Insight into the molecular pathophysiology of myelodysplastic syndromes: targets for novel therapy

Role of IL8 in myeloid malignancies

Aberrant overexpression of Interleukin-8 (IL8) has been reported in Myelodysplastic Syndromes (MDS), Acute Myeloid Leukemia (AML), Myeloproliferative Neoplasms (MPNs) and other myeloid malignancies. IL8 (CXCL8) is a CXC chemokine that is secreted by aberrant hematopoietic stem and progenitors as well as other cells in the tumor microenvironment. IL8 can bind to CXCR1/CXCR2 receptors and activate oncogenic signaling pathways, and also increase the recruitment of myeloid derived suppressor cells to the tumor microenvironment. IL8/CXCR1/2 overexpression has been associated with poorer prognosis in MDS and AML and increased bone marrow fibrosis in Myelofibrosis. Preclinical studies have demonstrated benefit of inhibiting the IL8/CXCR1/2 pathways via restricting the growth of leukemic stem cells as well as normalizing the immunosuppressive microenvironment in tumors. Targeting the IL8-CXCR1/2 pathway is a potential therapeutic strategy in myeloid neoplasms and is being evaluated with small molecule inhibitors as well as monoclonal antibodies in ongoing clinical trials. We review the role of IL8 signaling pathway in myeloid cancers and discuss future directions on therapeutic targeting of IL8 in these diseases.

Erythropoiesis in lower-risk myelodysplastic syndromes and beta-thalassemia

The hematologic disorders myelodysplastic syndromes and beta-thalassemia are characterized by ineffective erythropoiesis and anemia, often managed with regular blood transfusions. Erythropoiesis, the process by which sufficient numbers of functional erythrocytes are produced from hematopoietic stem cells, is highly regulated, and defects can negatively affect the proliferation, differentiation, and survival of erythroid precursors. Treatments that directly target the underlying mechanisms of ineffective erythropoiesis are limited, and management of anemia with regular blood transfusions imposes a significant burden on patients, caregivers, and health care systems. There is therefore a strong unmet need for treatments that can restore effective erythropoiesis. Novel therapies are beginning to address this need by targeting a variety of mechanisms underlying erythropoiesis. Herein, we provide an overview of the role of ineffective erythropoiesis in myelodysplastic syndromes and beta-thalassemia, discuss unmet needs in targeting ineffective erythropoiesis, and describe current management strategies and emerging treatments for these disorders.

Bone marrow confined IL-6 signaling mediates the progression of myelodysplastic syndromes to acute myeloid leukemia

Myelodysplastic syndromes (MDS) are age-related myeloid neoplasms with increased risk of progression to acute myeloid leukemia (AML). The mechanisms of transformation of MDS to AML are poorly understood, especially in relation to the aging microenvironment. We previously established an mDia1/miR-146a double knockout (DKO) mouse model phenocopying MDS. These mice develop age-related pancytopenia with oversecretion of proinflammatory cytokines. Here, we found that most of the DKO mice underwent leukemic transformation at 12–14 months of age. These mice showed myeloblast replacement of fibrotic bone marrow and widespread leukemic infiltration. Strikingly, depletion of IL-6 in these mice largely rescued the leukemic transformation and markedly extended survival. Single-cell RNA sequencing analyses revealed that DKO leukemic mice had increased monocytic blasts that were reduced with IL-6 knockout. We further revealed that the levels of surface and soluble IL-6 receptor (IL-6R) in the bone marrow were significantly increased in high-risk MDS patients. Similarly, IL-6R was also highly expressed in older DKO mice. Blocking of IL-6 signaling significantly ameliorated AML progression in the DKO model and clonogenicity of CD34-positive cells from MDS patients. Our study establishes a mouse model of progression of age-related MDS to AML and indicates the clinical significance of targeting IL-6 signaling in treating high-risk MDS.

Meta-analysis of the benefit of hypomethylating agents before allogeneic hematopoietic stem cell transplantation in myelodysplastic syndromes

Hypomethylating agents (HMAs) are effective therapies in myelodysplastic syndromes (MDS), but allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only way to cure MDS. According to the current literature, it is difficult to confirm whether HMAs bridging therapy is beneficial for MDS patients receiving allo-HSCT. Therefore, we tried to evaluate the effect of HMAs on long-term survival of the MDS patients. Databases, including PubMed, Embase Ovid, and the Cochrane Library, were searched for studies published up to January 10, 2021. Patients who accepted HMAs bridging to allo-HSCT were defined as experimental group, while patients who received the best supportive care (BSC) before allo-HSCT were control group. Overall survival (OS) was the primary end point. Seven studies were included in the final analysis. The final results showed no OS differences between patients accepted HMAs before allo-HSCT and those received BSC (HR = 0.86, 95% CI: 0.64-1.15, p = 0.32), indicating that MDS patients' long-term survival did not benefit from HMAs bridging therapy before allo-HSCT. This conclusion needs to be further verified by a large number of prospective randomized controlled trials, which have guiding significance for the treatment of MDS patients.

Different methylation signatures at diagnosis in patients with high-risk myelodysplastic syndromes and secondary acute myeloid leukemia predict azacitidine response and longer survival

BACKGROUND

Epigenetic therapy, using hypomethylating agents (HMA), is known to be effective in the treatment of high-risk myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) patients who are not suitable for intensive chemotherapy and/or allogeneic stem cell transplantation. However, response rates to HMA are low and there is an unmet need in finding prognostic and predictive biomarkers of treatment response and overall survival. We performed global methylation analysis of 75 patients with high-risk MDS and secondary AML who were included in CETLAM SMD-09 protocol, in which patients received HMA or intensive treatment according to age, comorbidities and cytogenetic.

RESULTS

Unsupervised analysis of global methylation pattern at diagnosis did not allow patients to be differentiated according to the cytological subtype, cytogenetic groups, treatment response or patient outcome. However, after a supervised analysis we found a methylation signature defined by 200 probes, which allowed differentiating between patients responding and non-responding to azacitidine (AZA) treatment and a different methylation pattern also defined by 200 probes that allowed to differentiate patients according to their survival. On studying follow-up samples, we confirmed that AZA decreases global DNA methylation, but in our cohort the degree of methylation decrease did not correlate with the type of response. The methylation signature detected at diagnosis was not useful in treated samples to distinguish patients who were going to relapse or progress.

CONCLUSIONS

Our findings suggest that in a subset of specific CpGs, altered DNA methylation patterns at diagnosis may be useful as a biomarker for predicting AZA response and survival.

Unravelling the Epigenome of Myelodysplastic Syndrome: Diagnosis, Prognosis, and Response to Therapy

Simple Summary

Myelodysplastic syndrome (MDS) is a type of blood cancer that mostly affects older individuals. Invasive tests to obtain bone samples are used to diagnose MDS and many patients do not respond to therapy or stop responding to therapy in the short-term. Less invasive tests to help diagnose, prognosticate, and predict response of patients is a felt need. Factors that influence gene expression without changing the DNA sequence (epigenetic modifiers) such as DNA methylation, micro-RNAs and long-coding RNAs play an important role in MDS, are potential biomarkers and may also serve as targets for therapy.

Abstract

Myelodysplastic syndrome (MDS) is a malignancy that disrupts normal blood cell production and commonly affects our ageing population. MDS patients are diagnosed using an invasive bone marrow biopsy and high-risk MDS patients are treated with hypomethylating agents (HMAs) such as decitabine and azacytidine. However, these therapies are only effective in 50% of patients, and many develop resistance to therapy, often resulting in bone marrow failure or leukemic transformation. Therefore, there is a strong need for less invasive, diagnostic tests for MDS, novel markers that can predict response to therapy and/or patient prognosis to aid treatment stratification, as well as new and effective therapeutics to enhance patient quality of life and survival. Epigenetic modifiers such as DNA methylation, long non-coding RNAs (lncRNAs) and micro-RNAs (miRNAs) are perturbed in MDS blasts and the bone marrow micro-environment, influencing disease progression and response to therapy. This review focusses on the potential utility of epigenetic modifiers in aiding diagnosis, prognosis, and predicting treatment response in MDS, and touches on the need for extensive and collaborative research using single-cell technologies and multi-omics to test the clinical utility of epigenetic markers for MDS patients in the future.

Azacitidine regulates DNA methylation of GADD45γ in myelodysplastic syndromes

Background

Myelodysplastic syndrome (MDS) is a heterogeneous clonal disease originated from hematopoietic stem cells. Epigenetic studies had demonstrated that DNA methylation and histone acetylation were abnormal in MDS. Azacitidine is an effective drug in the treatment of demethylation.

Methods

RT‐PCR was performed to determine GADD45γ in 15 MDS clinical samples. Myelodysplastic syndrome cell lines SKM‐1 and HS‐5 were transfected with GADD45γ eukaryotic expression vector and/or GADD45γ shRNA interference plasmid, and treated with azacitidine. Proliferation and apoptosis were examined by CCK‐8 and Western blot analysis to confirm the function role of GADD45γ and azacitidine. The methylation level of GADD45γ gene was detected by bisulfite conversion and PCR.

Results

This study found that GADD45γ gene was down‐expressed in MDS patients' bone marrow and MDS cell lines, and the down‐regulation of GADD45γ in MDS could inhibit MDS cell apoptosis and promote proliferation. Azacitidine, a demethylation drug, could restore the expression of GADD45γ in MDS cells and inhibit the proliferation of MDS cells by inducing apoptosis, which was related to prognosis and transformation.

Conclusion

This study indicated that GADD45γ was expected to become a new target of MDS‐targeted therapy. The findings of this study provided a new direction for the research and development of new MDS clinical drugs, and gave a new idea for the development of MDS demethylation drug to realize precise treatment.

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.

Genetic predisposition to MDS: diagnosis and management

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders characterized by clonal hematopoiesis with a propensity to evolve into acute myeloid leukemia. MDS presenting in children and young adults is associated with features clinically and biologically distinct from MDS arising in older adults. MDS presenting in children and young adults is associated with a higher likelihood of an underlying genetic predisposition; however, genetic predisposition is increasingly recognized in a subset of older adults. The diagnosis of a genetic predisposition to MDS informs clinical care and treatment selection. Early diagnosis allows a tailored approach to management and surveillance. Genetic testing now offers a powerful diagnostic approach but also poses new challenges and caveats. Clinical expertise in these disorders together with scientific expertise regarding the affected genes is essential for diagnosis. Understanding the basic mechanisms of genetic predisposition to myeloid malignancies may inform surveillance strategies and lead to novel therapies. The cases presented in this article illustrate challenges to the diagnosis of germline genetic predisposition to MDS and how the diagnosis affects clinical management and treatment.

Bone marrow mononuclear cell telomere length in acute myeloid leukaemia and high-risk myelodysplastic syndrome

OBJECTIVE

Short telomere length is a known risk factor for developing clonal haematopoietic stem cell disorders, probably due to chromosomal instability. We tested the hypotheses that bone marrow mononuclear cell telomere length change from diagnosis through chemotherapy-induced remission and relapse, and that long telomere length is associated with low risk of relapse and all-cause mortality in patients with acute myeloid leukaemia or high-risk myelodysplastic syndrome.

METHODS

We measured telomere length in bone marrow mononuclear cells from 233 patients at diagnosis, 112 patients at chemotherapy-induced remission and 58 patients at relapse of disease.

RESULTS

In patients with acute myeloid leukaemia or high-risk myelodysplastic syndrome, bone marrow mononuclear cell telomere length was similar at diagnosis and relapse, but increased after chemotherapy-induced remission. Furthermore, bone marrow mononuclear cell telomere length was longer in patients with higher age at diagnosis. There was no association between telomere length at diagnosis, remission or relapse and all-cause mortality, nor did we find any association between telomere length at diagnosis or remission and risk of relapse.

CONCLUSION

In patients with acute myeloid leukaemia or high-risk myelodysplastic syndrome, bone marrow mononuclear cell telomere length increased from diagnosis to remission. Furthermore, telomere length paradoxically was longer at higher age at diagnosis, even after adjusting for known risk factors of disease severity. Finally, we did not detect any prognostic information in telomere length.

The Molecular Pathology of Myelodysplastic Syndrome

The diagnosis and classification of myelodysplastic syndromes (MDS) are based on cytomorphology and cytogenetics (WHO classification). Prognosis is best defined by the Revised International Prognostic Scoring System (IPSS-R). In recent years, an increasing number of molecular aberrations have been discovered. They are already included in the classification (e.g., SF3B1) and, more importantly, have emerged as valuable markers for better classification, particularly for defining risk groups. Mutations in genes such as SF3B1 and IDH1/2 have already had an impact on targeted treatment approaches in MDS.

Chronic Myeloid Leukemia with an e6a2 BCR-ABL1 Fusion Transcript: Cooperating Mutations at Blast Crisis and Molecular Monitoring

A minority of chronic myeloid leukemia patients (CML) express a variety of atypical BCR-ABL1 fusion variants and, of these, the e6a2 BCR-ABL1 fusion is generally associated with an aggressive disease course. Progression of CML to blast crisis is associated with acquisition of additional somatic mutations yet these events have not been elucidated in patients with the e6a2 BCR-ABL1 genotype. Moreover, molecular monitoring is only sporadically performed in CML patients with atypical BCR-ABL1 fusion transcripts due to lack of consensus approaches or standardization. A case of CML is described in which comprehensive molecular analysis, including targeted next-generation sequencing, revealed a single ASXL1 mutation cooperating with an e6a2 BCR-ABL1 fusion transcript at blast crisis. A quantitative molecular monitoring approach was devised and adopted that reflected the disease response from initial treatment through allogeneic stem cell transplantation which resulted in undetectable e6a2 BCR-ABL1 transcripts. This case emphasizes the requirement for molecular monitoring in CML patients with atypical BCR-ABL1 fusion transcripts and emphasizes that comprehensive sequencing has the potential to identify targets for novel therapies in CML patients with advanced disease.

Transcriptome analysis of CD34+ cells from myelodysplastic syndrome patients

The myelodysplastic syndrome (MDS) represents a heterogeneous group of clonal hematologic stem cell disorders with the characteristic of ineffective hematopoiesis leading to low blood counts, and a risk of progression to acute myeloid leukemia (AML). To understand specific molecular characteristics of different MDS subtypes with del(5q), we analyzed the gene expression profiles of CD34+ cells from MDS patients of different databases and its enriched pathways. 44 genes, such as MME and RAG1, and eight related pathways were identified to be commonly changed, indicating their conserved roles in MDS development. Additionally, U43604 was identified to be specifically changed in three subtypes with del(5q), including refractory anemia (RA), refractory anemia with ringed sideroblasts (RARS) and refractory anemia with excess blasts (RAEB). C10orf10 and CD79B were specifically changed in RA patients with del(5q), while POU2AF1 were in RARS patients with del(5q). We also analyzed specific pathways of MDS subtypes, such as "Glycosaminoglycan biosynthesis-chondroitin sulfate" which was specific identified in RARS patients. Importantly, those findings can be validated well using another MDS database. Taken together, our analysis identified specific genes and pathways associated with different MDS subtypes with del(5q).

Myelodysplastic syndrome patients present more severe respiratory muscle impairment and reduced forced vital capacity: Is disordered inflammatory signaling the culprit?

BACKGROUND/OBJECTIVES

The ageing process is associated with gradual decline in respiratory system performance. Anemia is highly prevalent among older adults and usually associated with adverse outcomes. Myelodysplastic syndromes (MDS) are a heterogeneous group of hematologic malignancies with increasing incidence with age and characterized by anemia and other cytopenias. The main objectives of this study were to evaluate respiratory muscle strength and lung function in elderly patients with anemia, compare data between myelodysplastic syndromes and non-clonal anemias and evaluate the influence of serum IL-8 level and NF-kB activity on deteriorate pulmonary function in this specific population.

PARTICIPANTS

Individuals aged 60 and older with anemia secondary to MDS, non-clonal anemia and healthy elderly individuals.

MEASUREMENTS

Forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/ FVC ratio were measured by spirometry. Respiratory muscle strength was evaluated by maximal static respiratory pressures measurement. IL-8 analysis was performed by ELISA and activity of NF-kB by chemiluminescent assay.

RESULTS

Mean Hb concentration was comparable between patients with anemia. Significant differences were detected between all patients with anemia and controls for maximum-effort inspiratory mouth pressure (PImax) and also for maximum-effort expiratory mouth pressure (PEmax). The MDS group recorded a significantly lower PImax and PEmax percent predicted when compared to non-clonal anemia group. For FVC and FEV1, a significant difference was found in anemic patients, with even significantly lower values for FVC and FEV1 in MDS group. No significant differences were detected for PImax and PEmax and spirometry parameters when anemic patients were stratified according to the degree of anemia. A significant negative impact in FVC (% pred), PImax (% pred) and PEmax (% pred) was observed in patients with MDS and higher levels of IL-8 or increased activity of NF-kB.

CONCLUSION

A negative impact of anemia, independent of its degree, was demonstrated in respiratory muscle strength and lung function particularly in MDS. The well known elevated proinflammatory cytokines in MDS patients were proposed to play a role as was demonstrated by detrimental effect of higher IL-8 and NF-kB in pulmonary function tests in this population.

Interleukin-8 and nuclear factor kappa B are increased and positively correlated in myelodysplastic syndrome

The pathogenesis of myelodysplastic syndromes (MDS) is complex and depends on the interaction between aberrant hematopoietic cells and their microenvironment, probably including aberrations in cytokines and their signaling pathways. To evaluate interleukin-8 (IL-8) plasma levels and nuclear factor kappa B (NF-kB) in patients with MDS and to test possible correlation between IL-8 and NF-Kb, a total of 45 individuals were analyzed: 25 consecutive adult de novo MDS patients and 20 sex and age-matched healthy elderly volunteers. IL-8 analysis was performed by ELISA and activity of NF-kB by chemiluminescent assay. MDS patients showed higher level of IL-8 when compared to controls (p = 0.006). Patients aged 75 and above showed even higher levels (p = 0.035). NF-kB activity was significantly elevated in MDS patients when compared to controls (p < 0.0001) and higher in patients older than 75 years (p = 0.047). NF-kB activity was associated with higher serum ferritin (p = 0.042) and higher percentage of blasts (p = 0.028). A significant positive correlation between IL-8 and NF-kB was demonstrated (r = 0.480; p = 0.015). Many pathways involved in pathophysiology of MDS have been recently described, suggesting that an inflammatory process may act as a pathogenic driver. In this study, significantly elevated levels of IL-8 and NF-kB were demonstrated in MDS patients, with positive association of NF-kB with some markers of poor prognosis. A positive correlation between IL-8 and NF-kB suggests they cooperate as part of a complex networking of immune and inflammatory factors involved in MDS.