Is there a role for interleukin-3 in Diamond-Blackfan anaemia? Results of a European multicentre study

How I manage children with Diamond-Blackfan anaemia

Diamond‐Blackfan anaemia (DBA) is a rare inherited marrow failure disorder, characterized by hypoplastic anaemia, congenital anomalies and a predisposition to cancer as a result of ribosomal dysfunction. Historically, treatment is based on glucocorticoids and/or blood transfusions, which is accompanied by significant toxicity and long‐term sequelae. Currently, stem cell transplantation is the only curative option for the haematological DBA phenotype. Whereas this procedure has been quite successful in the last decade in selected patients, novel therapies and biological insights are still warranted to improve clinical care for all DBA patients. In addition to paediatric haematologists, other physicians (e.g. endocrinologist, gynaecologist) should ideally be involved in the care of this chronic condition from an early age, to improve lifelong management of haematological and non‐haematological symptoms, and screen for DBA‐associated malignancies. Here we provide an overview of current knowledge and recommendations for the day‐to‐day care of DBA patients.

Progress towards mechanism-based treatment for Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) is a congenital erythroid hypoplastic anemia, characterized by macrocytic anemia, reticulocytopenia, and severely reduced numbers of erythroid precursors in the bone marrow. For more than fifty years, glucocorticoids have remained the main option for pharmacological treatment of DBA. While continuous glucocorticoid administration increases hemoglobin levels in a majority of DBA patients, it also causes severe side effects. There is therefore a great need for more specific and effective treatments to boost or replace the use of glucocorticoids. Over the years, many alternative therapies have been tried out, but most of them have shown to be ineffective. Here we review previous and current attempts to develop such alternative therapies for DBA. We further discuss how emerging knowledge regarding the pathological mechanism in DBA and the therapeutic mechanism of glucocorticoids treatment may reveal novel drug targets for DBA treatment.

Frameshift mutation in p53 regulator RPL26 is associated with multiple physical abnormalities and a specific pre-ribosomal RNA processing defect in diamond-blackfan anemia

Diamond-Blackfan anemia (DBA) is an inherited form of pure red cell aplasia that usually presents in infancy or early childhood and is associated with congenital malformations in ∼30-50% of patients. DBA has been associated with mutations in nine ribosomal protein (RP) genes in about 53% of patients. We completed a large-scale screen of 79 RP genes by sequencing 16 RP genes (RPL3, RPL7, RPL8, RPL10, RPL14, RPL17, RPL19, RPL23A, RPL26, RPL27, RPL35, RPL36A, RPL39, RPS4X, RPS4Y1, and RPS21) in 96 DBA probands. We identified a de novo two-nucleotide deletion in RPL26 in one proband associated with multiple severe physical abnormalities. This mutation gives rise to a remarkable ribosome biogenesis defect that affects maturation of both the small and the large subunits. We also found a deletion in RPL19 and missense mutations in RPL3 and RPL23A, which may be variants of unknown significance. Together with RPL5, RPL11, and RPS7, RPL26 is the fourth RP regulating p53 activity that is linked to DBA.

Diamond-Blackfan anemia, ribosome and erythropoiesis

Diamond-Blackfan anemia is a rare inherited bone marrow failure syndrome (five to seven cases per million live births) characterized by an aregenerative, usually macrocytic anemia with an absence or less than 5% of erythroid precursors (erythroblastopenia) in an otherwise normal bone marrow. The platelet and the white cell counts are usually normal but neutropenia, thrombopenia or thrombocytosis have been noted at diagnosis. In 40 to 50% of DBA patients, congenital abnormalities mostly in the cephalic area and in thumbs and upper limbs have been described. Recent analysis did show a phenotype/genotype correlation. Congenital erythroblastopenia of DBA is the first human disease identified to result from defects in ribosomal biogenesis. The first ribosomal gene involved in DBA, ribosomal protein (RP) gene S19 (RPS19 gene), was identified in 1999. Subsequently, mutations in 12 other RP genes out of a total of 78 RP genes have been identified in DBA. All RP gene mutations described to date are heterozygous and dominant inheritance has been documented in 40 to 45% of affected individuals. As RP mutations are yet to be identified in approximately 50% of DBA cases, it is likely that other yet to be identified genes involved in ribosomal biogenesis or other pathways may be responsible for DBA phenotype.

Bone marrow transplantation for inherited bone marrow failure syndromes

The inherited bone marrow failure (BMF) syndromes are characterized by impaired hematopoiesis and cancer predisposition. Most inherited BMF syndromes are also associated with a range of congenital anomalies. Progress in improving the outcomes for children with inherited BMF syndromes has been limited by the rarity of these disorders, as well as disease-specific genetic, molecular, cellular, and clinical characteristics that increase the risks of complications associated with hematopoietic stem cell transplantation (HSCT). As a result, the ability to develop innovative transplant approaches to circumvent these problems has been limited. Recent progress has been made, as best evidenced in studies adding fludarabine to the preparative regimen for children undergoing unrelated donor HSCT for Fanconi anemia. The rarity of these diseases coupled with the far more likely incremental improvements that will result from ongoing research will require prospective international clinical trials to improve the outcome for these children.

Diagnosing and treating Diamond Blackfan anaemia: results of an international clinical consensus conference

Diamond Blackfan anaemia (DBA) is a rare, genetically and clinically heterogeneous, inherited red cell aplasia. Classical DBA affects about seven per million live births and presents during the first year of life. However, as mutated genes have been discovered in DBA, non-classical cases with less distinct phenotypes are being described in adults as well as children. In caring for these patients it is often difficult to have a clear understanding of the treatment options and their outcomes because of the lack of complete information on the natural history of the disease. The purpose of this document is to review the criteria for diagnosis, evaluate the available treatment options, including corticosteroid and transfusion therapies and stem cell transplantation, and propose a plan for optimizing patient care. Congenital anomalies, mode of inheritance, cancer predisposition, and pregnancy in DBA are also reviewed. Evidence-based conclusions will be made when possible; however, as in many rare diseases, the data are often anecdotal and the recommendations are based upon the best judgment of experienced clinicians. The recommendations regarding the diagnosis and management described in this report are the result of deliberations and discussions at an international consensus conference.

Diamond-Blackfan anemia: erythropoiesis lost in translation

Diamond-Blackfan anemia (DBA) is a congenital erythroid aplasia that usually presents as macrocytic anemia during infancy. Linkage analysis suggests that at least 4 genes are associated with DBA of which 2 have been identified so far. The known DBA genes encode the ribosomal proteins S19 and S24 accounting for 25% and 2% of the patients, respectively. Herein, we review possible links between ribosomal proteins and erythropoiesis that might explain DBA pathogenesis. Recent studies and emerging findings suggest that a malfunctioning translational machinery may be a cause of anemia in patients with DBA.

Diamond-blackfan anemia and growth status: the French registry

OBJECTIVES

To study the frequency and risk factors of growth retardation (GR) in patients with Diamond-Blackfan anemia.

STUDY DESIGN

A cross-sectional survey including the 95 patients followed by hematologists affiliated with the French Society of Pediatric Hematology and Immunology for whom growth data were available; 43 patients were transfusion dependent, 32 were steroid dependent, and 20 patients were off treatment. GR was defined as height below 2 SD.

RESULTS

Growth retardation was observed in 29.5% (28) patients. The proportion of GR increased significantly with age (16% <10, 32% among 10 to 16, 47.6% among 17 to 25, 41.7% among >16 years) and was higher in on-treatment than in off-treatment patients (35% among transfusion-dependent, 37% among steroid-dependent vs 5% among off-treatment). GR was significantly linked to associated malformations (OR, 2.3 [1.1 to 8.0]; P = .02) and intrauterine growth retardation (OR, 6.0 [1.1 to 11.6]; P = .021). GR remained independently associated with age, malformations, and treatment in a logistic regression.

CONCLUSIONS

Our study showed that the risk of GR increases with age and is associated with treatment dependence. This result addresses the question of the respective part, in the pathogenesis of GR, of the disease severity, illustrated by treatment dependence on the one hand and of the deleterious effects of long-term treatments on the other hand.

An RNA interference model of RPS19 deficiency in Diamond-Blackfan anemia recapitulates defective hematopoiesis and rescue by dexamethasone: identification of dexamethasone-responsive genes by microarray

Diamond-Blackfan anemia (DBA), a congenital erythroblastopenia, is a model disease for the study of erythroid differentiation but is poorly understood. RPS19 is the only gene yet to have been associated with DBA, but its relevance to erythroid differentiation is unclear. The molecular basis for the stimulation of erythropoiesis by glucocorticoids in patients with DBA has not been identified. We demonstrate that targeted degradation of the RPS19 transcript, through retroviral expression of short hairpin RNAs (shRNAs), blocks the proliferation and differentiation of erythroid progenitor cells in cultured human CD34(+) cells. Treatment of RPS19-deficient cells with dexamethasone restores erythroid differentiation to normal levels. We investigated the molecular basis of pharmacologic therapies for DBA using oligonucleotide microarrays to survey gene expression in CD34(+) cells treated with combinations of dexamethasone, erythropoietin, stem cell factor, and interleukin-3. Dexamethasone did not alter expression of RPS19 but activated a genetic program that includes a set of key hematopoietic regulatory genes. Genes specific to erythroid progenitor cells were up-regulated by dexamethasone, while genes specific to nonerythroid lineages were down-regulated. Deficiency of RPS19 therefore blocks proliferation of immature erythroid progenitor cells, and dexamethasone activates proliferation of the same cell population through mechanisms independent of RPS19.

Thrombopoietic Factors in Chronic Bone Marrow Failure States: The Platelet Problem Revisited: Table 1

Thrombocytopenia is a serious clinical problem in several different clinical settings. In chronic bone marrow failure states, which include aplastic anemia, myelodysplastic syndrome, and graft failure, the prolonged nature of thrombocytopenia often leads to alloimunization after repeated platelet transfusions, the consequence of which is a platelet-refractory state and enhanced risk of bleeding. Despite the introduction of several thrombopoietic factors into clinical trials, an effective way to alleviate thrombocytopenia has been elusive, and the problem in chronic bone marrow failure states has remained poorly addressed by clinical investigations. Even so, several studies by our group and others suggest that a subset of patients suffering from chronic bone marrow failure can respond to appropriate growth factor therapy. The temporal pace of response appears, however, to be much slower than that observed after administering growth factors which act on neutrophils. On the other hand, durable responses can be secured in some patients given thrombopoietic factors for long periods of time. Herein, we provide an overview of the clinical research investigations of thrombopoietic factors in chronic bone marrow failure, and the emerging insights these studies provide for understanding the process of thrombopoiesis and its therapy in this setting.

Two-phase culture in Diamond Blackfan anemia: localization of erythroid defect

The erythroid defect in Diamond Blackfan anemia (DBA) is known to be intrinsic to the stem cell, but its molecular pathophysiology remains obscure. Using a 2-phase liquid erythroid culture system, we have demonstrated a consistent defect in DBA, regardless of clinical severity, including 3 first-degree relatives with normal hemoglobin levels but increased erythrocyte adenosine deaminase activity. DBA cultures were indistinguishable from controls until the end of erythropoietin (Epo)-free phase 1, but failed to demonstrate the normal synchronized wave of erythroid expansion and terminal differentiation on exposure to Epo. Dexamethasone increased Epo sensitivity of erythroid progenitor cells, and enhanced erythroid expansion in phase 2 in both normal and DBA cultures. In DBA cultures treated with dexamethasone, Epo sensitivity was comparable to normal, but erythroid expansion remained subnormal. In clonogenic phase 2 cultures, the number of colonies did not significantly differ between normal cultures and DBA, in the presence or absence of dexamethasone, and at both low and high Epo concentrations. However, colonies were markedly smaller in DBA under all conditions. This suggests that the Epo-triggered onset of terminal maturation is intact in DBA, and the defect lies down-stream of the Epo receptor, influencing survival and/or proliferation of erythroid progenitors.

Marrow failure

This chapter describes the clinical presentation and molecular basis of two inherited bone marrow failure syndromes, Fanconi anemia (FA), and Diamond-Blackfan anemia (DBA). It also provides an update on diagnostic and therapeutic approaches to bone marrow failure of all types (inherited and acquired) in pediatric patients. In Section I, Dr. Alan D'Andrea reviews the wide range of clinical manifestations of Fanconi anemia. Significant advances have been made in understanding the molecular pathogenesis of FA. On the basis of these advances, new diagnostic assays and treatment options are now available. In Section II, Dr. Niklas Dahl examines the clinical features and molecular pathogenesis of Diamond-Blackfan anemia. The possible links between the RPS19 gene (DBA gene) and the erythropoiesis defect are considered. In Section III, Drs. Eva Guinan and Akiko Shimamura provide an algorithm for the diagnostic evaluation and treatment of children with inherited or acquired aplastic anemia. Through the presentation of a case study of a pediatric patient with bone marrow failure, he provides an overview of the newest tests and treatment options.

Diamond-Blackfan Anaemia: an overview

Diamond Blackfan Anaemia (DBA) is a congenital disease characterised by defective erythroid progenitor maturation. It is usually diagnosed during the first year of life. The main clinical sign is profound isolated normochromic or macrocytic anaemia, with normal numbers and function of the other haemopoietic cells. Reticulocyte counts in patients with DBA are very low. Bone marrow reflects the defective erythropoiesis, showing a very low number of erythropoietic precursors and a reduction of erythroid burst-forming unit progenitor cells. The proliferation and differentiation of the other lineages are normal. More than one-third of patients have malformations, most often involving the upper limbs and head, and the urogenital or cardiovascular systems. However, the link between these malformations and defective erythropoiesis is unclear and a defect in a molecule acting on both early embryonic development and haematopoiesis has been proposed. Whereas most cases are sporadic, inheritance is observed in 10% of patients, with a dominant or, more rarely, recessive pattern. One locus on chromosome 19q13.2 encoding ribosomal protein S19 accounts for a quarter of patients with either the dominant or the sporadic form. Families not linked with this locus have also been described. The diagnosis of DBA may be difficult and differential diagnoses include Fanconi's anaemia and acquired erythroid aplasias. Erythrocyte adenosine deaminase levels are generally high in DBA patients, which may help in the diagnosis, but they are not pathognomic. Corticosteroids are the main treatment option in DBA and these agents induce erythropoiesis in over 60% of patients. Some patients achieve complete remission, which may be either corticosteroid-induced or spontaneous. The increased in vitro erythropoiesis occasionally induced by the addition of specific cytokines, namely interleukin (IL)-3 and stem cell factor (SCF), has suggested their use in vivo. However, few patients have responded to IL-3, whereas SCF administration, though interesting in theory, has not yet been attempted. Patients who do not respond to corticosteroids and those who have to discontinue treatment because of adverse events must rely on long term transfusions, and are thus exposed to all of the associated complications. Bone marrow or cord blood transplantation has been performed in some patients. The former approach is burdened with severe complications and high mortality.

Diamond-Blackfan anaemia

Diamond-Blackfan anaemia (DBA) has had an intellectual allure for decades for clinical and experimental haematologists. The syndrome has a haematological phenotype of early-onset red-cell aplasia but is coupled with a baffling array of pleiotropy. There is discordance with modes of inheritance, physical anomalies, erythropoietic response to corticosteroid therapy, spontaneous 'remissions', and evolution to malignant myeloid transformation and to cancer. The recent discovery of two genes associated with DBA is the entry point for explaining the diversity of the phenotype and for understanding the molecular basis of the syndrome.

Diamond-Blackfan anaemia in the Italian population

Diamond-Blackfan anaemia (DBA) is a congenital disease characterized by defective erythroid progenitor maturation: 30% of patients have congenital malformations. The link between these malformations and defective erythropoiesis is unclear: a defect in a molecule acting both on embryo development and haemopoiesis has been proposed. Inheritance is autosomal dominant in most familial cases, but recessive families have also been reported. Many cases are sporadic. A DBA locus has been mapped on chromosome 19q13.2 (Gustavsson et al, 1997), but several families unlinked to this locus have also been reported (Gustavsson et al, 1998). This paper presents clinical, epidemiological and molecular data for DBA in the Italian population. Segregation analysis of 19q markers in patients with DBA showed exclusion of this locus in 5/12 families with inherited DBA. There was evidently locus heterogeneity for DBA in this population. A new microdeletion was identified in one patient. Other families, in which DBA segregates concordantly with the 19q critical region, suggest incomplete penetrance and expressivity of the DBA gene.

Interleukin-3: Promises and Perspectives

Interleukin-3 (IL-3) is a multipotent hematopoietic growth factor produced by activated T-cells, monocytes/macrophages and stroma cells. Human IL-3 gene is located on chromosome 5 near segment 5q31. The high affinity receptor for human IL-3 is composed of alpha and beta subunits. IL-3 shares common beta subunit with GM-CSF and IL-5 which has been mapped to chromosome 22q13.1. The biological effects of IL-3 have been studied in human and murine hematopoietic cell lines and normal human bone marrow cells. Addition of IL-3 to the culture medium induces proliferation, maturation and probably self renewal of pluripotent hematopoietic stem cells and cells of myeloid, erythroid and megakaryocytic lineages. Various clinical trials have assessed the in vivo potential of recombinant human interleukin 3 (rhIL-3). Initial results of phase I/II studies of IL-3 at a dose of 5-10 ug/kg subcutaneous (s/c) daily for 5-10 days in patients with relapsed lymphomas, small cell lung cancer, breast cancer and ovarian cancer have shown that post-chemotherapy application of IL-3 reduces chemotherapy delays and induces faster regeneration of granulocytes and platelets. However, these results were not confirmed in phase III studies. The role of IL-3 alone in the treatment of myelodysplastic syndromes (MDS), aplastic anemia (AA) and other bone marrow failure disorders have also been disappointing. However, preliminary studies of IL-3 in combination with chemotherapeutic agents and immunosuppression have demonstrated encouraging results in patients with MDS and aplastic anemia respectively. The therapeutic potential of IL-3 in peripheral blood stem cell harvesting and priming of stem cells before harvest is beginning to be identified. Initial results of IL-3 in combination with granulocyte macrophage colony stimulating factor (GM-CSF) or later acting growth factor like granulocyte colony stimulating factor (G-CSF) have yielded larger amounts of peripheral blood stem cells during PBSC harvesting. This approach and application of IL-3 with cocktail of other cytokines for ex-vivo expansion of stem cells, dendritic cell development and gene transfer requires further evaluation. The role of IL-3 in murine models of antiphospholipid syndrome (APLS) for prevention of recurrent abortion remains experimental and warrants careful assessment of adverse effects of IL-3 therapy on pregnant woman and fetus. The exact therapeutic role of IL-3 in oncology and nononcology patients is beginning to be identified. It appears that future application of IL-3 in combination with other cytokines is an attractive way forward in the prevention of treatment related mortality and morbidity in oncology patients. It also holds prospects for development of new therapeutic strategies for dose escalation and immune modulation for relapsed cancer patients.

IL-3 in the clinic

Since the cloning of human interleukin 3 (IL-3) in 1986 [1] and the demonstration of its proliferative effects on multiple hematopoietic progenitor cells, IL-3 has been widely studied to treat different states of bone marrow failure or hematologic malignancies, to mobilize or expand hematopoietic progenitor cells for transplantation, and to support engraftment after bone marrow transplantation. However, no condition for the clinical use of IL-3 has been established so far despite its theoretical advantages as an early-acting cytokine and in contrast to erythropoietin (EPO), G-CSF, or GM-CSF all of which have already been approved for several clinical modalities. Here we shortly review our current knowledge about the effects of IL-3 on the molecular and cellular level, summarize recent clinical studies with IL-3, and discuss further perspectives for the use of this cytokine.

The use of recombinant SCF protein for rapid determination of c-kit expression in normal and abnormal erythropoiesis

Stem cell factor (SCF) is the ligand for the dimeric c-kit tyrosine kinase receptor. Binding of SCF to c-kit is a crucial element in the developmental stimulus of late stem cells and early progenitor cells. In the erythroid lineage the SCF stimulus is important not only for proliferation and differentiation, but is also known to enhance later haemoglobin production. In an earlier report we described a rapid non-radioactive technique using the extended ester-attached labelled SCF protein itself for detecting c-kit expression in marrow and peripheral blood mononuclear populations. In the present study we have taken this a step further to analyse c-kit expression in developing erythroid cells in vitro, principally using normal donor samples. This was designed for use as a foundation for the comparison of haematological disorders. In this case we tested 4 patients with the congenital disorder of erythropoiesis, Diamond-Blackfan anaemia (DBA), finding that in all cases DBA c-kit expression was elevated over normal, in 1 case as high as 348% of the normal average. This may be indicative of the reduced state of progenitor development in these patients. These results show that the described technique is beneficial for analysis in the stem and progenitor compartment.