The Role of the Immune System in Myelodysplasia: Implications for Therapy

Immune dysregulation and potential targeted therapy in myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a heterogeneous group of clonal hematological diseases and a high risk for transformation to acute myeloid leukemia (AML). The identification of key genetic alterations in MDS has enhanced our understanding of the pathogenesis and evolution. In recent years, it has been found that both innate and adaptive immune signaling are activated in the hematopoietic niche of MDS with aberrant cytokine secretion in the bone marrow microenvironment. It is also clear that immune dysregulation plays an important role in the occurrence and progression of MDS, especially the destruction of the bone marrow microenvironment, including hematopoiesis and stromal components. The purpose of this review is to explore the role of immune cells, the immune microenvironment, and cytokines in the pathogenesis of MDS. Insights into the mechanisms of these variants may facilitate the development of novel effective treatments to prevent disease progression.

Analysis of Immune-Cell Distribution of Bone Marrow in Patients with Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) immunity plays an important role in the proliferation and apoptosis of aberrant cells. Immune dysregulation has been studied in various prognostic subgroups. This study analyzed 60 patients with MDS via multidimensional flow cytometry to evaluate the expression of aberrant markers, such as CD7 and cytoplasmic CD3 on lymphocytes. The Revised International Prognostic Scoring System (IPSS-R) scores were used to classify the patients into risk groups. The results showed a significant downregulation of CyCD3- T cells in low-intermediate versus high-risk patients (p = 0.013). This study is the first to show that a significant decrease in cyCD3- T cells in patients with a lower IPSS-R score may indicate microenvironmental changes conducive to transformation in MDS.

Bone Marrow Immune Microenvironment in Myelodysplastic Syndromes

The BM, the major hematopoietic organ in humans, consists of a pleiomorphic environment of cellular, extracellular, and bioactive compounds with continuous and complex interactions between them, leading to the formation of mature blood cells found in the peripheral circulation. Systemic and local inflammation in the BM elicit stress hematopoiesis and drive hematopoietic stem cells (HSCs) out of their quiescent state, as part of a protective pathophysiologic process. However, sustained chronic inflammation impairs HSC function, favors mutagenesis, and predisposes the development of hematologic malignancies, such as myelodysplastic syndromes (MDS). Apart from intrinsic cellular mechanisms, various extrinsic factors of the BM immune microenvironment (IME) emerge as potential determinants of disease initiation and evolution. In MDS, the IME is reprogrammed, initially to prevent the development, but ultimately to support and provide a survival advantage to the dysplastic clone. Specific cellular elements, such as myeloid-derived suppressor cells (MDSCs) are recruited to support and enhance clonal expansion. The immune-mediated inhibition of normal hematopoiesis contributes to peripheral cytopenias of MDS patients, while immunosuppression in late-stage MDS enables immune evasion and disease progression towards acute myeloid leukemia (AML). In this review, we aim to elucidate the role of the mediators of immune response in the initial pathogenesis of MDS and the evolution of the disease.

Bone Marrow CD3+ CD56+ Regulatory T lymphocytes (TR3-56 cells) are inversely associated with activation and expansion of Bone Marrow cytotoxic T cells in IPSS-R very-low/low risk MDS patients

Background

Emergence of dysplastic haematopoietic precursor/s, cytopenia and variable leukaemia risk characterise myelodysplastic syndromes (MDS). Impaired immune‐regulation, preferentially affecting cytotoxic T cells (CTL), has been largely observed in MDS. Recently, we described the T_R3−56 T cell subset, characterised by the co‐expression of CD3 and CD56, as a novel immune‐regulatory population, able to modulate cytotoxic functions. Here, we address the involvement of T_R3−56 cells in MDS pathogenesis/progression.

Objectives

To analyse the relationship between T_R3−56 and CTL activation/expansion in bone marrow (BM) of very‐low/low‐risk MDS subjects.

Methods

Peripheral blood and BM specimens, obtained at disease onset in a cohort of 58 subjects, were analysed by immune‐fluorescence and flow cytometry, to preserve the complexity of the biological sample.

Results

We observed that a trend‐increase of BM T_R3−56 in high/very‐high MDS stage, as compared with very‐low/low group, associates with a decreased activation of BM resident CTL; significant correlation of T_R3−56 with BM blasts has been also revealed. In addition, in very‐low/low‐risk subjects the T_R3−56 amount in BM inversely correlates with the presence of activated BM CTL showing a skewed Vβ T‐cell repertoire.

Conclusions

These data add T_R3−56 to the immune‐regulatory network involved in MDS pathogenesis/progression. Better knowledge of the immune‐mediated processes associated with the disease might improve MDS clinical management.

The Rising Era of Immune Checkpoint Inhibitors in Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of diseases characterized by ineffective hematopoiesis and a wide spectrum of manifestations ranging from indolent and asymptomatic cytopenias to acute myeloid leukemia (AML). MDS result from genetic and epigenetic derangements in clonal cells and their surrounding microenvironments. Studies have shown associations between MDS and other autoimmune diseases. Several immune mechanisms have been identified in MDS, suggesting that immune dysregulation might be at least partially implicated in its pathogenesis. This has led to rigorous investigations on the role of immunomodulatory drugs as potential treatment options. Epigenetic modification via immune check point inhibition, while well established as a treatment method for advanced solid tumors, is a new approach being considered in hematologic malignancies including high risk MDS. Several trials are looking at the efficacy of these agents in MDS, as frontline therapy and in relapse, both as monotherapy and in combination with other drugs. In this review, we explore the utility of immune checkpoint inhibitors in MDS and current research evaluating their efficacy.

Disordered Immune Regulation and its Therapeutic Targeting in Myelodysplastic Syndromes

PURPOSE OF REVIEW

Immune dysregulation is a defining feature of myelodysplastic syndromes (MDS). Recently, several studies have further defined the complex role of immune alterations within MDS. Herein, we will summarize some of these findings and discuss the therapeutic strategies currently in development.

RECENT FINDINGS

Immune alterations in MDS are complex, heterogeneous, and intertwined with clonal hematopoiesis and stromal cell dysfunction. Inflammation in MDS proceeds as a vicious cycle, mediated in large part by secreted factors, which induce cell death and activate innate immune signaling. Therapeutic targeting of this variable immune dysregulation has led to modest responses thus far, but incorporation of the growing repertoire of immunotherapy brings new potential for improved outcomes. The immune milieu is variable across the spectrum of MDS subtypes, with a changing balance of inflammatory and suppressive cellular forces from low- to high-risk disease.

Lenalidomide use in myelodysplastic syndromes: Insights into the biologic mechanisms and clinical applications

Myelosysplastic syndromes (MDS) include a heterogeneous group of clonal myeloid neoplasms characterized by ineffective hematopoiesis leading to blood cytopenias and a variable risk of progression into acute myeloid leukemia (AML). Although the hypomethylating agent azacitidine prolongs survival among patients with higher risk (HR)-MDS compared with conventional care, no drug has been shown conclusively to prolong survival or delay progression to AML among patients with lower-risk MDS (LR-MDS). Lenalidomide is the drug with the most impressive clinical activity in the subset of anemic LR-MDS patients who harbor a deletion of the long arm of chromosome 5 (5q-), where it leads to high rates of transfusion independence and cytogenetic responses. Furthermore, lenalidomide delays progression to AML and prolongs survival among responders. In this article, we review the recently recognized mechanisms of action of lenalidomide and discuss the most recent clinical data regarding its use in patients with both 5q- MDS as well as non-5q- MDS. Finally, we forecast the future directions to improve the efficacy of lenalidomide in MDS with and without 5q-. Cancer 2017;123:1703-1713. © 2017 American Cancer Society.

Bone Marrow Immunity and Myelodysplasia

Myelodysplastic syndrome (MDS) is characterized by an ineffective hematopoiesis with production of aberrant clones and a high cell apoptosis rate in bone marrow (BM). Macrophages are in charge of phagocytosis. Innate Immune cells and specific T cells are in charge of immunosurveillance. Little is known on BM cell recruitment and activity as BM aspirate is frequently contaminated with peripheral blood. But evidences suggest an active role of immune cells in protection against MDS and secondary leukemia. BM CD8⁺ CD28⁻ CD57⁺ T cells are directly cytotoxic and have a distinct cytokine signature in MDS, producing TNF-α, IL-6, CCL3, CCL4, IL-1RA, TNFα, FAS-L, TRAIL, and so on. These tools promote apoptosis of aberrant cells. On the other hand, they also increase MDS-related cytopenia and myelofibrosis together with TGFβ. IL-32 produced by stromal cells amplifies NK cytotoxicity but also the vicious circle of TNFα production. Myeloid-derived suppressing cells (MDSC) are increased in MDS and have ambiguous role in protection/progression of the diseases. CD33 is expressed on hematopoietic stem cells on MDS and might be a potential target for biotherapy. MDS also has impact on immunity and can favor chronic inflammation and emergence of autoimmune disorders. BM is the site of hematopoiesis and thus contains a complex population of cells at different stages of differentiation from stem cells and early engaged precursors up to almost mature cells of each lineage including erythrocytes, megakaryocytes, myelo-monocytic cells (monocyte/macrophage and granulocytes), NK cells, and B cells. Monocytes and B cell finalize their maturation in peripheral tissues or lymph nodes after migration through the blood. On the other hand, T cells develop in thymus and are present in BM only as mature cells, just like other well vascularized tissues. BM precursors have a strong proliferative capacity, which is usually associated with a high risk for genetic errors, cell dysfunction, and consequent cell death. Abnormal cells are prone to destruction through spontaneous apoptosis or because of the immunosurveillance that needs to stay highly vigilant. High rates of proliferation or differentiation failures lead to a high rate of cell death and massive release of debris to be captured and destroyed (1). Numerous macrophages reside in BM in charge of home-keeping. They have a high capacity of phagocytosis required for clearing all these debris.

Immune Mechanisms in Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) is a spectrum of diseases, characterized by debilitating cytopenias and a propensity of developing acute myeloid leukemia. Comprehensive sequencing efforts have revealed a range of mutations characteristic, but not specific, of MDS. Epidemiologically, autoimmune diseases are common in patients with MDS, fueling hypotheses of common etiological mechanisms. Both innate and adaptive immune pathways are overly active in the hematopoietic niche of MDS. Although supportive care, growth factors, and hypomethylating agents are the mainstay of MDS treatment, some patients—especially younger low-risk patients with HLA-DR15 tissue type—demonstrate impressive response rates after immunosuppressive therapy. This is in contrast to higher-risk MDS patients, where several immune activating treatments, such as immune checkpoint inhibitors, are in the pipeline. Thus, the dual role of immune mechanisms in MDS is challenging, and rigorous translational studies are needed to establish the value of immune manipulation as a treatment of MDS.

[Long- term outcome of thalidomide and cyclosporine in patients with IPSS low/intermediate- 1 myelodysplastic syndromes]

OBJECTIVE

To investigate the long- term outcome of cyclosporin A (CsA) combined with thalidomide regime for Chinese patients with IPSS low/intermediate- 1 myelodysplastic syndromes (MDS) without del（5q）and the predictive variables which could impact the response to the therapy.

METHODS

Seventy-six MDS patients who were treated with these drugs at a single institute in China were retrospectively analyzed. The polymorphism of cereblon gene, rs1672753, was detected in patients of this cohort by PCR and direct sequencing.

RESULTS

A total of 53% of patients showed hematological improvement（HI）to the therapy. Thirty-one patients（31/73, 43%）achieved erythrocyte response（HI-E）; 15 patients（15/50, 30%）achieved neutrophil response（HI-N); 18 patients（18/58, 31%）achieved platelet response（HI-P). Twenty-seven of the 50 patients（46%）who were dependent on red blood cell transfusion achieved HI- E and became independent of transfusion. The median duration of response among the responders was 22 months (range, 1- 131 + months). Bone marrow blasts ≤2% was the only factor associated with longer response duration in univariate analysis （P=0.010）. There was no significant difference between the two groups of celeblon gene rs1672753 polymorphism either on the response rate or the response duration. The median survival of 67 patients without stem cell transplantation was 82 months. In multivariate analyses, factors significantly correlated with survival were IPSS-R（HR=3.461, 95%CI 1.126-10.639, P=0.030), age ≥ 60 y（HR=4.120, 95%CI 1.070-15.867, P=0.040）and HI-N（HR=7.733, 95%CI 1.007-59.396, P=0.049).

CONCLUSION

CsA combined with thalidomide regime could improve the anemia symptom in low/int-1 risk MDS patients without del（5q）. The predictive value of cereblon gene polymorphism, rs1672753, could not be verified in this study.

Comparison of immune manifestations between refractory cytopenia of childhood and aplastic anemia in children: A single-center retrospective study

This retrospective single-center study assessed the incidence and clinical features of immune manifestations of refractory cytopenia of childhood (RCC) and childhood aplastic anemia (AA). We evaluated 72 children with RCC and 123 with AA between February 2008 and March 2013. RCC was associated with autoimmune disease in 4 children, including 1 case each with autoimmune hemolytic anemia, rheumatoid arthritis, systemic lupus erythematosus, and anaphylactoid purpura. No children with AA were diagnosed with autoimmune diseases. Immune abnormalities were common in both RCC and AA; the most significant reductions were in the relative numbers of CD3-CD56+ subsets found in RCC. Despite the many similar immunologic abnormalities in AA and RCC, the rate of autoimmune disease was significantly lower in childhood AA than RCC (p=0.008, χ2=6.976). The relative numbers of natural killer cells were significantly lower in RCC patients than AA patients. By month 6, there was no significant difference in autoimmune manifestations between RCC and AA in relation to the response to immunosuppressive therapy (p=0.907, χ2=0.014). The large overlap of analogous immunologic abnormalities indicates that RCC and childhood AA may share the same pathogenesis.

The inflammatory microenvironment in MDS

Myelodysplastic syndromes (MDS) are a collection of pre-malignancies characterized by impaired proliferation and differentiation of hematopoietic stem cells and a tendency to evolve into leukemia. Among MDS's pathogenic mechanisms are genetic, epigenetic, apoptotic, differentiation, and cytokine milieu abnormalities. Inflammatory changes are a prominent morphologic feature in some cases, with increased populations of plasma cells, mast cells, and lymphocytes in bone marrow aspirates. Accumulating evidence suggests that the bone marrow microenvironment contributes to MDS disease pathology, with microenvironment alterations and abnormality preceding, and facilitating clonal evolution in MDS patients. In this review, we focus on the inflammatory changes involved in the pathology of MDS, with an emphasis on immune dysfunction, stromal microenvironment, and cytokine imbalance in the microenvironment as well as activation of innate immune signaling in MDS patients. A better understanding of the mechanism of MDS pathophysiology will be beneficial to the development of molecular-targeted therapies in the future.

Dynamics of ASXL1 mutation and other associated genetic alterations during disease progression in patients with primary myelodysplastic syndrome

Recently, mutations of the additional sex comb-like 1 (ASXL1) gene were identified in patients with myelodysplastic syndrome (MDS), but the interaction of this mutation with other genetic alterations and its dynamic changes during disease progression remain to be determined. In this study, ASXL1 mutations were identified in 106 (22.7%) of the 466 patients with primary MDS based on the French-American-British (FAB) classification and 62 (17.1%) of the 362 patients based on the World Health Organization (WHO) classification. ASXL1 mutation was closely associated with trisomy 8 and mutations of RUNX1, EZH2, IDH, NRAS, JAK2, SETBP1 and SRSF2, but was negatively associated with SF3B1 mutation. Most ASXL1-mutated patients (85%) had concurrent other gene mutations at diagnosis. ASXL1 mutation was an independent poor prognostic factor for survival. Sequential studies showed that the original ASXL1 mutation remained unchanged at disease progression in all 32 ASXL1-mutated patients but were frequently accompanied with acquisition of mutations of other genes, including RUNX1, NRAS, KRAS, SF3B1, SETBP1 and chromosomal evolution. On the other side, among the 80 ASXL1-wild patients, only one acquired ASXL1 mutation at leukemia transformation. In conclusion, ASXL1 mutations in association with other genetic alterations may have a role in the development of MDS but contribute little to disease progression.

Clinical implications of U2AF1 mutation in patients with myelodysplastic syndrome and its stability during disease progression

We aimed to analyze clinical impacts of the U2AF1 mutation on patients with myelodysplastic syndrome (MDS) and its stability during disease progression. We checked mutation status of the U2AF1 by direct sequencing in 478 de novo MDS patients and correlated with the clinical characteristics and outcomes. We also sequentially analyzed the U2AF1 mutation in 421 samples from 142 patients to determine its stability during the disease courses. Thirty-six patients (7.5%) were found to have U2AF1 mutations, which occurred more frequently in younger patients (P = 0.033). U2AF1 mutation was an independent poor-risk factor for overall survival (OS) in all patients (P = 0.030) and younger patients (P = 0.041). U2AF1 mutation could also predict shorter time-to-leukemia transformation (TTL) in younger patients (P = 0.020). In addition, U2AF1 mutation was associated with shorter TTL in lower-risk MDS patients. Sequential analyses showed all original U2AF1 mutations in U2AF1-mutated patients were retained during follow-ups unless complete remission was achieved, whereas none of the U2AF1-wild patients acquired a novel mutation during disease evolution. U2AF1 mutation is more prevalent in younger MDS patients and associated with inferior outcomes although it is stable during the clinical course. The mutation may be used as a biomarker for risk stratification.

Acquired myelodysplasia or myelodysplastic syndrome: clearing the fog

Myelodysplastic syndromes (MDS) are clonal myeloid disorders characterized by progressive peripheral blood cytopenias associated with ineffective myelopoiesis. They are typically considered neoplasms because of frequent genetic aberrations and patient-limited survival with progression to acute myeloid leukemia (AML) or death related to the consequences of bone marrow failure including infection, hemorrhage, and iron overload. A progression to AML has always been recognized among the myeloproliferative disorders (MPD) but occurs only rarely among those with essential thrombocythemia (ET). Yet, the World Health Organization (WHO) has chosen to apply the designation myeloproliferative neoplasms (MPN), for all MPD but has not similarly recommended that all MDS become the myelodysplastic neoplasms (MDN). This apparent dichotomy may reflect the extremely diverse nature of MDS. Moreover, the term MDS is occasionally inappropriately applied to hematologic disorders associated with acquired morphologic myelodysplastic features which may rather represent potentially reversible hematological responses to immune-mediated factors, nutritional deficiency states, and disordered myelopoietic responses to various pharmaceutical, herbal, or other potentially myelotoxic compounds. We emphasize the clinical settings, and the histopathologic features, of such AMD that should trigger a search for a reversible underlying condition that may be nonneoplastic and not MDS.

Natural killer expansion, human leukocyte antigens-E expression and CD14(+) CD56(+) monocytes in a myelodysplastic syndrome patient

Myelodysplastic syndromes (MDS) are clonal disorders characterized by ineffective hematopoiesis and possible evolution to acute leukemia. Occurrence of stem cell defects and of immune-mediated mechanisms was evidenced as relevant for pathophysiology of MDS. Here, we described one case of MDS patient carrying CD14(+) CD56(+) monocytes in bone marrow (BM), in the presence of a defective human leukocyte antigen (HLA)-E expression on peripheral blood (PB) cells and of natural killer (NK) cell expansion in PB and BM. The defective HLA-E expression and the NK expansion are proposed to be relevant for the pathogenesis of myelodysplasia in those patients showing CD14(+) CD56(+) monocytes in BM.

HLA-E and HLA class I molecules on bone marrow and peripheral blood polymorphonuclear cells of myelodysplatic patients

Relevance of immune-dysregulation for emergence, dominance and progression of dysplastic clones in myelodysplastic syndromes (MDS) was suggested, but valuable or predictive criteria on this involvement are lacking. We previously reported that reduced T-regulatory cells (Treg) and high CD54 expression on T cell identify a sub-group of patients in whom an immune-pathogenesis might be inferred. Here, we suggest the occurrence of immune-selection of dysplastic clones in a subgroup of MDS patients, with reduced HLA-I and HLA-E on PMN, and propose that an altered immune profile might represent a valuable criterion to classify Low/Int-1 patients on the basis of immune-pathogenesis of MDS.

Immune dysregulation in myelodysplastic syndrome

Myelodysplastic syndrome (MDS) represents one of the most challenging health-related problems in the elderly. Characterized by dysplastic morphology in the bone marrow in association with ineffective hematopoiesis, pathophysiological causes of this disease are diverse including genetic abnormalities within myeloid progenitors, altered epigenetics, and changes in the bone marrow microenvironment. The concept that T-cell mediated autoimmunity contributes to bone marrow failure has been widely accepted due to hematologic improvement after immunosuppressive therapy (IST) in a subset of patients. Currently, IST for MDS primarily involves anti-thymocyte globulin (ATG)-based regimens in which responsiveness is strongly associated with younger (under 60 years) age at disease onset. In such cases, progressive cytopenia may occur as a consequence of expanded self-reactive CD8⁺ cytotoxic T lymphocytes (CTLs) that suppress hematopoietic progenitors. Although most hematologists agree that IST can offer durable hematologic remission in younger patients with MDS, an international clinical study and a better understanding of the molecular mechanisms contributing to the expansion of self-reactive CTLs is crucial. In this review, data accumulated in the US, Europe, and Asia will be summarized to provide insight and direction for a multi-center international trial.

The clinical implication of SRSF2 mutation in patients with myelodysplastic syndrome and its stability during disease evolution

Recurrent somatic mutation of SRSF2, one of the RNA splicing machinery genes, has been identified in a substantial proportion of patients with myelodysplastic syndrome (MDS). However, the clinical and biologic characteristics of MDS with this mutation remain to be addressed. In this study, 34 (14.6%) of the 233 MDS patients were found to have SRSF2 mutation. SRSF2 mutation was closely associated with male sex (P = .001) and older age (P < .001). It occurred concurrently with at least 1 additional mutation in 29 patients (85.3%) and was closely associated with RUNX1, IDH2, and ASXL1 mutations (P = .004, P < .001, and P < .001, respectively). Patients with SRSF2 mutation had an inferior overall survival (P = .010), especially in the lower risk patients. Further exploration showed that the prognostic impact of SRSF2 mutation might be attributed to its close association with old age. Sequential analyses in 173 samples from 66 patients showed that all SRSF2-mutated patients retained their original mutations, whereas none of the SRSF2-wild patients acquired a novel mutation during disease evolution. In conclusion, SRSF2 mutation is associated with distinct clinical and biologic features in MDS patients. It is stable during the clinical course and may play little role in disease progression.

Predicting survival of patients with hypocellular myelodysplastic syndrome: development of a disease-specific prognostic score system

BACKGROUND

Although most patients with myelodysplastic syndrome (MDS) exhibit bone marrow hypercellularity, a subset of them present with a hypocellular bone marrow. Specific factors associated with poor prognosis have not been investigated in patients with hypocellular MDS.

METHODS

The authors studied a cohort of 253 patients with hypocellular MDS diagnosed at The University of Texas MD Anderson Cancer Center between 1993 and 2007 and a cohort of 1725 patients with hyper-/normocellular MDS diagnosed during the same time period.

RESULTS

Patients with hypocellular MDS presented more frequently with thrombocytopenia (P < .019), neutropenia (P < .001), low serum β-2 microglobulin (P < .001), increased transfusion dependency (P < .001), and intermediate-2/high-risk disease (57% vs 42%, P = .02) compared with patients with hyper-/normocellular MDS. However, no difference in overall survival was observed between the 2 groups (P = .28). Multivariate analysis identified poor performance status (Eastern Cooperative Oncology Group ≥2), low hemoglobin (<10 g/dL), unfavorable cytogenetics (-7/7q or complex), increased bone marrow blasts (≥5%), and high serum lactate dehydrogenase (>600 IU/L) as adverse independent factors for survival.

CONCLUSIONS

A new prognostic model based on these factors was built that segregated patients into 3 distinct risk categories independent of International Prognostic Scoring System (IPSS) score. This model is independent from the IPSS, further refines IPSS-based prognostication, and may be used to develop of risk-adapted therapeutic approaches for patients with hypocellular MDS.

Bone marrow mesenchymal stem cells in myelodysplastic syndromes: cytogenetic characterization

AIM

This study compared genetic aberrations in hematopoietic cells (HCs) and mesenchymal stem cells of myelodysplastic syndrome (MDS-MSCs) patients.

METHODS

We obtained chromosomes with aberrations from 22 patients with MDS and chromosomes from 7 healthy individuals. Chromosomal aberrations in both HCs and MSCs were identified using G-banding. We then performed DNA content analysis of the HCs and MSCs.

RESULTS

Cytogenetic aberrations were detected in HCs from 13 of the 22 MDS patients (59%). Chromosomal aberrations in MSCs were detected in 15 of the 22 MDS patients (68%). No chromosomal abnormalities were identified in MSCs of the 7 healthy volunteers. We demonstrate herein that MSCs have distinct genetic abnormalities compared to HCs from the same individual. We observed a random loss of chromosomal material in significant proportions of MSCs. A high proportion of random loss may be a marker of chromosomal instability of MDS-MSCs. However, two case results showed that HCs and MSCs have different altered structural changes.

CONCLUSION

Our results suggest enhanced genetic susceptibility of these cells in MDS patients. Our data indicates that the genetic alterations in MSCs may constitute a particular biological mechanism of MDS pathogenesis.

Bone marrow mesenchymal stem cells: biological properties and their role in hematopoiesis and hematopoietic stem cell transplantation

Mesenchymal stem cells (MSCs) are multipotent adult stem cells that are present in practically all tissues as a specialized population of mural cells/pericytes that lie on the abluminal side of blood vessels. Originally identified within the bone marrow (BM) stroma, not only do they provide microenvironmental support for hematopoietic stem cells (HSCs), but can also differentiate into various mesodermal lineages. MSCs can easily be isolated from the BM and subsequently expand in vitro and in addition they exhibit intriguing immunomodulatory properties, thereby emerging as attractive candidates for various therapeutic applications. This review addresses the concept of BM MSCs via a hematologist's point of view. In this context it discusses the stem cell properties that have been attributed to BM MSCs, as compared to those of the prototypic hematopoietic stem cell model and then gives a brief overview of the in vitro and vivo features of the former, emphasizing on their immunoregulatory properties and their hematopoiesis-supporting role. In addition, the qualitative and quantitative characteristics of BM MSCs within the context of a defective microenvironment, such as the one characterizing Myelodysplastic Syndromes are described and the potential involvement of these cells in the pathophysiology of the disease is discussed. Finally, emerging clinical applications of BM MSCs in the field of hematopoietic stem cell transplantation are reviewed and potential hazards from MSC use are outlined.

CD4+CD25highFoxP3+ regulatory T-cells in hematologic diseases

BACKGROUND

CD4+CD25+ regulatory T-cells (Tregs) play a critical role in immune responses. We explored the status of Tregs in neoplastic and autoimmune hematologic diseases. We also evaluated the technical aspects of Treg measurement in terms of sample type and detection markers.

METHODS

A total of 68 subjects were enrolled: 11 with AML, 8 with MDS, 10 with autoimmune diseases, and 39 controls. Tregs were analyzed in peripheral blood (PB) and bone marrow (BM) samples from each subject. Flow cytometry and the Human Regulatory T cell Staining Kit (eBioscience, USA) for CD4, CD25, and FoxP3 (forkhead box P3) were used.

RESULTS

The CD4+CD25(high)/CD4 and CD4+CD25(high)FoxP3+/CD4 populations were significantly correlated (P<0.0001). The AML and high-risk MDS groups had significantly larger CD4+CD25(high)/CD4 and CD4+CD25(high)FoxP3+/CD4 populations in PB than the autoimmune (P=0.007 and 0.012, respectively) and control groups (P=0.004 and 0.006, respectively). Comparable findings were observed in BM. The CD4+CD25(high)FoxP3+/CD4 population was significantly larger in PB than in BM (P=0.0003).

CONCLUSIONS

This study provides comparison data for Tregs in AML, MDS, and autoimmune hematologic diseases, and would be helpful for understanding the different immunologic bases of various hematologic diseases. Treg measurement using CD4, CD25, and/or FoxP3 in PB rather than in BM seems to be practical for routine hematologic purposes. Large-scale analysis of the diagnostic role of Treg measurement is needed.

Myelodysplastic syndromes: an update on molecular pathology

The myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid disorders characterised by impaired peripheral blood cell production due to bone marrow dysplasia affecting one or more of the major myeloid cell lines. MDS are one of five major categories of myeloid neoplasms according to the World Health Organization (WHO) classification system for haematological cancers. Given their cytological and cytogenetic heterogeneity, these diseases probably constitute a group of molecularly distinct entities with variable degrees of ineffective haematopoiesis and susceptibility to leukaemic transformation. Recent studies provide some insights into the physiopathology of MDS. In the early stages, one mechanism contributing to hypercellular marrow and peripheral blood cytopenia is a significant increase in programmed cell death (apoptosis) in haematopoietic cells. Furthermore, altered responses in relation to cytokines, the immune system and bone marrow stroma also contribute to the disease phenotype. Deletions of chromosome 5q31-q32 are the most common recurring cytogenetic abnormalities detected in MDS. The 5q- syndrome is a new entity recognised in the WHO classification since 2001 and is associated with a good prognosis. Haploinsufficiency of multiple genes mapping to the common deleted region at 5q31-32 may contribute to the pathogenesis of 5q- syndrome and other MDS with 5q- deletion. Many studies have demonstrated that altered DNA methylation and histone acetylation can alter gene transcription. Abnormal methylation of transcription promoter sites is universal in patients with MDS, and the number of involved loci is increased in high-risk disease and secondary leukaemias. A better understanding of the pathogenesis of MDS can contribute to the development of new treatments such as hypomethylating drugs, immunomodulatory agents such as lenalidomide, and immunosuppressive drugs aimed at reversing the specific alteration that results in improvement in patients with MDS.

Current and future management options for myelodysplastic syndromes

The management of the myelodysplastic syndromes (MDS) requires insight into the complex biology of the disease. Despite this challenge, two recent developments have contributed significantly to advancements in the treatment of MDS: (i) improvements in classification systems and prognostic models; and (ii) the emergence of US FDA-approved agents such as lenalidomide, azacitidine and decitabine. Prior to these developments, supportive care measures consisting of blood and platelet transfusions, haematopoietic growth factors and antimicrobials remained standard of care for the treatment of MDS. As a result of these developments, clinicians are able to provide patient-tailored therapy for specific MDS subgroups. Clinical trials addressing combination therapies with multiple investigational agents as well as novel combination regimens are ongoing. This review focuses on supportive care modalities, the approved agents indicated for the treatment of MDS and future directions for the treatment of MDS, including agents under clinical investigation.

Deregulated gene expression pathways in myelodysplastic syndrome hematopoietic stem cells

To gain insight into the molecular pathogenesis of the myelodysplastic syndromes (MDS), we performed global gene expression profiling and pathway analysis on the hematopoietic stem cells (HSC) of 183 MDS patients as compared with the HSC of 17 healthy controls. The most significantly deregulated pathways in MDS include interferon signaling, thrombopoietin signaling and the Wnt pathways. Among the most significantly deregulated gene pathways in early MDS are immunodeficiency, apoptosis and chemokine signaling, whereas advanced MDS is characterized by deregulation of DNA damage response and checkpoint pathways. We have identified distinct gene expression profiles and deregulated gene pathways in patients with del(5q), trisomy 8 or -7/del(7q). Patients with trisomy 8 are characterized by deregulation of pathways involved in the immune response, patients with -7/del(7q) by pathways involved in cell survival, whereas patients with del(5q) show deregulation of integrin signaling and cell cycle regulation pathways. This is the first study to determine deregulated gene pathways and ontology groups in the HSC of a large group of MDS patients. The deregulated pathways identified are likely to be critical to the MDS HSC phenotype and give new insights into the molecular pathogenesis of this disorder, thereby providing new targets for therapeutic intervention.

Optimal sequencing of treatments for patients with myelodysplastic syndromes

PURPOSE OF REVIEW

Myelodysplastic syndromes (MDS) are characterized by chronic cytopenias and a high risk of transformation to acute myeloid leukemia. To date, only allogeneic stem cell transplantation has shown curative potential in MDS. The heterogeneous nature of MDS, and the paucity of randomized studies make individual therapeutic decisions, still largely based on the international prognostic scoring system, difficult.

RECENT FINDINGS

In lower-risk MDS, recent advances include demonstration of a possible survival advantage with erythropoiesis stimulating agents, the role of lenalidomide in cases with del 5q (which lead to its approval in the treatment of lower-risk MDS with del 5q by the Food and Drug Administration), and recognition of the importance of iron overload on prognosis. In higher-risk patients, progress has come from the use of reduced intensity conditioning allogeneic SCT in elderly patients, and from results obtained with the hypomethylating agents azacytidine and decitabine, leading to their approval for the treatment of symptomatic MDS by the Food and Drug Administration. In particular, results of a phase III trial show a significant survival benefit for azacytidine over conventional treatments in higher-risk MDS. This is the first time a drug demonstrates a survival impact in higher-risk MDS.

SUMMARY

We review these recent advances in this paper.

Myelodysplastic syndromes

Session 4 of the 2007 Workshop of the Society for Hematopathology/European Association for Haematopathology was devoted to myelodysplastic syndromes (MDSs). Submitted cases highlighted important issues and difficulties in relation to the diagnosis and classification of MDS. Much of the discussion focused on the correlation, or lack of it, between morphologic examination and other diagnostic techniques, cytogenetics in particular. The cases included examples of isolated del(5q) chromosomal abnormality, including the "classical" 5q- syndrome and other myeloid neoplasms. Other cytogenetic abnormalities in MDSs and the role of cytogenetics in diagnosing MDSs were addressed. Particularly challenging is the correct identification of fibrotic subtypes of MDSs and their separation from subsets of acute myeloid leukemia with myelofibrosis such as acute panmyelosis with myelofibrosis. The association and eventual relation of MDSs (hypoplastic in particular) with aplastic anemia, paroxysmal nocturnal hemoglobinuria, and other nonneoplastic disorders were illustrated. Novel cytogenetic and molecular genetic approaches are likely to revolutionize the classification of MDSs. However, it is unlikely that these new techniques will be capable, on their own, of adequately stratifying patients for treatment purposes. At least for the foreseeable future, the diagnosis of MDS requires integration of morphologic, immunophenotypic, and genetic features in the light of patient history and clinical manifestations.

Myelodysplastic syndromes: biology and treatment

Optimal management of patients with myelodysplastic syndromes (MDS) requires an insight into the biology of the disease and the mechanisms of action of the available therapies. This review focuses on low-risk MDS, for which chronic anaemia and eventual progression to acute myeloid leukaemia are the main concerns. We cover the updated World Health Organization classification, the latest prognostic scoring system, and describe novel findings in the pathogenesis of 5q- syndrome. We perform in depth analyses of two of the most widely used treatments, erythropoietin and lenalidomide, discussing mechanisms of action, reasons for treatment failure and influence on survival.

Kinetics, function and bone marrow trafficking of CD4+CD25+FOXP3+ regulatory T cells in myelodysplastic syndromes (MDS)

CD4(+)CD25(+)FOXP3(+) T regulatory cells (T(regs)) prevent autoimmunity by restricting overexuberant immune responses, but the same subpopulation can incur detrimental effects on antitumor responses. In both cases, the suppressor potential of T(regs) appears to be strongly influenced by their compartmentalization. In myelodysplastic syndromes (MDS), immune deregulation and autoimmunity in the early stages might lead to ineffective hematopoiesis and bone marrow (BM) failure, whereas late-stage disease is characterized by the immune escape of the malignant clone. We show that these two stages of MDS are associated with differential T(reg) activity. Specifically, we found that in early stage MDS, compared with normal hematopoiesis and late stage MDS, T(regs) are dysfunctional and their BM homing through the CXCL12/CXCR4 axis is seriously impaired as a result of CXCR4 downregulation. Conversely, in late stage MDS, T(regs) are systemically and locally expanded and retain their function and migratory capacity. Moreover, T(reg) levels follow the disease course and are significantly reduced in treatment responding patients. Our findings indicate T(reg) involvement in the pathophysiology of MDS; defective suppressor function and BM trafficking of T(regs) may be important in the autoimmune process of early MDS, but increased T(reg) activity could favor leukemic clone progression in late stage disease.