Myelodysplastic syndrome hematopoietic stem cell

U2AF1 mutation promotes tumorigenicity through facilitating autophagy flux mediated by FOXO3a activation in myelodysplastic syndromes

Mutations in the U2 small nuclear RNA auxiliary factor 1 (U2AF1) gene are the common feature of a major subset in myelodysplastic syndromes (MDS). However, the genetic landscape and molecular pathogenesis of oncogenic U2AF1^S34F mutation in MDS are not totally understood. We performed comprehensive analysis for prognostic significance of U2AF1 mutations in acute myeloid leukemia (AML) cohort based on The Cancer Genome Atlas (TCGA) database. Functional analysis of U2AF1^S34F mutation was performed in vitro. Differentially expressed genes (DEGs) and significantly enriched pathways were identified by RNA sequencing. The forkhead box protein O3a (FOXO3a) was investigated to mediate the function of U2AF1^S34F mutation in cell models using lentivirus. Chromatin immunoprecipitation, immunoblotting analyses, and immunofluorescence assays were also conducted. U2AF1 mutations were associated with poor prognosis in MDS and AML samples, which significantly inhibited cell proliferation and induced cellular apoptosis in cell models. Our data identified that U2AF1-mutant cell lines undergo FOXO3a-dependent apoptosis and NLRP3 inflammasome activation, which induces pyroptotic cell death. Particularly, an increase in the level of FOXO3a promoted the progression of MDS in association with restored autophagy program leading to NLRP3 inflammasome activation in response to U2AF1^S34F mutation. Based on the result that U2AF1^S34F mutation promoted the transcriptional activity of Bim through upregulating FOXO3a with transactivation of cell cycle regulators p21^Cip1 and p27^Kip1, FOXO3a, a potentially cancer-associated transcription factor, was identified as the key molecule on which these pathways converge. Overall, our studies provide new insights that U2AF1^S34F mutation functions the crucial roles in mediating MDS disease progression via FOXO3a activation, and demonstrate novel targets of U2AF1 mutations to the pathogenesis of MDS.

Upfront transplantation may have better outcomes than pretransplant cytoreductive therapy for treating patients with MDS-EB-1 or MDS-EB-2

Whether patients with myelodysplastic syndrome (MDS) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) benefit from pretransplant cytoreductive therapy remains controversial. Our study compared the outcomes of upfront transplantation with those of pretransplant cytoreductive therapy in the patients who received transplantation and those who dropped out due to cytoreductive therapy-related adverse effects. Patients with MDS-EB-1 or MDS-EB-2 were enrolled and divided into three groups based on therapy pretransplantation: upfront transplantation (upfront, n = 54), induction chemotherapy (CT, n = 66) and hypomethylating agents (HMA, n = 37) alone. One hundred fifty-seven patients were enrolled and 124 received allo-HSCT, with 5.6%, 28.8% and 29.7% of drop-out rate of transplantation in upfront, CT and HMA groups (P = .030), respectively. Overall therapy-related mortality (TRM), cytoreductive therapy and transplant-related mortality was 13.0%, 32.4% and 28.4% (P = .028), and 5-year overall survival (OS) was 73.6%, 43.4% and 46.9% (P = .033). Multivariate analysis showed that CT and HMA were risk factors for TRM and OS, and transplantation was a protective factor for OS. In transplant patients, 3-year cumulative incidence of relapse was 10.6%, 20.4% and 20.3% (P = .033), 5-year TRM was 14.5%, 20.0% and 17.6% (P = .651), OS was 77.3%, 64.3% and 68.8% (P = .047) and DFS was 74.0%, 63.0% and 65.8% (P = .042). Multivariate analysis showed that CT was a risk factor for DFS, while CT, HMA and poor karyotype were risk factors for relapse. Results suggested that pretransplant cytoreductive therapy was not associated with better outcomes in the patients who had undergone transplantation. Therefore, upfront transplantation may be preferable for MDS patients.

Identification of latent core genes and pathways associated with myelodysplastic syndromes based on integrated bioinformatics analysis

Background: Myelodysplastic syndromes (MDS) are relatively common hematological malignancies characterized by dysplastic hematopoiesis in one or more of the lineages of the bone marrow. This study aimed to identify critical pathogenic biomarkers associated with the carcinogenesis and progression of MDS. Methods: To explore the candidate genes, the expression profiles of GSE2779, GSE4619, and GSE19429 were downloaded from the Gene Expression Omnibus (GEO) database, which contained CD34+ cells isolated from MDS patients and normal controls. The three microarray datasets were integrated to obtain differentially expressed genes (DEGs) and were deeply analyzed by bioinformatics methods. The construction of protein-protein interaction (PPI) network together with module analysis was performed based on Cytoscape software and the Search Tool for the Retrieval of Interacting Genes (STRING) database. Results: Our study identified 114 DEGs, which were highly enriched in various key pathways, including forkhead box protein O (FoxO) signaling pathway, the primary immunodeficiency, and hematopoietic cell lineage. Twelve core genes, such as FOXO1, PAX5 and CXCR4 were identified with a high degree of connectivity. It is plausible that FoxO signaling pathway plays an important role in MDS, and the dysregulation of FOXO1 was significantly associated with TGFβ, IL2/STAT5, Notch signaling and apoptosis pathways. Conclusion: The current study for the first time identified twelve latent indicators and their downstream targets, which might become significant biomarkers for worse clinical characteristics in MDS.

Role of Plasma Gelsolin Protein in the Final Stage of Erythropoiesis and in Correction of Erythroid Dysplasia In Vitro

Gelsolin, an actin-remodeling protein, is involved in cell motility, cytoskeletal remodeling, and cytokinesis and is abnormally expressed in many cancers. Recently, human recombinant plasma gelsolin protein (pGSN) was reported to have important roles in cell cycle and maturation of primary erythroblasts. However, the role of human plasma gelsolin in late stage erythroblasts prior to enucleation and putative clinical relevance in patients with myelodysplastic syndrome (MDS) and hemato-oncologic diseases have not been reported. Polychromatic and orthochromatic erythroblasts differentiated from human cord blood CD34+ cells, and human bone marrow (BM) cells derived from patients with MDS, were cultured in serum-free medium containing pGSN. Effects of pGSN on mitochondria, erythroid dysplasia, and enucleation were assessed in cellular and transcriptional levels. With pGSN treatment, terminal maturation at the stage of poly- and ortho-chromatic erythroblasts was enhanced, with higher numbers of orthochromatic erythroblasts and enucleated red blood cells (RBCs). pGSN also significantly decreased dysplastic features of cell morphology. Moreover, we found that patients with MDS with multi-lineage dysplasia or with excess blasts-1 showed significantly decreased expression of gelsolin mRNA (GSN) in their peripheral blood. When BM erythroblasts of MDS patients were cultured with pGSN, levels of mRNA transcripts related to terminal erythropoiesis and enucleation were markedly increased, with significantly decreased erythroid dysplasia. Moreover, pGSN treatment enhanced mitochondrial transmembrane potential that is unregulated in MDS and cultured cells. Our findings demonstrate a key role for plasma gelsolin in erythropoiesis and in gelsolin-depleted MDS patients, and raises the possibility that pGSN administration may promote erythropoiesis in erythroid dysplasia.

Smad2/3-pathway ligand trap luspatercept enhances erythroid differentiation in murine β-thalassaemia by increasing GATA-1 availability

In β‐thalassaemia, anaemia results from ineffective erythropoiesis characterized by inhibition of late‐stage erythroid differentiation. We earlier used luspatercept and RAP‐536 protein traps for certain Smad2/3‐pathway ligands to implicate Smad2/3‐pathway overactivation in dysregulated erythroid differentiation associated with murine β‐thalassaemia and myelodysplasia. Importantly, luspatercept alleviates anaemia and has been shown to reduce transfusion burden in patients with β‐thalassaemia or myelodysplasia. Here, we investigated the molecular mechanisms underlying luspatercept action and pSmad2/3‐mediated inhibition of erythroid differentiation. In murine erythroleukemic (MEL) cells in vitro, ligand‐mediated overactivation of the Smad2/3 pathway reduced nuclear levels of GATA‐1 (GATA‐binding factor‐1) and its transcriptional activator TIF1γ (transcription intermediary factor 1γ), increased levels of reactive oxygen species, reduced cell viability and haemoglobin levels, and inhibited erythroid differentiation. Co‐treatment with luspatercept in MEL cells partially or completely restored each of these. In β‐thalassaemic mice, RAP‐536 up‐regulated Gata1 and its target gene signature in erythroid precursors determined by transcriptional profiling and gene set enrichment analysis, restored nuclear levels of GATA‐1 in erythroid precursors, and nuclear distribution of TIF1γ in erythroblasts. Bone marrow cells from β‐thalassaemic mice treated with luspatercept also exhibited restored nuclear availability of GATA‐1 ex vivo. Our results implicate GATA‐1, and likely TIF1γ, as key mediators of luspatercept/RAP‐536 action in alleviating ineffective erythropoiesis.

The prognostic value of serum erythropoietin in patients with lower-risk myelodysplastic syndromes: a review of the literature and expert opinion

Myelodysplastic syndromes (MDS) are hematopoietic stem cell malignancies associated with an erythroid maturation defect, resulting in anemia. Treatments for MDS include erythropoiesis-stimulating agents (ESAs). The identification of prognostic markers is important to help predict response and improve outcomes. Various scoring systems have been developed to help predict response to ESAs. Despite limitations in its assessment, serum erythropoietin (sEPO) level is an important predictor of hematologic response to ESAs in patients with lower-risk MDS. Numerous studies have reported significantly lower sEPO levels among responders versus non-responders. Furthermore, treatment response is significantly more likely among those with sEPO levels below versus those above various cutoffs. Other prognostic indicators for response to ESAs include lower transfusion requirement, fewer bone marrow blasts, higher hemoglobin, lower serum ferritin, lower-risk MDS, and more normal cytogenetics. Studies of other MDS therapies (e.g., lenalidomide and luspatercept) have also reported that lower sEPO levels are indicative of hematologic response. In addition, lower sEPO levels (up to 500 IU/L) have been included in treatment algorithms for patients with lower-risk MDS to define whether ESAs are indicated. Lower sEPO levels are predictive of hematologic response—particularly to ESAs. Further, clinical trials should use sEPO thresholds to ensure more homogeneous cohorts.

Therapeutic Modulation of Autophagy in Leukaemia and Lymphoma

Haematopoiesis is a tightly orchestrated process where a pool of hematopoietic stem and progenitor cells (HSPCs) with high self-renewal potential can give rise to both lymphoid and myeloid lineages. The HSPCs pool is reduced with ageing resulting in few HSPC clones maintaining haematopoiesis thereby reducing blood cell diversity, a phenomenon called clonal haematopoiesis. Clonal expansion of HSPCs carrying specific genetic mutations leads to increased risk for haematological malignancies. Therefore, it comes as no surprise that hematopoietic tumours develop in higher frequency in elderly people. Unfortunately, elderly patients with leukaemia or lymphoma still have an unsatisfactory prognosis compared to younger ones highlighting the need to develop more efficient therapies for this group of patients. Growing evidence indicates that macroautophagy (hereafter referred to as autophagy) is essential for health and longevity. This review is focusing on the role of autophagy in normal haematopoiesis as well as in leukaemia and lymphoma development. Attenuated autophagy may support early hematopoietic neoplasia whereas activation of autophagy in later stages of tumour development and in response to a variety of therapies rather triggers a pro-tumoral response. Novel insights into the role of autophagy in haematopoiesis will be discussed in light of designing new autophagy modulating therapies in hematopoietic cancers.

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).

Derepression of the DNA Methylation Machinery of the Gata1 Gene Triggers the Differentiation Cue for Erythropoiesis

GATA1 is a critical regulator of erythropoiesis. While the mechanisms underlying the high-level expression of GATA1 in maturing erythroid cells have been studied extensively, the initial activation of the Gata1 gene in early hematopoietic progenitors remains to be elucidated. We previously identified a hematopoietic stem and progenitor cell (HSPC)-specific silencer element (the Gata1 methylation-determining region [G1MDR]) that recruits DNA methyltransferase 1 (Dnmt1) and provokes methylation of the Gata1 gene enhancer. In the present study, we hypothesized that removal of the G1MDR-mediated silencing machinery is the molecular basis of the initial activation of the Gata1 gene and erythropoiesis. To address this hypothesis, we generated transgenic mouse lines harboring a Gata1 bacterial artificial chromosome in which the G1MDR was deleted. The mice exhibited abundant GATA1 expression in HSPCs, in a GATA2-dependent manner. The ectopic GATA1 expression repressed Gata2 transcription and induced erythropoiesis and apoptosis of HSPCs. Furthermore, genetic deletion of Dnmt1 in HSPCs activated Gata1 expression and depleted HSPCs, thus recapitulating the HSC phenotype associated with GATA1 gain of function. These results demonstrate that the G1MDR holds the key to HSPC maintenance and suggest that release from this suppressive mechanism is a fundamental requirement for subsequent initiation of erythroid differentiation.

The role of microRNA in myelodysplastic syndromes: beyond DNA methylation and histone modification

Myelodysplastic syndromes (MDS) are heterogeneous group of hematologic disorders of mostly elderly and based on distinct clinical phenotypes. Current paradigm of their pathogenesis relies on somatic gene mutations combined with the predisposing defective osteohematopoietic niche, but due to the breakout in epigenetic research scientific focus has steered toward two most common epigenetic modifications: methylation mechanisms and histone modification. At the same time, relatively few studies have been undertaken regarding the third epigenetic pathway - microRNAs - in MDS. The main aim of this review is to provide the basics of microRNA biology and function in oncogenesis, showing the complexity of mechanisms behind this single-stranded 22 nucleotides long RNA molecule, with further focus on its implication in MDS pathology and clinical context. By extensive literature search, we have shown enough evidence for their deregulation in MDS. However, few studies have addressed the issue on pathogenic events in MDS and its association with specific microRNAs. Preliminary research in clinical setting has shown the possible utility of microRNAs in terms of prognosis and therapy, although we are only beginning to understand various implications of microRNAs in MDS and further extensive research is warranted to answer multiple questions arising from interconnection of this epigenetic mechanism in MDS.

Fucoidan inhibits proliferation of the SKM-1 acute myeloid leukaemia cell line via the activation of apoptotic pathways and production of reactive oxygen species

Myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid disorders characterized by peripheral blood cytopenias and a high risk of progression to acute myeloid leukaemia (AML). Fucoidan, a complex sulphated polysaccharide isolated from the cell wall of brown seaweeds, has recently attracted attention for its multiple biological activities and its potential as a novel candidate for cancer therapy. In the present study, the anti‑cancer activity of fucoidan was investigated in the MDS/AML cell line SKM‑1. Fucoidan inhibited proliferation, induced apoptosis and caused G1-phase arrest of the cell cycle in SKM‑1 cells as determined by a cell counting kit 8 assay and flow cytometry. Furthermore, reverse transcription quantitative polymerase chain reaction and western blot analyses indicated that treatment with fucoidan (100 µg/ml for 48 h) activated Fas and caspase‑8 in SKM‑1 cells, which are critical for the extrinsic apoptotic pathway; furthermore, caspase‑9 was activated via decreases in phosphoinositide-3 kinase/Akt signaling as indicated by reduced levels of phosphorylated Akt, suggesting the involvement of the intrinsic apoptotic pathway. In addition, fucoidan treatment of SKM‑1 cells resulted in the generation of reactive oxygen species (ROS) as determined by staining with dichloro-dihydro-fluorescein diacetate. These results suggested that the mechanisms of the anti‑cancer effects of fucoidan in SKM‑1 are closely associated with cell cycle arrest and apoptotic cell death, which partly attributed to the activation of apoptotic pathways and accumulation of intracellular ROS. Our results demonstrated that Fucoidan inhibits proliferation and induces the apoptosis of SKM‑1 cells, which provides substantial therapeutic potential for MDS treatment.

Genetics factors associated with myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a clinically and cytogenetically heterogeneous group of clonal diseases. Clonal chromosomal abnormalities are observed in 30-50% of patients with MDS. The deletions are among the most common alterations, and often involve the long arms of chromosomes 5, 7, 8, 13, and 20 and the short arms of chromosomes 12 and 17. The advent of new technologies for the detection of genetic abnormalities led to the description of a new set of recurrent mutations, leading to new insights into the pathophysiology of MDS. The recent recognition that genes involved in the regulation of histone function (EZH2, ASXL1, and UTX) and DNA methylation (DNMT3A, IDH1/IDH2, and TET2) are frequently mutated in MDS, has led to the proposal that there is an important link between genetic and epigenetic alterations in this disease. In fact, regulatory factors have also been considered as miR-143/miR-145, miR-146a, miR-125a and MiR-21. Somatic mutations may influence the clinical phenotype but are not included in current prognostic scoring systems. In recent years research has brought new insights into these diseases, but few of the findings are sufficiently robust to be incorporated into the clinical routine at this time. Thus, the aim of this study was to review the role of genetic factors involved in the diagnosis and development of the different phenotypes of MDS.

Autophagy in acute leukemias: a double-edged sword with important therapeutic implications

Macroautophagy, usually referred to as autophagy, is a degradative pathway wherein cytoplasmatic components such as aggregated/misfolded proteins and organelles are engulfed within double-membrane vesicles (autophagosomes) and then delivered to lysosomes for degradation. Autophagy plays an important role in the regulation of numerous physiological functions, including hematopoiesis, through elimination of aggregated/misfolded proteins, and damaged/superfluous organelles. The catabolic products of autophagy (amino acids, fatty acids, nucleotides) are released into the cytosol from autophagolysosomes and recycled into bio-energetic pathways. Therefore, autophagy allows cells to survive starvation and other unfavorable conditions, including hypoxia, heat shock, and microbial pathogens. Nevertheless, depending upon the cell context and functional status, autophagy can also serve as a death mechanism. The cohort of proteins that constitute the autophagy machinery function in a complex, multistep biochemical pathway which has been partially identified over the past decade. Dysregulation of autophagy may contribute to the development of several disorders, including acute leukemias. In this kind of hematologic malignancies, autophagy can either act as a chemo-resistance mechanism or have tumor suppressive functions, depending on the context. Therefore, strategies exploiting autophagy, either for activating or inhibiting it, could find a broad application for innovative treatment of acute leukemias and could significantly contribute to improved clinical outcomes. These aspects are discussed here after a brief introduction to the autophagic molecular machinery and its roles in hematopoiesis.

Detection of an activated JAK3 variant and a Xq26.3 microdeletion causing loss of PHF6 and miR-424 expression in myelodysplastic syndromes by combined targeted next generation sequencing and SNP array analysis

Myelodysplastic syndromes (MDS) are hematopoietic disorders characterized by ineffective hematopoiesis and progression to acute leukemia. In patients ineligible for hematopoietic stem cell transplantation, azacitidine is the only treatment shown to prolong survival. However, with the availability of a growing compendium of cancer biomarkers and related drugs, analysis of relevant genetic alterations for individual MDS patients might become part of routine evaluation. Therefore and in order to cover the entire bone marrow microenvironment involved in the pathogenesis of MDS, SNP array analysis and targeted next generation sequencing (tNGS) for the mostly therapy relevant 46 onco- and tumor-suppressor genes were performed on bone marrow biopsies from 29 MDS patients. In addition to the detection of mutations known to be associated with MDS in NRAS, KRAS, MPL, NPM1, IDH1, PTPN11, APC and MET, single nucleotide variants so far unrelated to MDS in STK11 (n=1), KDR (n=3), ATM (n=1) and JAK3 (n=2) were identified. Moreover, a recurrent microdeletion was detected in Xq26.3 (n=2), causing loss of PHF6 expression, a potential tumor suppressor gene, and the miR-424, which is involved in the development of acute myeloid leukemia. Finally, combined genetic aberrations affecting the VEGF/VEGFR pathway were found in the majority of cases demonstrating the diversity of mutations affecting different nodes of a particular signaling network as an intrinsic feature in MDS patients. We conclude that combined SNP array analyses and tNGS can identify established and novel therapy relevant genomic aberrations in MDS patients and track them in a clinical setting for individual therapy selection.

Embryonic stem cells markers SOX2, OCT4 and Nanog expression and their correlations with epithelial-mesenchymal transition in nasopharyngeal carcinoma

Expression of embryonic stem cells (ESCs) markers (SOX2, OCT4, Nanog and Nestin) is crucial for progression of various human malignancies. The purpose of this study was to investigate the expression and prognostic impact of these molecules in nasopharyngeal carcinoma (NPC) patients by immunohistochemistry and immunofluorescence. In the present study, we found that the expression levels of SOX2, OCT4 and Nanog were highly expressed in NPC compared with the non-tumorous tissues. Furthermore, these proteins correlated significantly with several clinicalpathological factors and epithelial-mesenchymal transition (EMT)-associated indicators (E-cadherin/N-cadherin and Snail). In multivariate analyses, high expression of OCT4 (P = 0.013) and Nanog (P = 0.040), but not that of SOX2, was associated with worse survival and had strongly independent prognostic effects. Of note, OCT4 and Nanog were more frequently located at the invasive front of tumors, and correlated significantly with various aggressive behaviors including T classification, N classification, M classification and clinical stage. Furthermore, patients with co-expression of OCT4 and Nanog in the invasive front had significantly worse survival (P = 0.005). Interestingly, at the invasive front, these molecules correlated significantly with Nestin expression in endothelial cells (P<0.001). These findings provide evidence that ESCs biomarkers OCT4 and Nanog serves as independent prognostic factors for NPC. Additionally, cancer cells in the invasive front of NPC acquiring ESCs-like features should be maintained by vascular niches.