Hypothesis: myelodysplastic syndromes may have a viral etiology

Acquired and hereditary bone marrow failure: A mitochondrial perspective

The disorders known as bone marrow failure syndromes (BMFS) are life-threatening disorders characterized by absence of one or more hematopoietic lineages in the peripheral blood. Myelodysplastic syndromes (MDS) are now considered BMF disorders with associated cellular dysplasia. BMFs and MDS are caused by decreased fitness of hematopoietic stem cells (HSC) and poor hematopoiesis. BMF and MDS can occur de novo or secondary to hematopoietic stress, including following bone marrow transplantation or myeloablative therapy. De novo BMF and MDS are usually associated with specific genetic mutations. Genes that are commonly mutated in BMF/MDS are in DNA repair pathways, epigenetic regulators, heme synthesis. Despite known and common gene mutations, BMF and MDS are very heterogenous in nature and non-genetic factors contribute to disease phenotype. Inflammation is commonly found in BMF and MDS, and contribute to ineffective hematopoiesis. Another common feature of BMF and MDS, albeit less known, is abnormal mitochondrial functions. Mitochondria are the power house of the cells. Beyond energy producing machinery, mitochondrial communicate with the rest of the cells via triggering stress signaling pathways and by releasing numerous metabolite intermediates. As a result, mitochondria play significant roles in chromatin regulation and innate immune signaling pathways. The main goal of this review is to investigate BMF processes, with a focus mitochondria-mediated signaling in acquired and inherited BMF.

miRNA expression profiles in myelodysplastic syndromes reveal Epstein-Barr virus miR-BART13 dysregulation

Recently, the microRNA (miRNA) signature has been used for better characterization and understanding of the pathogenesis of different malignancies, including myelodysplastic syndromes (MDS). MDS are a heterogeneous group of stem cell disorders in which the genetic and molecular defects are not well defined. In the present study, we applied array based miRNA profiling to study 19 bone marrow cell samples of de novo MDS compared with eight healthy individuals. In addition, integration of the miRNA profiling data with our previous array comparative genomic hybridization data, from the same cohort of patients, was performed. We observed up-regulation of hsa-miR-720 and hsa-miR-21, and down-regulation of hsa-miR-671-5p and one human virus miRNA (Epstein-Barr virus miR-BART13) in MDS samples compared with normal samples. In our study, the copy number alteration harboring miRNA was not affecting miRNA expression, but a distinct microRNA expression pattern was observed, not only in MDS compared with controls, but also between MDS entities.

Myelodysplastic syndrome and histone deacetylase inhibitors: "to be or not to be acetylated"?

Myelodysplastic syndrome (MDS) represents a heterogeneous group of diseases with clonal proliferation, bone marrow failure and increasing risk of transformation into an acute myeloid leukaemia. Structured guidelines are developed for selective therapy based on prognostic subgroups, age, and performance status. Although many driving forces of disease phenotype and biology are described, the complete and possibly interacting pathogenetic pathways still remain unclear. Epigenetic investigations of cancer and haematologic diseases like MDS give new insights into the pathogenesis of this complex disease. Modifications of DNA or histones via methylation or acetylation lead to gene silencing and altered physiology relevant for MDS. First clinical trials give evidence that patients with MDS could benefit from epigenetic treatment with, for example, DNA methyl transferase inhibitors (DNMTi) or histone deacetylase inhibitors (HDACi). Nevertheless, many issues of HDACi remain incompletely understood and pose clinical and translational challenges. In this paper, major aspects of MDS, MDS-associated epigenetics and the potential use of HDACi are discussed.

Epidemiology of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are one of the most common hematological conditions among the elderly. Differences in disease classification and diagnosis have made population-based studies an arduous endeavor. A variety of risk factors have been linked with increased risk (smoking and exposure to solvents and agrochemicals) or decreased risk of MDS (wine drinking), but the majority of cases remain unexplained. One area that has not been explored is the influence of diet in MDS development. Much still needs to be learned about what causes MDS and the genetic factors that increase susceptibility. Multi-institutional studies with a molecular-epidemiologic approach are necessary to develop a MDS risk predictive model.

Characterization of trisomic natural killer cell abnormalities in a patient with constitutional trisomy 8 mosaicism

Malignancies found in children and adults with constitutional trisomy 8 mosaicism (CT8M) could be in part the consequence of dysfunction of trisomic immune cells. An adult patient exhibiting trisomy in the entire natural killer (NK) cell population has made possible the characterization of trisomy 8-positive NK cells. The study showed normal cytotoxic activity but predominance of an immunosenescent phenotype (CD56(dim)CD94/NKG2(bright)) characterized by a weak response to IL-2, increased upregulation of CD95/Fas, and impaired TNF-alpha production. As these defects may contribute to the escape and expansion of neoplastic cells, the authors hypothesize that cancer predisposition in CT8M may be partly a result of altered immunosurveillance.

Myelodysplasia-associated autoimmunity: clinical and pathophysiologic concepts

Myelodysplastic syndrome (MDS), an acquired clonal disorder of haemopoietic progenitor cells, is characterized by haemopoietic insufficiency associated with cytopenias, leading to serious morbidity plus the additional risk of leukaemic transformation. In MDS an acquired insult to the haemopoietic stem cell leads to impaired differentiation and myelodysplasia. However, there is increasing evidence that the marrow failure of MDS is immune-mediated. A model of MDS pathophysiology suggests that transformation of normal stem cells induces an autoimmune T-cell response with the bone marrow as the target organ. This autoimmune attack results in chronic overproduction of pro-apoptotic cytokines, especially tumour necrosis factor alpha (TNFalpha). In addition, several reports have revealed that approximately 10% of MDS patients have clinical autoimmune disorders. This review illustrates the cellular/molecular mechanisms and the implication of the tumour suppressor gene interferon regulatory factor-1 (IRF-1) in the pathophysiology of MDS-associated autoimmune deregulation.

Bone marrow stroma in childhood myelodysplastic syndrome: composition, ability to sustain hematopoiesis in vitro, and altered gene expression

We studied bone marrow stromal cell cultures from patients with childhood myelodysplastic syndromes (MDS, refractory anemia with excess of blasts, RAEB) and from matched normal donors. Stromal cell monolayers were characterized as myofibroblasts by the expression of smooth muscle alpha-actin, collagen IV, laminin and fibronectin. When normal cord blood cells were plated onto myelodysplastic stromas, a pathologic cell differentiation was observed, indicating altered myelosupportive properties. cDNA array analysis showed that patient stromas expressed increased levels of thrombospondin-1, collagen-I alpha2-chain, osteoblast-specific factor-2 and osteonectin, indicating the presence of increased osteoblast content, as confirmed by enhanced alkaline phosphatase synthesis. Alterations in the myelodysplastic stroma environment might contribute to abnormal hematopoiesis in this pathology.

Quantification and cytokine production of circulating lymphoid and myeloid cells in acute myelogenous leukaemia

A simple assay was developed to assess the potential of patients with acute myelogenous leukaemia (AML) to respond to immunotherapy. Lymphocytes, monocytes and leukaemic blasts with their corresponding intracellular cytokine profiles were evaluated by four-colour flow cytometry. In 50 microl samples of whole blood, surface labelling for CD45, CD8 and CD3 was used for cell identification prior to intracellular staining for interleukin (IL)-4, IL-10, IL-12 and interferon (IFN)-gamma. Absolute numbers of CD8(+) and CD8(-) (putative CD4(+)) T-cells, NK cells (CD8(+)/CD3(-)) and monocytes were determined by reference to a fixed number of added fluorescent beads. The absolute numbers of CD8(-) and CD8(+) T-cells in the blood of patients with AML were similar to those of normal controls. More of the lymphocytes in the blood of leukaemic patients spontaneously produced cytokines compared with those of controls. Furthermore, primary AML blasts secreted predominantly IFN-gamma. After recovery from chemotherapy, lymphocyte counts tended to be lower than in normals and reduction of NK cells reached significance after the second chemotherapy (P=0.01). A prominent CD8(lo)/CD3(lo-int) lymphocyte subset appeared after recovery in some patients. This laboratory application of the study of cell subsets and intracellular cytokines in patients undergoing treatment may be helpful in monitoring immunological responses in AML.

Bone marrow lymphoid aggregates in myelodysplastic syndromes: incidence, immunomorphological characteristics and correlation with clinical features and survival

Lymphoid aggregates (LA) are a common finding in bone marrow biopsies but little is known about their clinical implications and biological significance. We found LA in 51/206 patients with myelodysplastic syndromes (MDS). There was no correlation with age, disease progression or overall survival. The group with LA had lower hemoglobin values (P=0.03), and was associated with an increase in reticulin fibres (P=0.01). Although they were more frequent in RAEB, this did not reach statistical significance. Most LA had a benign morphology and showed CD20 expression in three distinct patterns: central, perinodular or diffuse. No evidence of an association with lymphoproliferative disease was observed. LA probably represent an ongoing immune stimulation and are probably related to an altered bone marrow microenvironment, with no impact on prognosis.

Excessive apoptosis, increased phagocytosis, nuclear inclusion bodies and cylindrical confronting cisternae in bone marrow biopsies of myelodysplastic syndrome patients

Transmission electron microscopic (TEM) studies have not been reported in bone marrow (BM) biopsies of patients with myelodysplastic syndromes (MDS) owing to failure to overcome the technical impediment of maintaining ultrastructural detail in decalcified tissue. Using a modified technique to physically separate pieces of bone from marrow tissue under a dissecting microscope, and embedding the material directly for TEM, ultrastructural studies were performed in 15 MDS patients and four normal BM biopsies. Biopsy tissue was also used to initiate long-term in vitro cultures and 12-week plates were sacrificed for TEM analysis. Features noted in freshly obtained decorticated tissue included an excessive apoptosis in both haematopoietic and stromal cells, ringed sideroblasts with iron-laden mitochondria and highly active, enormously increased phagocytosis. In addition, type IV nuclear inclusion body variants (NIB-v) and confronting cylindrical cisternae (CCC) were readily identified in up to 40% of stromal cells in vivo, providing an important footprint of a possible infectious agent in the pathology of MDS. Cultured stromal cells did not show excessive apoptosis and only 2-4% fibroblasts showed the presence of NIB-v or CCC, underscoring the artificial nature of ex vivo systems. We conclude that ultrastructure studies using decorticated tissue can be a powerful tool to investigate the biology and aetiology of a variety of haematopoietic disorders as it enables the direct examination of BM biopsies with their intimate stromal parenchymal cell associations preserved intact.

Oligoclonal T cell expansion in myelodysplastic syndrome: evidence for an autoimmune process

There is accumulating evidence that the marrow-failure of myelodysplastic syndrome (MDS) is immune-mediated. We studied patients with MDS to look for oligoclonal or clonal expansion in T cells indicative of an autoimmune process. We used a PCR-based technique (spectratyping) to characterize the T cell repertoire in MDS (n=15; 9 RA, 4 RARS, 2 RAEB) and compared results with age-matched healthy donors (n=20) and transfusion-dependent (TD) patients with hemoglobinopathy (n=5). We found a significantly higher number of skewed Vbeta profiles in the MDS patients compared with controls. In peripheral blood T cells, 60/345 Vbeta profiles examined were skewed in MDS patients compared with 3/115 Vbeta profiles in TD controls (P<0.0001), and 58/460 Vbeta profiles in age-matched controls (P=0.05). A study of Jbeta region within the skewed Vbeta profiles revealed preferential usage of Jbeta 2.1 in MDS in contrast with a wide distribution over the entire Jbeta spectrum in controls, consistent with non-random T cell clonal expansion in MDS. These findings provide further evidence that T cell mediated immune processes are a feature of MDS.

Presence of activation-related m-RNA for EBV and CMV in the bone marrow of patients with myelodysplastic syndromes

The bone marrow (BM) in myelodysplastic syndromes (MDS) undergoes pathobiological changes that mimic an inflammatory process, and hence, an infectious etiology was suspected in these disorders. In the present report, we examined the bone marrow mononuclear cells (BMMNC) of 19 MDS patients and seven normal donors for the expression of one latency-related (Latency membrane protein 1 (LMP-1) and immediate early protein (IEP)) and one activation-related (BZLF and DNA-Pol) m-RNA each for two herpes viruses, Epstein-Barr virus (EBV) and cytomegalovirus (CMV), respectively. Reverse transcriptase polymerase chain reaction was used for this purpose. The latency-related transcripts (EBV-LMP-1 and CMV-IEP) were present in all the MDS and normal specimens. Intriguingly, 10/19 MDS specimens ( approximately 53%) and 2/7 normal donors ( approximately 28%) were positive for active EBV-BZLF (P=0.0067), while 2/19 MDS specimens ( approximately 11%) with 1/7 normal ( approximately 14%) showed active CMV-DNA-Pol (P=0.1588). Later, from another set of MDS patients (n=7) and normal donors (n=4), BM stromal cultures were established, which, at a 75% confluency, were overlaid with cord blood mononuclear cells (CBMNC). IEP was detectable in the CBMNC before and after co-incubation with MDS, as well as normal stroma. So, it was also present both in MDS and normal stromal cells. The other three were absent both in MDS and normal stromal layers. In CBMNC though, active EBV-BZLF and CMV-DNA-Pol m-RNA were detectable in one of seven MDS co-cultures each, albeit from different patients. None of the normal co-cultures showed active virus, either in stroma or CBMNC. Thus, the present report demonstrates, for the first time, the presence of active herpes viruses in the BMMNC of MDS patients and reveals the ability of the MDS stroma to support the viral activation.

Anti-TNF therapies in rheumatoid arthritis, Crohn's disease, sepsis, and myelodysplastic syndromes

An attempt has been made in this article to summarize the state-of-the-art clinical experience with the use of anti-TNF therapies in four diseased states with special emphasis on myelodysplastic syndromes. Given the central role of TNF-alpha in initiating and perpetuating the chronic damage produced in the diseased organs by controlling a cascade of pro-inflammatory cytokines, as well as its acute role in sepsis, theoretically speaking, neutralization of this peptide was a natural therapeutic choice. Results of the initial clinical trials appear encouraging and sometimes dramatic in their efficacy. The mechanism of response however, is interesting in that even when TNF-alpha is directly targeted by a monoclonal antibody, the resulting benefits can frequently not be attributed to TNF suppression alone. Rather, it appears that a more general effect on the T-lymphocytes is also contributing to the responses being seen. This raises the new possibility of combining anti-cytokine and anti-T-cell strategies to treat at least the more chronic diseases such as Crohn's disease and myelodysplastic syndromes. Continued clinical trials testing these strategies are clearly warranted.

Patients with myelodysplastic syndromes benefit from palliative therapy with amifostine, pentoxifylline, and ciprofloxacin with or without dexamethasone

Thirty-five patients with myelodysplastic syndrome (MDS) were registered on protocol MDS 96-02 and were receiving continuous therapy with pentoxifylline 800 mg 3 times a day and ciprofloxacin 500 mg twice a day by mouth; dexamethasone was added to the regimen for the partial responders and the nonresponders after 12 weeks at a dose of 4 mg by mouth every morning for 4 weeks. Amifostine was administered intravenously 3 times a week at 3 dose levels (200 mg/M2, 300 mg/M2, and 400 mg/M2) to cohorts of 10 patients each. Therapy has been continued for 1 year in responders. Twenty-nine have completed at least 12 weeks of therapy and are available for response evaluation. Of the 21 men and 8 women (median age, 67 years), 20 had refractory anemia (RA), 3 had RA with ringed sideroblasts (RARS), 5 had RA with excess blasts (RAEB), and 1 had chronic myelomonocytic leukemia (CMMoL). Five had secondary MDS. No differences were noted in response rates among the 3 dose levels. Seven patients did not respond at all, and 22 showed an improvement in cytopenias (76%). Three had a triple lineage response, 10 had a double lineage response, and 9 had a single lineage response (8 of 9 in absolute neutrophil count [ANC] and 1 had more than a 50% reduction in packed red blood cell transfusions). Fifteen patients responded only after the addition of dexamethasone, whereas 7 responded before. When examined by lineage, 19 of 22 showed improved ANC, 11 of 22 demonstrated more than 50% reduction in blood transfusions, improved Hb levels, or both, and 7 of 22 showed improvement in platelet counts. Interestingly, the responses were frequently slow to appear, and continued improvement in counts was seen up to 12 months of therapy and beyond. This study supports the feasibility of treating patients with MDS with the unique approach of cytoprotection and anticytokine therapies as well as the principle that prolonged commitment to treatment is desirable when noncytotoxic agents are administered.

Consilience across evolving dysplasias affecting myeloid, cervical, esophageal, gastric and liver cells: common themes and emerging patterns

In the present paper, an attempt is made to identify common biologic themes across dysplastic states affecting the marrow, gastro intestinal tissue, the cervix and liver as well as unifying patterns during disease evolution. The following algorithm appears generally applicable, although individual variations must necessarily be anticipated. It appears that there is an initial transforming event which in all dysplasias except that affecting the marrow has been found to be infectious. Increased cellular proliferation-increased apoptosis, telomere shortening, appearance of telomerase expression and clonal expansion follow the initial insult. Abnormalities in the cytokine environment are universally described and it is likely that the quintessential monoclonality aspect of dysplasia predisposes to accumulation of genetic mutations, and microsatellite instability leading to the appearance of evolved sub-clones. The conversion of a dysplastic phenotype to a malignant one reflects the success of one such sub-clone in developing a survival advantage over a large population of prematurely apoptotic neighbors. This state is usually acquired by silencing tumor suppressor genes through hypermethylation or actual loss or dysfunction. Thus, excessive apoptosis of cells resulting from a persistent infectious process predisposes the organ towards developing a cancerous phenotype. Evidence for the shared pathology is presented at length with the hope that these parallels between dysplastic states will be helpful in both biologic and therapeutic research.