Iron: The cancer connection

Iron-Sensitive Prodrugs That Trigger Active Ferroptosis in Drug-Tolerant Pancreatic Cancer Cells

Persister cancer cells represent rare populations of cells resistant to therapy. Cancer cells can exploit epithelial-mesenchymal plasticity to adopt a drug-tolerant state that does not depend on genetic alterations. Small molecules that can interfere with cell plasticity or kill cells in a cell state-dependent manner are highly sought after. Salinomycin has been shown to kill cancer cells in the mesenchymal state by sequestering iron in lysosomes, taking advantage of the iron addiction of this cell state. Here, we report the chemo- and stereoselective synthesis of a series of structurally complex small molecule chimeras of salinomycin derivatives and the iron-reactive dihydroartemisinin. We show that these chimeras accumulate in lysosomes and can react with iron to release bioactive species, thereby inducing ferroptosis in drug-tolerant pancreatic cancer cells and biopsy-derived organoids of pancreatic ductal adenocarcinoma. This work paves the way toward the development of new cancer medicines acting through active ferroptosis.

Poly(rC)-binding protein 1 represses ferritinophagy-mediated ferroptosis in head and neck cancer

A cytosolic iron chaperone poly(rC)-binding protein 1 (PCBP1) is a multifunctional RNA-binding protein involving gene transcription, RNA regulation, and iron loading to ferritins. PCBP1 is also known to repress autophagy, but the role of PCBP1 in ferritinophagy and ferroptosis remains unrevealed. Therefore, we examined the role of PCBP1 in ferritinophagy-mediated ferroptosis in head and neck cancer (HNC) cells. The effects of system xc^– cystine/glutamate antiporter (xCT) inhibitors and PCBP1 gene silencing/overexpression were tested on HNC cell lines and mouse tumor xenograft models. These effects were analyzed by assessing cell viability and death, lipid reactive oxygen species and iron production, lipid, malondialdehyde, mRNA/protein expression, and autophagy flux assays. Interaction between PCBP1 and BECN1 mRNA was also examined by luciferase and RNA-protein pull-down assays. PCBP1 gene silencing increased autophagosome generation and autophagic flux. Conversely, PCBP1 upregulation inhibited autophagy activation via direct binding to the CU-rich elements on the 3′-untranslated region (3′-UTR) of BECN1 mRNA. The internal deletion or mutation of the 3′-UTR F2 region recovered BECN1 mRNA stability repressed by PCBP1, resulting in enhanced ferritinophagy-mediated ferroptosis. Besides, PCBP1 knockdown promoted polyunsaturated fatty acid peroxidation by increasing ALOX15 expression. Further, excess iron accumulation caused mitochondrial dysfunction in PCBP1-suppressed cells. A ferroptosis inducer sulfasalazine significantly suppressed tumor growth in mice with the transplantation of PCBP1-silenced HNC. Our data suggest that the dual functions of PCBP1 repressing BECN1 and ALOX15 mRNAs contribute to attenuating cancer susceptibility to ferroptosis inducers.

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PCBP1 expression is related to head and neck cancer survival and response to ferroptosis inducers.

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Knockdown of PCBP1 increased ferroptosis sensitivity by inducing an increased labile iron pool.

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PCBP1 negatively regulated ferritinophagy by the 3′-UTR binding of BECN1 mRNA.

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Knockdown of PCBP1 increased lipid peroxidation by ALOX15 expression.

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PCBP1 depletion promoted ferroptosis susceptibility in vitro and in vivo.

Identification of a Novel Inhibitor of TfR1 from Designed and Synthesized Muriceidine A Derivatives

The transferrin receptor 1 (TfR1) plays a key role in cellular iron uptake through its interaction with iron-bound Tf. TfR1 is often reported to be overexpressed in malignant cells, and this increase may be associated with poor prognosis in different types of cancer, which makes it an attractive target for antitumor therapy. The marine natural product Muriceidine A is a potent anticancer agent reported in our previous work. In this study, we designed and synthesized a series of Muriceidine A derivatives and described the systematic investigation into their cytotoxic activities against four tumor cells. Most of the derivatives showed stronger antitumor activity and we found that the introduction of electron-donating groups at position C-2 of unsaturated piperidine was beneficial to anticancer activity and unsaturated piperidine was responsible for the antiproliferative activity. Among these compounds, 12b (methyl at position C-2 of unsaturated piperidine) exhibited the strongest cytotoxicity against MDA-MB-231 cells. Further pharmacological research showed that 12b bound to Transferrin receptor 1 (TfR1) directly caused iron deprivation and ROS imbalance along with the degradations of several oncoproteins, especially FGFR1, through the proteasome pathway; thus, inducing cell cycle arrest and apoptosis in MDA-MB-231 breast cancer cells. Our findings indicate that 12b is a promising lead compound targeting TfR1 for triple negative breast cancer.

High-Affinity Single-Domain Antibodies for Analyzing Human Apo- and Holo-Transferrin

A highly efficient technology for generating new monoclonal single-domain recombinant antibodies (nanobodies) was used to obtain a panel of nanobodies recognizing human apo- and/or holo-transferrin. This article is devoted to the primary analysis of the properties of two different variants of the new nanobodies obtained by us, as well as to the demonstration of the unique potential of their application for diagnostic studies. The simultaneous use of immunosorbents based on these nanobodies apparently makes it possible to detect changes in the relative abundance of apo- and holo-transferrin in human biological fluids. Such changes could potentially be indicative of an increased risk or degree of development of pathological processes, such as malignant neoplasms in humans.

Iron Metabolism in Aging and Age-Related Diseases

Iron is a trace metal element necessary to maintain life and is also involved in a variety of biological processes. Aging refers to the natural life process in which the physiological functions of the various systems, organs, and tissues decline, affected by genetic and environmental factors. Therefore, it is imperative to investigate the relationship between iron metabolism and aging-related diseases, including neurodegenerative diseases. During aging, the accumulation of nonheme iron destroys the stability of the intracellular environment. The destruction of iron homeostasis can induce cell damage by producing hydroxyl free radicals, leading to mitochondrial dysfunction, brain aging, and even organismal aging. In this review, we have briefly summarized the role of the metabolic process of iron in the body, then discussed recent developments of iron metabolism in aging and age-related neurodegenerative diseases, and finally, explored some iron chelators as treatment strategies for those disorders. Understanding the roles of iron metabolism in aging and neurodegenerative diseases will fill the knowledge gap in the field. This review could provide new insights into the research on iron metabolism and age-related neurodegenerative diseases.

Near-infrared chemiluminescence imaging of superoxide anion production in kidneys with iron3+-nitrilotriacetate-induced acute renal oxidative stress in rats

Iron-catalyzed oxidative stress generates reactive oxygen species in the kidney and induces oxidative damage including lipid, protein, and DNA modifications which induces renal injury and may lead to cancer. An analysis of oxidative stress dynamics by reactive oxygen species has not been performed non-invasively in real time in intact kidneys and is a significant challenge in biology and medicine. Here, I report that MCLA-800 is a near-infrared chemiluminescent probe that visualizes the dynamics of superoxide anion (O₂^•-) production and the upstream generation of reactive oxygen species in living rat kidneys suffering acute renal oxidative stress induced by intraperitoneal administration of iron³⁺-nitrilotriacetate (Fe³⁺-NTA) as a representative Fe³⁺ chelate. MCLA-800 was intravenously injected at 250 nmol/kg body weight and immediately transported to the kidneys with the emitting light dependent on O₂^•- production. The magnitude of O₂^•- production correlated with the Fe³⁺-NTA dose. O₂^•- was continuously produced in the blood stream following Fe³⁺-NTA injection at 0.15 mmol/kg body weight, while peak production in the renal cortex occurred at 24 h, then decreased to the background level at 72 h. This study clearly revealed the dynamics of Fe³⁺-NTA-mediated O₂^•- production in the living kidney by chemiluminescent imaging of O₂^•- production using MCLA-800.

Persister cancer cells: Iron addiction and vulnerability to ferroptosis

Ferroptosis is a unique type of non-apoptotic cell death resulting from the unrestrained occurrence of peroxidized phospholipids, which are subject to iron-mediated production of lethal oxygen radicals. This cell death modality has been detected across many organisms, including in mammals, where it can be used as a defense mechanism against pathogens or even harnessed by T cells to sensitize tumor cells toward effective killing. Conversely, ferroptosis is considered one of the main cell death mechanisms promoting degenerative diseases. Emerging evidence suggests that ferroptosis represents a vulnerability in certain cancers. Here, we critically review recent advances linking ferroptosis vulnerabilities of dedifferentiating and persister cancer cells to the dependency of these cells on iron, a potential Achilles heel for small-molecule intervention. We provide a perspective on the mechanisms reliant on iron that contribute to the persister cancer cell state and how this dependency may be exploited for therapeutic benefits.

Double chelation of Iron through dimer formation of favipiravir: Density functional theory analysis

This work was performed to examine an idea about full chelation of Iron (Fe) by well-known favipiravir (Fav) as a possible mechanism of action for medication of COVID-19 patients. To this aim, formations of Fe- mediated dimers of Fav were investigated by performing density functional theory (DFT) computations of electronic and structural features for singular and dimer models. The results indicated that the models of dimers were suitable for formation, in which two cis (D1) and trans (D2) models were obtained regarding the configurations of two Fav counterparts towards each other. Energy results indicated that formation of D1 was slightly more favorable than formation of D2. Molecular orbital features affirmed hypothesized interacting sites of Fav for Fe-mediated dimers formations, in which atomic charges and other molecular orbital related representations affirmed such achievements. Moreover, detection of such dimer formation was also possible by monitoring variations of molecular orbitals features. As a consequence, formations of Fe-mediated dimers of Fav could be achievable for possible removal of excess of Fe as a proposed mechanism of action for Fav in medication of COVID-19 patients.

Insight into the influence of the polymerization time of polydopamine nanoparticles on their size, surface properties and nanomedical applications

In the last decade, novel strategies to synthesize polydopamine nanoparticles (PDA NPs) have been continuously developed owing to useful applications of this synthetic melanin analog in nanotechnology.

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.

Ferroptosis: Cancer Stem Cells Rely on Iron until "to Die for" It

Cancer stem cells (CSCs) are a distinct subpopulation of tumor cells with stem cell-like features. Able to initiate and sustain tumor growth and mostly resistant to anti-cancer therapies, they are thought responsible for tumor recurrence and metastasis. Recent accumulated evidence supports that iron metabolism with the recent discovery of ferroptosis constitutes a promising new lead in the field of anti-CSC therapeutic strategies. Indeed, iron uptake, efflux, storage and regulation pathways are all over-engaged in the tumor microenvironment suggesting that the reprogramming of iron metabolism is a crucial occurrence in tumor cell survival. In particular, recent studies have highlighted the importance of iron metabolism in the maintenance of CSCs. Furthermore, the high concentration of iron found in CSCs, as compared to non-CSCs, underlines their iron addiction. In line with this, if iron is an essential macronutrient that is nevertheless highly reactive, it represents their Achilles’ heel by inducing ferroptosis cell death and therefore providing opportunities to target CSCs. In this review, we first summarize our current understanding of iron metabolism and its regulation in CSCs. Then, we provide an overview of the current knowledge of ferroptosis and discuss the role of autophagy in the (regulation of) ferroptotic pathways. Finally, we discuss the potential therapeutic strategies that could be used for inducing ferroptosis in CSCs to treat cancer.

RNA m6A Demethylase ALKBH5 Protects Against Pancreatic Ductal Adenocarcinoma via Targeting Regulators of Iron Metabolism

Although RNA m6A regulators have been implicated in the tumorigenesis of several different types of tumors, including pancreatic cancer, their clinical relevance and intrinsic regulatory mechanism remain elusive. This study analyzed eight m6A regulators (METTL3, METTL14, WTAP, FTO, ALKBH5, and YTHDF1-3) in pancreatic ductal adenocarcinoma (PDAC) and found that only RNA m6A demethylase ALKBH5 serves as an independent favorable prognostic marker for this tumor. To better understand the molecular mechanism underlying the protective effect conferred by ALKBH5 against pancreatic tumorigenesis, we performed a transcriptome-wide analysis of m6A methylation, gene expression, and alternative splicing (AS) using the MIA PaCa-2 stable cell line with ALKBH5 overexpression. We demonstrated that ALKBH5 overexpression induced a reduction in RNA m6A levels globally. Furthermore, mRNAs encoding ubiquitin ligase FBXL5, and mitochondrial iron importers SLC25A28 and SLC25A37, were identified as substrates of ALKBH5. Mechanistically, the RNA stabilities of FBXL5 and SLC25A28, and the AS of SLC25A37 were affected, which led to their upregulation in pancreatic cancer cell line. Particularly, we observed that downregulation of FBXL5 in tumor samples correlated with shorter survival time of patients. Owing to FBXL5-mediated degradation, ALKBH5 overexpression incurred a significant reduction in iron-regulatory protein IRP2 and the modulator of epithelial-mesenchymal transition (EMT) SNAI1. Notably, ALKBH5 overexpression led to a significant reduction in intracellular iron levels as well as cell migratory and invasive abilities, which could be rescued by knocking down FBXL5. Overall, our results reveal a previously uncharacterized mechanism of ALKBH5 in protecting against PDAC through modulating regulators of iron metabolism and underscore the multifaceted role of m6A in pancreatic cancer.

Genomic analysis uncovers prognostic and immunogenic characteristics of ferroptosis for clear cell renal cell carcinoma

In this study, the characteristic patterns of ferroptosis in clear cell renal cell carcinoma (ccRCC) were systematically investigated with the interactions between ferroptosis and the tumor microenvironment (TME). On the mRNA expression profiles of 57 ferroptosis-related genes (FRGs), three ferroptosis patterns were constructed, with distinct prognosis and immune cell infiltrations (especially T cells and dendritic cells). The high ferroptosis scores were characterized by poorer prognosis, increased T cell infiltration, higher immune and stromal scores, elevated tumor mutation burden, and enhanced response to anti-CTLA4 immunotherapy. Meanwhile, the low ferroptosis scores were distinctly associated with enhanced tumor purity and amino acid and fatty acid metabolism pathways. Following validation, the ferroptosis score was an independent and effective prognostic factor. Collectively, ferroptosis could be involved in the diverse and complex TME. Evaluation of the ferroptosis patterns may heighten the comprehension about immune infiltrations in the TME, assisting oncologists to generate individualized immunotherapeutic strategies.

Development of Novel Antimicrobial and Antiviral Green Synthesized Silver Nanocomposites for the Visual Detection of Fe3+ Ions

In the current research, we present a single-step, one-pot, room temperature green synthesis approach for the development of functional poly(tannic acid)-based silver nanocomposites. Silver nanocomposites were synthesized using only tannic acid (plant polyphenol) as a reducing and capping agent. At room temperature and under mildly alkaline conditions, tannic acid reduces the silver salt into nanoparticles. Tannic acid undergoes oxidation and self-polymerization before the encapsulating of the synthesized silver nanoparticle and forms silver nanocomposites with a thick capping layer of poly(tannic acid). No organic solvents, special instruments, or toxic chemicals were used during the synthesis process. The results for the silver nanocomposites prepared under optimum conditions confirmed the successful synthesis of nearly spherical and fine nanocomposites (10.61 ± 1.55 nm) with a thick capping layer of poly(tannic acid) (~3 nm). With these nanocomposites, iron could be detected without any special instrument or technique. It was also demonstrated that, in the presence of Fe³⁺ ions (visual detection limit ~20 μM), nanocomposites aggregated using the coordination chemistry and exhibited visible color change. Ultraviolet-visible (UV–vis) and scanning electron microscopy (SEM) analysis also confirmed the formation of aggregate after the addition of the analyte in the detection system (colored nanocomposites). The unique analytic performance, simplicity, and ease of synthesis of the developed functional nanocomposites make them suitable for large-scale applications, especially in the fields of medical, sensing, and environmental monitoring. For the medical application, it is shown that synthesized nanocomposites can strongly inhibit the growth of Escherichia coli and Staphylococcus aureus. Furthermore, the particles also exhibit very good antifungal and antiviral activity.

An out of box thinking: the changes of iron-porphyrin during meat processing and gastrointestinal tract and some methods for reducing its potential health hazard

Iron-porphyrin is a very important substance in organisms, especially in animals. It is not only the source of iron in human body, but is also the catalytic center of many reactions. Previous studies suggested that adequate intake of iron was important for the health of human, especially for children and pregnant women. However, associated diseases caused by iron over-intake and excessive meat consumption suggested its potential harmfulness for human health. During meat processing, Iron-porphyrin will cause the oxidation of proteins and fatty acids. In the gastrointestinal tract, iron-porphyrin can induce the production of malondialdehyde, fats oxidation, and indirectly cause oxidation of amino acids and nitrates etc. Iron-porphyrin enters the intestinal tract and disturbs the balance of intestinal flora. Finally, some common measures for inhibiting its activity are introduced, including the use of chelating agent, antioxidants, competitive inhibitor, etc., as well as give the hypothesis that sodium chloride increases the catalytic activity of iron-porphyrin. The purpose of this review is to present an overview of current knowledge about the changes of iron-porphyrin in the whole technico- and gastrointesto- processing axis and to provide ideas for further research in meat nutrition.

Mesenchymal stem cells: ideal seeds for treating diseases

Mesenchymal stem cells (MSCs), a kind of multipotent stem cells with self-renewal ability and multi-differentiation ability, have become the “practical stem cells” for the treatment of diseases. MSCs have immunomodulatory properties and can be used to treat autoimmune diseases, such as systemic lupus erythematosus (SLE) and Crohn’s disease. MSCs also can be used in cancer and aging. At present, many clinical experiments are using MSCs. MSCs can reduce the occurrence of inflammation and apoptosis of tissue cells, and promote the proliferation of endogenous tissue and organ cells, so as to achieve the effect of repairing tissue and organs. MSCs presumably also play an important role in Corona Virus Disease 2019 (COVID-19) infection.

Consequences of NaCT/SLC13A5/mINDY deficiency: good versus evil, separated only by the blood-brain barrier

NaCT/SLC13A5 is a Na⁺-coupled transporter for citrate in hepatocytes, neurons, and testes. It is also called mINDY (mammalian ortholog of ‘I'm Not Dead Yet’ in Drosophila). Deletion of Slc13a5 in mice leads to an advantageous phenotype, protecting against diet-induced obesity, and diabetes. In contrast, loss-of-function mutations in SLC13A5 in humans cause a severe disease, EIEE25/DEE25 (early infantile epileptic encephalopathy-25/developmental epileptic encephalopathy-25). The difference between mice and humans in the consequences of the transporter deficiency is intriguing but probably explainable by the species-specific differences in the functional features of the transporter. Mouse Slc13a5 is a low-capacity transporter, whereas human SLC13A5 is a high-capacity transporter, thus leading to quantitative differences in citrate entry into cells via the transporter. These findings raise doubts as to the utility of mouse models to evaluate NaCT biology in humans. NaCT-mediated citrate entry in the liver impacts fatty acid and cholesterol synthesis, fatty acid oxidation, glycolysis, and gluconeogenesis; in neurons, this process is essential for the synthesis of the neurotransmitters glutamate, GABA, and acetylcholine. Thus, SLC13A5 deficiency protects against obesity and diabetes based on what the transporter does in hepatocytes, but leads to severe brain deficits based on what the transporter does in neurons. These beneficial versus detrimental effects of SLC13A5 deficiency are separable only by the blood-brain barrier. Can we harness the beneficial effects of SLC13A5 deficiency without the detrimental effects? In theory, this should be feasible with selective inhibitors of NaCT, which work only in the liver and do not get across the blood-brain barrier.

Pancreatic Ductal Adenocarcinoma: The Dawn of the Era of Nuclear Medicine?

Pancreatic ductal adenocarcinoma (PDAC), accounting for 90-95% of all pancreatic tumors, is a highly devastating disease associated with poor prognosis. The lack of accurate diagnostic tests and failure of conventional therapies contribute to this pejorative issue. Over the last decade, the advent of theranostics in nuclear medicine has opened great opportunities for the diagnosis and treatment of several solid tumors. Several radiotracers dedicated to PDAC imaging or internal vectorized radiotherapy have been developed and some of them are currently under clinical consideration. The functional information provided by Positron Emission Tomography (PET) or Single Photon Emission Computed Tomography (SPECT) could indeed provide an additive diagnostic value and thus help in the selection of patients for targeted therapies. Moreover, the therapeutic potential of β-- and α-emitter-radiolabeled agents could also overcome the resistance to conventional therapies. This review summarizes the current knowledge concerning the recent developments in the nuclear medicine field for the management of PDAC patients.

Chemistry and biology of ferritin

Iron is an essential element required by cells and has been described as a key player in ferroptosis. Ferritin operates as a fundamental iron storage protein in cells forming multimeric assemblies with crystalline iron cores. We discuss the latest findings on ferritin structure and activity and its link to cell metabolism and ferroptosis. The chemistry of iron, including its oxidation states, is important for its biological functions, its reactivity, and the biology of ferritin. Ferritin can be localized in different cellular compartments and secreted by cells with a variety of functions depending on its spatial context. Here, we discuss how cellular ferritin localization is tightly linked to its function in a tissue-specific manner, and how impairment of iron homeostasis is implicated in diseases, including cancer and coronavirus disease 2019. Ferritin is a potential biomarker and we discuss latest research where it has been employed for imaging purposes and drug delivery.

Role of iron in cancer

Iron is an essential metal for cellular metabolism. The reduced form of iron is a cofactor in numerous redox reactions in the cell and is therefore required for many vital physiological functions. Since iron is an oxidatively active metal, its homeostasis is tightly regulated in healthy cell. Most of iron exists in a protein-bound form, in erythrocytes as the heme compound hemoglobin, and in storage proteins such as ferritin, hemosiderin and myoglobin. Iron also is bound to proteins and non-heme enzymes involved in oxidation-reduction reactions and the transfer of electrons. There is no free iron inside the cell, however a small fraction of loosely bound iron is found in the cytoplasm. This poorly defined pool of ferrous iron is called labile iron pool. Under pathological conditions iron homeostasis may be disrupted at different levels including absorption, systemic transportation, and cellular uptake and storage. Cancer cells display dysregulated iron homeostasis and, for reasons yet poorly understood, require more iron for their metabolism and growth. As a result, in cancer cells labile iron pool is increased, and loosely bound iron catalyzes Fenton reaction and perhaps other reactions that generate reactive oxygen species. Oxygen-derived free radicals produce DNA mutations, damage proteins and lipids resulting in either cell death or cell transformation.

Emerging mechanisms and targeted therapy of ferroptosis in cancer

Ferroptosis is an iron- and lipid reactive oxygen species (ROS)-dependent form of programmed cell death that is distinct from other forms of regulatory cell death at the morphological, biological, and genetic levels. Emerging evidence suggests critical roles for ferroptosis in cell metabolism, the redox status, and various diseases, such as cancers, nervous system diseases, and ischemia-reperfusion injury, with ferroptosis-related proteins. Ferroptosis is inhibited in diverse cancer types and functions as a dynamic tumor suppressor in cancer development, indicating that the regulation of ferroptosis can be utilized as an interventional target for tumor treatment. Small molecules and nanomaterials that reprogram cancer cells to undergo ferroptosis are considered effective drugs for cancer therapy. Here, we systematically summarize the molecular basis of ferroptosis, the suppressive effect of ferroptosis on tumors, the effect of ferroptosis on cellular metabolism and the tumor microenvironment (TME), and ferroptosis-inducing agents for tumor therapeutics. An understanding of the latest progress in ferroptosis could provide references for proposing new potential targets for the treatment of cancers.

Global miRNA/proteomic analyses identify miRNAs at 14q32 and 3p21, which contribute to features of chronic iron-exposed fallopian tube epithelial cells

Malignant transformation of fallopian tube secretory epithelial cells (FTSECs) is a key contributing event to the development of high-grade serous ovarian carcinoma (HGSOC). Our recent findings implicate oncogenic transformative events in chronic iron-exposed FTSECs, including increased expression of oncogenic mediators, increased telomerase transcripts, and increased growth/migratory potential. Herein, we extend these studies by implementing an integrated transcriptomic and mass spectrometry-based proteomics approach to identify global miRNA and protein alterations, for which we also investigate a subset of these targets to iron-induced functional alterations. Proteomic analysis identified > 4500 proteins, of which 243 targets were differentially expressed. Sixty-five differentially expressed miRNAs were identified, of which 35 were associated with the “top” proteomic molecules (> fourfold change) identified by Ingenuity Pathway Analysis. Twenty of these 35 miRNAs are at the 14q32 locus (encoding a cluster of 54 miRNAs) with potential to be regulated by DNA methylation and histone deacetylation. At 14q32, miR-432-5p and miR-127-3p were ~ 100-fold downregulated whereas miR-138-5p was 16-fold downregulated at 3p21 in chronic iron-exposed FTSECs. Combinatorial treatment with methyltransferase and deacetylation inhibitors reversed expression of these miRNAs, suggesting chronic iron exposure alters miRNA expression via epigenetic alterations. In addition, PAX8, an important target in HGSOC and a potential miRNA target (from IPA) was epigenetically deregulated in iron-exposed FTSECs. However, both PAX8 and ALDH1A2 (another IPA-predicted target) were experimentally identified to be independently regulated by these miRNAs although TERT RNA was partially regulated by miR-138-5p. Interestingly, overexpression of miR-432-5p diminished cell numbers induced by long-term iron exposure in FTSECs. Collectively, our global profiling approaches uncovered patterns of miRNA and proteomic alterations that may be regulated by genome-wide epigenetic alterations and contribute to functional alterations induced by chronic iron exposure in FTSECs. This study may provide a platform to identify future biomarkers for early ovarian cancer detection and new targets for therapy.

Antibodies Targeting the Transferrin Receptor 1 (TfR1) as Direct Anti-cancer Agents

The transferrin receptor 1 (TfR1), also known as cluster of differentiation 71 (CD71), is a type II transmembrane glycoprotein that binds transferrin (Tf) and performs a critical role in cellular iron uptake through the interaction with iron-bound Tf. Iron is required for multiple cellular processes and is essential for DNA synthesis and, thus, cellular proliferation. Due to its central role in cancer cell pathology, malignant cells often overexpress TfR1 and this increased expression can be associated with poor prognosis in different types of cancer. The elevated levels of TfR1 expression on malignant cells, together with its extracellular accessibility, ability to internalize, and central role in cancer cell pathology make this receptor an attractive target for antibody-mediated therapy. The TfR1 can be targeted by antibodies for cancer therapy in two distinct ways: (1) indirectly through the use of antibodies conjugated to anti-cancer agents that are internalized by receptor-mediated endocytosis or (2) directly through the use of antibodies that disrupt the function of the receptor and/or induce Fc effector functions, such as antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cell-mediated phagocytosis (ADCP), or complement-dependent cytotoxicity (CDC). Although TfR1 has been used extensively as a target for antibody-mediated cancer therapy over the years, interest continues to increase for both targeting the receptor for delivery purposes and for its use as direct anti-cancer agents. This review focuses on the developments in the use of antibodies targeting TfR1 as direct anti-tumor agents.

MGST1 is a redox-sensitive repressor of ferroptosis in pancreatic cancer cells

Ferroptosis is a type of nonapoptotic cell death driven by lipid peroxidation. Here, we show a key role of MGST1 in inhibiting ferroptosis in cell cultures and mouse xenograft models. Ferroptosis activators induce MGST1 upregulation in human pancreatic ductal adenocarcinoma (PDAC) cell lines in an NFE2L2-dependent manner. The genetic depletion of MGST1 or NFE2L2 has a similar effect in promoting ferroptosis, whereas the re-expression of MGST1 restores the resistance of NFE2L2-knockdown cells to ferroptosis. MGST1 inhibits ferroptotic cancer cell death partly by binding to ALOX5, resulting in reduced lipid peroxidation. The expression of MGST1 is positively correlated with NFE2L2 expression in pancreatic tumors, which is implicated in the poor prognosis of patients with PDAC. These findings not only provide a valuable insight into the defense mechanism against ferroptotic cell death, but also indicate that targeting the MGST1 redox-sensitive pathway may be a promising strategy for the treatment of PDAC.

The iron chelator deferoxamine decreases myeloma cell survival

OBJECTIVE

This study evaluated serum ferritin (SF) levels and investigated their relationships with various clinical markers in patients with multiple myeloma (MM). Furthermore, the effects and molecular mechanism of deferoxamine (DFO) in myeloma cells were studied.

METHODS

Clinical data from 84 patients with MM were collected to evaluate SF content and its relationship with several important clinical parameters. MM1S and MM1R myeloma cells were chosen to investigate the effects of iron and DFO on cell survival and apoptosis.

RESULTS

Increased SF levels were detected in newly diagnosed patients, especially those with stage III disease or the κ isotype. SF content was positively correlated with β2-microglobulin, interleukin-6, and lactate dehydrogenase expression. Furthermore, patients with progressive or relapsed disease had higher SF levels. Importantly, iron chelation with DFO efficiently inhibited myeloma cell survival and accelerated apoptosis by regulating apoptosis-related genes.

CONCLUSIONS

The importance of SF for MM was highlighted. Additionally, it is suggested that DFO may be a good therapeutic option for MM.

Iron in immune cell function and host defense

The control over iron availability is crucial under homeostatic conditions and even more in the case of an infection. This results from diverse properties of iron: first, iron is an important trace element for the host as well as for the pathogen for various cellular and metabolic processes, second, free iron catalyzes Fenton reaction and is therefore producing reactive oxygen species as a part of the host defense machinery, third, iron exhibits important effects on immune cell function and differentiation and fourth almost every immune activation in turn impacts on iron metabolism and spatio-temporal iron distribution. The central importance of iron in the host and microbe interplay and thus for the course of infections led to diverse strategies to restrict iron for invading pathogens. In this review, we focus on how iron restriction to the pathogen is a powerful innate immune defense mechanism of the host called "nutritional immunity". Important proteins in the iron-host-pathogen interplay will be discussed as well as the influence of iron on the efficacy of innate and adaptive immunity. Recently described processes like ferritinophagy and ferroptosis are further covered in respect to their impact on inflammation and infection control and how they impact on our understanding of the interaction of host and pathogen.

Iron Supplementation Interferes With Immune Therapy of Murine Mammary Carcinoma by Inhibiting Anti-Tumor T Cell Function

Iron is both, an essential compound for many metabolic processes, and iron deficiency can impact on the proliferation of cells including lymphocytes but also tumor cells. On the other hand, excess iron-catalyzed radical formation can induce cellular toxicity which has been previously demonstrated for T cells in hereditary iron overload. Despite these interconnections, little is known on the effects of clinically approved intravenous iron supplements for curing cancer-related anemia, on T cell differentiation, tumor proliferation, anti-tumor T cell responses and, of clinical importance, on efficacy of cancer immunotherapies. Herein, we analyzed the effects of intravenous iron supplementation on T cell function and on the effectiveness of anti-cancer chemotherapy with IL-2/doxorubicin or immunotherapy with checkpoint-inhibitor anti-PD-L1 in C57Bl/6N female mice with implanted E0771 mammary carcinomas. We found that iron application resulted to an increased availability of iron in the tumor microenvironment and stimulation of tumor growth. In parallel, iron application inhibited the activation, expansion and survival of cytotoxic CD8⁺ T cells and of CD4⁺ T helper cells type 1 and significantly reduced the efficacy of the investigated anti-cancer treatments. Our results indicate that iron administration has a tumor growth promoting effect and impairs anti-cancer responses of tumor infiltrating T lymphocytes along with a reduced efficacy of anti-cancer therapies. Iron supplementation in cancer patients, especially in those treated with immunotherapies in a curative setting, may be thus used cautiously and prospective studies have to clarify the impact of such intervention on the outcome of patients.

Iron Dysregulation in Human Cancer: Altered Metabolism, Biomarkers for Diagnosis, Prognosis, Monitoring and Rationale for Therapy

Simple Summary

Iron is the more abundant metal ion in humans. It is essential for life as it has a role in various cellular processes involved, for instance, in cell metabolism and DNA synthesis. These functions are crucial for cell proliferation, and it is therefore not surprising that iron is accumulated in tumors. In this review, we describe normal and altered iron homeostasis mechanisms. We also provide a vision of iron-related proteins with altered expression in cancers and discuss their potential as diagnostic and/or prognostic biomarkers. Finally, we give an overview of therapeutic strategies acting on iron metabolism to fight against cancers.

Abstract

Iron (Fe) is a trace element that plays essential roles in various biological processes such as DNA synthesis and repair, as well as cellular energy production and oxygen transport, and it is currently widely recognized that iron homeostasis is dysregulated in many cancers. Indeed, several iron homeostasis proteins may be responsible for malignant tumor initiation, proliferation, and for the metastatic spread of tumors. A large number of studies demonstrated the potential clinical value of utilizing these deregulated proteins as prognostic and/or predictive biomarkers of malignancy and/or response to anticancer treatments. Additionally, the iron present in cancer cells and the importance of iron in ferroptosis cell death signaling pathways prompted the development of therapeutic strategies against advanced stage or resistant cancers. In this review, we select relevant and promising studies in the field of iron metabolism in cancer research and clinical oncology. Besides this, we discuss some co-existing discrepant findings. We also present and discuss the latest lines of research related to targeting iron, or its regulatory pathways, as potential promising anticancer strategies for human therapy. Iron chelators, such as deferoxamine or iron-oxide-based nanoparticles, which are already tested in clinical trials, alone or in combination with chemotherapy, are also reported.

Updates on the applications of iron-based nanoplatforms in tumor theranostics

With the development of biomedicine and materials science, the emerging research of iron-based nanoplatforms (INPs) have provided a bright future for tumor theranostics. Thanks to its excellent biocompatibility and diverse application potential, some INPs have successfully transformed from the laboratory to the clinic and market, making it one of the most successful nanoplatforms. Further investigations associated with its enormous biomedical potential is continuing, and new features of them are being demonstrated. The discovery of ferroptosis therapy opens up new avenue for the applications of INPs in tumor therapy, which is attracting tremendous attention from worldwide. It is well established that some of the INPs are capable of triggering the tumor cell ferroptosis efficiently, accelerating the tumor cell death process. Combined with anti-tumor drugs or other tumor therapy approaches, the INPs-induced ferroptosis are expected to break the bottleneck in the treatment of drug-resistant malignant tumors. In addition, other applications of INPs in tumor theranostics field are still active. Featured with the catalase-like ability, INPs were also well documented to reverse the tumor hypoxia as nanozymes, assisting and enhancing the oxygen-consuming tumor therapy approaches. And the unique magnetic property of INPs endow it with great potential in tumor diagnosis, hyperthermal therapy and target drug delivery. It is of great significance to summarize these new advances. Herein, the latest reports of the applications of INPs in tumor theranostics are classified to expound the trend of its research and development. The featured functions of it will be discussed in detail to provide a new insight. The key issues needing to be addressed and the development prospective will be put forward. We hope that this review will be helpful to understand the ample potential of INPs in tumor theranostics field.

A new survival model based on ferroptosis-related genes for prognostic prediction in clear cell renal cell carcinoma

In this study, we analyzed the clinical significance of ferroptosis-related genes (FRGs) in 32 cancer types in the GSCA database. We detected a 2-82% mutation rate among 36 FRGs. In clear cell renal cell carcinoma (ccRCC; n=539) tissues from the The Cancer Genome Atlas database, 30 of 36 FRGs were differentially expressed (up- or down-regulated) compared to normal kidney tissues (n=72). Consensus clustering analysis identified two clusters of FRGs based on similar co-expression in ccRCC tissues. We then used LASSO regression analysis to build a new survival model based on five risk-related FRGs (CARS, NCOA4, FANCD2, HMGCR, and SLC7A11). Receiver operating characteristic curve analysis confirmed good prognostic performance of the new survival model with an area under the curve of 0.73. High FANCD2, CARS, and SLC7A11 expression and low HMGCR and NCOA4 expression were associated with high-risk ccRCC patients. Multivariate analysis showed that risk score, age, stage, and grade were independent risk factors associated with prognosis in ccRCC. These findings demonstrate that this five risk-related FRG-based survival model accurately predicts prognosis in ccRCC patients, and suggest FRGs are potential prognostic biomarkers and therapeutic targets in several cancer types.