Iron overload in patients with myelodysplastic syndromes: An updated overview

Targeted therapies for myelodysplastic syndromes/neoplasms (MDS): current landscape and future directions

INTRODUCTION

Myelodysplastic syndromes/neoplasms (MDS) are a heterogeneous group of hematologic malignancies that are stratified into high-risk (HR-MDS) and low-risk (LR-MDS) categories. Until recently, LR-MDS has been typically managed by supportive measures and erythropoiesis-stimulating agents (ESAs); whereas management of HR-MDS typically included hypomethylating agents and allogeneic hematopoietic stem cell transplant. However, the limited rates and durations of response observed with these interventions prompted the search for targeted therapies to improve the outcomes among patients with MDS.

AREAS COVERED

Here, we review the current landscape of targeted therapies in MDS. These include pyruvate kinase and hypoxia-inducible factor (HIF) activators; TGF-beta, telomerase, BCL2 and isocitrate dehydrogenase (IDH) inhibitors; as well as novel approaches targeting inflammation, pyroptosis, immune evasion, and RNA splicing machinery.

EXPERT OPINION

This review highlights the progress and challenges in MDS treatment. Despite some promising results, many therapies remain in early development or have faced setbacks, emphasizing the need for a more comprehensive understanding of the disease's pathobiology. Continued research into targeted therapies, homogenous clinical trial designs, as well as increased incorporation of molecular prognostic tools and artificial intelligence into trial design are essential for developing effective treatments for MDS and improving patient outcomes.

The Role of Hepcidin in Myelodysplastic Syndromes (MDS): A Systematic Review of Observational Studies

Iron overload emerges as a serious complication in myelodysplastic syndromes (MDS), particularly associated with frequent transfusions during the course of the disease. The discovery and description of hepcidin's mechanisms of action have contributed to a deeper understanding of iron metabolism. The existing literature reports a potential role of hepcidin in MDS, yet these data are fragmented and presented in an unstructured, somewhat chaotic manner. Hence, to address the existing data, we performed a systematic review of observational studies examining hepcidin levels in MDS. An extensive review of three bibliographic databases (Pubmed, Web of Science, and Scopus) enabled us to identify 12 observational studies. These studies focused primarily on adult patients with low-risk MDS who underwent transfusions and chelation therapy. An in-depth analysis of these manuscripts led to four main conclusions: (1) although high serum hepcidin levels are associated with MDS, most studies generally have not found a significant difference in these levels between patients and healthy individuals; (2) serum hepcidin levels are specific to MDS type; (3) serum hepcidin levels in MDS are strongly associated with transfusions and the genetic status of patients; and (4) high-risk MDS is associated with high serum hepcidin levels. While we have furnished a comprehensive summary of the significance of hepcidin in MDS, there are still gaps that future research should address. This pertains primarily to the capacity of hepcidin in predicting adverse outcomes for MDS patients and evaluating the efficacy of chelation therapy or the need for transfusion.

Quality of life considerations and management in patients with myelodysplastic syndrome

INTRODUCTION

This study aimed to identify the factors affecting the quality of life (QOL) and functional status of patients with MDS.

AREAS COVERED

We reviewed the literature published in PUBMED over the past 30 years and searched for keywords such as 'quality of life' and 'myelodysplastic syndromes'. By observing the influence of their symptoms, the possibility of improving patients' QOL was considered by improving these related factors. Concurrently, the effects of related clinical treatments based on the unique disease characteristics of MDS on the patients' QOL were examined, and lifestyle factors were considered in clinical practice, providing an important path to improve the QOL and functional status of patients with MDS.

EXPERT OPINION

This review summarized several areas that can improve the quality of survival of MDS patients and discusses them in depth. Although the clinical benefits may be minimal, we still hope to improve patients' daily life outcomes and enhance their quality of life at minimal cost. Also, we hope more researchers will focus on this area in the future to find more factors that may exist to supplement the limitations of these understanding and thinking, and to provide assistance in clinical work.

Evolution of Therapeutic Benefit Measurement Criteria in Myelodysplastic Syndromes/Neoplasms

ABSTRACT

Myelodysplastic syndromes/neoplasms (MDS) are heterogeneous, clonal myeloid neoplasms characterized by ineffective hematopoiesis, progressive cytopenias, and an increased risk of progression to acute myeloid leukemia. The diversity in disease severity, morphology, and genetic landscape challenges not only novel drug development but also therapeutic response assessment. The MDS International Working Group (IWG) response criteria were first published in the year 2000 focusing on measures of blast burden reduction and hematologic recovery. Despite revision of the IWG criteria in 2006, correlation between IWG-defined responses and patient-focused outcomes, including long-term benefits, remains limited and has potentially contributed to failures of several phase III clinical trials. Several IWG 2006 criteria also lacked clear definitions leading to problems in practical applications and interobserver and intraobserver consistency of response reporting. Although the 2018 revision addressed lower-risk MDS, the most recent update in 2023 redefined responses for higher-risk MDS and has set out to provide clear definitions to enhance consistency while focusing on clinically meaningful outcomes and patient-centered responses. In this review, we analyze the evolution of the MDS response criteria, limitations, and areas of improvement.

Plasma Non-transferrin-Bound Iron Could Enter into Mice Duodenum and Negatively Affect Duodenal Defense Response to Virus and Immune Responses

Plasma non-transferrin-bound iron (NTBI) exists when the plasma iron content exceeds the carrying capacity of transferrin and can be quickly cleared by the liver, pancreas, and other organs. However, whether it could enter the small intestine and its effects still remain unclear. Herein, these issues were explored. Mice were intravenously administrated of ferric citrate (treatment) or citrate acid (control) 10 min after the saturation of the transferrin. Two hours later, hepatic, duodenal, and jejunal iron content and distribution were measured and duodenal transcriptome sequencing was performed. Significant increase of duodenal and hepatic iron content was detected, indicating that plasma NTBI could be absorbed by the duodenum as well as the liver. A total of 103 differentially expressed genes were identified in the duodenum of mice in the treatment group compared to the control group. Gene Ontology (GO) functional analysis of these genes showed that they were mainly involved in defense response to virus and immune response. The results of Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) analysis revealed that there were major changes in the hematopoietic cell lineage and some virus infection pathways between the two groups. Determination of 7 cytokines in the duodenum were further conducted, which demonstrated that the anti-inflammatory factors interferon (IL)-4 and IL-10 in the duodenum were significantly decreased after NTBI uptake. Our findings revealed that NTBI in plasma can enter the duodenum, which would change the duodenal hematopoietic cell lineage and have a negative impact on defense response to the virus and immune responses.

Clinical view versus guideline adherence in ferritin monitoring and initiating iron chelation therapy in patients with myelodysplastic syndromes

OBJECTIVES

In patients with myelodysplastic syndromes (MDS) with >20 transfusions and ferritin levels >1000 μg/L, international guidelines recommend iron chelation therapy (ICT). The study's objective was to determine guideline adherence and the intensity of ferritin monitoring in clinical practice.

METHODS

We performed an observational population-based study using the HemoBase Registry, which contains data of all MDS patients diagnosed since 2005 in Friesland, the Netherlands. Clinical information on transfusions, ferritin measurements, ICT, and clinical performance as defined by age ≤ 80 years, Charlson Comorbidity Index <2 and lower-risk MDS was collected from health records.

RESULTS

Two hundred and thirty seven of 292 patients (81.1%) received ≥1 transfusion, and 121 (41.4%) received >20 transfusions. In 57 of these 121 patients (47.1%), ferritin measurements were performed at least once. Clinical performance was significantly associated with monitoring ferritin around the 20th transfusion (RR: 2.49, p = .016). Clinical performance was also associated with initiating ICT (RR: 5.99, p < .001). ICT was offered to 22.3% (n = 25) of eligible patients.

CONCLUSIONS

In this population-based study, ferritin levels were measured in <50% of MDS patients who received >20 transfusions, and clinical performance was significantly associated with measuring ferritin. Our study suggests that in heavily transfused MDS patients, ferritin monitoring is primarily based on patients' clinical performance rather than guideline recommendations.

Transfusional iron overload in heavily transfused patients: real-life data from a 10-year retrospective study of 611 cases managed in a French general hospital

OBJECTIVES

Epidemiological studies on transfusional iron overload (TIO) in the general population of heavily transfused patients are scarce. The aim of this work was to provide a picture on the distribution and management of this complication within the context of unselected individuals attending a general hospital.

METHODS

We retrospectively assessed the characteristics of 611 patients from a single institution having received at least 20 red blood cell (RBC) units over a 10-year period.

RESULTS

About two-thirds of these individuals were males and their median age at the 20^th RBC was 72 years (range: 10-98). Myelodysplastic syndromes (MDS) and acute myeloid leukemia represented the most frequent underlying conditions (53%) but lymphoid malignancies and solid malignancies accounted for 13.6 and 7.3% respectively. In the vast majority of cases various comorbidities (range: 1-6 per patient) were registered including especially cardiovascular disorders. The highest cumulative RBC numbers were observed in MDS patients. Serum ferritin was assessed in 451 patients (73.8%) and ≥ 1000 μg/L in 250 cases, ≥ 2000 μg/L in 100 cases and ≥ 2500 μg/L in 71 cases. Only 97 patients (15.9%) received a treatment for TIO using either a chelator (n=93) or phlebotomy (n=4).

CONCLUSION

TIO is not limited to MDS or hemoglobin disorders. Its assessment and management are suboptimal in clinical practice. The ratio of patients receiving iron chelation is markedly lower than theoretically expected mainly because of comorbidities or drug intolerance.

Iron and platelets: A subtle, under-recognized relationship

The role of iron in the formation and functioning of erythrocytes, and to a lesser degree of white blood cells, is well established, but the relationship between iron and platelets is less documented. Physiologically, iron plays an important role in hematopoiesis, including thrombopoiesis; iron levels direct, together with genetic factors, the lineage commitment of megakaryocytic/erythroid progenitors toward either megakaryocyte or erythroid progenitors. Megakaryocytic iron contributes to cellular machinery, especially energy production in platelet mitochondria. Thrombocytosis, possibly favoring vascular thrombosis, is a classical feature observed with abnormally low total body iron stores (mainly due to blood losses or decreased duodenal iron intake), but thrombocytopenia can also occur in severe iron deficiency anemia. Iron sequestration, as seen in inflammatory conditions, can be associated with early thrombocytopenia due to platelet consumption and followed by reactive replenishment of the platelet pool with possibility of thrombocytosis. Iron overload of genetic origin (hemochromatosis), despite expected mitochondrial damage related to ferroptosis, has not been reported to cause thrombocytopenia (except in case of high degree of hepatic fibrosis), and iron-related alteration of platelet function is still a matter of debate. In acquired iron overload (of transfusional and/or dyserythropoiesis origin), quantitative or qualitative platelet changes are difficult to attribute to iron alone due to the interference of the underlying hematological conditions; likewise, hematological improvement, including increased blood platelet counts, observed under iron oral chelation is likely to reflect mechanisms other than the sole beneficial impact of iron depletion.

Salvia miltiorrhiza (SM) Injection Ameliorates Iron Overload-Associated Cardiac Dysfunction by Regulating the Expression of DMT1, TfR1, and FP1 in Rats

Previous studies have found that Salvia miltiorrhiza (SM) injection have a protective effect on the iron overloaded (IO) heart. However, the mechanisms are not completely known. In the present study, we investigated the underlying mechanisms based on the iron transport-related proteins. The rats were randomly divided into five groups: control, IO group, low-dose SM group, high-dose SM group, and deferoxamine control group. Iron dextran was injected to establish the IO model. After 14 days of treatment, cardiac histological changes were observed by hematoxylin and eosin (H&E) staining. Iron uptake-related proteins divalent metal transporter-1 (DMT-1), transferrin receptor-1 (TfR-1), and iron export-related proteins ferroportin1 (FP1) in the heart were detected by Western blotting. The results showed that SM injection decreased cardiac iron deposition, ameliorated cardiac function, and inhibited cardiac oxidation. Most important of all, SM injection downregulated the expression of DMT-1 and TfR-1 and upregulated FP1 protein levels compared with the IO group. Our results indicated that reducing cardiac iron uptake and increasing iron excretion may be one of the important mechanisms of SM injection reducing cardiac iron deposition and improving cardiac function under the conditions of IO.

Targeting health-related quality of life in patients with myelodysplastic syndromes - Current knowledge and lessons to be learned

Using a range of health-related quality of life (HRQoL) instruments, most - but not all - studies of myelodysplastic syndromes (MDS) have reported that lower hemoglobin levels and red blood cell transfusion dependency are associated with worse HRQoL. In addition, some MDS treatments may significantly improve HRQoL, particularly among those patients who respond to therapy; however, the majority of these studies were underpowered for this secondary endpoint. Furthermore, decreased HRQoL has been associated with worse survival outcomes, and HRQoL scores can be used to refine classical prognostic systems. Despite the subjective nature of HRQoL, the importance and validity of measuring it in trials and clinical practice are increasingly being recognized, but properly validated MDS-specific instruments are required. We describe what is currently known about HRQoL in patients with MDS, and the limitations of measuring HRQoL, and we provide some recommendations to improve the measurement of this outcome in future trials.

The Iron Curtain: Macrophages at the Interface of Systemic and Microenvironmental Iron Metabolism and Immune Response in Cancer

Macrophages fulfill central functions in systemic iron metabolism and immune response. Infiltration and polarization of macrophages in the tumor microenvironment is associated with differential cancer prognosis. Distinct metabolic iron and immune phenotypes in tumor associated macrophages have been observed in most cancers. While this prompts the hypothesis that macroenvironmental manifestations of dysfunctional iron metabolism have direct associations with microenvironmental tumor immune response, these functional connections are still emerging. We review our current understanding of the role of macrophages in systemic and microenvironmental immune response and iron metabolism and discuss these functions in the context of cancer and immunometabolic precision therapy approaches. Accumulation of tumor associated macrophages with distinct iron pathologies at the invasive tumor front suggests an "Iron Curtain" presenting as an innate functional interface between systemic and microenvironmental iron metabolism and immune response that can be harnessed therapeutically to further our goal of treating and eliminating cancer.

The Dynamic Interface Between the Bone Marrow Vascular Niche and Hematopoietic Stem Cells in Myeloid Malignancy

Hematopoietic stem cells interact with bone marrow niches, including highly specialized blood vessels. Recent studies have revealed the phenotypic and functional heterogeneity of bone marrow endothelial cells. This has facilitated the analysis of the vascular microenvironment in steady state and malignant hematopoiesis. In this review, we provide an overview of the bone marrow microenvironment, focusing on refined analyses of the marrow vascular compartment performed in mouse studies. We also discuss the emerging role of the vascular niche in “inflamm-aging” and clonal hematopoiesis, and how the endothelial microenvironment influences, supports and interacts with hematopoietic cells in acute myeloid leukemia and myelodysplastic syndromes, as exemplar states of malignant myelopoiesis. Finally, we provide an overview of strategies for modulating these bidirectional interactions to therapeutic effect in myeloid malignancies.

Transfusional iron overload in patients with myelodysplastic syndromes: A 10-year retrospective survey from a French general hospital

We retrospectively assessed the characteristics of 165 MDS patients from our institution having received at least 20 RBC units. In the vast majority of them various comorbidities (range: 1-6 per patient) were registered including mainly cardiovascular disorders. Serum ferritin was over 1000μg/L in about half of tested individuals. A chelator agent was initiated in 43.6% of patients (mainly low-risk MDS). Transformation in AML occurred in 46 cases (27.8%). Overall, 112 patients died during follow up. The cause of death was documented in 65 cases and included mainly MDS or AML resistance to therapy. There was a context of bacterial or fungal-related sepsis in 35.3% of cases. We noticed a correlation between survival and number of RBC transfusions. Median OS from the 20th RBC unit was significantly prolonged among the chelated subgroup. Consequences of transfusional iron overload and chelation need to be clarified in MDS patients.

Controversies on the Consequences of Iron Overload and Chelation in MDS

Many patients with MDS are prone to develop systemic and tissue iron overload in part as a consequence of disease-immanent ineffective erythropoiesis. However, chronic red blood cell transfusions, which are part of the supportive care regimen to correct anemia, are the major source of iron overload in MDS. Increased systemic iron levels eventually lead to the saturation of the physiological systemic iron carrier transferrin and the occurrence of non-transferrin-bound iron (NTBI) together with its reactive fraction, the labile plasma iron (LPI). NTBI/LPI-mediated toxicity and tissue iron overload may exert multiple detrimental effects that contribute to the pathogenesis, complications and eventually evolution of MDS. Until recently, the evidence supporting the use of iron chelation in MDS was based on anecdotal reports, uncontrolled clinical trials or prospective registries. Despite not fully conclusive, these and more recent studies, including the TELESTO trial, unravel an overall adverse action of iron overload and therapeutic benefit of chelation, ranging from improved hematological outcome, reduced transfusion dependence and superior survival of iron-loaded MDS patients. The still limited and somehow controversial experimental and clinical data available from preclinical studies and randomized trials highlight the need for further investigation to fully elucidate the mechanisms underlying the pathological impact of iron overload-mediated toxicity as well as the effect of classic and novel iron restriction approaches in MDS. This review aims at providing an overview of the current clinical and translational debated landscape about the consequences of iron overload and chelation in the setting of MDS.

Iron overload regulate the cytokine of mesenchymal stromal cells through ROS/HIF-1α pathway in Myelodysplastic syndromes

Iron overload is a significant feature of myelodysplastic syndromes (MDS) patients due to ineffective hematopoiesis and transfusion dependence. Excess iron results in organ dysfunction through the generation of reactive oxygen species (ROS) which can cause oxidative stress even mutation. Mesenchymal stromal cells (MSCs) are responsible for supporting and regulating hematopoiesis, whether MSCs is involved in the pathogenesis of MDS still need further elucidation. Hypoxia-inducible factors-1 (HIF-1) is an integral signal of inflammation that has been shown to up-regulating in MDS patient. We found that MDS-derived MSC had disorganized clones and increased level of apoptosis (n = 53). Iron transportation-related gene, such as DMT1 and ZIP14, and ROS level were increased in iron overload-MDS-MSC (n = 23). HIF-1a, as a crucial part of HIF-1, was also elevated in iron overload-group and PHD2 involved in the degradation of HIF-1a was reduced. Furthermore, HIF-1 downstream cytokines such IL-6, IL-8, TGF-βand VEGF that were also involved in the pathogenesis of MDS were increased in IO-MDS-MSC. When treated with DFO and NAC for iron chelation and antioxidation, the level of HIF-1a and related cytokines could decrease. We conclude that iron overload regulates the cytokine of mesenchymal stromal cells through ROS/HIF-1α pathway in Myelodysplastic syndromes, result in dysfunction of MSC and damage of microenvironment that may be involved in the pathogenesis of MDS.

The Effects of Human BDH2 on the Cell Cycle, Differentiation, and Apoptosis and Associations with Leukemia Transformation in Myelodysplastic Syndrome

Iron overload is related to leukemia transformation in myelodysplastic syndrome (MDS) patients. Siderophores help to transport iron. Type 2-hydroxybutyrate dehydrogenase (BDH2) is a rate-limiting factor in the biogenesis of siderophores. Using qRT-PCR, we analyze BDH2mRNA expression in the bone marrow (BM) of 187 MDS patients, 119 de novo acute myeloid leukemia (AML) patients, and 43 lymphoma patients with normal BM. Elevated BDH2mRNA expression in BM is observed in MDS patients (n = 187 vs. 43, normal BM; P = 0.009), and this is related to ferritin levels. Patients with higher BDH2 expression show a greater risk of leukemia progression (15.25% vs. 3.77%, lower expression; P = 0.017) and shorter leukemia-free-survival (medium LFS, 9 years vs. 7 years; P = 0.024), as do patients with a ferritin level ≥350 ng/mL. Additionally, we investigate the mechanisms related to the prognostic ability of BDH2 by using BDH2-KD THP1. The cell cycle analysis, surface markers, and special stain studies indicate that BDH2-KD induces differentiation and decreases the growth rate of THP1 cells, which is associated with the retardation of the cell cycle. Moreover, many genes, including genes related to mitochondrial catabolism, oncogenes, tumor suppressor genes, and genes related to cell differentiation and proliferation influence BDH2-KD THP1 cells. Herein, we demonstrate that BDH2 is involved in cell cycle arrest and the inhibition of differentiation in malignant cells. Furthermore, the high BDH2 expression in MDS patients could be suggestive of a poor prognostic factor. This study provides a foundation for further research on the roles of BDH2 and iron metabolism in the pathogenesis of MDS.

The impact of iron chelation therapy on patients with lower/intermediate IPSS MDS and the prognostic role of elevated serum ferritin in patients with MDS and AML: A meta-analysis

Serum ferritin (SF) has been identified as a potential prognostic factor for patients undergoing stem cell transplantation, but the prognostic value of SF in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) patients and the impact of iron chelation therapy (ICT) on MDS patients are controversial. The present meta-analysis aimed to better elucidate these relationships.Three electronic databases were searched systematically to identify reports on the prognostic role of SF in MDS and AML patients, and those investigating the impact of ICT on prognosis of MDS patients. The hazard ratios (HRs) and its 95% confidence interval (95%CI) were extracted from the identified studies using Cox proportional hazard regression model for overall survival (OS) and progression of MDS to AML.Twenty reports including 1066 AML patients and 4054 MDS patients were included in present study. The overall pooled HRs for OS of AML and MDS patients with elevated SF prior to transplantation was 1.73 (1.40-2.14), subgroup analyses stratified by the cut-off value of SF ≥1400/1000 ng/mL showed that the pooled HRs were 1.45 (0.98-2.15) and 1.65 (1.30-2.10), respectively. The pooled HRs for ICT in MDS patients was 0.30 (0.23-0.40). For ICT, the pooled HRs for the progression of MDS to AML was 0.84 (0.61-1.61).SF has a negative impact on the OS of AML and MDS patients when it is higher than 1000 ng/mL. ICT can improve the OS of MDS patients with iron overload but it is not associated with the progression of MDS to AML.

Pathophysiology and classification of iron overload diseases; update 2018

Iron overload pathophysiology has benefited from significant advances in the knowledge of iron metabolism and in molecular genetics. As a consequence, iron overload nosology has been revisited. The hematologist may be confronted to a number of iron overload syndromes, from genetic or acquired origin. Hemochromatoses, mostly but not exclusively related to the HFE gene, correspond to systemic iron overload of genetic origin in which iron excess is the consequence of hepcidin deficiency, hepcidin being the hormone regulating negatively plasma iron. Iron excess develops following hypersideremia and the formation of non-transferrin-bound iron, which targets preferentially parenchymal cells (hepatocytes). The ferroportin disease has a totally different iron overload mechanism consisting of defective egress of cellular iron into the plasma, iron deposition taking place mostly within the macrophages (spleen). Hereditary aceruloplasminemia is peculiar since systemic iron overload involves the brain. Two main types of acquired iron overload can be seen by the hematologist, one related to dyserythropoiesis (involving hypohepcidinemia ), the other related to multiple transfusions (thalassemias, myelodysplasia, hematopoietic stem cell transplantation). Congenital sideroblastic anemias, either monosyndromic (anemia) or polysyndromic (anemia plus extra-hematological syndromes), develop both compartimental iron excess within the erythroblast mitochondria, and systemic iron overload (through dyserythropoiesis and/or transfusions).