Non transferrin bound iron (NTBI) in acute leukemias throughout conventional intensive chemotherapy: kinetics of its appearance and potential predictive role in infectious complications

Iron, Copper, and Selenium: Cancer's Thing for Redox Bling

Cells require micronutrients for numerous basic functions. Among these, iron, copper, and selenium are particularly critical for redox metabolism, and their importance is heightened during oncogene-driven perturbations in cancer. In this review, which particularly focuses on iron, we describe how these micronutrients are carefully chaperoned about the body and made available to tissues, a process that is designed to limit the toxicity of free iron and copper or by-products of selenium metabolism. We delineate perturbations in iron metabolism and iron-dependent proteins that are observed in cancer, and describe the current approaches being used to target iron metabolism and iron-dependent processes.

Deferasirox Causes Leukaemia Cell Death through Nrf2-Induced Ferroptosis

Acute lymphoblastic leukaemia (ALL) is the most prevalent cancer in children, and excessive iron buildup resulting from blood transfusions and chemotherapy potentially has a negative impact on treatment outcomes and prognosis in patients with ALL. Therefore, initiating early iron chelation therapy during ALL treatment is a logical approach. Ideally, the selected iron chelator should also possess anti-leukaemia properties. The aim of the present study was to explore the potential impact and underlying mechanism of deferasirox (DFX) in ALL therapy. This study proved that DFX, an iron chelator, is capable of inducing leukaemia cell death through ferroptosis, which is achievable by increasing the expression of acetylated nuclear factor erythroid 2-related factor 2 (NRF2). More specifically, NRF2 acetylation on Lys599 was facilitated by acetyltransferase-p300/CBP. These findings indicate that DFX could serve as a potent adjunctive medication for patients with ALL. Moreover, DFX may offer dual benefits in ALL treatment, functioning as both an iron chelator and NRF2-modulating agent. Further research and clinical trials are necessary to fully elucidate the therapeutic potential of DFX in patients with ALL and incorporate it into treatment protocols.

Hypoferremia of inflammation: Innate host defense against infections

Iron is an essential nutrient for microbes, plants and animals. Multicellular organisms have evolved multiple strategies to control invading microbes by restricting microbial access to iron. Hypoferremia of inflammation is a rapidly-acting organismal response that prevents the formation of iron species that would be readily accessible to microbes. This review takes an evolutionary perspective to explore the mechanisms and host defense function of hypoferremia of inflammation and its clinical implications.

Iron Load Toxicity in Medicine: From Molecular and Cellular Aspects to Clinical Implications

Iron is essential for all organisms and cells. Diseases of iron imbalance affect billions of patients, including those with iron overload and other forms of iron toxicity. Excess iron load is an adverse prognostic factor for all diseases and can cause serious organ damage and fatalities following chronic red blood cell transfusions in patients of many conditions, including hemoglobinopathies, myelodyspasia, and hematopoietic stem cell transplantation. Similar toxicity of excess body iron load but at a slower rate of disease progression is found in idiopathic haemochromatosis patients. Excess iron deposition in different regions of the brain with suspected toxicity has been identified by MRI T2* and similar methods in many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Based on its role as the major biological catalyst of free radical reactions and the Fenton reaction, iron has also been implicated in all diseases associated with free radical pathology and tissue damage. Furthermore, the recent discovery of ferroptosis, which is a cell death program based on free radical generation by iron and cell membrane lipid oxidation, sparked thousands of investigations and the association of iron with cardiac, kidney, liver, and many other diseases, including cancer and infections. The toxicity implications of iron in a labile, non-protein bound form and its complexes with dietary molecules such as vitamin C and drugs such as doxorubicin and other xenobiotic molecules in relation to carcinogenesis and other forms of toxicity are also discussed. In each case and form of iron toxicity, the mechanistic insights, diagnostic criteria, and molecular interactions are essential for the design of new and effective therapeutic interventions and of future targeted therapeutic strategies. In particular, this approach has been successful for the treatment of most iron loading conditions and especially for the transition of thalassemia from a fatal to a chronic disease due to new therapeutic protocols resulting in the complete elimination of iron overload and of iron toxicity.

Unbalance in Iron Metabolism in Childhood Leukemia Converges with Treatment Intensity: Biochemical and Clinical Analysis

Simple Summary

In children undergoing therapy for acute leukemia or after hematopoietic cell transplantation, the following iron metabolism parameters were analyzed in the context of iron overload: (1) parameters measuring functional and storage iron pools: non-transferrin-bound iron (NTBI) and labile plasma iron (LPI) levels, iron, transferrin, total iron-binding capacity, ferritin, ferritin heavy and light chains; (2) proteins regulating iron absorption and its release from tissue stores: hepcidin, soluble hemojuvelin, soluble ferroportin-1; (3) proteins regulating the erythropoietic activity of bone marrow: erythroferrone, erythropoietin, soluble transferrin receptor. It has been shown that the occurrence of NTBI and LPI in the circulation and the intensification of disturbances in iron metabolism were associated with the intensity of anti-leukemic treatment and were the highest in the transplant group followed by the acute leukemia after treatment and de novo groups. In patients after transplantation, the most significant changes were found in NTBI, LPI, iron, ferritin, hepcidin, and ferroportin-1 levels.

Abstract

Objective: The aim of this study was to evaluate non-transferrin-bound iron (NTBI) and labile plasma iron (LPI) levels and other parameters of iron metabolism in children undergoing therapy for acute leukemia or after hematopoietic cell transplantation (HCT), in the context of iron overload. Patients: A total number of 85 children were prospectively included into four groups: controls, acute leukemia de novo, acute leukemia after intensive treatment, and after HCT. Methods: The following iron metabolism parameters were analyzed: (1) parameters measuring functional and storage iron pools: NTBI, LPI, iron, transferrin, total iron-binding capacity, ferritin, ferritin heavy and light chains; (2) proteins regulating iron absorption and its release from tissue stores: hepcidin, soluble hemojuvelin, soluble ferroportin-1; (3) proteins regulating the erythropoietic activity of bone marrow: erythroferrone, erythropoietin, soluble transferrin receptor. Results: Intensive treatment of leukemia in children was associated with the presence of serum NTBI and LPI, which was the highest in the HCT group followed by the acute leukemia after treatment and de novo groups. In patients after HCT, the most significant changes were found in NTBI, LPI, iron, ferritin, hepcidin, and ferroportin-1 levels. Conclusions: The occurrence of NTBI and LPI in the circulation and the intensification of disturbances in iron metabolism were associated with the intensity of the anti-leukemic treatment.

PROGNOSIS OF ACUTE LEUKEMIA DEPENDING ON THE IRON METABOLISM PARAMETERS IN CHILDREN AFTER CHORNOBYL NUCLEAR POWER PLANT ACCIDENT

OBJECTIVE

To determine the influence of iron metabolism on the prognosis of acute lymphoblastic (ALL) and (AML)myeloblastic leukemia at the different phases of chemotherapy in children after Chоrnobyl accident.

MATERIALS AND METHODS

333 children (295 - ALL, 38 - AML) were examined at the stages of chemotherapy. Thecomparison group included 93 children without leukemia. Acute leukemia variants, patients survival, relapses, thenature of disease (live child or died), iron methabolism (morphometric parameters of erythrocytes, SI, SF, STf, TS),manifestations of dyserythropoiesis, bone marrow sideroblast and patients radiation dose were taken into account.

RESULTS

In 295 patients with ALL the following variants of leukemia were established: pro-B-ALL in 23, «common»type of ALL in 224, pre-B-ALL in 29, T-ALL in 19. Thirty eight patients were diagnosed with AML (11 - M1, 19 - M2,8 - M4). Doses of radiation in patients with AL were (2.78 ± 0.10) mSv and they did not correlate with clinical andhematological parameters, disease variant. Relapse rates and shorter survival were in patients with T-ALL, pro-B-ALLand AML with SF levels > 500 ng/ml (p < 0.05). The amount of children with normochromic-normocytic anemias andmanifestations of dysplasia of erythroid lineage elements was greater in the AML than in ALL. SF content in patientswas elevated during chemotherapy and was lower than the initial one only in the remission period. Transferrin wasreliably overloaded with iron: TS (70.2 ± 2.3) % compared with the control group (32.7 ± 2.1) %. Correlationbetween TS and survival of patients was detected (rs = -0.45). Direct correlation between the number of iron granules in erythrocariocytes and SF level (rs = 0.43) was established, indicating the phenomena of ineffective erythropoiesis.

CONCLUSIONS

The negative influence of iron excess in the patients body on the hemopoiesis function, manifestations of ineffective erythropoiesis and the course of acute leukemia in children have been established. Changes inferrokinetic processes in children can be the basis of leukemоgenesis development.

Iron in infection and immunity

Iron is an essential micronutrient for virtually all living cells. In infectious diseases, both invading pathogens and mammalian cells including those of the immune system require iron to sustain their function, metabolism and proliferation. On the one hand, microbial iron uptake is linked to the virulence of most human pathogens. On the other hand, the sequestration of iron from bacteria and other microorganisms is an efficient strategy of host defense in line with the principles of 'nutritional immunity'. In an acute infection, host-driven iron withdrawal inhibits the growth of pathogens. Chronic immune activation due to persistent infection, autoimmune disease or malignancy however, sequesters iron not only from infectious agents, autoreactive lymphocytes and neoplastic cells but also from erythroid progenitors. This is one of the key mechanisms which collectively result in the anemia of chronic inflammation. In this review, we highlight the most important interconnections between iron metabolism and immunity, focusing on host defense against relevant infections and on the clinical consequences of anemia of inflammation.

Iron overload and its impact on outcome of patients with hematological diseases

Systemic iron overload (SIO) is a common challenge in patients with hematological diseases and develops as a result of ineffective erythropoiesis, multiple red blood cell (RBC) transfusions and disease-specific therapies. Iron homeostasis is tightly regulated as there is no physiological pathway to excrete iron from the body. Excess iron is, therefore, stored in tissues like liver, heart and bone marrow and can lead to progressive organ damage. The presence of free iron in the form of non-transferrin bound iron (NTBI) is especially detrimental. Reactive oxygen species can also cause stromal damage in the bone marrow and promote leukemic cell growth in vitro. In acute leukemias and myelodysplastic syndromes outcome is worse in patients with SIO compared to patients without. Especially in patients undergoing allogeneic HSCT presence of NTBI before or during transplant has been shown to negatively affect non-relapse mortality and overall survival. Although the mechanisms, of how these effects are mediated by SIO are not very well understood monitoring of iron status by serum markers and imaging techniques is, therefore, mandatory especially in these patients. Whether peri-interventional iron chelation may improve outcome of these patients is part of current clinical research.

High Serum Iron level is Associated with Increased Mortality in Patients with Sepsis

Iron is an essential nutrient for bacterial survival and thus higher iron levels may precipitate bacterial infections. We investigated the association between the serum iron level and prognosis in patients with sepsis by using the single-centre Medical Information Mart for Intensive Care III (MIMIC-III) database. Sepsis patients with iron parameters measured on ICU admission were included and stratified according to quartiles of serum iron levels. A total of 1,891 patients diagnosed with sepsis according to the Sepsis-3 criteria were included in this study, 324 of whom were septic shock. After adjusting for confounding variables, higher iron quartile was associated with an increase in 90-day mortality in the Cox regression analysis. Moreover, a stepwise increase in the risk of 90-day mortality was observed as the quartiles of serum iron levels increased in the patients with sepsis. In conclusion, higher serum iron levels were independently associated with increased 90-day mortality in this large cohort of patients with sepsis.

Enhanced labile plasma iron and outcome in acute myeloid leukaemia and myelodysplastic syndrome after allogeneic haemopoietic cell transplantation (ALLIVE): a prospective, multicentre, observational trial

BACKGROUND

The effect of systemic iron overload on outcomes after allogeneic haemopoietic cell transplantation (HCT) has been a matter of substantial debate. We aimed to investigate the predictive value of both stored (MRI-derived liver iron content) and biologically active iron (enhanced labile plasma iron; eLPI) on post-transplantation outcomes in patients with acute myeloid leukaemia or myelodysplastic syndrome undergoing allogenic HCT.

METHODS

The prospective, multicentre, observational, ALLogeneic Iron inVEstigators (ALLIVE) trial recruited patients at five centres in Germany. We enrolled patients with acute myeloid leukaemia or myelodysplastic syndrome undergoing allogeneic HCT. Patients underwent cytotoxic conditioning for a median of 6 days (IQR 6-7) before undergoing allogeneic HCT and were followed up for up to 1 year (±3 months) post-transplantation. eLPI was measured in serum samples with the FeROS eLPI kit (Aferrix, Tel-Aviv, Israel) and values greater than 0·4 μmol/L were considered to represent raised eLPI. Liver iron content was measured by MRI. The primary endpoints were the quantitative delineation of eLPI dynamics during allogeneic HCT and the correlation coefficient between liver iron content before HCT and dynamic eLPI (eLPI_dyn; maximum eLPI minus baseline eLPI). All patients with available data were included in all analyses. This is the final analysis of this completed trial, which is registered with ClinicalTrials.gov, number NCT01746147.

FINDINGS

Between Dec 13, 2012, and Dec 23, 2014, 112 patients underwent allogeneic HCT. Liver iron content before allogeneic HCT was not significantly correlated with eLPI_dyn (ρ=0·116, p=0·22). Serum eLPI concentrations rapidly increased during conditioning, and most (79 [73%] of 108) patients had raised eLPI by the day of transplantation. Patients with a pretransplant liver iron content greater than or equal to 125 μmol/g had an increased incidence of non-relapse mortality (20%, 95% CI 14-26) compared with those with lower concentrations (7%, 2-12; p=0·039) at day 100. Patients who had raised eLPI at baseline also had a significantly increased incidence of non-relapse mortality at day 100 (33%, 15-52) compared with those who had normal eLPI at baseline (7%, 2-13; p=0·00034).

INTERPRETATION

eLPI is a possible biological mediator of iron-related toxicity. Peritransplantation eLPI-scavenging strategies could be explored in prospective interventional clinical trials for patients with systemic iron overload.

FUNDING

The Technical University of Dresden and Novartis.

The Tumor Suppressor, P53, Decreases the Metal Transporter, ZIP14

Loss of p53’s proper function accounts for over half of identified human cancers. We identified the metal transporter ZIP14 (Zinc-regulated transporter (ZRT) and Iron-regulated transporter (IRT)-like Protein 14) as a p53-regulated protein. ZIP14 protein levels were upregulated by lack of p53 and downregulated by increased p53 expression. This regulation did not fully depend on the changes in ZIP14’s mRNA expression. Co-precipitation studies indicated that p53 interacts with ZIP14 and increases its ubiquitination and degradation. Moreover, knockdown of p53 resulted in higher non-transferrin-bound iron uptake, which was mediated by increased ZIP14 levels. Our study highlights a role for p53 in regulating nutrient metabolism and provides insight into how iron and possibly other metals such as zinc and manganese could be regulated in p53-inactivated tumor cells.

Effect of red blood cell storage time on markers of hemolysis and inflammation in transfused very low birth weight infants

BackgroundProlonged storage of transfused red blood cells (RBCs) is associated with hemolysis in healthy adults and inflammation in animal models. We aimed to determine whether storage duration affects markers of hemolysis (e.g., serum bilirubin, iron, and non-transferrin-bound iron (NTBI)) and inflammation (e.g., interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1) in transfused very low birth weight (VLBW) infants.MethodsBlood samples from 23 independent transfusion events were collected by heel stick before and 2-6 h after transfusion.ResultsSerum iron, total bilirubin, NTBI, and MCP-1 levels were significantly increased after transfusion of RBCs (P<0.05 for each comparison). The storage age of transfused RBCs positively correlated with increases in NTBI following transfusion (P<0.001; R²=0.44). No associations between storage duration and changes in the other analytes were observed.ConclusionTransfusion of RBCs into VLBW infants is associated with increased markers of hemolysis and the inflammatory chemokine MCP-1. RBC-storage duration only correlated with increases in NTBI levels following transfusion. NTBI was only observed in healthy adults following 35 days of storage; however, this study suggests that VLBW infants are potentially more susceptible to produce this pathological form of iron, with increased levels observed after transfusion of only 20-day-old RBCs.

The Impact of Iron Overload in Acute Leukemia: Chronic Inflammation, But Not the Presence of Nontransferrin Bound Iron is a Determinant of Oxidative Stress

In the literature, studies on the oxidant effects of nontransferrin bound iron [NTBI (eLPI assay)] during chemotherapy of acute lymphoblastic leukemia and acute myeloblastic leukemia are lacking. We established NTBI and oxidative stress determinants (OSD), iron parameters, high-sensitive C-reactive protein (hs-CRP) levels, liver tests, cumulative chemotherapeutic doses, and transfused blood in 36 children with acute leukemia throughout chemotherapy. These parameters were determined at the beginning and end of chemotherapy blocks (11 time points) and in 20 healthy children using enzyme-linked immunosorbent assay, and colorimetric and fluorometric enzymatic methods. In acute lymphoblastic leukemia, NTBI, OSD, and hs-CRP were higher than controls at 4/11, 7/11, and 9/11 time points (P<0.05). At 3 time points, NTBI and OSD concurrently increased. Ferritin, soluble transferrin receptor, serum iron, and transferrin saturation were higher than in controls at 5 to 11/11 time points (P<0.05). Those with NTBI had higher iron parameters than those without NTBI (P<0.05), but showed similar OSD, hs-CRP, liver enzymes, cumulative chemotherapeutics, and transfused blood (P>0.05). OSD did not correlate with NTBI, but correlated with hs-CRP. In conclusion, NTBI is a poor predictor of OSD in acute leukemia possibly because of the heterogeneity of NTBI and chronic inflammation. Further studies are needed to delineate the pathophysiology of these diseases.

Endogenous hepcidin and its agonist mediate resistance to selected infections by clearing non-transferrin-bound iron

The iron-regulatory hormone hepcidin is induced early in infection, causing iron sequestration in macrophages and decreased plasma iron; this is proposed to limit the replication of extracellular microbes, but could also promote infection with macrophage-tropic pathogens. The mechanisms by which hepcidin and hypoferremia modulate host defense, and the spectrum of microbes affected, are poorly understood. Using mouse models, we show that hepcidin was selectively protective against siderophilic extracellular pathogens (Yersinia enterocolitica O9) by controlling non-transferrin-bound iron (NTBI) rather than iron-transferrin concentration. NTBI promoted the rapid growth of siderophilic but not nonsiderophilic bacteria in mice with either genetic or iatrogenic iron overload and in human plasma. Hepcidin or iron loading did not affect other key components of innate immunity, did not indiscriminately promote intracellular infections (Mycobacterium tuberculosis), and had no effect on extracellular nonsiderophilic Y enterocolitica O8 or Staphylococcus aureus Hepcidin analogs may be useful for treatment of siderophilic infections.

Prolonged red cell storage before transfusion increases extravascular hemolysis

BACKGROUND

Some countries have limited the maximum allowable storage duration for red cells to 5 weeks before transfusion. In the US, red blood cells can be stored for up to 6 weeks, but randomized trials have not assessed the effects of this final week of storage on clinical outcomes.

METHODS

Sixty healthy adult volunteers were randomized to a single standard, autologous, leukoreduced, packed red cell transfusion after 1, 2, 3, 4, 5, or 6 weeks of storage (n = 10 per group). 51-Chromium posttransfusion red cell recovery studies were performed and laboratory parameters measured before and at defined times after transfusion.

RESULTS

Extravascular hemolysis after transfusion progressively increased with increasing storage time (P < 0.001 for linear trend in the AUC of serum indirect bilirubin and iron levels). Longer storage duration was associated with decreasing posttransfusion red cell recovery (P = 0.002), decreasing elevations in hematocrit (P = 0.02), and increasing serum ferritin (P < 0.0001). After 6 weeks of refrigerated storage, transfusion was followed by increases in AUC for serum iron (P < 0.01), transferrin saturation (P < 0.001), and nontransferrin-bound iron (P < 0.001) as compared with transfusion after 1 to 5 weeks of storage.

CONCLUSIONS

After 6 weeks of refrigerated storage, transfusion of autologous red cells to healthy human volunteers increased extravascular hemolysis, saturated serum transferrin, and produced circulating nontransferrin-bound iron. These outcomes, associated with increased risks of harm, provide evidence that the maximal allowable red cell storage duration should be reduced to the minimum sustainable by the blood supply, with 35 days as an attainable goal.REGISTRATION. ClinicalTrials.gov NCT02087514.

FUNDING

NIH grant HL115557 and UL1 TR000040.