molecular mechanisms underlying iron-mediated drug resistance are described. A dual role of this vital element in cancer treatment is also addressed. On one hand, the need to administer iron chelators to surmount iron overload and improve the sensitivity of tumor cells to chemotherapy is discussed. On the other hand, the necessary application of iron as a therapeutic option by iron-oxide nanoparticles or ferroptosis inducers is explained. Authors hope that this paper can help unravel the clinical complications related to iron in cancer therapy.

Transferrin receptor-mediated liposomal drug delivery: recent trends in targeted therapy of cancer

INTRODUCTION

Compared to normal cells, malignant cancer cells require more iron for their growth and rapid proliferation, which can be supplied by a high expression level of transferrin receptor (TfR). It is well known that the expression of TfR on the tumor cells is considerably higher than that of normal cells, which makes TfR an attractive target in cancer therapy.

AREAS COVERED

In this review, the primary focus is on the role of TfR as a valuable tool for cancer-targeted drug delivery, followed by the full coverage of available TfR ligands and their conjugation chemistry to the surface of liposomes. Finally, the most recent studies investigating the potential of TfR-targeted liposomes as promising drug delivery vehicles to different cancer cells are highlighted with emphasis on their improvement possibilities to become a part of future cancer medicines.

EXPERT OPINION

Liposomes as a valuable class of nanocarriers have gained much attention toward cancer therapy. From all the studies that have exploited the therapeutic and diagnostic potential of TfR on cancer cells, it can be realized that the systematic assessment of TfR ligands applied for liposomal targeted delivery has yet to be entirely accomplished.

FDX2 and ISCU Gene Variations Lead to Rhabdomyolysis With Distinct Severity and Iron Regulation

Background and Objectives

To determine common clinical and biological traits in 2 individuals with variants in ISCU and FDX2, displaying severe and recurrent rhabdomyolyses and lactic acidosis.

Methods

We performed a clinical characterization of 2 distinct individuals with biallelic ISCU or FDX2 variants from 2 separate families and a biological characterization with muscle and cells from those patients.

Results

The individual with FDX2 variants was clinically more affected than the individual with ISCU variants. Affected FDX2 individual fibroblasts and myoblasts showed reduced oxygen consumption rates and mitochondrial complex I and PDHc activities, associated with high levels of blood FGF21. ISCU individual fibroblasts showed no oxidative phosphorylation deficiency and moderate increase of blood FGF21 levels relative to controls. The severity of the FDX2 individual was not due to dysfunctional autophagy. Iron was excessively accumulated in ISCU-deficient skeletal muscle, which was accompanied by a downregulation of IRP1 and mitoferrin2 genes and an upregulation of frataxin (FXN) gene expression. This excessive iron accumulation was absent from FDX2 affected muscle and could not be correlated with variable gene expression in muscle cells.

Discussion

We conclude that FDX2 and ISCU variants result in a similar muscle phenotype, that differ in severity and skeletal muscle iron accumulation. ISCU and FDX2 are not involved in mitochondrial iron influx contrary to frataxin.

Rapid Access to Ironomycin Derivatives by Click Chemistry

Salinomycin, a natural carboxylic polyether ionophore, shows a very interesting spectrum of biological activities, including selective toxicity toward cancer stem cells (CSCs). Recently, we have developed a C20-propargylamine derivative of salinomycin (ironomycin) that exhibits more potent activity in vivo and greater selectivity against breast CSCs compared to the parent natural product. Since ironomycin contains a terminal alkyne motif, it stands out as being an ideal candidate for further functionalization. Using copper-catalyzed azide-alkyne cycloaddition (CuAAC), we synthesized a series of 1,2,3-triazole analogs of ironomycin in good overall yields. The in vitro screening of these derivatives against a well-established model of breast CSCs (HMLER CD24^low/CD44^high) and its corresponding epithelial counterpart (HMLER CD24^high/CD44^low) revealed four new products characterized by higher potency and improved selectivity toward CSCs compared to the reference compound ironomycin. The present study highlights the therapeutic potential of a new class of semisynthetic salinomycin derivatives for targeting selectively the CSC niche and highlights ironomycin as a promising starting material for the development of new anticancer drug candidates.

E-Cadherin, Integrin Alpha2 (Cd49b), and Transferrin Receptor-1 (Tfr1) Are Promising Immunohistochemical Markers of Selected Adverse Pathological Features in Patients Treated with Radical Prostatectomy

In patients treated for prostate cancer (PCa) with radical prostatectomy (RP), determining the risk of extraprostatic extension (EPE) and nodal involvement (NI) remains crucial for planning nerve-sparing and extended lymphadenectomy. The study aimed to determine proteins that could serve as immunohistochemical markers of locally advanced PCa. To select candidate proteins associated with adverse pathologic features (APF) reverse-phase protein array data of 498 patients was retrieved from The Cancer Genome Atlas. The analysis yielded 6 proteins which were then validated as predictors of APF utilizing immunohistochemistry in a randomly selected retrospective cohort of 53 patients. For univariate and multivariate analysis, logistic regression was used. Positive expression of TfR1 (OR 13.74; p = 0.015), reduced expression of CD49b (OR 10.15; p = 0.013), and PSA (OR 1.29; p = 0.013) constituted independent predictors of EPE, whereas reduced expression of e-cadherin (OR 10.22; p = 0.005), reduced expression of CD49b (OR 24.44; p = 0.017), and PSA (OR 1.18; p = 0.002) were independently associated with NI. Both models achieved high discrimination (AUROC 0.879 and 0.888, respectively). Immunohistochemistry constitutes a straightforward tool that might be easily utilized before RP. Expression of TfR1 and CD49b is associated with EPE, whereas expression of e-cadherin and CD49b is associated with NI. Since following immunohistochemical markers predicts respective APFs independently from PSA, in the future they might supplement existing preoperative nomograms or be implemented in novel tools.

Cancer: The role of iron and ferroptosis

Iron is an essential element for virtually all living things. Body iron levels are tightly controlled as both increased iron levels and iron deficiency are associated with many clinical conditions. Increased iron levels are associated with a worse prognosis in some cancers, so understanding the role of iron in cancer development has thus been an active area of research. Regulated forms of cell death are important in development and disease pathogenesis. In this Medicine in Focus review article, we discuss the role of iron in cancer, and ferroptosis, a new form of iron-regulated cell death triggered by increased iron and peroxidation of lipids. We also review the pathogenesis of cancer, potential therapeutics for targeting the increased requirement of iron, as well as how ferroptosis activation may have a role in treatment of cancers.

Targeting iron metabolism in cancer therapy

Iron is a critical component of many cellular functions including DNA replication and repair, and it is essential for cell vitality. As an essential element, iron is critical for maintaining human health. However, excess iron can be highly toxic, resulting in oxidative DNA damage. Many studies have observed significant associations between iron and cancer, and the association appears to be more than just coincidental. The chief characteristic of cancers, hyper-proliferation, makes them even more dependent on iron than normal cells. Cancer therapeutics are becoming as diverse as the disease itself. Targeting iron metabolism in cancer cells is an emerging, formidable field of therapeutics. It is a strategy that is highly diverse with regard to specific targets and the various ways to reach them. This review will discuss the importance of iron metabolism in cancer and highlight the ways in which it is being explored as the medicine of tomorrow.

Exosomes From miR-19b-3p-Modified ADSCs Inhibit Ferroptosis in Intracerebral Hemorrhage Mice

Objectives: Effective treatments for intracerebral hemorrhage (ICH) are limited until now. Ferroptosis, a novel form of iron-dependent cell death, is implicated in neurodegeneration diseases. Here, we attempted to investigate the impact of exosomes from miR-19b-3p-modified adipose-derived stem cells (ADSCs) on ferroptosis in ICH.

Methods: Collagenase was used to induce a mouse model of ICH and hemin was used to induce ferroptosis in cultured neurons. Exosomes were isolated from mimic NC- or miR-19b-3p mimic-transfected ADSCs (ADSCs-MNC-Exos or ADSCs-19bM-Exos, respectively) and then administered to ICH mice or hemin-treated neurons. ICH damage was evaluated by assessing the neurological function of ICH mice and cell viability of neurons. Ferroptosis was evaluated in mouse brains or cultured neurons. The interaction between miR-19b-3p and iron regulatory protein 2 (IRP2) 3′-UTR was analyzed by performing luciferase reporter assay.

Results: Ferroptosis occurred in ICH mice, which also exhibited decreased miR-19b-3p and increased IRP2 expression. IRP2 was a direct target of miR-19b-3p, and IRP2 expression was repressed by ADSCs-19bM-Exos. Importantly, ADSCs-19bM-Exos effectively attenuated hemin-induced cell injury and ferroptosis. Moreover, ADSCs-19bM-Exos administration significantly improved neurologic function and inhibited ferroptosis in ICH mice.

Conclusion: Exosomes from miR-19b-3p-modified ADSCs inhibit ferroptosis in ICH mice.

Iron Metabolism in the Tumor Microenvironment: Contributions of Innate Immune Cells

Cells of the innate immune system are a major component of the tumor microenvironment. They play complex and multifaceted roles in the regulation of cancer initiation, growth, metastasis and responses to therapeutics. Innate immune cells like neutrophils and macrophages are recruited to cancerous tissues by chemotactic molecules released by cancer cells and cancer-associated stromal cells. Once they reach the tumor, they can be instructed by a network of proteins, nucleic acids and metabolites to exert protumoral or antitumoral functions. Altered iron metabolism is a feature of cancer. Epidemiological studies suggest that increased presence of iron and/or iron binding proteins is associated with increased risks of cancer development. It has been shown that iron metabolism is involved in shaping the immune landscapes in inflammatory/infectious diseases and cancer-associated inflammation. In this article, we will dissect the contribution of macrophages and neutrophils to dysregulated iron metabolism in malignant cells and its impact on cancer growth and metastasis. The mechanisms involved in regulating the actions of macrophages and neutrophils will also be discussed. Moreover, we will examine the effects of iron metabolism on the phenotypes of innate immune cells. Both iron chelating and overloading agents are being explored in cancer treatment. This review highlights alternative strategies for management of iron content in cancer cells by targeting the iron donation and modulation properties of macrophages and neutrophils in the tumor microenvironment.

Iron: An Essential Element of Cancer Metabolism

Cancer cells undergo considerable metabolic changes to foster uncontrolled proliferation in a hostile environment characterized by nutrient deprivation, poor vascularization and immune infiltration. While metabolic reprogramming has been recognized as a hallmark of cancer, the role of micronutrients in shaping these adaptations remains scarcely investigated. In particular, the broad electron-transferring abilities of iron make it a versatile cofactor that is involved in a myriad of biochemical reactions vital to cellular homeostasis, including cell respiration and DNA replication. In cancer patients, systemic iron metabolism is commonly altered. Moreover, cancer cells deploy diverse mechanisms to increase iron bioavailability to fuel tumor growth. Although iron itself can readily participate in redox reactions enabling vital processes, its reactivity also gives rise to reactive oxygen species (ROS). Hence, cancer cells further rely on antioxidant mechanisms to withstand such stress. The present review provides an overview of the common alterations of iron metabolism occurring in cancer and the mechanisms through which iron promotes tumor growth.

Iron: Key player in cancer and cell cycle?

BACKGROUND

Iron is an essential element for growth and metabolic activities of all living organisms but remains in its oxyhydroxide ferric ion form in the surrounding. Unavailability of iron in soluble ferrous form led to development of specific pathways and machinery in different organisms to make it available for use and maintain its homeostasis. Iron homeostasis is essential as under different circumstances iron in excess as well as deprivation leads to different pathological conditions in human.

OBJECTIVE

This review highlights the current findings related to iron excess as well as deprivation with regards to cellular proliferation.

CONCLUSIONS

Iron excess is extensively associated with different types of cancers viz. colorectal cancer, breast cancer etc. by producing an oxidative stressed condition and alteration of immune system. Ironically its deprivation also results in anaemic conditions and leads to cell cycle arrest at different phases with mechanism yet to be explored. Iron deprivation arrests cell cycle at G1/S and in some cases at G2/M checkpoints resulting in growth arrest. However, in some cases iron overload arrests cell cycle at G1 phase by blocking certain signalling pathways. Certain natural and synthetic iron chelators are being explored from few decades to combat diseases caused by alteration in iron homeostasis.

Iron and Cancer: 2020 Vision

New and provocative insights into the relationships between iron and cancer have been uncovered in recent years. These include delineation of connections that link cellular iron to DNA repair, genomic integrity, and oncogenic signaling as well as the discovery of ferroptosis, a novel iron-dependent form of cell death. In parallel, new molecules and pathways that regulate iron influx, intracellular iron trafficking, and egress in normal cells, and their perturbations in cancer have been discovered. In addition, insights into the unique properties of iron handling in tumor-initiating cells (cancer stem cells), novel contributions of the tumor microenvironment to the uptake and regulation of iron in cancer cells, and new therapeutic modalities that leverage the iron dependence of cancer have emerged.

Knockdown of ferritin heavy chain (FTH) inhibits the migration of prostate cancer through reducing S100A4, S100A2, and S100P expression

BACKGROUND

Ferritin plays a key role in the development of prostate cancer (PCa). Our earlier studies showed that the knockdown of ferritin heavy chain (FTH) suppressed the migration and invasion of the prostate cancer cell line (PC3). However, the mechanisms behind FTH in the cell migration regulation of PCa have not been thoroughly investigated.

METHODS

Isobaric tags for relative and absolute quantitation (iTRAQ) proteomics was used to analyze the protein expression in PC3 cells with FTH knockdown by small interfering RNAs and negative control cells. We subsequently ranked the differentially expressed proteins according to the change in expression. We further performed Gene Ontology (GO) analysis for the changing-expression protein. Finally, Western blot analysis was performed to determine the expression of the target protein.

RESULTS

Compared with the negative group, 420 proteins were downregulated, including proteins S100A4, S100P, and S100A2, while the expression of 442 protein was elevated in FTH-silencing PC3 cells (P<0.05, fold change >1.2). The mass spectrometry results showing decreased expression of protein S100A4, S100P, and S100A2 in the cells were further validated by Western blot (P<0.05). Levels of protein S100A4, S100A2, and S100P were reduced in FTH-silencing PC3 cells (P<0.05, fold change >1.6).

CONCLUSIONS

The downregulation of FTH expression reduced the level of protein S100A4, S100A2, and S100P, which all play a key role in the migration and invasion of tumor cells. Therefore, it is reasonable to assume that there are correlations between the expression of the S100A4, S100A2, and S100P genes with FTH. Based on this research, FTH may be a new biomarker for the diagnosis of PCa.

Iron: The cancer connection

Iron plays an essential role in normal biological processes: The generation of cellular energy, oxygen transport, DNA synthesis and repair are all processes that require iron-coordinated proteins, either as elemental iron, heme or iron-sulfur clusters. As a transition metal with two major biological oxidation states, iron is also a critical intermediate in the generation of reactive oxygen species that can damage cellular structures and contribute to both aging and cancer. In this review, we focus on experimental and epidemiologic evidence that links iron and cancer, as well as strategies that have been proposed to either reduce or increase cellular iron for cancer therapy.

Altered Iron Metabolism and Impact in Cancer Biology, Metastasis, and Immunology

Iron is an essential nutrient that plays a complex role in cancer biology. Iron metabolism must be tightly controlled within cells. Whilst fundamental to many cellular processes and required for cell survival, excess labile iron is toxic to cells. Increased iron metabolism is associated with malignant transformation, cancer progression, drug resistance and immune evasion. Depleting intracellular iron stores, either with the use of iron chelating agents or mimicking endogenous regulation mechanisms, such as microRNAs, present attractive therapeutic opportunities, some of which are currently under clinical investigation. Alternatively, iron overload can result in a form of regulated cell death, ferroptosis, which can be activated in cancer cells presenting an alternative anti-cancer strategy. This review focuses on alterations in iron metabolism that enable cancer cells to meet metabolic demands required during different stages of tumorigenesis in relation to metastasis and immune response. The strength of current evidence is considered, gaps in knowledge are highlighted and controversies relating to the role of iron and therapeutic targeting potential are discussed. The key question we address within this review is whether iron modulation represents a useful approach for treating metastatic disease and whether it could be employed in combination with existing targeted drugs and immune-based therapies to enhance their efficacy.

Iron in the Tumor Microenvironment

Cancer metabolism is a well-known target of cancer therapeutics. Classically, cancer metabolism has been studied in terms of the dependence of cancer cells on crucial metabolites, such as glucose and glutamine. But, the accumulating data show that iron metabolism in tumor microenvironment is also an important factor in preserving the survival of cancer cells. Cancer cells have a distinct phenotype of iron metabolism, which secures the much-needed iron for these metabolically active cells. In order to use this iron efficiently, cancer cells need to increase their iron supply and decrease iron loss. As recent research suggests, this is not only done by modifying the expression of iron-related proteins in cancer cells, but also by interaction of cancer cells with other cells from the tumor milieu. Tumor microenvironment is a dynamic environment characterized with intricate relationship between cancer cells, tumor-associated macrophages, fibroblasts, and other cells. Some of the mechanistic aspects of this relationship have been elucidated, while others are yet to be identified. In any case, identifying the details of the iron phenotype of the cells in tumor microenvironment presents with a new therapeutic opportunity to treat this deadly disease.

Mdm2 is a target and mediator of IRP2 in cell growth control

Iron is an essential element to all living organisms and plays a vital role in many cellular processes, such as DNA synthesis and energy production. The Mdm2 oncogene is an E3 ligase and known to promote tumor growth. However, the role of Mdm2 in iron homeostasis is not certain. Here, we showed that Mdm2 expression was increased by iron depletion but decreased by iron repletion. We also showed that Iron Regulatory Protein 2 (IRP2) mediated iron-regulated Mdm2 expression. Specifically, Mdm2 expression was increased by ectopic IRP2 but decreased by knockdown or knockout of IRP2 in human cancer cells as well as in mouse embryonic fibroblasts. In addition, we showed that IRP2-regulated Mdm2 expression was independent of tumor suppressor p53. Mechanistically, we found that IRP2 stabilized Mdm2 transcript via binding to an iron response element (IRE) in the 3'UTR of Mdm2 mRNA. Finally, we showed that Mdm2 is required for IRP2-mediated cell proliferation and Mdm2 expression is highly associated with IRP2 in both the normal and cancerous liver tissues. Together, we uncover a novel regulation of Mdm2 by IRP2 via mRNA stability and that the IRP2-Mdm2 axis may play a critical role in cell growth.

Erastin, a ferroptosis-inducing agent, sensitized cancer cells to X-ray irradiation via glutathione starvation in vitro and in vivo

High concentrations of antioxidants in cancer cells are huge obstacle in cancer radiotherapy. Erastin was first discovered as an inducer of iron-dependent cell death called ferroptosis accompanied by antioxidant depletion caused by cystine glutamate antiporter inhibition. Therefore, treatment with erastin is expected to potentially enhance cellular radiosensitivity. In this study, we investigated the influence of treatment with erastin on the radiation efficiency against cancers. The clonogenic ability, glutathione peroxidase 4 (GPX4) expression, and glutathione concentration were evaluated using HeLa and NCI-H1975 adenocarcinoma cell lines treated with erastin and/or X-ray irradiation. For in vivo studies, NCI-H1975 cells were transplanted in the left shoulder of nude mice, and then radiosensitizing effect of erastin and glutathione concentration in the cancer were evaluated. Treatment with erastin induced ferroptosis and decreased the concentration of glutathione and GPX4 protein expression levels in the two tumor cell lines. Moreover, erastin enhanced X-ray irradiation-induced cell death in both human tumor cell lines. Furthermore, erastin treatment of a tumor-transplanted mouse model similarly demonstrated the radiosensitizing effect and decrease in intratumoral glutathione concentration in the in vitro study. In conclusion, our study demonstrated the radiosensitizing effect of erastin on two adenocarcinoma cell lines and the tumor xenograft model accompanied by glutathione depletion, indicating that ferroptosis inducers that reduce glutathione concentration could be applied as a novel cancer therapy in combination with radiotherapy.

Stearoyl-CoA Desaturase 1 Protects Ovarian Cancer Cells from Ferroptotic Cell Death

Activation of ferroptosis, a recently described mechanism of regulated cell death, dramatically inhibits growth of ovarian cancer cells. Given the importance of lipid metabolism in ferroptosis and the key role of lipids in ovarian cancer, we examined the contribution to ferroptosis of stearoyl-CoA desaturase (SCD1, SCD), an enzyme that catalyzes the rate-limiting step in monounsaturated fatty acid synthesis in ovarian cancer cells. SCD1 was highly expressed in ovarian cancer tissue, cell lines, and a genetic model of ovarian cancer stem cells. Inhibition of SCD1 induced lipid oxidation and cell death. Conversely, overexpression of SCD or exogenous administration of its C16:1 and C18:1 products, palmitoleic acid or oleate, protected cells from death. Inhibition of SCD1 induced both ferroptosis and apoptosis. Inhibition of SCD1 decreased CoQ₁₀, an endogenous membrane antioxidant whose depletion has been linked to ferroptosis, while concomitantly decreasing unsaturated fatty acyl chains in membrane phospholipids and increasing long-chain saturated ceramides, changes previously linked to apoptosis. Simultaneous triggering of two death pathways suggests SCD1 inhibition may be an effective component of antitumor therapy, because overcoming this dual mechanism of cell death may present a significant barrier to the emergence of drug resistance. Supporting this concept, we observed that inhibition of SCD1 significantly potentiated the antitumor effect of ferroptosis inducers in both ovarian cancer cell lines and a mouse orthotopic xenograft model. Our results suggest that the use of combined treatment with SCD1 inhibitors and ferroptosis inducers may provide a new therapeutic strategy for patients with ovarian cancer. SIGNIFICANCE: The combination of SCD1 inhibitors and ferroptosis inducers may provide a new therapeutic strategy for the treatment of ovarian cancer patients.See related commentary by Carbone and Melino, p. 5149.

Iron and Cancer

This review explores the multifaceted role that iron has in cancer biology. Epidemiological studies have demonstrated an association between excess iron and increased cancer incidence and risk, while experimental studies have implicated iron in cancer initiation, tumor growth, and metastasis. The roles of iron in proliferation, metabolism, and metastasis underpin the association of iron with tumor growth and progression. Cancer cells exhibit an iron-seeking phenotype achieved through dysregulation of iron metabolic proteins. These changes are mediated, at least in part, by oncogenes and tumor suppressors. The dependence of cancer cells on iron has implications in a number of cell death pathways, including ferroptosis, an iron-dependent form of cell death. Uniquely, both iron excess and iron depletion can be utilized in anticancer therapies. Investigating the efficacy of these therapeutic approaches is an area of active research that promises substantial clinical impact.

Iron Metabolism in Cancer

Demanded as an essential trace element that supports cell growth and basic functions, iron can be harmful and cancerogenic though. By exchanging between its different oxidized forms, iron overload induces free radical formation, lipid peroxidation, DNA, and protein damages, leading to carcinogenesis or ferroptosis. Iron also plays profound roles in modulating tumor microenvironment and metastasis, maintaining genomic stability and controlling epigenetics. in order to meet the high requirement of iron, neoplastic cells have remodeled iron metabolism pathways, including acquisition, storage, and efflux, which makes manipulating iron homeostasis a considerable approach for cancer therapy. Several iron chelators and iron oxide nanoparticles (IONPs) has recently been developed for cancer intervention and presented considerable effects. This review summarizes some latest findings about iron metabolism function and regulation mechanism in cancer and the application of iron chelators and IONPs in cancer diagnosis and therapy.

Iron Metabolism in Prostate Cancer; From Basic Science to New Therapeutic Strategies

An increasing amount of research has recently strengthened the case for the existence of iron dysmetabolism in prostate cancer. It is characterized with a wide array of differential expression of iron-related proteins compared to normal cells. These proteins control iron entry, cellular iron distribution but also iron exit from prostate cells. Iron dysmetabolism is not an exclusive feature of prostate cancer cells, but it is observed in other cells of the tumor microenvironment. Disrupting the machinery that secures iron for prostate cancer cells can retard tumor growth and its invasive potential. This review unveils the current understanding of the ways that prostate cancer cells secure iron in the tumor milieu and how can we exploit this knowledge for therapeutic purposes.

Iron in the Tumor Microenvironment-Connecting the Dots

Iron metabolism and tumor biology are intimately linked. Iron facilitates the production of oxygen radicals, which may either result in iron-induced cell death, ferroptosis, or contribute to mutagenicity and malignant transformation. Once transformed, malignant cells require high amounts of iron for proliferation. In addition, iron has multiple regulatory effects on the immune system, thus affecting tumor surveillance by immune cells. For these reasons, inconsiderate iron supplementation in cancer patients has the potential of worsening disease course and outcome. On the other hand, chronic immune activation in the setting of malignancy alters systemic iron homeostasis and directs iron fluxes into myeloid cells. While this response aims at withdrawing iron from tumor cells, it may impair the effector functions of tumor-associated macrophages and will result in iron-restricted erythropoiesis and the development of anemia, subsequently. This review summarizes our current knowledge of the interconnections of iron homeostasis with cancer biology, discusses current clinical controversies in the treatment of anemia of cancer and focuses on the potential roles of iron in the solid tumor microenvironment, also speculating on yet unknown molecular mechanisms.

The role of transferrin receptor in the Helicobacter pylori pathogenesis; L-ferritin as a novel marker for intestinal metaplasia

Helicobacter pylori growth requirements is a prerequisite to invade gastric epithelium and the process of injury to gastric cells will eventually lead to gastric cancer. The aim of this study is to investigate the effect of iron challenge on the expression of genes involved in iron homeostasis. The presence of Phosphoglucosamine mutase (glmM), cytotoxin-associated gene A (cagA) and vacuolating cytotoxin A (vacA) genes and mRNA expression of Iron Regulatory Protein 2 (IRP2), Transferrin Receptor (TFRC) and Ferritin Light Chain (FTL) genes in samples of 28 normal gastric mucosa, 33 chronic gastritis, 29 gastritis with intestinal metaplasia, 29 intestinal type adenocarcinoma patients were examined by real-time PCR. Immunohistochemistry was used to analyze cellular localization and protein levels. In the all H. pylori positive tissues, particularly in the basal regions of foveolar cells, TFRC was overexpressed (P < 0.05), and regardless of the H. pylori infection, FTL was overexpressed in all patient, exclusively in metaplastic glandular cells (P < 0.05). Furthermore, overexpression of IRP2 was associated with H. pylori positive chronic gastritis and intestinal metaplasia (P < 0.05). Our findings confirm the role of transferrin receptor in H. pylori attachment into the gastric mucosa to capture iron. Overexpression of FTL gene in metaplastic cells could be considered as a research background to investigate the role of this gene in the differentiation of gastric cells into intestinal metaplasia. In addition, this gene could be suggested as a diagnostic marker to be included among the other markers routinely performed by clinical diagnostic laboratories.