Increased apoptosis of circulating T cells in myelodysplastic syndromes

Erythropoietin administration is associated with improved T-cell properties in patients with myelodysplastic syndromes

The immune system is impaired in myelodysplastic syndromes (MDS) and plays a role in the pathogenesis of the disease. Here we show effects of recombinant human erythropoietin (rHuEPO) on T cell (CD4⁺, CD8⁺ and CD4⁺CD25⁺) number and function in MDS patients. Healthy (20 subjects), MDS patients without rHuEPO treatment ('MDS', 13), and MDS patients treated with rHuEPO ('MDS+EPO', 17) were examined. CD4⁺ and CD8⁺ T cell numbers were reduced and increased respectively in MDS compared to healthy subjects. EPO treatment normalized these levels. CD4⁺CD25⁺ cell numbers, lower in MDS, were normalized in MDS+EPO. In vitro activation of CD4⁺ and CD8⁺ cells with phytohemagglutinin as measured by CD69 expression, demonstrated a 7.2 fold increase in CD4⁺ activation vs 13.6 fold for MDS and MDS+EPO respectively (p=0.004); and 10.2 fold (MDS) vs 18.6 fold (MDS+EPO, p<0.003) for CD8⁺ T cells. Expression of the co-stimulatory marker CD28, decreased in CD4⁺ and CD8⁺ T cells in MDS, was normalized in MDS+EPO CD4⁺ T cells. Subgroup analysis of milder disease (WHO RA and RARS) and more advanced disease revealed no difference in CD4⁺ and CD8⁺ T cell numbers. However, the activation of these cells in the RA/RARS subgroup was impaired in EPO-untreated and enhanced in EPO-treated MDS patients. Our data suggest that EPO treatment improves immune abnormalities in MDS and may depend on disease severity.

Infections in myelodysplastic syndromes

Myelodysplastic syndromes are associated with a risk of severe infections. While neutropenia is likely to be the main predisposing factor, several other immune defects have been reported, including impaired neutrophil function, B-, T- and NK-cell defects and the possible consequences of iron overload due to red blood cell transfusions. The advanced age of most patients, their frequent comorbidities, and the fact that drugs such as hypomethylating agents and lenalidomide, which are effective in myelodysplastic syndromes but can transiently worsen neutropenia, may increase the risk of infection and their severity in this context. The majority of infections in myelodysplastic syndromes are bacterial, while the incidence of fungal infections is not well known and viral infections seem to be rare. No prophylactic measures against infections have demonstrated efficacy in myelodysplastic syndromes. However, pending more data, we propose here some recommendations for the management of patients with myelodysplastic syndromes. In the future, an important contribution can be made by prospective trials testing the efficacy of prophylactic and therapeutic approaches to infection in these patients, especially in the context of the new drugs available for myelodysplastic syndromes.

Disease progression mechanism in myelodysplastic syndromes: insight into the role of the microenvironment

The somatic mutation theory proposing that a sequential accumulation of genetic abnormalities plays a major role in cancer pathogenesis has not yet been confirmed for myelodysplastic syndromes (MDS). Meanwhile, recent data in some cancers has underscored the role of the microenvironment in tumor growth. MDS CD34+CD38- cells usually fail to repopulate after transplantation in mice, suggesting the importance of the microenvironment for MDS cells. Our recent data have provided a disease-progression model in which overproduction of interferon-γ and tumor necrosis factor-α in the microenvironment is the primary event. This causes B7-H1 molecule expression on MDS blasts, which generates a bifunctional signal inducing T-cell apoptosis and enhancing blast proliferation. The latter may provide more opportunity for developing secondary genetic changes.

Immune alterations in untreated and treated myelodysplastic syndrome

INTRODUCTION

Current literature suggests a variety of immune abnormalities are present in myelodysplastic syndrome (MDS) patients. However, they have not been comprehensively characterized or systematized to date. As a result, their clinical implications remain largely unknown. In addition, an increased incidence of various autoimmune conditions has been documented in MDS patients.

AREAS COVERED

The authors offer a comprehensive review of the existing literature on immune mechanisms involved in the pathogenesis of MDS, various immune abnormalities documented in its course, their link with the clonal evolution of MDS as well as immune alterations induced by the existing MDS therapies.

EXPERT OPINION

The course of MDS is accompanied by complex immune alterations, including T-cell and NK-cell defects, decreased functional abilities of neutrophils and antigen-presenting cells, altered antibody and cytokine production. While contemporary MDS therapies are shown to possess some immunomodulatory properties, authentic autoimmune conditions have also been documented with lenalidomide and recombinant erythropoietin. Caution should be exerted with the use of these agents in MDS patients with evidence of autoimmune disorders, as exacerbation of autoimmune phenomena can be anticipated. While the heterogeneity of MDS represents an inherent limitation, integration of emerging information from molecular biology, genetics, immunology research and clinical practice could translate into improved outcomes of this disease spectrum.

Interferon-gamma and tumor necrosis factor-alpha induce an immunoinhibitory molecule, B7-H1, via nuclear factor-kappaB activation in blasts in myelodysplastic syndromes

During disease progression in myelodysplastic syndromes (MDS), clonal blasts gain a more aggressive nature, whereas nonclonal immune cells become less efficient via an unknown mechanism. Using MDS cell lines and patient samples, we showed that the expression of an immunoinhibitory molecule, B7-H1 (CD274), was induced by interferon-gamma (IFNgamma) and tumor necrosis factor-alpha (TNFalpha) on MDS blasts. This induction was associated with the activation of nuclear factor-kappaB (NF-kappaB) and nearly completely blocked by an NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC). B7-H1(+) MDS blasts had greater intrinsic proliferative capacity than B7-H1(-) MDS blasts when examined in various assays. Furthermore, B7-H1(+) blasts suppressed T-cell proliferation and induced T-cell apoptosis in allogeneic cocultures. When fresh bone marrow samples from patients were examined, blasts from high-risk MDS patients expressed B7-H1 molecules more often compared with those from low-risk MDS patients. Moreover, MDS T cells often overexpressed programmed cell death 1 (PD-1) molecules that transmit an inhibitory signal from B7-H1 molecules. Taken together, these findings provide new insight into MDS pathophysiology. IFNgamma and TNFalpha activate NF-kappaB that in turn induces B7-H1 expression on MDS blasts. B7-H1(+) MDS blasts have an intrinsic proliferative advantage and induce T-cell suppression, which may be associated with disease progression in MDS.

Myelodysplastic syndromes associated with interstitial deletion of chromosome 5q: clinicopathologic correlations and new insights from the pre-lenalidomide era

To better estimate prognosis for patients with myelodysplastic syndromes (MDS) associated with clonal interstitial deletions of the long arm of chromosome 5 (del(5q)), we reviewed the medical records of 130 adults with del(5q) MDS seen at our institution over a 15-year period. Overall median survival of this cohort was 9.5 months, shorter than reported in earlier series. The least favorable outcomes are associated with complex cytogenetics, lack of any normal metaphases, normocytic rather than macrocytic erythrocyte indices, and low baseline lymphocyte counts. Lymphopenia but not neutropenia at the time of diagnosis appears to be a new adverse prognostic indicator. Cytogenetic breakpoints defined by G-banded karyotyping correlate poorly with particular disease features. Surprisingly, survival of patients with treatment-related MDS was equivalent to that of de novo MDS with del(5q) in this series. Morphologic features associated with del(5q) are diverse. Most patients with del(5q) MDS do not meet criteria for WHO-defined 5q-syndrome, and the presence of del(5q) does not appear to modify the clinical phenotype otherwise risk-stratified by the International Prognostic Scoring System (IPSS). Additional important prognostic factors not taken into account by the IPSS include the baseline erythrocyte indices, lymphocyte count, and clonal burden.