The iron chelator deferriferrichrysin induces paraptosis via extracellular signal-related kinase activation in cancer cells.

Cancer cells generally exhibit increased iron uptake, which contributes to their abnormal growth and metastatic ability. Iron chelators have thus recently attracted attention as potential anticancer agents. Here, we show that deferriferrichrysin (Dfcy), a natural product from Aspergillus oryzae acts as an iron chelator to induce paraptosis (a programmed cell death pathway characterized by ER dilation) in MCF-7 human breast cancer cells and H1299 human lung cancer cells. We first examined the anticancer efficacy of Dfcy in cancer cells and found that Dfcy induced ER dilation and reduced the number of viable cells. Extracellular signal-related kinase (ERK) was activated by Dfcy treatment, and the MEK inhibitor U0126, a small molecule commonly used to inhibit ERK activity, prevented the increase in ER dilation in Dfcy-treated cells. Concomitantly, the decrease in the number of viable cells upon treatment with Dfcy was attenuated by U0126. Taken together, these results demonstrate that the iron chelator Dfcy exhibits anticancer effects via induction of ERK-dependent paraptosis.

Design, synthesis and biological evaluation of 5H-[1,2,4]triazino[5,6-b]indole derivatives bearing a pyridinocycloalkyl moiety as iron chelators.

The avidity of cancer cells for iron highlights the potential for iron chelators to be used in cancer therapy. Herein, we designed and synthesized a novel series of 5H-[1,2,4]triazino[5,6-b]indole derivatives bearing a pyridinocycloalkyl moiety using a ring-fusion strategy based on the structure of an iron chelator, VLX600. The antiproliferative activity evaluation against cancer cells and normal cells led to the identification of compound 3k, which displayed the strongest antiproliferative activity in vitro against A549, MCF-7, Hela and HepG-2 with IC50 values of 0.59, 0.86, 1.31 and 0.92 µM, respectively, and had lower cytotoxicity against HEK293 than VLX600. Further investigations revealed that unlike VLX600, compound 3k selectively bound to ferrous ions, but not to ferric ions, and addition of Fe2+ abolished the cytotoxicity of 3k. Flow cytometry assays demonstrated that 3k arrested the cell cycle at the G1 phase and induced significant apoptosis in A549 cells in dose and time-dependent manners, corresponding to JC-1 staining assay results. Western blot analysis of Bcl-2, Bax and cleaved caspase-3 proteins further provided evidences that induction of apoptosis by 3k in A549 cells might be at least via the mitochondria pathway. These above results highlight that 3k is a valuable lead compound that deserves further investigation as an iron chelator for the treatment of cancer.

Amphetamine-like Deferiprone and Clioquinol Derivatives as Iron Chelating Agents.

The accumulation of iron in dopaminergic neurons can cause oxidative stress and dopaminergic neuron degeneration. Iron chelation therapy may reduce dopaminergic neurodegeneration, but chelators should be targeted towards dopaminergic cells. In this work, two series of compounds based on 8-hydroxyquinoline and deferiprone, iron chelators that have amphetamine-like structures, have been designed, synthesized and characterized. Each of these compounds chelated iron ions in aqueous solution. The hydroxyquinoline-based compounds exhibited stronger iron-binding constants than those of the deferiprone derivatives. The hydroxyquinoline-based compounds also exhibited greater free radical scavenging activities compared to the deferiprone derivatives. Molecular dynamics simulations showed that the hydroxyquinoline-based compounds generally bound well within human dopamine transporter cavities. Thus, these compounds are excellent candidates for future exploration as drugs against diseases that are affected by iron-induced dopaminergic neuron damage, such as Parkinson's disease.

ß-catenin-IRP2-primed iron availability to mitochondrial metabolism is druggable for active ß-catenin-mediated cancer.

BACKGROUND: Although ß-catenin signaling cascade is frequently altered in human cancers, targeting this pathway has not been approved for cancer treatment. METHODS: High-throughput screening of an FDA-approved drug library was conducted to identify therapeutics that selectively inhibited the cells with activated ß-catenin. Efficacy of iron chelator and mitochondrial inhibitor was evaluated for suppression of cell proliferation and tumorigenesis. Cellular chelatable iron levels were measured to gain insight into the potential vulnerability of ß-catenin-activated cells to iron deprivation. Extracellular flux analysis of mitochondrial function was conducted to evaluate the downstream events of iron deprivation. Chromatin immunoprecipitation, real-time quantitative PCR and immunoblotting were performed to identify ß-catenin targets. Depletion of iron-regulatory protein 2 (IRP2), a key regulator of cellular iron homeostasis, was carried out to elucidate its significance in ß-catenin-activated cells. Online databases were analyzed for correlation between ß-catenin activity and IRP2-TfR1 axis in human cancers. RESULTS: Iron chelators were identified as selective inhibitors against ß-catenin-activated cells. Deferoxamine mesylate, an iron chelator, preferentially repressed ß-catenin-activated cell proliferation and tumor formation in mice. Mechanically, ß-catenin stimulated the transcription of IRP2 to increase labile iron level. Depletion of IRP2-sequered iron impaired ß-catenin-invigorated mitochondrial function. Moreover, mitochondrial inhibitor S-Gboxin selectively reduced ß-catenin-associated cell viability and tumor formation. CONCLUSIONS: ß-catenin/IRP2/iron stimulation of mitochondrial energetics is targetable vulnerability of ß-catenin-potentiated cancer.

In vitro effect of the iron chelator deferiprone on the antimicrobial susceptibility and biofilms of Burkholderia pseudomallei.

This study evaluated the effect of the iron chelator deferiprone (DFP) on antimicrobial susceptibility and biofilm formation and maintenance by Burkholderia pseudomallei. Planktonic susceptibility to DFP alone and in combination with antibiotics was evaluated by broth microdilution and biofilm metabolic activity was determined with resazurin. DFP minimum inhibitory concentration (MIC) range was 4-64 µg/mL and in combination reduced the MIC for amoxicillin/clavulanate and meropenem. DFP reduced the biomass of biofilms by 21 and 12% at MIC and MIC/2, respectively. As for mature biofilms, DFP reduced the biomass by 47%, 59%, 52% and 30% at 512, 256, 128 and 64 µg/mL, respectively, but did not affect B. pseudomallei biofilm viability nor increased biofilm susceptibility to amoxicillin/clavulanate, meropenem and doxycycline. DFP inhibits planktonic growth and potentiates the effect of ß-lactams against B. pseudomallei in the planktonic state and reduces biofilm formation and the biomass of B. pseudomallei biofilms.

Site-activated multi target iron chelators with acetylcholinesterase (AChE) and monoamine oxidase (MAO) inhibitory activities for Alzheimer's disease therapy.

The first class of site-activated chelators with dual inhibition of acetyl-cholinesterase (AChE) and monoamine oxidase (MAO), rationally designed for simultaneously targeting the multiple pathogenic processes in Alzheimer's disease (AD) without significantly disrupting healthy metal metabolism in the body are discussed. It is demonstrated that the novel prochelator 2 was a selective and potent MAO-A inhibitor in vitro (IC50: 0.0077 ± 0.0007 µM) with moderate inhibition of MAO-B (IC50: 7.90 ± 1.34 µM). In vitro prochelator 2 also selectively inhibited AChE in a time-dependent manner and reach maximum inhibition of AChE after 2 h preincubation (IC50: 0.52 ± 0.07 µM for AChE, versus 44.90 ± 6.10 µM for BuChE). Prochelator 2 showed little affinity for metal (Fe, Cu, and Zn) ions until it bound to and was activated by AChE that is located predominately in the brain, releasing an active iron chelator M30. M30 is an efficient chelator for metal (Fe, Cu, and Zn) ions with the capabilities to suppress oxidative stress, to selectively inhibit MAO-A and B in the brain, and to regulate cerebral biometals dyshomeostasis in vivo; M30 is also a neuroprotective-neurorestorative chelator with a broad spectrum of activities against ß-amyloid (Aß) generation, amyloid plaques and neurofibrillary tangles (NFT) formation, and Aß aggregation induced by metal (Cu and Zn) ions. Both M30 and prochelator 2 were not toxic to Human SH-SY5Y neuroblastoma cells at low concentrations, but prochelator 2 shows limited cytotoxicity, at high concentrations. Together, these data suggest that prochelator 2 is a promise lead for simultaneously modulating multiple targets in AD.

Iron loss triggers mitophagy through induction of mitochondrial ferritin.

Mitochondrial quality is controlled by the selective removal of damaged mitochondria through mitophagy. Mitophagy impairment is associated with aging and many pathological conditions. An iron loss induced by iron chelator triggers mitophagy by a yet unknown mechanism. This type of mitophagy may have therapeutic potential, since iron chelators are clinically used. Here, we aimed to clarify the mechanisms by which iron loss induces mitophagy. Deferiprone, an iron chelator, treatment resulted in the increased expression of mitochondrial ferritin (FTMT) and the localization of FTMT precursor on the mitochondrial outer membrane. Specific protein 1 and its regulator hypoxia-inducible factor 1α were necessary for deferiprone-induced increase in FTMT. FTMT specifically interacted with nuclear receptor coactivator 4, an autophagic cargo receptor. Deferiprone-induced mitophagy occurred selectively for depolarized mitochondria. Additionally, deferiprone suppressed the development of hepatocellular carcinoma (HCC) in mice by inducing mitophagy. Silencing FTMT abrogated deferiprone-induced mitophagy and suppression of HCC. These results demonstrate the mechanisms by which iron loss induces mitophagy and provide a rationale for targeting mitophagic activation as a therapeutic strategy.

Improvement of Left Ventricular Graft Function Using an Iron-Chelator-Supplemented Bretschneider Solution in a Canine Model of Orthotopic Heart Transplantation.

Demand for organs is increasing while the number of donors remains constant. Nevertheless, not all organs are utilized due to the limited time window for heart transplantation (HTX). Therefore, we aimed to evaluate whether an iron-chelator-supplemented Bretschneider solution could protect the graft in a clinically relevant canine model of HTX with prolonged ischemic storage. HTX was performed in foxhounds. The ischemic time was standardized to 4 h, 8 h, 12 h or 16 h, depending on the experimental group. Left ventricular (LV) and vascular function were measured. Additionally, the myocardial high energy phosphate and iron content and the in-vitro myocyte force were evaluated. Iron chelator supplementation proved superior at a routine preservation time of 4 h, as well as for prolonged times of 8 h and longer. The supplementation groups recovered quickly compared to their controls. The LV function was preserved and coronary blood flow increased. This was also confirmed by in vitro myocyte force and vasorelaxation experiments. Additionally, the biochemical results showed significantly higher adenosine triphosphate content in the supplementation groups. The iron chelator LK614 played an important role in this mechanism by reducing the chelatable iron content. This study shows that an iron-chelator-supplemented Bretschneider solution effectively prevents myocardial/endothelial damage during short- as well as long-term conservation.

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.

The interaction between lipocalin 2 and dipyridine ketone hydrazone dithiocarbamte may influence respective function in proliferation and metastasis-related gene expressions in HepG2 cell.

LCN2 (Lipocalins) was first identified as iron transporter through associating with its siderophores and also involved in many cancer metastases, but its function is still paradoxical. We questioned that whether LCN2 might also associate exogenous iron chelator as does in inherent way and the association may influence their respective function. To address this issue, we investigated the effect of LCN2 on action of DpdtC (2,2'-dipyridine ketone hydrazone dithiocarbamte), an iron chelator in proliferation and metastasis-related gene expression. The results showed that exogenous LCN2 and DpdtC could inhibit growth of HepG2 cells, while the combination treatment enhanced their inhibitory effect both in proliferation and colony formation. This encouraged us to investigate the effect of the interaction on metastasis-related gene expression. The results revealed that both LCN2 and DpdtC impaired the wound healing of HepG2, but the inhibitory effect of DpdtC was significantly enhanced upon association with LCN2. Undergoing epithelium-mesenchymal transition (EMT) is a crucial step for cancer metastasis, LCN2 and DpdtC had opposite effects on EMT markers, the binding of DpdtC to LCN2 significantly weakened the regulation of it (or its iron chelate) on EMT markers. To insight into the interaction between LCN2 and DpdtC-iron, fluorescence titration and molecular docking were performed to obtain the association constant (~ 104 M-1) and thermodynamic parameters (ΔG = - 26.10 kJ/mol). Importantly this study provided evidence that siderophores-loading state of LCN2 may influence its function, which be helpful for understanding the contradictory role of LCN2 in the metastasis of cancer.

Benefits of Iron Chelators in the Treatment of Parkinson's Disease.

As a novel discovered regulated cell death pattern, ferroptosis has been associated with the development of Parkinson's disease (PD) and has attracted widespread attention. Nevertheless, the relationship between ferroptosis and PD pathogenesis is still unclear. This study aims to investigate the effect of iron overload on dopaminergic (DA) neurons and its correlation with ferroptosis. Here we use nerve growth factor (NGF) induced PC12 cells which are derived from pheochromocytoma of the rat adrenal to establish a classical PD in vitro model. We found significantly decreased cell viability in NGF-PC12 cell under ammonium ferric citrate (FAC) administration. Moreover, excessive intracellular iron ions induced the increase of (reactive oxygen species) ROS release as well as the decrease of mitochondrial membrane potential in PC12-NGF cells. In addition, we also found that overloaded iron can activate cell apoptosis and ferroptosis pathways, which led to cell death. Furthermore, MPP-induced PD cells were characterized by mitochondrial shrinkage, decreased expression of glutathione peroxidase 4 (Gpx4) and ferritin heavy chain (FTH1), and increased divalent metal transporter (DMT1) and transferrin receptor 1 (TfR1) expression level. In contrast, Lip-1 and DFO increased the expression level of GPX4 and FTH1 compared to MPP-induced PD cell. In conclusion, we indicated that overloaded intracellular iron contributes to neurons death via apoptosis and ferroptosis pathways, while DFO, an iron chelator, can inhibit ferroptosis in order to protect the neurons in vitro.

Further SAR studies on natural template based neuroprotective molecules for the treatment of Alzheimer's disease.

In our earlier paper, we described ferulic acid (FA) template based novel series of multifunctional cholinesterase (ChE) inhibitors for the management of AD. This report has further extended the structure-activity relationship (SAR) studies of this series of molecules in a calibrated manner to improve upon the ChEs inhibition and antioxidant property to identify the novel potent multifunctional molecules. To investigate the effect of replacement of phenylpiperazine ring with benzylpiperazine, increase in the linker length between FA and substituted phenyl ring, and replacement of indole moiety with tryptamine on this molecular template, three series of novel molecules were developed. All synthesized compounds were tested for their acetyl and butyryl cholinestrases (AChE and BChE) inhibitory properties. Enzyme inhibition and PAS binding studies identified compound 13b as a lead molecule with potent inhibitor property towards AChE/BChE (AChE IC50 = 0.96 ± 0.14 µM, BChE IC50 = 1.23 ± 0.23 µM) compared to earlier identified lead molecule EJMC-G (AChE IC50 = 5.74 ± 0.13 µM, BChE IC50 = 14.05 ± 0.10 µM, respectively). Molecular docking and dynamics studies revealed that 13b fits well into the active sites of AChE and BChE, forming stable and strong interactions with key residues Trp86, Ser125, Glu202, Trp 286, Phe295, Tyr 337 in AChE, and with Trp 82, Gly115, Tyr128, and Ser287 in BChE. The compound, 13b was found to be three times more potent antioxidant in a DPPH assay (IC50 = 20.25 ± 0.26 µM) over the earlier identified EJMC-B (IC50 = 61.98 ± 0.30 µM) and it also was able to chelate iron. Co-treatment of 13b with H2O2, significantly attenuated and reversed H2O2-induced toxicity in the SH-SY5Y cells. The parallel artificial membrane permeability assay-blood brain barrier (PAMPA-BBB) revealed that 13b could cross BBB efficiently. Finally, the in-vivo efficacy of 13b at dose of 10 mg/kg in scopolamine AD model has been demonstrated. The present study strongly suggests that the naturally inspired multifunctional molecule 13b may behave as a potential novel therapeutic agent for AD management.

Biofilm-specific uptake of a 4-pyridone-based iron chelator by Pseudomonas aeruginosa.

Iron is an essential nutrient for virtually all microbes and limiting the concentration of available iron is a potential strategy to be used as an alternative to antibiotic treatment. In this study we analysed the antimicrobial activity of two chelators, specifically 3-hydroxy-1,2-dimethyl-4(1H)-pyridone (deferiprone, DFP), which is clinically approved for the treatment of iron overload disorders, and its 1,2-diethyl homologue, CP94. Both compounds showed moderate activity towards planktonically growing P. aeruginosa cells, and the mechanism of action of these chelators was indeed by limiting the amount of free iron. Surprisingly, the compounds behaved very differently when the cells were grown in biofilms. DFP also showed inhibitory effects on biofilm formation but in contrast, CP94 stimulated this process, in particular at high concentrations. We hypothesised that CP94 behaves as an iron carrier, which was confirmed by our observation that it had antimicrobial synergy with the toxic metals, gallium and copper. This suggests that P. aeruginosa produces a biofilm-specific transport protein that recognises CP94 but not the closely related compound DFP.

Deferoxamine deconditioning increases neuronal vulnerability to hemoglobin.

Concomitant treatment with deferoxamine (DFO) protects neural cells from iron and heme-mediated oxidative injury, but also disrupts cell responses to iron loading that may be protective. We hypothesized that DFO treatment and withdrawal would subsequently increase neuronal vulnerability to hemoglobin. Pretreatment with DFO followed by its washout increased neuronal loss after subsequent hemoglobin exposure by 3-4-fold compared with control vehicle-pretreated cultures. This was associated with reduced ferritin induction by hemoglobin; expression of heme oxygenase-1, which catalyzes iron release from heme, was not altered. Increased neuronal loss was prevented by exogenous apoferritin or by continuing DFO or antioxidants throughout the experimental course. Cell nonheme iron levels after hemoglobin treatment were similar in DFO-pretreated and control cultures. These results indicate that DFO deconditions neurons and subsequently increases their vulnerability to heme-mediated injury. Its net effect after CNS hemorrhage may be highly dependent on the timing and duration of its administration. Withdrawal of DFO while heme or iron levels remain elevated may be deleterious, and may negate any benefit of prior concomitant therapy.

Novel retinal findings in ß-thalassemia major: older age and higher ferritin level as the risk factors.

PURPOSE: To investigate retinal changes in ß-thalassemia major patients and identify their association with systemic risk factors. METHODS: In this prospective study, 120 ß-thalassemia major patients received complete ophthalmic examinations (best-corrected visual acuity, contrast sensitivity, color vision, and indirect ophthalmoscopy) and retinal imaging using color fundus photography and fundus autofluorescence imaging. Patients were grouped according to the presence of thalassemia-related retinal changes. The association between systemic risk factors (age, type and duration of iron chelator use, history of splenectomy, hemoglobin level, and ferritin level) and thalassemia-related retinal changes was investigated using logistic regression analysis. RESULTS: Thalassemia-related retinal changes were identified in 36.7% of patients. Several distinct retinal changes were observed, including retinal refractile bodies in 10% of patients and retinal hemorrhage in 5.8% of patients. Fundus autofluorescence imaging showed abnormal patterns in 36.3% of patients with thalassemia-related retinal changes and 18.4% of patients without thalassemia-related retinal changes. Age (odds ratio [OR] = 1.10, 95% confidence interval [CI] 1.03-1.18) and ferritin level (OR 1.16, 95% CI 1.01-1.33) were associated with thalassemia-related retinal changes. CONCLUSION: Novel retinal changes were observed in ß-thalassemia major patients. This study identified older age and higher ferritin level as risk factors for thalassemia-related retinal changes.

Magnetospirillum magneticum as a Living Iron Chelator Induces TfR1 Upregulation and Decreases Cell Viability in Cancer Cells.

Interest has grown in harnessing biological agents for cancer treatment as dynamic vectors with enhanced tumor targeting. While bacterial traits such as proliferation in tumors, modulation of an immune response, and local secretion of toxins have been well studied, less is known about bacteria as competitors for nutrients. Here, we investigated the use of a bacterial strain as a living iron chelator, competing for this nutrient vital to tumor growth and progression. We established an in vitro co-culture system consisting of the magnetotactic strain Magnetospirillum magneticum AMB-1 incubated under hypoxic conditions with human melanoma cells. Siderophore production by 108 AMB-1/mL in human transferrin (Tf)-supplemented media was quantified and found to be equivalent to a concentration of 3.78 µM ± 0.117 µM deferoxamine (DFO), a potent drug used in iron chelation therapy. Our experiments revealed an increased expression of transferrin receptor 1 (TfR1) and a significant decrease of cancer cell viability, indicating the bacteria's ability to alter iron homeostasis in human melanoma cells. Our results show the potential of a bacterial strain acting as a self-replicating iron-chelating agent, which could serve as an additional mechanism reinforcing current bacterial cancer therapies.

Identifying a Deferiprone-Resveratrol Hybrid as an Effective Lipophilic Anti-Plasmodial Agent.

Malaria i a serious health problem caused by Plasmodium spp. that can be treated by an anti-folate pyrimethamine (PYR) drug. Deferiprone (DFP) is an oral iron chelator used for the treatment of iron overload and has been recognized for its potential anti-malarial activity. Deferiprone-resveratrol hybrids (DFP-RVT) have been synthesized to present therapeutic efficacy at a level which is superior to DFP. We have focused on determining the lipophilicity, toxicity and inhibitory effects on P. falciparum growth and the iron-chelating activity of labile iron pools (LIPs) by DFP-RVT. According to our findings, DFP-RVT was more lipophilic than DFP (p < 0.05) and nontoxic to blood mononuclear cells. Potency for the inhibition of P. falciparum was PYR > DFP-RVT > DFP in the 3D7 strain (IC50 = 0.05, 16.82 and 47.67 µM, respectively) and DFP-RVT > DFP > PYR in the K1 strain (IC50 = 13.38, 42.02 and 105.61 µM, respectively). The combined treatment of DFP-RVT with PYR additionally enhanced the PYR activity in both strains. DFP-RVT dose-dependently lowered LIP levels in PRBCs and was observed to be more effective than DFP at equal concentrations. Thus, the DFP-RVT hybrid should be considered a candidate as an adjuvant anti-malarial drug through the deprivation of cellular iron.

Regulators of Iron Homeostasis: New Players in Metabolism, Cell Death, and Disease.

Iron is necessary for life, but can also cause cell death. Accordingly, cells evolved a robust, tightly regulated suite of genes for maintaining iron homeostasis. Previous mechanistic studies on iron homeostasis have granted insight into the role of iron in human health and disease. We highlight new regulators of iron metabolism, including iron-trafficking proteins [solute carrier family 39, SLC39, also known as ZRT/IRT-like protein, ZIP; and poly-(rC)-binding protein, PCBP] and a cargo receptor (NCOA4) that is crucial for release of ferritin-bound iron. We also discuss emerging roles of iron in apoptosis and a novel iron-dependent cell death pathway termed 'ferroptosis', the dysregulation of iron metabolism in human pathologies, and the use of iron chelators in cancer therapy.

Scavenging Bacterial Siderophores with Engineered Lipocalin Proteins as an Alternative Antimicrobial Strategy.

Iron acquisition mediated by siderophores, high-affinity chelators for which bacteria have evolved specific synthesis and uptake mechanisms, plays a crucial role in microbiology and in host-pathogen interactions. In the ongoing fight against bacterial infections, this area has attracted biomedical interest. Beyond several approaches to interfere with siderophore-mediated iron uptake from medicinal and immunochemistry, the development of high-affinity protein scavengers that tightly complex the siderophores produced by pathogenic bacteria has appeared as a novel strategy. Such binding proteins have been engineered based on siderocalin-also known as lipocalin 2-an endogenous human scavenger of enterobactin and bacillibactin that controls the systemic spreading of commensal bacteria such as Escherichia coli. By using combinatorial protein design, siderocalin was reshaped to bind several siderophores from Pseudomonas aeruginosa and, in particular, petrobactin from Bacillus anthracis, none of which is recognized by the natural protein. Such engineered versions of siderocalin effectively suppress the growth of corresponding pathogenic bacteria by depriving them of their iron supply and offer the potential to complement antibiotic therapy in situations of acute or persistent infection.

Inhibitory effects of iron depletion plus eribulin on the breast cancer microenvironment.

BACKGROUND: Iron is required for the proliferation of cancer cells, and its depletion suppresses tumor growth. Eribulin mesylate (eribulin), a non-taxane microtubule inhibitor, disrupts the tumor microenvironment via vascular remodeling and obstruction of the epithelial-mesenchymal transition (EMT). Herein, we investigated the effects of the iron chelator on tumor-related properties of breast cancer cells and the effects of iron chelator plus eribulin on tumor growth in vivo. METHODS: Two triple-negative breast cancer (TNBC) cell lines, MDA-MB-231 and BT-549, and one hormone-receptor positive breast cancer cell line, MCF-7, were used in our study. Cell proliferation, cell migration, cell cycle position, and gene expression were analyzed via MTT assays, wound-healing assays, flow cytometry, and quantitative real-time-polymerase chain reaction, respectively. For the in vivo experiments, mice with breast cancer xenografts were treated with the inhibitors, alone or together, and tumor volume was determined. RESULTS: Iron chelator inhibited breast cancer cell proliferation and decreased the proportion of S-phase cells. Conversely, it induced hypoxia, angiogenesis, EMT, and immune checkpoints, as determined by quantifying the expression of marker mRNAs in MDA-MB-231 and MCF-7 cells. Eribulin suppressed the expression of the hypoxia and EMT related marker mRNAs in the presence of iron chelator. Iron chelator plus eribulin inhibited tumor growth in vivo to a greater extent than did either inhibitor alone. CONCLUSIONS: Although iron chelator induces oncogenic events (hypoxia, angiogenesis, EMT, and immune checkpoints), it may be an effective treatment for breast cancer when administered in combination with eribulin.