A role for tumour necrosis factor-alpha, Fas and Fas-Ligand in marrow failure associated with myelodysplastic syndrome

Incorporating novel agents in the treatment of myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a group of heterogeneous clonal stem cell (SC) disorders that mainly affect the elderly population. They are characterized by ineffective hematopoiesis which results in quantitative and qualitative cellular defects and high incidence of leukemic transformation. Recent advances in MDS research have led to the development of novel agents which appears to improve remission rates and survival when compared to best supportive care. Currently azacitidine, decitabine, and lenalidomide are approved by the US FDA for the treatment of MDS, while the activity of other novel agents such as histone deacetylase inhibitors, farnesyl-transferase inhibitors, novel thrombopoietic agents, and anti-angiogenesis molecules is under evaluation. Erythropoietin-stimulating agents, iron chelating therapy and thrombopoietin receptor ligands may also improve quality of life and possibly prolong survival in MDS patients. The only treatment modality that can achieve long-term survival is the allogeneic SC transplantation which is given only in selected patients. Moreover the heterogeneity of MDS and the patient's advanced age and co-morbidity are significant factors besides cytogenetics, IPSS and WPSS that should be taken into account during the decision-making process. Therefore clinicians should treat patients with MDS on an individual basis aiming the increase of the response rates and the decrease of treatment-associated toxicities. This can only be achieved through the better understanding of the MDS subgroups. If we can better define MDS subgroups we will be able to identify patients who will benefit from the incorporation of the novel agents, as monotherapy or in combinations regimens along with supportive care.

Infliximab chimeric antitumor necrosis factor-α monoclonal antibody as potential treatment for myelodysplastic syndromes

Accumulating evidence indicates tumor necrosis factor-a (TNF-a) as a key cytokine in the pathogenesis of the myelodysplastic syndromes (MDS). The identification of TNF-a as a regulator of apoptosis and the increased susceptibility of MDS cells to this cytokine provided the basis for several clinical trials of TNF inhibitors. Infliximab is an IgG1 chimeric anti-TNF-a monoclonal antibody composed of human constant and murine variable regions that bind specifically to both soluble and membrane-bound TNF-a. To date, only 2 studies have investigated the use of infliximab in patients with low-risk MDS. In both reports the drug showed a limited but significant activity and a favorable side-effect profile. In some patients, hematopoietic response was associated with decreased apoptosis as well as a decrease in abnormal metaphases by 50%. Further studies are currently underway and should provide useful information to define the more responsive subtypes of MDS, the patient characteristics, and the proper dosing regimen.

Megakaryocytopoiesis and apoptosis in patients with myelodysplastic syndromes

In order to investigate simultaneously the megakaryocytopoiesis and apoptotic characteristics in bone marrow in patients with myelodysplastic syndromes (MDS), we used CD41 immunoenzyme (alkaline phosphatase anti-alkaline phosphatase) and DNA in situ end-labeling techniques on plastic embedded bone marrow biopsy sections of 29 MDS patients. Fourteen patients with iron deficiency anemia served as controls. The results showed that CD41-positive cells in MDS marrow numbered 26.2 +/- 18.2/mm2 (mean +/- standard deviation) compared with 15.6 +/- 7.1/mm2 in controls (P < 0.05). Numbers of cells with the morphology of micro-megakaryocytes in MDS marrow were significantly higher than in controls (P < 0.01). Furthermore, megakaryocytes in MDS marrow were frequently distributed along trabeculae (in 27 cases) and formed clusters (in 25 cases). Apoptotic megakaryocytes in MDS marrow accounted for just 4.4 and 9.3% of all CD41-positive cells and all apoptotic cells, respectively (P > 0.05 compared with controls), but apoptosis occurred only in micro-megakaryocytes. Based on these observations, we conclude that megakaryocytosis and dysmegakaryocytosis are the features of dyshematopoiesis in MDS marrow. Decreased thrombocyte production and thrombocyte release coming from increased dys(micro)megakaryocytes and abnormally located megakaryocytes perhaps play a more important role in peripheral thrombocytopenia than megakaryocytic apoptosis itself. Apoptosis of micro-megakaryocytes may be a protective biological mechanism to remove useless megakaryocytes.

Altered naive and memory CD4+ T-cell homeostasis and immunosenescence characterize younger patients with myelodysplastic syndrome

Response to immunosuppressive therapy (IST) in younger patients with myelodysplastic syndrome (MDS) has been linked to a T-cell-dominant autoimmune process that impairs hematopoiesis. Analysis of the age-adjusted CD4:CD8 ratio in 76 MDS patients compared with 54 healthy controls showed that inadequate CD4+, rather than expansion of CD8+ T cells, was associated with a lower ratio in a group that included both lower and higher risk MDS patients defined by the International Prognostic Scoring System. In younger MDS patients, naive and memory phenotypes defined by CD45RA and CD62L display showed depletion of naive CD4+ and CD8+ T cells, suggesting a possible relationship to IST responsiveness. To determine the correlation between T-cell subset distribution, T-cell turnover and autoimmunity, a cohort of 20 patients were studied before and after IST. The CD4:CD8 ratio correlated inversely with the proliferative T-cell index before treatment in IST-responsive patients, suggesting that proliferation may be linked to accelerated CD4+ T-cell turnover and hematopoietic failure. Our data show seminal findings that both CD4+ and CD8+ T-cell subsets are dysregulated in MDS. Association between these T-cell defects and response to IST suggests that aberrant T-cell homeostasis and chronic activation are critical determinants influencing autoimmune hematopoietic suppression in younger patients.

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.

Linking anemia to inflammation and cancer: the crucial role of TNFalpha

Erythropoiesis is considered as a multistep and tightly regulated process under the control of a series of cytokines including erythropoietin (Epo). Epo activates specific signaling pathways and leads to activation of key transcription factors such as GATA-1, in order to ensure erythroid differentiation. Deregulation leads to a decreased number of red blood cells, a hemoglobin deficiency, thus a limited oxygen-carrying capacity in the blood. Anemia represents a frequent complication in various diseases such as cancer or inflammatory diseases. It reduces both quality of life and prognosis in patients. Tumor necrosis factor alpha (TNFalpha) was described to be involved in the pathogenesis of inflammation and cancer related anemia. Blood transfusions and erythroid stimulating agents (ESAs) including human recombinant Epo (rhuEpo) are currently used as efficient treatments. Moreover, the recently described conflicting effects of ESAs in distinct studies require further investigations on the molecular mechanisms involved in TNFalpha-caused anemia. The present study aims to evaluate the current knowledge and the importance of the effect of the proinflammatory cytokine TNFalpha on erythropoiesis in inflammatory and malignant conditions.

Treatment strategies to optimize clinical benefit in the patient with myelodysplastic syndromes

In recent years we have witnessed a transformation in care for patients with myelodysplastic syndromes (MDS) following approval by the US Food and Drug Administration of the first agents for treatment of the disease. Emerging evidence indicates that active treatment strategies modify the natural history of the underlying disease and hence lower the potential for leukemic transformation while prolonging survival. The methyltransferase inhibitor (MTI) azacitidine, in particular, has shown the capacity to extend survival in higher-risk disease in a post-approval phase III trial while demonstrating an improved risk/benefit profile in a new dosing schedule. By utilizing an MTI as a bridge to transplantation, allogeneic stem cell transplantation can now be postponed for appropriate candidates until a suitable donor is identified. Results of iron chelation studies indicate that the improved compliance of an oral iron chelator yields greater iron storage reduction with sustained suppression of the labile plasma form. The current active treatment paradigm for MDS incorporates the most recent strategies yielding improved disease outcomes and patient 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.

Differential responses of FLIPLong and FLIPShort-overexpressing human myeloid leukemia cells to TNF-alpha and TRAIL-initiated apoptotic signals

OBJECTIVE

Clonal marrow cells from patients with early myelodysplastic syndrome (MDS) undergo apoptosis in response to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). Cells from advanced MDS are resistant to TRAIL. Two isoforms of the Flice inhibitory protein (FLIP) short (FLIPS) and FLIP long (FLIPL), which modulate TRAIL signals, showed disease-stage-dependent differential regulation. Therefore, we aimed at characterizing potential differential effects of FLIPL and FLIPS, on TRAIL and TNF-alpha-induced apoptosis in model leukemic cell lines.

MATERIALS AND METHODS

Using lentiviral constructs, FLIPL and FLIPS, as well as a green fluorescent protein control were overexpressed in ML-1 cells, which constitutively express very low levels of FLIP and are highly sensitive to apoptosis induction. Cells were then exposed to TRAIL or TNF-alpha, and effects on the extrinsic and intrinsic pathways of apoptosis induction were assessed.

RESULTS

Overexpression of FLIP reduced TRAIL and TNF-alpha-induced apoptosis in ML-1 cells. However, while FLIPL completely abrogated apoptosis, FLIPS allowed for BID cleavage and caspase-3 activation. Concurrently, there was a decline of Bcl-xL and X-linked inhibitor of apoptosis protein (XIAP) in FLIPS cells followed by apoptosis. Further, inhibition of nuclear factor-kappaB (NF-kappaB) activation in TNF-alpha-treated cells resulted in profound apoptosis in FLIPS, but not in FLIPL-overexpressing cells, consistent with the observations in patients with early stage MDS. Inhibition of NF-kappaB had only minimal effects on TRAIL signaling.

CONCLUSION

Thus, FLIPL and FLIPS exerted differential effects in myeloid leukemic cell lines in response to TRAIL and TNF-alpha. It might be possible to therapeutically exploit those differences with effector molecules specific for the FLIP isoforms.

Impaired differentiation and apoptosis of hematopoietic precursors in a mouse model of myelodysplastic syndrome

Expression of a NUP98-HOXD13 (NHD13) fusion gene, initially identified in a patient with myelodysplastic syndrome, leads to a highly penetrant myelodysplastic syndrome in mice that recapitulates all of the key features of the human disease. Expansion of undifferentiated lineage negative (lin(neg)) hematopoietic precursors that express NHD13 was markedly inhibited (30-fold) in vitro. Decreased expansion was accompanied by decreased production of terminally differentiated cells, indicating impaired differentiation of NHD13 precursors. Rather than differentiate, the majority (80%) of NHD13 lin(neg) precursors underwent apoptotic cell death when induced to differentiate. These findings demonstrate that NHD13 lin(neg) cells provide a tractable in vitro system for studies of myelodysplastic syndrome.

Dysregulation of IL-32 in myelodysplastic syndrome and chronic myelomonocytic leukemia modulates apoptosis and impairs NK function

TNFalpha levels are elevated in the marrows of patients with myelodysplastic syndrome (MDS) and are associated with high rates of apoptosis, which contributes to hematopoietic failure. We observed that exposure of human marrow stroma cell lines HS5 and HS27a to TNFalpha increases levels of IL-32 mRNA. IL-32, in turn, induces TNFalpha. Marrow stroma from patients with MDS expressed 14- to 17-fold higher levels of IL-32 mRNA than healthy controls. In contrast, cells from patients with chronic myelomonocytic leukemia (CMML) expressed only one tenth the level of IL-32 measured in healthy controls. Human KG1a leukemia cells underwent apoptosis when cocultured with HS5 stromal cells, but knockdown of IL-32 in the stromal cells by using siRNA abrogated apoptosis in the leukemia cells. IL-32 knockdown cells also showed dysregulation of VEGF and other cytokines. Furthermore, CD56(+) natural killer cells from patients with MDS and CMML expressed IL-32 at lower levels than controls and exhibited reduced cytotoxic activity, which was unaffected by IL-2 treatment. We propose that IL-32 is a marrow stromal marker that distinguishes patients with MDS and CMML. Furthermore, IL-32 appears to contribute to the pathophysiology of MDS and may be a therapeutic target.

Polymorphisms in TGFbeta and TNFalpha are associated with the myelodysplastic syndrome phenotype

CONTEXT

Myelodysplastic syndromes (MDSs) are characterized by ineffective hematopoiesis, excessive apoptosis, and the aberrant expression of a number of cytokines. The genes encoding these cytokines are significantly polymorphic. It is unknown whether these cytokine polymorphisms are associated with, and may therefore be playing a role in the pathogenesis of, MDS.

OBJECTIVE

To determine if certain polymorphisms in the tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) cytokines are overrepresented in a cohort of patients with MDSs.

DESIGN

DNA was isolated from the peripheral blood or bone marrow aspirate of 21 patients with MDS. The genotypes for 4 different polymorphisms, 2 in TNFalpha and 2 in TGFbeta1, were determined using single-specific-primer polymerase chain reaction. The allele and genotype frequencies were compared with similar populations in the National Cancer Institute SNP500 database.

RESULTS

In our MDS population, the -308A/A genotype of the TNFalpha gene and the TGFbeta1 allele +29T and genotype +29T/T, each associated with higher levels of expression, were overrepresented in our MDS population.

CONCLUSIONS

Polymorphisms associated with increased expression in the cytokines TNFalpha and TGFbeta1 are overrepresented in the MDS population suggesting that increased TNF-alpha and TGF-beta1 activity may contribute to the susceptibility and/or pathogenesis of MDS. Further studies with larger sample sizes are warranted to confirm our observation.

Apoptosis and antiapoptotic mechanisms in the progression of myelodysplastic syndrome

Myelodysplastic syndrome (MDS), previously known as preleukemia, comprises a spectrum of heterogeneous, clonal disorders of hematopoiesis. A patient's life expectancy can range from a few months to more than a decade. Recent studies provide some insight into the pathophysiology of MDS. One mechanism contributing to the constellation of hypercellular marrow and peripheral blood cytopenia is a significant increase in programmed cell death (apoptosis) in hematopoietic cells. Tumor necrosis factor (TNF)-alpha, Fas ligand, TNF-related apoptosis-inducing ligand, and other proapoptotic cytokines are upregulated in early-stage/low-risk MDS, and neutralization of these signals can improve hematopoiesis. TNF-related apoptosis inducing ligand induces apoptosis preferentially in clonal cells, which can contribute to containment of the clone. In a proportion of patients, MDS will eventually evolve to acute leukemia. This progression has been correlated with upregulation of nuclear factor kappaB; altered expression of adaptor molecules, such as Flice inhibitory protein; and enhanced activity of antiapoptotic members of the Bcl-2 and inhibitors of apoptosis protein families. Also, the ratio of TNF receptors 1 and 2 changes in favor of receptor 2. The role of the microenvironment in the pathophysiology and progression of MDS has remained controversial, although there is evidence that stroma and matrix components, and their interactions with clonal cells, play an important role. Microarray gene-expression studies are consistent with dysregulation of apoptosis, but not all data are in agreement.

Tumour necrosis factor-induced gene expression in human marrow stroma: clues to the pathophysiology of MDS?

Aberrant regulation of the tumour necrosis factor alpha gene (TNF) and stroma-derived signals are involved in the pathophysiology of myelodysplasia. Therefore, KG1a, a myeloid leukaemia cell line, was exposed to Tnf in the absence or presence of either HS-5 or HS-27a cells, two human stroma cell lines. While KG1a cells were resistant to Tnf-induced apoptosis in the absence of stroma cells, Tnf-promoted apoptosis of KG1a cells in co-culture experiments with stroma cells. To investigate the Tnf-induced signals from the stroma cells, we examined expression changes in HS-5 and HS-27a cells after Tnf exposure. DNA microarray studies found both discordant and concordant Tnf-induced expression responses in the two stroma cell lines. Tnf promoted an increased mRNA expression of pro-inflammatory cytokines [e.g. interleukin (IL)6, IL8 and IL32]. At the same time, Tnf decreased the mRNA expression of anti-apoptotic genes (e.g. BCL2L1) and increased the mRNA expression of pro-apoptotic genes (e.g. BID). Overall, the results suggested that Tnf induced a complex set of pro-inflammatory and pro-apoptotic signals in stroma cells that promote apoptosis in malignant myeloid clones. Additional studies will be required to determine which of these signals are critical for the induction of apoptosis in the malignant clones. Those insights, in turn, may point the way to novel therapeutic approaches.

Bone marrow mononuclear cells of MDS patients are characterized by in vitro proliferation and increased apoptosis independently of stromal interactions

Enhanced proliferation of MDS progenitors is abrogated by increased apoptosis of their progeny in vivo. We investigated whether bone marrow mononuclear cells (BMMNC) of MDS patients also showed enhanced proliferation and apoptosis in vitro in comparison with acute myeloid leukemia (AML) and normal BM (NBM). NBM showed a decrease in the number of clusters in time due to apoptosis of clusters and due to development of clusters into colonies with low apoptotic level. In MDS patients, about two-fold more clusters have developed at day 4, and in contrast with NBM, the total number of clusters at day 7 remained high in spite of an increasing percentage of apoptotic clusters (from 52 to 76%) in combination with more colony formation. The number of clusters and colonies showed a sharp decrease at day 10 because of persistently high apoptosis at cluster level and increasing apoptosis in colonies. BMMNC of AML patients showed a decreased proliferation with enhanced apoptosis at cluster level in contrast to a relatively low apoptotic levels in the colony-forming cells. This data show that increased proliferation is abrogated by enhanced apoptosis in MDS, whereas AML showed decreased proliferation with a low level of apoptosis in colony-forming cells. These growth profiles of BMMNC are independent of stromal influences and may represent intrinsic features of the MDS progenitors and accessory cell interactions.

Increased apoptosis of circulating T cells in myelodysplastic syndromes

The mechanism of T cell lymphopenia in myelodysplastic syndromes (MDS) is unknown. We investigated apoptosis in freshly isolated and cultured lymphocytes; the latter were used to detect cells not yet apoptotic but destined for apoptosis. Apoptosis increased in both fresh and cultured T cells in MDS compared with those from healthy controls. Furthermore, in lymphopenic MDS patients the lymphocyte count correlated negatively with the degree of T cell apoptosis. MDS T cells showed increased Fas expression. However, in MDS but not in controls, the degree of T cell apoptosis was independent of the Fas expression level, and exogenous anti-Fas antibodies did not modulate T cell apoptosis. Mechanisms other than the Fas-Fas ligand pathway may induce T cell apoptosis in MDS.

Treatment of myelodysplastic syndrome with cyclosporin A

A multicenter prospective study was carried out to evaluate the efficacy of cyclosporin A (CsA) in 32 patients with myelodysplastic syndromes. The FAB subtypes of the patients included refractory anemia, refractory anemia with ringed sideroblasts, and refractory anemia with excess blasts. The dosage of CsA was 3 to 6 mg/kg per day and was adjusted according to the blood concentration of CsA and the responses of patients. The drug was administered twice a day for more than 3 months. After 3 months of treatment, hematological improvement was observed in 18 of 32 patients (56.3%) by the criteria of the International Working Group. At the end of the follow-up (median time, 14 months), 4 patients showed alteration of disease progression, including 1 complete remission and 3 partial remissions, and 16 patients showed hematological improvement. There were a total of 20 responders. The response rate was 62.5% (20/32). It was shown that the CsA therapy was effective in patients with refractory anemia or refractory anemia with excess blasts and both hypo- and hyperplastic bone marrows might respond to the therapy. The survival time was significantly longer in responders than in nonresponders. The study shows that CsA therapy is potentially the most effective therapy for myelodysplastic syndromes.

The TNF-alpha 238A polymorphism is associated with susceptibility to persistent bone marrow dysplasia following chronic exposure to benzene

Chronic exposure to benzene can result in transient hematotoxicity (benzene poisoning, BP) or persistent bone marrow pathology including dysplasia and/or acute myeloid leukemia. We recently described a persistent bone marrow dysplasia with unique dysplastic and inflammatory features developing in individuals previously exposed to benzene (BID) [Irons RD, Lv L, Gross SA, Ye X, Bao L, Wang XQ, et al. Chronic exposure to benzene results in a unique form of dysplasia. Leuk Res 2005;29:1371-80]. In this study we investigated the association of single nucleotide polymorphisms (SNP) (-863 (C-->A), -857 (C-->T), -308 (G-->A), -238 (G-->A)) in the promoter region of the cytokine, tumor necrosis factor-alpha (TNF-alpha) on the development of BP, persistent BID and de novo myelodysplastic syndrome (MDS) in 394 individuals. Only the -238 (G-->A) polymorphism was significantly associated with the development of BID (odds ratio (OR)=7.4; 95% C.I. 1.23-44.7) and was specific for BID and not de novo MDS or BP. These findings are consistent with a role for inflammation in the development of BID and suggest that cell-specific alterations in TNF-alpha expression may promote clonal selection in the evolution of neoplastic hematopoietic disease.

Serum levels of sCD137 (4-1BB) ligand are prognostic factors for progression in acute myeloid leukemia but not in non-Hodgkin's lymphoma

CD178 (Fas/APO-1 ligand) and CD137 ligand (CD137L) have previously been described in sera of patients with various malignancies and play an important role in the pathogenesis of various diseases. Recently, we demonstrated that low levels of soluble (s) CD137L and high levels of sCD178 correlate significantly with a long progression free survival in patients with myelodysplastic syndrome (MDS). In this study, we correlated sCD137L and sCD178 levels in sera of 42 samples of patients with acute myeloid leukemia (AML) and 46 samples of patients with non-Hodgkin's lymphoma (NHL) with stages, subtypes, and the clinical course of the diseases and determined cut-off values with maximum probability for significant differentiation between cases with higher/lower probability for progress free survival. In contrast to patients with MDS, surprisingly no correlation between sCD178 levels and different subtypes and stages or with prognosis in AML or NHL were observed. Regarding sCD137L, NHL-patients displayed lower levels compared with AML. Statistically significant higher median levels of sCD137L are present in patients with undifferentiated AML (M1/M2, 1,470 pg/mL), poor cytogenetic risk (288 pg/mL) and higher levels of BM-blasts (186 pg/mL) compared with patients with monocytoid AML (M4/M5, 89 pg/mL), intermediate cytogenetic risk (59 pg/mL) and lower levels of BM-blasts (14 pg/mL) respectively. Furthermore, in AML patients sCD137L levels correlate significantly with the probabilities to achieve complete remission (CR), stay in CR or with progress of the disease. Taken together, our data demonstrate that sCD137L can be used as a prognostic factor not only in MDS but also in AML.

Impact of growth factors in the regulation of apoptosis in low-risk myelodysplastic syndromes

Increased apoptosis of hematopoietic progenitors is a hallmark of myelodysplastic syndromes (MDS) and results in ineffective hematopoiesis. Erythroid apoptosis is thought to be the main mechanism underlying the severe anemia observed in the low-risk subgroups, refractory anemia (RA) and RA with ringed sideroblasts (RARS). Treatment with erythropoietin (Epo) alone or in combination with granulocyte colony-stimulating factor (G-CSF) may significantly improve anemia and reduce bone marrow apoptosis. A synergistic effect between Epo and G-CSF has been observed in the clinic, in particular in RARS. However, the molecular mechanisms beyond the anti-apoptotic effect of these growth factors have not been fully understood. This paper outlines the potential mechanisms underlying the augmented apoptosis during the erythroid differentiation in low-risk MDS as well as the anti-apoptotic effect of the growth factors.

Effect of cA2 Anti–Tumor Necrosis Factor-α Antibody Therapy on Hematopoiesis of Patients with Myelodysplastic Syndromes

PURPOSE

Tumor necrosis factor alpha (TNF-alpha) plays a prominent role in the pathophysiology of myelodysplastic syndromes (MDS). The aim of this study was to explore the biological and immunoregulatory effect of the treatment with the anti-tumor necrosis factor-alpha monoclonal antibody cA2 on bone marrow (BM) progenitor/precursor and stromal cells and lymphocyte subsets, as well as the clinical response in MDS patients.

EXPERIMENTAL DESIGN

Ten low-intermediate risk MDS patients received i.v. cA2 (3 mg/kg) at weeks 0, 2, 6, and 12. The number, survival, and clonogenic potential of BM progenitor/precursor cells, the hematopoiesis-supporting capacity of BM stromal cells, and the lymphocyte activation status were investigated in the patients at baseline and following treatment using flow cytometry, clonogenic assays, and long-term BM cultures (LTBMC). Clinical response was evaluated according to standardized criteria.

RESULTS

cA2 administration reduced the proportion of apoptotic and Fas+ cells in the CD34+ cell compartment (P = 0.0215 and P = 0.0344, respectively) and increased the clonogenic potential of BM mononuclear and CD34+ cells (P = 0.0399 and P = 0.0304, respectively) compared with baseline. The antibody reduced tumor necrosis factor-alpha levels in LTBMC supernatants (P = 0.0043) and significantly improved the hematopoiesis-supporting capacity of LTBMC adherent cells. The proportion of activated peripheral blood and BM T-lymphocytes decreased significantly after treatment, suggesting an immunomodulatory effect of cA2. Two patients displayed minor hematologic responses whereas the remaining patients displayed stable disease with no disease progression.

CONCLUSIONS

The encouraging biological insights from cA2 administration may be useful in conducting further clinical trials using cA2 for selected MDS patients, particularly those with evidence of immune-mediated inhibition of hematopoiesis.

Suppression of the cell-mediated immune response by a Fas-immunoglobulin fusion protein

INTRODUCTION

Immunosuppressive agents must not only be effective in impairing the host's allo-immune response, but should also be selective in targeting only those elements of the immune system activated by the allograft. The fact that allo-activated T cells express surface protein molecules that are not typically present on resting T cells can be exploited to specifically target this population. Fas ligand is one such molecule whose cell surface expression on T cells is dramatically up-regulated upon activation.

METHODS

We constructed a murine fusion protein by linking the extracellular domain of Fas to the Fc region of IgG2a. The rationale being to selectively target activated T cells via binding of its Fas moiety to cell surface Fas ligand, and then to allow the Fc moiety to invoke its usual effector mechanisms resulting in the destruction of the allo-activated T cell. Here, we describe the design and expression of Fas-IgG2a and characterize several key in vitro and in vivo properties of this fusion protein including its ability to impact on both cell-mediated immune responses and cellular apoptotic activity using a murine model of delayed-type hypersensitivity.

RESULTS

In vitro, our Fas-IgG2a construct bound activated T cells via FasL and invoked cytotoxicity. In vivo, it demonstrated a prolonged half-life characteristic of an immunoglobulin-like molecule. Most significantly, it suppressed the cell-mediated immune response and diminished cellular apoptotic activity in lymphoid tissue in our murine model.

CONCLUSION

Fas-IgG2a is a novel agent for delivering target-specific immunosuppression with potential applicability in the transplant setting.

Frequent elevation of Akt kinase phosphorylation in blood marrow and peripheral blood mononuclear cells from high-risk myelodysplastic syndrome patients

The serine/threonine kinase Akt, a downstream effector of phosphatidylinositol 3-kinase (PI3K), is known to play an important role in antiapoptotic signaling and has been implicated in the aggressiveness of a number of different human cancers including acute myeloid leukemia (AML). The progression of myelodysplastic syndromes (MDSs) to AML is thought to be associated with abrogation of apoptotic control mechanisms. However, little is known about signal transduction pathways which may be involved in enhanced survival of MDS cells. In this report, we have performed immunocytochemical and flow cytometric analysis to evaluate the levels of activated Akt in bone marrow or peripheral blood mononuclear cells from patients diagnosed with MDS. We observed high levels of Ser473 phosphorylated Akt (p-Akt) staining in 90% of the cases (n=22) diagnosed as high-risk MDS, whereas mononuclear cells from normal bone marrow or low-risk MDS patients showed low or absent Ser473 p-Akt staining. Furthermore, all high-risk MDS patients also demonstrated high expression of the Class I PI3K p110delta catalytic subunit and a decreased expression of PTEN. Taken together, our results suggest that Akt activation might be one of the factors contributing to the decreased apoptosis rate observed in patients with high-risk MDS.

Suppression of Fas-FasL coexpression by erythropoietin mediates erythroblast expansion during the erythropoietic stress response in vivo

Erythropoietin (Epo) is the principal regulator of the erythropoietic response to hypoxic stress, through its receptor, EpoR. The EpoR signals mediating the stress response are largely unknown, and the spectrum of progenitors that are stress responsive is not fully defined. Here, we used flow cytometry to identify stress-responsive Ter119+CD71highFSChigh early erythroblast subsets in vivo. In the mouse spleen, an erythropoietic reserve organ, early erythroblasts were present at lower frequencies and were undergoing higher rates of apoptosis than equivalent cells in bone marrow. A high proportion of splenic early erythroblasts coexpressed the death receptor Fas, and its ligand, FasL. Fas-positive early erythroblasts were significantly more likely to coexpress annexin V than equivalent, Fas-negative cells, suggesting that Fas mediates early erythroblast apoptosis in vivo. We examined several mouse models of erythropoietic stress, including erythrocytosis and beta-thalassemia. We found a dramatic increase in the frequency of splenic early erythroblasts that correlated with down-regulation of Fas and FasL from their cell surface. Further, a single injection of Epo specifically suppressed early erythroblast Fas and FasL mRNA and cell-surface expression. Therefore, Fas and FasL are negative regulators of erythropoiesis. Epo-mediated suppression of erythroblast Fas and FasL is a novel stress response pathway that facilitates erythroblast expansion in vivo.

New agents in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematopoietic disorders characterized by ineffective hematopoiesis resulting in peripheral cytopenia and by increased progression to acute myeloid leukemia (AML). Therapeutic interventions for MDS other than allogeneic stem cell transplantation have been palliative. Novel and targeted therapeutic agents such as the inhibition of farnesyltransferases and receptor tyrosine kinases, more potent thalidomide analogs, arsenic trioxide, immunomodulating agents, hypomethylating agents, and histone deacetylase inhibitors have shown encouraging results and may offer durable benefit to patients with MDS. Further development of rational therapies and improvements in the outcome of patients with MDS are likely to emerge from an increased understanding of the pathophysiology of these diseases.

Genetic polymorphisms in patients with myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a family of clonal disorders characterized by dyshematopoiesis and susceptibility to acute myelogenous leukemia. Tumor necrosis factor-a (TNF-alpha) and transforming growth factor-beta (TGF-beta) are cytokines that play key roles in the pathogenesis of MDS. There have been several reports on the presence of genetic polymorphisms in the DNA sequence encoding the leader sequence of the TGF-beta protein, and in the -308 promoter region of TNF-alpha. The association between TNF-alpha and TGF-beta1 gene polymorphism and the susceptibility to MDS and the progression of the disease was investigated. As compared with healthy control subjects (n = 74), patients with MDS (n = 55) showed no significant deviations in genotype or allele frequencies of TNF-alpha. Similarly, there were no differences in the distribution of TNF-alpha genotypes between the MDS patients with only anemia (mild group) and those with bi- or pancytopenia (severe group). On the other hand the TT homozygosity at codon 10 in exon 1 of TGF-beta1 gene was associated with a severe degree of cytopenia [95% CI OR = 4.889, p = 0.0071]. These findings suggest that the investigated genetic polymorphisms do not predispose to the development of MDS, but that TGF-beta1 gene polymorphism may affect the disease progression.

The hematologic response to anti-apoptotic cytokine therapy: results of pentoxifylline, ciprofloxacin, and dexamethasone treatment for patients with myelodysplastic syndrome

TNF-alpha mediated apoptosis of the hematopoietic cells has been thought to contribute to the ineffective hematopoiesis observed in myelodysplastic syndrome (MDS). The combination of pentoxifylline (P) and ciprofloxacin (C) has been shown to reduce the serum levels of TNF-alpha, and an earlier trial of P and C with dexamethasone (D) provided good palliation for patients with MDS. The purpose of this study is to assess the hematologic response to PCD therapy for patients suffering with MDS. 21 of 25 patients who completed at least of 12 weeks of treatment were evaluable for the treatment efficacy. At baseline, the patient's median age was 60 yr (range: 18-75 yr). The diagnoses according to WHO classification included: RA (n=5), RCMD (n=10), RARS (n=1), RCMD/RS (n=1), RAEB (3), and CMML (n=1). 11 patients (52%) had at least single lineage response. 3 patients (11%) showed improvement of triple lineage cytopenia. There were no differences in the response rates between the FAB subtypes. The median time to response was 4 weeks (range: 2-12 weeks), and it is interesting that 9 of 11 patients who had a response remained without relapse for a median of 177 days (range: 78-634 days). These preliminary results indicate that anti-cytokine therapy with PCD is an effective and well tolerated palliative treatment for patients with MDS.

Myelodysplastic syndromes: clinicopathologic features, pathobiology, and molecular pathogenesis

CONTEXT

Myelodysplastic syndromes (MDSs) are clonal stem cell diseases characterized by ineffective hematopoiesis, multilineage dysplasia, and peripheral cytopenias with normocellular or hypercellular marrow. They represent a heterogeneous group of disorders with a varied spectrum of clinical, morphologic, biologic, and genetic characteristics. This heterogeneity in disease characterization has led to evolving classification systems, developing prognostic models, and continuing research efforts to elucidate its pathobiology and pathogenesis.

OBJECTIVE

To summarize updated information and provide a general overview of the clinicopathologic features, pathobiology, and cytogenetic and molecular pathogenesis of MDSs.

DATA SOURCES

Relevant articles indexed in PubMed (National Library of Medicine) between 1982 and 2005 and reference medical texts.

CONCLUSIONS

Although MDSs remain a relatively poorly defined disease entity, recent advancements in cytogenetic and molecular studies have significantly contributed to our present knowledge of MDSs. Novel strategies for studying the pathogenesis and evolution of MDSs continue to shape our understanding of this disease and guide our approaches to diagnosis and treatment.

Characterization of the hemopoietic defect in early stages of the myelodysplastic syndromes

Myelodysplasia (MDS) is a heterogeneous disorder characterised by bone marrow failure and progression to acute myeloid leukaemia where the molecular and cellular haematopoietic defects are poorly understood. To gain insight into this the pathogenesis of this condition, we analyzed gene expression profiles of bone marrow CD34+ stem/progenitor cells from patients with MDS at a early stage in the disease and compared them with profiles from CD34+ cells from age-matched controls and patients with non-MDS anaemia. Given the heterogeneity of early MDS, a surprisingly consistent finding was decreased expression of B-cell lineage affiliated genes in MDS patients compared to normal controls and samples with non-MDS anaemia. These findings were then confirmed in the original samples and further samples from a new MDS patient group by Taqman Real Time PCR. Flow cytometry on unfractionated marrow from independent samples also demonstrated reduced B-cell progenitors in MDS patients compared to normal controls. These novel findings suggest a common perturbation in early MDS haematopoiesis. They also provide the rationale for a larger study to evaluate the diagnostic utility of reduced B-cell progenitor number as a diagnostic biomarker of early low risk MDS which can pose a diagnostic challenge.

Over-expression of tumor necrosis factor-alpha in bone marrow biopsies from patients with myelodysplastic syndromes: relationship to anemia and prognosis

OBJECTIVES

An excessive intramedullar progenitor cell apoptosis, to which elevated expression of tumor necrosis factor-alpha (TNF-alpha) might contribute, is considered the main cause of inefficient hematopoiesis in myelodysplastic syndromes (MDS). Enhanced bone marrow (BM) angiogenesis is regarded as an essential cofactor in the progression of MDS to acute myelogenous leukemia (AML) and microvessel formation may be induced by TNF-alpha as well. To investigate TNF-alpha signaling and neoangiogenesis as potential molecular pathways for therapeutic intervention in MDS with respect to the various MDS subtypes, we performed a morphological and clinico-pathological study on a large series of paraffin-embedded trephine BM biopsies.

METHODS

TNF-alpha expression and BM vessels were immunohistochemically analyzed on 89 paraffin-embedded BM biopsies from patients with MDS and secondary AML, including 12 control samples. Data were correlated with clinico-pathological and laboratory parameters and analyzed for their prognostic significance considering overall survival.

RESULTS

TNF-alpha was over-expressed in MDS patients, especially in those with refractory anemia and its expression correlated with BM cellularity and with magnitude of anemia as well as with microvessel density (MVD). TNF-alpha over-expression was associated with premature deaths. MVD was increased in MDS and secondary AML and correlated with marrow cellularity and expression of TNF-alpha, but was not of prognostic significance.

CONCLUSIONS

TNF-alpha expression and MVD are elevated in MDS and secondary AML. TNF-alpha expression in BM progenitor cells appears to negatively impact erythropoiesis and overall survival in MDS, and may serve as a potential therapeutic target in patients with hypercellular MDS with marked anemia.

Role of the p38 Mitogen-Activated Protein Kinase Pathway in Cytokine-Mediated Hematopoietic Suppression in Myelodysplastic Syndromes

The p38 mitogen-activated protein kinase (MAPK) pathway is activated by IFNs and other cytokines to mediate signals for important cellular functions, including transcriptional regulation and apoptosis. We examined the role of the p38 pathway in the generation of the effects of myelosuppressive cytokines on human hematopoiesis. Pharmacologic inhibition of p38 using BIX-01208 resulted in reversal of IFN-, tumor necrosis factor-alpha (TNF-alpha)-, and transforming growth factor-beta (TGF-beta)-mediated suppression of human erythroid (blast-forming unit-erythroid) and myeloid (granulocyte-macrophage colony-forming unit) colony formation, consistent with a key role for p38 in the generation of myelosuppressive signals by different cytokines. Similarly, the myelosuppressive effects of TNF-alpha and TGF-beta were reversed by small interfering RNAs targeting p38alpha expression, further establishing the requirement of this kinase in the induction of myelosuppressive responses. As TNF overproduction has been implicated in the pathophysiology of bone marrow failure states, we determined whether pharmacologic inhibition of p38 reverses the hematopoietic defects seen in bone marrows from patients with myelodysplastic syndromes (MDS) and the anemia of chronic disease. Addition of pharmacologic inhibitors of p38 on such bone marrows resulted in increased numbers of erythroid and myeloid progenitors. Similarly, inhibition of the activity of the downstream effectors of p38, MAPK activated protein kinase-2, and mitogen and stress activated kinase 1 partially restored the hematopoietic defect seen in these bone marrows. Taken altogether, our data implicate the p38 MAPK in the pathophysiology of myelodysplasias and suggest that p38 pharmacologic inhibitors may have therapeutic applications in the treatment of MDS.

NF-kappaB and FLIP in arsenic trioxide (ATO)-induced apoptosis in myelodysplastic syndromes (MDSs)

Tumor necrosis factor (TNF)-alpha, a potent stimulus of nuclear factor-kappaB (NF-kappaB), is up-regulated in myelodysplastic syndrome (MDS). Here, we show that bone marrow mononuclear cells (BMMCs) and purified CD34+ cells from patients with low-grade/early-stage MDS (refractory anemia/refractory anemia with ring sideroblasts [RA/RARS]) have low levels of NF-kappaB activity in nuclear extracts comparable with normal marrow, while patients with RA with excess blasts (RAEB) show significantly increased levels of activity (P = .008). Exogenous TNF-alpha enhanced NF-kappaB nuclear translocation in MDS BMMCs above baseline levels. Treatment with arsenic trioxide (ATO; 2-200 microM) inhibited NF-kappaB activity in normal marrow, primary MDS, and ML1 cells, even in the presence of exogenous TNF-alpha (20 ng/mL), and down-regulated NF-kappaB-dependent antiapoptotic proteins, B-cell leukemia XL (Bcl-XL), Bcl-2, X-linked inhibitor of apoptosis (XIAP), and Fas-associated death domain (FADD)-like interleukin-1beta-converting enzyme (FLICE) inhibitory protein (FLIP), leading to apoptosis. However, overexpression of FLIP resulted in increased NF-kappaB activity and rendered ML1 cells resistant to ATO-induced apoptosis. These data are consistent with the observed up-regulation of FLIP and resistance to apoptosis with advanced MDS, where ATO as a single agent may show only limited efficacy. However, the data also suggest that combinations of ATO with agents that interfere with other pathways, such as FLIP autoamplification via NF-kappaB, may have considerable therapeutic activity.

Anaemia in systemic lupus erythematosus: from pathophysiology to clinical assessment

Haematological abnormalities are common in systemic lupus erythematosus. Anaemia is found in about 50% of patients, with anaemia of chronic disease being the most common form. Impaired erythropoietin response and presence of antibodies against erythropoietin may contribute to the pathogenesis of this type of anaemia. Patients with autoimmune haemolytic anaemia usually belong to a distinct category, which is associated with anticardiolipin antibodies, thrombosis, thrombocytopenia, and renal disease, often in the context of secondary antiphospholipid syndrome. Autoantibodies, T lymphocytes, and deregulation of the cytokine network can affect bone marrow erythropoiesis, leading to anaemia.

Preferential suppression of trisomy 8 compared with normal hematopoietic cell growth by autologous lymphocytes in patients with trisomy 8 myelodysplastic syndrome

Clinical observations and experimental evidence link bone marrow failure in myelodysplastic syndrome (MDS) with a T cell-dominated autoimmune process. Immunosuppressive therapy is effective in improving cytopenias in selected patients. Trisomy 8 is a frequent cytogenetic abnormality in bone marrow cells in patients with MDS, and its presence has been associated anecdotally with good response to immunotherapy. We studied 34 patients with trisomy 8 in bone marrow cells, some of whom were undergoing treatment with antithymocyte globulin (ATG). All had significant CD8+ T-cell expansions of one or more T-cell receptor (TCR) Vbeta subfamilies, as measured by flow cytometry; expanded subfamilies showed CDR3 skewing by spectratyping. Sorted T cells of the expanded Vbeta subfamilies, but not of the remaining subfamilies, inhibited trisomy 8 cell growth in short-term hematopoietic culture. The negative effects of Vbeta-expanded T cells were inhibited by major histocompatibility complex (MHC) class 1 monoclonal antibody (mAb) and Fas antagonist and required direct cell-to-cell contact. Sixty-seven percent of patients who had de novo MDS with trisomy 8 as the sole karyotypic abnormality responded to ATG with durable reversal of cytopenias and restoration of transfusion independence, with stable increase in the proportion of trisomy 8 bone marrow cells and normalization of the T-cell repertoire. An increased number of T cells with apparent specificity for trisomy 8 cells is consistent with an autoimmune pathophysiology in trisomy 8 MDS.

High IGFBP-3 levels in marrow plasma in early-stage MDS: effects on apoptosis and hemopoiesis

The pathophysiology of the myelodysplastic syndromes (MDS) is incompletely understood. Tumor necrosis factor (TNF)alpha levels are elevated, particularly in early-stage MDS, and apoptosis in marrow cells is upregulated. Observations in other models have shown a role for insulin-like growth factor binding protein 3 (IGFBP-3) in TNFalpha-mediated apoptosis. We observed increased levels of IGFBP-3 in the marrow plasma of patients with MDS (P = 0.005) and hypothesized that altered IGFBP-3 levels contribute to the dysregulation of hemopoiesis in MDS by affecting proliferation and apoptosis. Western analysis of marrow plasma from MDS patients revealed an increase in the ratio of intact vs fragmented IGFBP-3 in early-stage MDS (relative to controls) that decreased with MDS disease progression, suggesting increased proteolysis with more advanced disease. Thus, these results provide evidence for dysregulation of IGFBP-3 in patients with MDS. While the data are complex, they are consistent with a modulatory effect of IGFBP-3 on hemopoiesis in MDS. Conceivably, understanding these mechanisms may allow for the development of novel therapeutic strategies.

Programmed cell death is an intrinsic feature of MDS progenitors, predominantly found in the cluster-forming cells

OBJECTIVE

Bone marrows (BM) of myelodysplastic syndrome (MDS) patients show increased proliferation and premature programmed cell death (PCD) in vivo as well as in vitro. We explored the proliferative capacity and apoptotic propensity of CD34+ progenitor cells of MDS patients excluding accessory cell interference.

MATERIALS AND METHODS

CD34+/CD3-/CD19- cells of 5 MDS patients and 5 normal BM were sorted as single cells into single wells and were cultured in liquid medium. Wells were evaluated on days 4, 7, 10, and 14. PCD was determined by staining with annexin V-FITC. Growth rate and cell doubling time (Td) were calculated for each colony-forming cell.

RESULTS

Normal BM CD34+ cells formed clusters and colonies and both showed increasing PCD in time, although within colonies the degree of apoptosis was twice as high (about 25%) as compared with clusters at all time points. In MDS increased cluster formation was observed at all evaluation points when compared to normal BM, whereas the number of colonies was markedly reduced (1/7 of normal). These colonies were also smaller, usually smaller than 100 cells. Significantly enhanced levels of PCD of clusters (53-79%) in combination with longer cell doubling times explain this slower formation of smaller colonies. Surprisingly, these colonies showed considerably lower levels of PCD (7-32%) as compared to normal (1-48%, median values).

CONCLUSIONS

In the absence of stromal influences and accessory cells, this study in MDS patients showed intrinsically enhanced proliferation and apoptosis of cluster-forming cells, as the opposite was true for colony-forming cells.

Increased peripheral platelet destruction and caspase-3–independent programmed cell death of bone marrow megakaryocytes in myelodysplastic patients

To investigate underlying mechanisms of thrombocytopenia in myelodysplastic syndrome (MDS), radiolabeled platelet studies were performed in 30 MDS patients with platelet counts less than 100 × 109/L. Furthermore, plasma thrombopoietin and glycocalicin index (a parameter of platelet or megakaryocyte destruction) were determined. Mean platelet life (MPL), corrected for the degree of thrombocytopenia, was reduced in 15 of 30 patients (4.3 ± 0.9 days [mean ± SD] vs 6.0 ± 1.3, P = .0003). Platelet production rate (PPR) was reduced in 25 of 30 patients (68 ± 34 × 109/d vs 220 ± 65, P &lt; .0001). Thrombopoietin levels were not significantly correlated with the PPR. However, the glycocalicin index was significantly higher compared with controls (15 ± 16 vs 0.7 ± 0.2, P = .001) and significantly correlated with the PPR (P = .02, r = -0.5), but not with the MPL (P = 1.8). Ultrastructural studies demonstrated necrosis-like programmed cell death (PCD) in mature and immature megakaryocytes (n = 9). Immunohistochemistry of the bone marrow biopsies demonstrated no positive staining of MDS megakaryocytes for activated caspase-3 (n = 24) or cathepsin D (n = 21), while activated caspase-8 was demonstrated in a subgroup of patients (5/21) in less than 10% of megakaryocytes. These results indicate that the main cause of thrombocytopenia in MDS is caspase-3–independent necrosis-like PCD resulting in a decreased PPR in conjunction with an increased glycocalicin index.