Treatment of the 5q– Syndrome

Ribosomopathies: New Therapeutic Perspectives

Ribosomopathies are a group of rare diseases in which genetic mutations cause defects in either ribosome biogenesis or function, given specific phenotypes. Ribosomal proteins, and multiple other factors that are necessary for ribosome biogenesis (rRNA processing, assembly of subunits, export to cytoplasm), can be affected in ribosomopathies. Despite the need for ribosomes in all cell types, these diseases result mainly in tissue-specific impairments. Depending on the type of ribosomopathy and its pathogenicity, there are many potential therapeutic targets. The present manuscript will review our knowledge of ribosomopathies, discuss current treatments, and introduce the new therapeutic perspectives based on recent research. Diamond–Blackfan anemia, currently treated with blood transfusion prior to steroids, could be managed with a range of new compounds, acting mainly on anemia, such as L-leucine. Treacher Collins syndrome could be managed by various treatments, but it has recently been shown that proteasomal inhibition by MG132 or Bortezomib may improve cranial skeleton malformations. Developmental defects resulting from ribosomopathies could be also treated pharmacologically after birth. It might thus be possible to treat certain ribosomopathies without using multiple treatments such as surgery and transplants. Ribosomopathies remain an open field in the search for new therapeutic approaches based on our recent understanding of the role of ribosomes and progress in gene therapy for curing genetic disorders.

Genomic alterations in abnormal neutrophils isolated from adult patients with systemic lupus erythematosus

INTRODUCTION

Patients with systemic lupus erythematosus (SLE) have an abnormal population of neutrophils, called low-density granulocytes (LDGs), that express the surface markers of mature neutrophils, yet their nuclear morphology resembles an immature cell. Because a similar discrepancy in maturation status is observed in myelodysplasias, and disruption of neutrophil development is frequently associated with genomic alterations, genomic DNA isolated from autologous pairs of LDGs and normal-density neutrophils was compared for genomic changes.

METHODS

Alterations in copy number and losses of heterozygosity (LOH) were detected by cytogenetic microarray analysis. Microsatellite instability (MSI) was detected by capillary gel electrophoresis of fluorescently labeled PCR products.

RESULTS

Control neutrophils and normal-density SLE neutrophils had similar levels of copy number variations, while the autologous SLE LDGs had an over twofold greater number of copy number alterations per genome. The additional copy number alterations found in LDGs were prevalent in six of the thirteen SLE patients, and occurred preferentially on chromosome 19, 17, 8, and X. These same SLE patients also displayed an increase in LOH. Several SLE patients had a common LOH on chromosome 5q that includes several cytokine genes and a DNA repair enzyme. In addition, three SLE patients displayed MSI. Two patients displayed MSI in greater than one marker, and one patient had MSI and increased copy number alterations. No correlations between genomic instability and immunosuppressive drugs, disease activity or disease manifestations were apparent.

CONCLUSIONS

The increased level of copy number alterations and LOH in the LDG samples relative to autologous normal-density SLE neutrophils suggests somatic alterations that are consistent with DNA strand break repair, while MSI suggests a replication error-prone status. Thus, the LDGs isolated have elevated levels of somatic alterations that are consistent with genetic damage or genomic instability. This suggests that the LDGs in adult SLE patients are derived from cell progenitors that are distinct from the autologous normal-density neutrophils, and may reflect a role for genomic instability in the disease.

Myelodysplastic syndromes with 5q deletion: pathophysiology and role of lenalidomide

Myelodysplastic syndrome (MDS) is a hematopoietic stem cell disorder primarily affecting CD34+ cells, characterized by ineffective hematopoiesis, often transforming into acute myelogenous leukemia (AML). A subset of patients has 5q deletion (del(5q)) as the culprit pathogenetic trigger. Del(5q) affects critical regions 5q31 and 5q33, leading to gene haplodeficiency with subsequent RPS14 haplodeficiency and P53 activation. Subsequent to P53 activation, erythroid cell apoptosis and ineffective erythropoiesis occur. Other pathogenetic elements include protein phosphatase 2a and CDC25C haplodeficiency and decreased miR-145 and miR-146a expression. Lenalidomide is an immunomodulatory agent that selectively suppresses the del(5q) clone. While the mechanism is not fully understood, it is associated with diverse molecular changes including stabilization of MDM2 with subsequent enhanced P53 degradation. Lenalidomide showed success in low- and intermediate-1-risk MDS as reported in the 002, 003, and 004 trials. However, in higher-risk MDS, the results of lenalidomide monotherapy were modest, mandating the use of combination therapy. The role and priority of lenalidomide varies between different guidelines, and accordingly, future efforts are necessary to reach a unified therapeutic algorithm. TP53 mutations are important predictors of AML progression and possible resistance to lenalidomide. It is recommended to identify TP53 mutation early in the disease since it may change the decision regarding choice of therapy. Challenges with lenalidomide therapy remain the long-term effects and timing of its discontinuation.

Routine diagnostic procedures of myelodysplastic syndromes: value of a structural blood cell parameter (NEUT-X) determined by the Sysmex XE-2100™

INTRODUCTION

Diagnostic features of myelodysplastic syndromes (MDS) are often polymorphic and nonspecific including anemia in most cases. Standard parameters provided by an automated analyzer seldom bring any argument for this diagnosis. The aim of this study was to investigate whether some structural parameters, not routinely provided by Sysmex™ XE 2100 analyzer, could help diagnose MDS in a simple way, adapted to routine practice.

METHODS

Blood samples from 184 MDS fully annotated cases and 3545 normal blood count controls were performed with XE 2100 Sysmex™ analyzer. Quantitative and structural parameters were considered.

RESULTS

We found that the structural neutrophil parameter, NEUT-X, converted into a semi-quantitative parameter, the granularity index (GI), could be used as a flag for MDS in front of anemia. Negative GI and anemia were able to make otherwise unrecognized MDS stand out in routine practice, increasing the number of slides addressed to review from 67% to 96%, without leading to a large excess of unfounded slide review among non-MDS.

CONCLUSION

Including the GI index in the routine parameters provided by the Sysmex analyzer could be of major help for nonspecialized routine laboratories in detecting MDS.

Advances in the 5q- syndrome

The 5q- syndrome is the most distinct of all the myelodysplastic syndromes with a clear genotype/phenotype relationship. The significant progress made during recent years has been based on the determination of the commonly deleted region and the demonstration of haploinsufficiency for the ribosomal gene RPS14. The functional screening of all the genes in the commonly deleted region determined that RPS14 haploinsufficiency is the probable cause of the erythroid defect in the 5q- syndrome. A mouse model of the human 5q- syndrome has now been created by chromosomal engineering involving a large-scale deletion of the Cd74-Nid67 interval (containing RPS14). A variety of lines of evidence support the model of ribosomal deficiency causing p53 activation and defective erythropoiesis, including most notably the crossing of the "5q- mice" with p53-deficient mice, thereby ameliorating the erythroid progenitor defect. Emerging evidence supports the notion that the p53 activation observed in the mouse model may also apply to the human 5q- syndrome. Other mouse modeling data suggest that haploinsufficiency of the microRNA genes miR-145 and miR-146a may contribute to the thrombocytosis seen in the 5q- syndrome. Lenalidomide has become an established therapy for the 5q- syndrome, although its precise mode of action remains uncertain.

[Extramedullary blastic transformation revealed by a prolonged fever during the course of a 5q- syndrome]

INTRODUCTION

Fever during a myelodysplastic syndrome can be due to infectious complications, systemic disease or acute transformation with clonal evolution.

CASE REPORT

A 51-year-old woman, with a 5q- syndrome and neutropenia, presented with a several week fever duration. Infectious work-up was negative and therapy with antibiotics had no influence on the clinical course. Neither bone marrow nor blood blasts were detected, but liver biopsy demonstrated significant blast infiltration compatible with the diagnosis of acute myeloid leukaemia (AML).

CONCLUSION

The absence of blasts in blood or bone marrow does not exclude the malignant transformation of a myelodysplastic syndrome to AML. Tissue biopsy may be necessary to confirm the leukaemic progression.

Myelodysplastic syndromes: the complexity of stem-cell diseases

The prevalence of patients with myelodysplastic syndromes (MDS) is increasing owing to an ageing population and increased awareness of these diseases. MDS represent many different conditions, not just a single disease, that are grouped together by several clinical characteristics. A striking feature of MDS is genetic instability, and a large proportion of cases result in acute myeloid leukaemia (AML). We Review three emerging principles of MDS biology: stem-cell dysfunction and the overlap with AML, genetic instability and the deregulation of apoptosis, in the context of inherited bone marrow-failure syndromes, and treatment-related MDS and AML.