Leukemia in Down syndrome: a review

Specific JAK2 mutation (JAK2R683) and multiple gene deletions in Down syndrome acute lymphoblastic leukemia

Children with Down syndrome (DS) have a greatly increased risk of acute megakaryoblastic leukemia (AMKL) and acute lymphoblastic leukemia (ALL). Both DS-AMKL and the related transient myeloproliferative disorder (TMD) have GATA1 mutations as obligatory, early events. To identify mutations contributing to leukemogenesis in DS-ALL, we undertook sequencing of candidate genes, including FLT3, RAS, PTPN11, BRAF, and JAK2. Sequencing of the JAK2 pseudokinase domain identified a specific, acquired mutation, JAK2R683, in 12 (28%) of 42 DS-ALL cases. Functional studies of the common JAK2R683G mutation in murine Ba/F3 cells showed growth factor independence and constitutive activation of the JAK/STAT signaling pathway. High-resolution SNP array analysis of 9 DS-ALL cases identified additional submicroscopic deletions in key genes, including ETV6, CDKN2A, and PAX5. These results infer a complex molecular pathogenesis for DS-ALL leukemogenesis, with trisomy 21 as an initiating or first hit and with chromosome aneuploidy, gene deletions, and activating JAK2 mutations as complementary genetic events.

Acute megakaryoblastic leukemia in Down syndrome

Children with Down syndrome (DS) have a 10- to 20-fold increased risk of developing acute leukemia. An estimated 10% of newborns with DS develop Transient Myeloproliferative Disease (TMD) or Transient Leukemia (TL), a clonal accumulation of megakaryoblasts that resolves spontaneously within months. Acute megakaryoblastic leukemia (AMKL) develops in approximately 20% of cases of TMD/TL by 4 years of age. Both the blasts of AMKL and TMD/TL in DS harbor somatic mutations of GATA1, an essential transcriptional regulator of megakaryocytic differentiation. The distinct phenotypes of megakaryoblastic leukemia in DS are a unique biological model of the incremental process of leukemic transformation.

Haematology of Down syndrome

Down syndrome is a common congenital disorder affecting approximately 1/1000 live births. Newborns and children with Down syndrome may present with many haematological problems. In addition, benign abnormalities of the blood count and blood film, which may manifest at any age, population-based and cancer-based registries and clinical trials suggest there is a approximately 12-fold increased risk of acute lymphoblastic leukaemia in the age group of 5-30 years that rises to approximately 40-fold in children younger than 5 years, and that there is a approximately 150-fold increased risk of acute myeloid leukaemia in children younger than 5 years. There is also a virtually unique predisposition to a transient neonatal leukaemia, known as transient abnormal myelopoiesis. Deaths from leukaemia, in part, account for the excess mortality associated with Down syndrome. This article reviews the clinical presentation and the progress made in the management of these disorders over the past decade. It also briefly considers the recent exciting scientific advances that have potential to transform management of leukaemia in children with Down syndrome and also have implications for management of childhood leukaemia more generally.

Transcription factor GATA-1 and Down syndrome leukemogenesis

Mutations in transcription factors constitute one means by which normal hematopoietic progenitors are converted to leukemic stem cells. Recently, acquired mutations in the megakaryocytic regulator GATA1 have been found in essentially all cases of acute megakaryoblastic leukemia (AMkL) in children with Down syndrome and in the closely related malignancy transient myeloproliferative disorder. In all cases, mutations in GATA1 lead to the expression of a shorter isoform of GATA-1, named GATA-1s. Because GATA-1s retains both DNA binding zinc fingers, but is missing the N-terminal transactivation domain, it has been predicted that the inability of GATA-1s to regulate its normal class of megakaryocytic target genes is the mechanism by which mutations in GATA1 contribute to the disease. Indeed, several recent reports have confirmed that GATA-1s fails to properly regulate the growth of megakaryocytic precursors, likely through aberrant transcriptional regulation. Although the specific target genes of GATA-1 mis-regulated by GATA-1s that drive this abnormal growth remain undefined, multiple candidate genes have been identified via gene array studies. Finally, the inability of GATA-1s to promote expression of important metabolic genes, such as cytadine deaminase, likely contributes to the remarkable hypersensitivity of AMkL blasts to cytosine arabinoside. Future studies to define the entire class of genes dysregulated by mutations in GATA1 will provide important insights into the etiology of these malignancies.

Incidence and clinical implications of GATA1 mutations in newborns with Down syndrome

Somatic mutations in the GATA1 gene are present in almost all cases of Down syndrome (DS)–associated acute megakaryoblastic leukemia (AMKL) and transient leukemia (TL). An in utero origin of the GATA1 mutation suggests it is an early leukemogenic event. To determine the detectable incidence and clinical relevance of GATA1 mutations in DS newborns, we screened Guthrie cards from 590 DS infants for mutations in the GATA1 gene. Twenty-two (3.8%) of 585 evaluable infants harbored a predicted functional GATA1 mutation; 2 were identified exclusively within intron 1. Hispanic newborns were 2.6 times more likely to have a mutated GATA1 gene than non-Hispanics (P = .02). Two newborns with a GATA1 mutation subsequently developed AMKL, and none of the infants without a functional GATA1 mutation were reported to have developed leukemia. In addition to screening for TL, a GATA1 mutation at birth might serve as a biomarker for an increased risk of DS-related AMKL.

Mortality in adults with moderate to profound intellectual disability: a population-based study

BACKGROUND

People with intellectual disability (ID) experience a variety of health inequalities compared with the general population including higher mortality rates. This is the first UK population-based study to measure the extent of excess mortality in people with ID compared with the general population.

METHOD

Indirectly standardized all-cause and disease mortality ratios (SMRs) and exact Poisson confidence intervals were calculated by age and sex for all adults, aged 20 years or over, with moderate to profound ID living in Leicestershire and Rutland, UK, between 1993 and 2005. The general population of Leicestershire and Rutland, which has a population of approximately 700,000 individuals in this age range, was used for comparison. To explore differences within the study population, overall SMRs were also calculated by presence of Down syndrome and last place of residence (city or county).

RESULTS

Of 2436 adults identified, 409 (17%) died during 23,000 person-years of follow-up. Both all-cause and disease-specific mortality were around three times higher than the general population but varied considerably with age. The largest differences were observed in people in their twenties, where all-cause mortality was almost nine times higher in men (SMR=883; 95% CI=560-1325) and more than 17 times higher in women (SMR=1722; 95% CI=964-2840). At a particular disadvantage were people with Down syndrome and women with ID living in the city.

CONCLUSIONS

The relatively high SMRs observed in young people and in women, particularly those living in inner city areas and with Down syndrome, deserve further investigation for possible explanations, including socio-economic factors.

Extranodal natural killer/t-cell lymphoma, nasal type, in a patient with a constitutional 11q terminal deletion disorder

BACKGROUND

Most cases of constitutional 11q terminal deletion disorder are children. Malignancy is a potential concern, as these children reach adulthood. However, since the majority of patients are young, their risk of developing malignancy in adulthood is essentially unknown.

AIM

To report the first hematologic malignancy [extranodal natural killer (NK)/T-cell lymphoma, nasal type] arising in the trachea of a patient with constitutional 11q terminal deletion disorder. Our patient is the oldest patient reported in the literature. It is of note that this cytogenetic abnormality has not been described as a recurring abnormality in extranodal NK/T-cell lymphoma.

CASE REPORT

A 36-year-old male with congenital psychomotor retardation was transferred to our hospital. Pathologic evaluation was diagnostic of extranodal NK/T-cell lymphoma, nasal type. Staging marrow was negative for lymphoma, but cytogenetic analysis revealed a constitutional deletion of chromosome 11 at band q23 [46,XY,del(11)(q23)(c)]. This abnormality was present in a subsequent bone marrow specimen, along with an acquired abnormality, namely an extra copy of part of the long arm of chromosome 1 translocated to the short arm of chromosome 14.

CONCLUSION

Patients with 11q terminal deletion disorder who reach adulthood may be predisposed to develop neoplasias by virtue of the constitutional deletion.

Transient myeloproliferative disorder associated with trisomy 21

Transient myeloproliferative disorder (TMD) is a spontaneously resolving condition affecting infants born with trisomy 21 syndrome. Although TMD is rather rare among infants with trisomy 21, its ramifications can become severe enough that neonatal nurses should be aware of the condition, its manifestations, and its management. The spectrum of TMD presentation ranges from subtle blastemia in an otherwise healthy infant to severe, life-threatening expression of the disease. TMD may be a precursor to congenital leukemia—thus, the importance of nurses’ becoming aware of this condition. This article addresses the pathology of TMD, case reports in the literature, potential complications of the disorder, and nursing implications. A case study of an infant with dermatologic manifestations of TMD is presented, including history, differential diagnoses, treatment, and follow-up.

Clinical manifestations of hematologic and oncologic disorders in patients with Down syndrome

Hematologic abnormalities are common in individuals with Down syndrome (DS). Increased erythrocyte mean corpuscular volume (MCV) is frequently found among DS infants and remains elevated throughout life in two-thirds of patients, making interpretation of red cell indices for diagnosis of nutritional anemias or bone marrow failure disorders more challenging. Transient myeloproliferative disorder (TMD) associated with pancytopenia, hepatosplenomegaly, and circulating immature WBCs, is found almost exclusively in DS infants with an incidence of approximately 10%. In most cases, TMD regresses spontaneously within the first 3 months of life, but in some children, it can be life threatening or even fatal. Despite the high rate of spontaneous regression, TMD can be a preleukemic disorder in 20-30% of children with DS. The types of malignancy, response to therapy, and clinical outcome in children with DS are also unique. There is an increased risk of leukemia with an equal incidence of lymphoid and myeloid leukemia. Acute megakaryocytic leukemia (AMKL) subtype is the most common form of acute myeloid leukemia (AML) in this setting, and is uncommon in children without DS. Somatic mutations of the gene encoding the hematopoetic growth factor GATA1 have been shown to be specific for TMD and AMKL in children with DS. Myelodysplastic syndrome can precede AML. Children with DS and leukemia are more sensitive to some chemotherapeutic agents such as methotrexate than other children which requires careful monitoring for toxicity. Although the risk for leukemia is higher in individuals with DS, these patients have a lower risk of developing solid tumors, with the exception of germ cell tumors, and perhaps retinoblastoma and lymphoma.

Down syndrome with low hypodiploidy in precursor B-cell acute lymphoblastic leukemia

We describe the rare finding of a 33-month-old child neonatally diagnosed with Down syndrome, who presented with pre-B acute lymphoblastic leukemia (ALL) with a pretreatment bone marrow karyotype in which a low hypodiploid cell line (38 chromosomes) was identified in 17/19 cells studied. The abnormal cell line retained the extra constitutional chromosome 21. Hypodiploidy (loss of one or more chromosomes) is seen in approximately 5% of all childhood pre-B ALL cases and in approximately 2.2% cases of individuals with a constitutional trisomy 21. Low hypodiploidy, associated with a high risk of relapse, is rare in pediatric ALL cases in the general population, and, to our knowledge, is previously unreported in patients with trisomy 21.

Cloning and characterization of the novel chimeric gene p53/FXR2 in the acute megakaryoblastic leukemia cell line CMK11-5

The loss of p53 function is a key event in tumorigenesis. Inactivation of p53 in primary tumors and cell lines is mediated by several molecular mechanisms, including deletions and rearrangements. However, generation of a p53 fusion gene has not yet been reported. Here we report a novel p53/an autosomal homolog of the fragile X mental retardation (FXR2) chimeric gene generated by an interstitial deletion. Western blot analyses have shown that the p53/FXR2 protein is indeed expressed in a Down syndrome-related acute megakaryoblastic leukemia cell line, CMK11-5 cells. To investigate the properties of the p53/FXR2 protein, we observed its subcellular localization. Flag-tagged expression vectors were transfected into COS-7 cells and the proteins were stained with an anti-Flag antibody. The p53/FXR2 protein was expressed at high levels in the cytoplasm, whereas wild-type p53 and FXR2 were localized primarily in the nucleus and in the periphery of the nucleus, respectively. Treatment with a topoisomerase II inhibitor, VP16, failed to induce expression of a p53 target gene, the cyclin-dependent kinase inhibitor p21(WAF-1/CIP1), in CMK11-5 cells, and transient transfection analysis showed that the p53/FXR2 protein failed to transactivate the p21(WAF-1/CIP1) promoter. These results suggest that the p53/FXR2 fusion protein lacks the ability of wild-type p53 to function as a transcription factor. The p53/FXR2 gene is the first reported p53 fusion gene.

JAK2T875N is a novel activating mutation that results in myeloproliferative disease with features of megakaryoblastic leukemia in a murine bone marrow transplantation model

Acute megakaryoblastic leukemia (AMKL) is a subtype of acute myeloid leukemia associated with a poor prognosis. However, there are relatively few insights into the genetic etiology of AMKL. We developed a screening assay for mutations that cause AMKL, based on the hypothesis that constitutive activation of STAT5 would be a biochemical indicator of mutation in an upstream effector tyrosine kinase. We screened human AMKL cell lines for constitutive STAT5 activation, and then used an approach combining mass spectrometry identification of tyrosine phosphorylated proteins and growth inhibition in the presence of selective small molecule tyrosine kinase inhibitors that would inform DNA sequence analysis of candidate tyrosine kinases. Using this strategy, we identified a new JAK2T875N mutation in the AMKL cell line CHRF-288-11. JAK2T875N is a constitutively activated tyrosine kinase that activates downstream effectors including STAT5 in hematopoietic cells in vitro. In a murine transplant model, JAK2T875N induced a myeloproliferative disease characterized by features of AMKL, including megakaryocytic hyperplasia in the spleen; impaired megakaryocyte polyploidization; and increased reticulin fibrosis of the bone marrow and spleen. These findings provide new insights into pathways and therapeutic targets that contribute to the pathogenesis of AMKL.

Treatment for myeloid leukaemia of Down syndrome: population-based experience in the UK and results from the Medical Research Council AML 10 and AML 12 trials

Down syndrome (DS) children are at an increased risk of developing myelodysplasia and acute myeloid leukaemia (AML). We retrospectively analysed the population-based data on 81 children with myeloid leukaemia of Down syndrome (ML-DS) from the UK National Registry of Childhood Tumours and experience in the Medical Research Council (MRC) AML 10 and AML 12 trials, which enrolled 46 children with ML-DS from 1988 to 2002. Eight per cent of UK children with AML had DS, but DS children comprised only 5% of children registered in MRC trials. The unique clinical characteristics of ML-DS were confirmed. Overall survival (OS) of ML-DS at 5 years increased from 47% in UK children diagnosed from 1988 to 1995 to 75% in children diagnosed from 1996 to 2002. OS for DS children registered in AML 10 and AML 12 was 74% in 5 years and improved from AML 10 to AML 12 (56% vs. 83%) There was no significant difference in OS between DS and non-DS children (OS: 74% vs. 62%, P = 0.4) in the trials, but this result masked a significant increase in early death amongst DS children, with a significant reduction in mortality later on. Relapse was significantly reduced (3% vs. 39%, P = 0.0003), leading to the improved disease-free survival (83% vs. 56%, P = 0.02). Given the increased number of early treatment-related deaths, future treatment protocols should aim to reduce chemotherapy dosage or intensity whilst maintaining low rates of resistant and recurrent disease.

GATA1 mutations in acute leukemia in children with Down syndrome

It has been reported that somatic mutations in the X-linked GATA1 gene are present in hematological clonal disorders in children with Down syndrome (DS). We analyzed retrospective samples of DS children with acute myeloid leukemia, transient leukemia (TL), and myelodysplastic syndrome (MDS) to test whether the specificity of GATA1 mutations can be helpful in distinguishing these hematopoietic disorders. A total of 49 samples were subjected to GATA1 mutation screening by direct sequencing and denaturing polyacrylamide gel electrophoresis (PAGE). Mutations in exon 2 of GATA1 were detected in six of eight DS-AML M7 samples and in four of six DS-TL; no mutation was detected in 13 children with acute lymphoblastic leukemia (DS-ALL), 6 with DS-AML (M0, M2, and M5), 6 with DS-MDS and in 8 DS infants without hematological disorders and 2 children with AML M7 without DS. Blast cells proportion in the sample represented a critical aspect on the sensitivity of mutation detection in GATA1, and a combination of sequence analysis and PAGE is necessary to detect mutations when blast percentage is low. The absence of detected mutations in any of the DS-MDS cases raises the question whether MDS in DS children is an intermediate stage between TL and AML M7, as previously suggested.

A prospective study of the natural history of transient leukemia (TL) in neonates with Down syndrome (DS): Children's Oncology Group (COG) study POG-9481

A unique transient leukemia (TL) has been described in newborns with Down syndrome (DS; or trisomy 21 mosaics). This leukemia has a high incidence of spontaneous remission; however, early death and subsequent development of acute megakaryoblastic leukemia (AMKL) have been reported. We prospectively evaluated 48 infants with DS and TL to determine the natural history and biologic characteristics of this disease, identify the clinical characteristics associated with early death or subsequent leukemia, and assess the incidence of subsequent leukemia. Blast cells associated with TL in DS infants exhibited FAB M(7) morphology and phenotype. Most infants (74%) had trisomy 21 (or mosaicism) as the only cytogenetic abnormality in the blast cells. Most children were able to spontaneously clear peripheral blasts (89%), normalize blood counts (74%), and maintain a complete remission (64%). Early death occurred in 17% of infants and was significantly correlated with higher white blood cell count at diagnosis (P < .001), increased bilirubin and liver enzymes (P < .005), and a failure to normalize the blood count (P = .001). Recurrence of leukemia occurred in 19% of infants at a mean of 20 months. Development of leukemia was significantly correlated with karyotypic abnormalities in addition to trisomy 21 (P = .037). Ongoing collaborative clinical studies are needed to determine the optimal role of chemotherapy for infants at risk for increased mortality or disease recurrence and to further the knowledge of the unique biologic features of this TL.

Isochromosome 7q in Down syndrome

Isochromosome 7q is not an uncommon chromosomal abnormality. It has been reported in association with Shwachman-Diamond syndrome, Wilms tumor, and hepatosplenic T-cell lymphoma. In other hematolymphoid malignancies, it occurs almost invariably as a secondary change. A notable example is its association with t(4;11)(q21;q23) in acute lymphoblastic leukemia. It has rarely been described in myelodysplastic syndrome and acute myeloid leukemia. We report the occurrence of i(7q) as the primary abnormality in a 2-year-old boy with Down syndrome and minimally differentiated acute myeloid leukemia.

GATA Transcription Factors and Hematological Diseases

The development of mature blood cells from hematopoietic stem cells is regulated by transcription factors that control and coordinate the expression of lineage-specific genes. The GATA family consists of six transcription factors that function in hematopoietic and endodermal development. Among them, GATA-1 is expressed in erythroid, megakaryocytic, eosinophil and mast cell lineages, and GATA-2 is expressed in stem and progenitor cells, at more immature stage compared with GATA-1. Based on the characteristic phenotypes of GATA-1 and GATA-2 mutant mice, it has been suggested that mutations of these GATA genes in humans may result in the onset of certain clinical diseases. To date, mutations of GATA-1 gene have been found in inherited anemia and thrombocytopenia, and Down syndrome-related acute leukemia, which exhibits megakaryocytic phenotypes and frequently occurs in patients with Down syndrome. In contrast, no mutation of GATA-2 gene has been identified in hematological diseases; however, we found the expression level of GATA-2 is significantly decreased in CD34 positive cells in patients with aplastic anemia. Since GATA-2 functions in the proliferation of hematopoietic stem cells, the reduction of GATA-2 expression in CD34 positive cells may result in the decreased number of hematopoietic stem cells, which is the characteristic feature of aplastic anemia. Based on these lines of evidence, some types of hematological diseases may be defined as transcription factor diseases.

Moyamoya syndrome associated with Down syndrome: outcome after surgical revascularization

OBJECTIVES

This study was undertaken to describe the clinical, radiologic, and angiographic features of moyamoya syndrome in a surgical series of children and adults with Down syndrome. We wished to define the features of moyamoya syndrome associated with Down syndrome and to determine the results of surgical revascularization among these patients at early and late follow-up times.

METHODS

We reviewed the clinical, radiologic, and angiographic records of all patients with moyamoya syndrome associated with Down syndrome, as a subset of a previously reported, consecutive series of patients who underwent cerebral revascularization surgery with a standardized surgical procedure, pial synangiosis, between January 1, 1985, and June 30, 2004.

RESULTS

Of 181 patients with moyamoya syndrome from the initial series who were treated surgically during the study period, 16 patients had Down syndrome (10 female patients and 6 male patients). The average age at onset was 9.3 years (range: 1-29 years); the average age at the time of surgery was 9.8 years (range: 2-29 years). Although the presenting symptoms were transient ischemic attacks for 10 patients and strokes for 6 patients, computed tomographic and/or MRI scans demonstrated bilateral infarctions for 9 patients and unilateral infarctions for 6, with only 1 patient having no imaging evidence of a previous stroke. No cases presented with intracerebral hemorrhage. Preoperative angiography showed the presence of bilateral moyamoya syndrome changes for all patients, including posterior circulation involvement for 8 patients. Surgical treatment included pial synangiosis for all patients, although 1 patient underwent a superficial temporal artery-middle cerebral artery bypass in the contralateral hemisphere. Surgical complications included symptomatic subdural hematomas requiring evacuation, at 48 days and 54 days postoperatively (2 cases), seizures (2 cases), and strokes within 30 days after surgery, at 1 day and 7 days postoperatively (2 cases). Late clinical and radiologic follow-up data (average: 67.6 months; range: 6-146 months) demonstrated no worsening in neurologic status for any patient except for 1 patient who developed a seizure disorder with associated chronic hypocalcemia; she was totally dependent at the 10-year follow-up evaluation, despite no evidence of new infarction since her surgery. There was no clinical or radiologic evidence of new infarction for any patient in late follow-up evaluations. Postoperative angiography, conducted 1 year after surgery for 11 patients, revealed radiologic evidence of good to excellent cerebral revascularization in 85% of the surgically treated hemispheres. Patients were maintained on lifetime aspirin therapy.

CONCLUSIONS

The clinical, radiologic, and angiographic features of moyamoya syndrome associated with Down syndrome seem comparable to those of primary moyamoya disease. Cerebral revascularization surgery with the pial synangiosis technique seems to confer long-lasting protection against additional strokes in this patient population. The presence of moyamoya syndrome should be considered in the evaluation of patients with Down syndrome who present with transient ischemic attack-like symptoms.

Optimizing therapy for myeloid disorders of Down syndrome

Children with Down syndrome (DS) are at increased risk of leukaemia. Myeloid disorders include transient abnormal myelopoiesis (TAM), myelodysplasia (MDS) and acute myeloid leukaemia (AML). Mutations in the GATA-1 gene, which encodes for a transcription factor central to the normal development of the erythroid and megakaryocytic lineages, are found in cases of TAM, MDS and AML in DS children. DS children with MDS/AML mostly present between the ages of 1 and 4 years, and have a large predominance of megakaryoblastic disease (French-American-British type M7). The MDS and AML are part of a single disease entity (myeloid leukaemia of Down syndrome) that is extremely sensitive to chemotherapy. Resistant disease and relapse are rare, but treatment-related toxicity is high, and deaths in remission have exceeded those due to disease in most series. Accordingly, controlled dosage reduction is the focus of contemporary treatment studies.

Hematological disorders in Down syndrome: ten-year experience at a Tertiary Care Centre in North India

A total of 239 cases of Down syndrome (DS) were seen in the genetic clinic between 1992 and 2003, of which of 15 had hematological manifestations at presentation. These comprised 4 cases of transient myeloproliferative disorder (TMD), 3 cases of TMD/acute leukemia, 4 cases of acute leukemia (AL), 2 of dual deficiency anemia, and 1 case each of myelofibrosis and idiopathic thrombocytopenia. This study emphasizes the fact that an abnormal hemogram in a DS patient does not necessarily indicate AL/TMD, as a considerable number of the cases in this study had other hematological abnormalities. TMD can be differentiated from acute leukemia only on follow-up.

The RUNX genes: gain or loss of function in cancer

The RUNX genes have come to prominence recently because of their roles as essential regulators of cell fate in development and their paradoxical effects in cancer, in which they can function either as tumour-suppressor genes or dominant oncogenes according to context. How can this family of transcription factors have such an ambiguous role in cancer? How and where do these genes impinge on the pathways that regulate growth control and differentiation? And what is the evidence for a wider role for the RUNX genes in non-haematopoietic cancers?

Eyelid mass as the presenting finding in a child with Down syndrome and acute megakaryoblastic leukemia

Children with Down syndrome are at increased risk of developing acute megakaryoblastic leukemia (AML). Therefore, physicians caring for children with Down syndrome should be familiar with the presenting features of AML. We describe a child with Down syndrome presenting with a left eyelid mass 1 month before a diagnosis of acute AML.

Acute leukaemia in children with Down syndrome: a population-based Nordic study

To determine the epidemiology and outcome of children with Down syndrome (DS) diagnosed with acute leukaemia in the Nordic countries, data registered in the Nordic Society of Paediatric Haematology and Oncology (NOPHO) population-based leukaemia registry were analysed. Of 3494 children with acute leukaemia diagnosed between July 1984 and December 2001, 136 patients (3.9%) with DS were identified. 2.1% of the children with acute lymphoid leukaemia (ALL) and 14.0% of the children with acute myeloid leukaemia (AML) had DS. In ALL, DS patients had similar age and sex distribution and no major differences in blood counts compared with non-DS children. None of the DS patients had T cell leukaemia. Outcome was inferior to that of non-DS children and treatment results did not improve over time. In AML, DS patients showed a significant female predominance and all but one were <5 years old. DS patients with AML had significantly lower platelet and white blood cell counts and two-thirds were type M7 as according to the French-American-British classification. None of the patients <5 years of age had typical AML cytogenetic aberrations. Outcome was far better in the DS group. DS patients treated for AML after 1992 had an excellent outcome (probability of event-free survival, 83 +/- 6%). The high proportion of female DS patients with AML is unexplained. The differing treatment results in AML versus ALL need further evaluation and represent a challenge for the coming years.

Epidemiology of leukemia in children with Down syndrome

Studies suggest nearly a 20-fold increased risk of leukemia in individuals with Down syndrome. Most of this increased risk appears in the first few decades of life, with the highest incidence in children less than 5 years of age. It is unknown why children with Down syndrome are at such an increased risk of leukemia. With respect to environmental exposures, it will be important to investigate risk factors associated with childhood leukemia in general (including diagnostic x-rays, pesticides, and other occupational exposures) as well as experiences common to children with Down syndrome (including routine medical screening tests, increased susceptibility to infections, and increased vitamin deficiencies).

A case of myelodysplastic syndrome with acquired monosomy 7 in a child with a constitutional t(1;19) and a mosaicism for trisomy 21

A 3-year-old patient presented with anemia, thrombocytopenia, and blasts in the peripheral blood. A bone marrow aspirate revealed a myelodysplastic syndrome (MDS). A mosaic abnormal female karyotype 46,XX, t(1;19)(q42; p13.1)c[12]/ 47,idem,+21c[3]/ 47,idem,-7,+21c,+mar[7] was obtained on G-banded metaphases from unstimulated bone marrow aspirate cell culture. To rule out constitutional abnormalities, we performed a cytogenetic analysis on the patient's phytohemagglutinin-stimulated peripheral blood and cultured skin fibroblasts. A karyotype of 46,XX,t(1;19) (q42;p13.1)c was found in all 20 peripheral lymphocytes analyzed, confirming the constitutional origin of the translocation. In addition, 5 out of 50 cells from two separate cultures of the skin fibroblasts contained an extra chromosome 21. The presence of two cell lines in multiple cultures indicates that the patient is a true low-level mosaic for trisomy 21. Because of the finding of monosomy 7 and a marker chromosome only in the trisomy 21 clone, we conclude that the leukemic clone arose from a hematopoietic precursor with constitutional trisomy 21. It is also possible that the t(1;19) played some role in the development of the MDS. Because acute myelogenous leukemia (AML) and MDS with Down syndrome (DS) have distinct biologic and clinical features, the identification of DS patients with a mild or normal phenotype in the AML/MDS population is of fundamental importance for clinical diagnosis and management.

Origins of leukaemia in children with Down syndrome

Transient megakaryoblastic leukaemia is found in 10% of newborns with Down syndrome, characterized by constitutional trisomy 21. Although in most cases the leukaemic cells disappear spontaneously after the first months of life, irreversible acute megakaryoblastic leukaemia develops in 20% of these individuals within 4 years. The leukaemic cells typically harbour somatic mutations of the gene encoding GATA1, an essential transcriptional regulator of normal megakaryocytic differentiation. Leukaemia that specifically arises in the context of constitutional trisomy 21 and somatic GATA1 mutations is a unique biological model of the incremental process of leukaemic transformation.

Transient leukemia in newborns with Down syndrome

Children with Down syndrome (DS) have a 10- to 20-fold increased risk of developing leukemia, particularly acute megakaryocytic leukemia. Newborns with DS or trisomy 21 mosaicism may exhibit a particularly unique form of leukemia that historically has been associated with a high rate of spontaneous remission. This transient leukemia (TL) has been shown to be a clonal proliferation of blast cells exhibiting megakaryocytic features. Its true incidence remains to be determined. At presentation, many infants are clinically well with only an incidental finding of abnormal blood counts and circulating blasts in the peripheral blood. However, in approximately 20% of cases, the disease is severe and life-threatening, manifesting as hydrops faetalis, multiple effusions, and liver or multi-organ system failure resulting in death. Of those children who enter a spontaneous remission, 13-33% have been found to develop subsequent acute megakaryoblastic leukemia, usually within the first 3 years of life, which if left untreated is fatal. This unique TL of the DS newborn has been the subject of recent clinical cooperative group trials as well as many biological and genetic research efforts. We summarize here the known clinical, biological, and cytogenetic features of TL associated with DS.

Leukemogenesis caused by incapacitated GATA-1 function

GATA-1 is essential for the development of erythroid and megakaryocytic lineages. We found that GATA-1 gene knockdown female (GATA-1.05/X) mice frequently develop a hematopoietic disorder resembling myelodysplastic syndrome that is characterized by the accumulation of progenitors expressing low levels of GATA-1. In this study, we demonstrate that GATA-1.05/X mice suffer from two distinct types of acute leukemia, an early-onset c-Kit-positive nonlymphoid leukemia and a late-onset B-lymphocytic leukemia. Since GATA-1 is an X chromosome gene, two types of hematopoietic cells reside within heterozygous GATA-1 knockdown mice, bearing either an active wild-type GATA-1 allele or an active mutant GATA-1.05 allele. In the hematopoietic progenitors with the latter allele, low-level GATA-1 expression is sufficient to support survival and proliferation but not differentiation, leading to the accumulation of progenitors that are easily targeted by oncogenic stimuli. Since such leukemia has not been observed in GATA-1-null/X mutant mice, we conclude that the residual GATA-1 activity in the knockdown mice contributes to the development of the malignancy. This de novo model recapitulates the acute crisis found in preleukemic conditions in humans.

Transient myeloproliferative disorder causing a vesiculopustular eruption in a phenotypically normal neonate

We report an unusual congenital vesiculopustular eruption arising in a neonate as the result of the transient myeloproliferative disorder (TMD) associated with trisomy 21. In this instance, the neonate was phenotypically normal, making the diagnosis more elusive. Initially the lesions were clinically suspicious for herpetic infection. The clinical scenario quickly became highly suggestive of leukemia cutis, given the infant's extremely high white blood cell count. Further examination revealed trisomy 21 in the leukemic cells and disomy 21 in the buccal keratinocytes, and a diagnosis of self-resolving TMD was made. Biopsy specimens of the lesions showed a sparse, perivascular, atypical, mononuclear infiltrate. We suggest that examination for a TMD be undertaken in neonates with a vesiculopustular eruption and leukemic white blood cell counts.

Gene expression profiling of normal and malignant CD34-derived megakaryocytic cells

Gene expression profiles of bone marrow (BM) CD34-derived megakaryocytic cells (MKs) were compared in patients with essential thrombocythemia (ET) and healthy subjects using oligonucleotide microarray analysis to identify differentially expressed genes and disease-specific transcripts. We found that proapoptotic genes such as BAX, BNIP3, and BNIP3L were down-regulated in ET MKs together with genes that are components of the mitochondrial permeability transition pore complex, a system with a pivotal role in apoptosis. Conversely, antiapoptotic genes such as IGF1-R and CFLAR were up-regulated in the malignant cells, as was the SDF1 gene, which favors cell survival. On the basis of the array results, we characterized apoptosis of normal and ET MKs by time-course evaluation of annexin-V and sub-G1 peak DNA stainings of immature and mature MKs after culture in serum-free medium with an optimal thrombopoietin concentration, and annexin-V-positive MKs only, with decreasing thrombopoietin concentrations. ET MKs were more resistant to apoptosis than their normal counterparts. We conclude that imbalance between proliferation and apoptosis seems to be an important step in malignant ET megakaryocytopoiesis.

Life-threatening complications of transient abnormal myelopoiesis in neonates with Down syndrome

Neonates with Down syndrome can present with a haematological disorder called transient abnormal myelopoiesis (TAM). While TAM is usually a self-limiting disease, patients with severe complications such as hydrops fetalis, cardiorespiratory failure and liver fibrosis have been described. Here, we present five consecutive neonates with trisomy 21 and TAM, four of whom were critically ill and were therefore treated with cytosine-arabinoside. All five patients survived.

CONCLUSION

severely affected neonates with Down syndrome and transient abnormal myelopoiesis might benefit from early cytostatic treatment with cytosine-arabinoside.

Leukaemia - a developmental perspective

Leukaemia is characterized by the accumulation of malignant haematopoietic precursors. Recent studies have revealed that acquired alterations in genes that regulate normal haematopoiesis are frequently detected in leukaemia. The progression to leukaemia depends on additional mutations that promote the survival of developmentally arrested cells. This review describes three examples of this general paradigm of leukaemogenesis: RUNX1 abnormalities in acute leukaemias, GATA1 mutations in the leukaemias of Down syndrome, and SCL and LMO2 ectopic expression in T cell acute lymphoblastic leukaemia.

Microarray transcript profiling distinguishes the transient from the acute type of megakaryoblastic leukaemia (M7) in Down's syndrome, revealing PRAME as a specific discriminating marker

Transient myeloproliferative disorder (TMD) is a unique, spontaneously regressing neoplasia specific to Down's syndrome (DS), affecting up to 10% of DS neonates. In 20-30% of cases, it reoccurs as progressive acute megakaryoblastic leukaemia (AMKL) at 2-4 years of age. The TMD and AMKL blasts are morphologically and immuno-phenotypically identical, and have the same acquired mutations in GATA1. We performed transcript profiling of nine TMD patients comparing them with seven AMKL patients using Affymetrix HG-U133A microarrays. Similar overall transcript profiles were observed between the two conditions, which were only separable by supervised clustering. Taqman analysis on 10 TMD and 10 AMKL RNA samples verified the expression of selected differing genes, with statistical significance (P < 0.05) by Student's t-test. The Taqman differences were also reproduced on TMD and AMKL blasts sorted by a fluorescence-activated cell sorter. Among the significant differences, CDKN2C, the effector of GATA1-mediated cell cycle arrest, was increased in AMKL but not TMD, despite the similar level of GATA1. In contrast, MYCN (neuroblastoma-derived oncogene) was expressed in TMD at a significantly greater level than in AMKL. MYCN has not previously been described in leukaemogenesis. Finally, the tumour antigen PRAME was identified as a specific marker for AMKL blasts, with no expression in TMD. This study provides markers discriminating TMD from AMKL-M7 in DS. These markers have the potential as predictive, diagnostic and therapeutic targets. In addition, the study provides further clues into the pathomechanisms discerning self-regressive from the progressive phenotype.

Fatal familial infantile myelofibrosis

Malignant megakaryopoiesis can cause chronic or acute myelofibrosis through production of fibrogenic cytokines. Chronic myelofibrosis is a clonal disorder with marrow fibrosis, myeloid metaplasia, gross splenomegaly, and teardrop cells. Acute myelofibrosis differs by its aggressiveness, by the fact that it is more common in children, and by lack of organomegaly or anisopoikilocytosis. Surprisingly, in early childhood and infancy, splenomegaly and teardrop red cells become an important feature. Infantile myelofibrosis is a rare disease, except in Down syndrome. Familial occurrence of infantile myelofibrosis is exceedingly rare. The author describes an unfortunate family whose four consecutive children died of a very fulminant form of acute myelofibrosis during their first year of life. The fulminant nature of the disease, the degree of splenomegaly, and the prominence of anisopoikilocytosis were even more marked than in currently reported cases of infantile myelofibrosis. The mode of inheritance remained illusive. With two female children, sex-linked inheritance was not possible. It could not have been inherited in an autosomal dominant fashion with normal parents and with two normal children from the father's second marriage. A new autosomal dominant mutation in the germ cell of either parent is another possibility. Autosomal recessive inheritance remained a logical explanation, although such a high degree of disease presentation in a non-consanguineous marriage seems to put that possibility in question.

Linkage disequilibrium mapping in trisomic populations: Analytical approaches and an application to congenital heart defects in Down syndrome

Many of the birth defects associated with trisomy exhibit both variable expressivity and incomplete penetrance. This variability suggests that it is allelic variation and not simply the presence of an additional chromosome that leads to the development of certain trisomy-associated birth defects. With the proper tools, one may use trisomic populations to identify genes involved in the development of specific birth defects. A trisomic population may be advantageous over a normal population if the defect is over-represented in the trisomic population. Alternatively, one can view the trisomic populations as a "model system" to offer insight into aspects of both normal and abnormal embryonic development. Standard disomic linkage disequilibrium mapping approaches need to be adjusted to account for the presence of the additional genetic material in the trisomic individuals. We present an approach for linkage disequilibrium mapping of variable phenotypes in a trisomic population that adequately accounts for the additional alleles and the pattern of non-independent inheritance. We establish the laboratory methods and statistical tools necessary to conduct an association study in a trisomic population. As an example, we have applied these tools to a pilot study of Down syndrome-associated congenital heart defects.

A case of down syndrome with acute lymphoblastic leukemia and isochromosome Xp

A 3-year, 9-month-old girl with trisomy 21 was diagnosed with acute lymphoblastic leukemia (ALL). The karyotype of her leukemic cells at diagnosis-48,XX,+i(X)(p10),+21c-included an extra, structurally abnormal X chromosome as the sole acquired abnormality. While an extra X chromosome is a common abnormality in childhood ALL, it is seldom the only acquired aberration. Furthermore, an additional X chromosome that is structurally abnormal is rare, and has not been reported previously as a solitary abnormality. Here we report a novel karyotype in childhood ALL and review the eight previously described cases of ALL with an extra X isochromosome as the only acquired abnormality.

Long-term prognosis of children with Down's syndrome and leukaemia: a 34-year nation-wide experience

BACKGROUND

Although the characteristics of leukaemia in patients with Down's syndrome (DS) have been well documented, little is known about the long-term results of treatment.

METHOD

Retrospectively from 1968 to 1981 and prospectively from 1982 to 2002, the present authors collected data on every child with DS in Finland who had been diagnosed with leukaemia between 1968 and 1994.

RESULTS

Forty-one children with DS had acute leukaemia: 28 had acute lymphoblastic leukaemia (ALL); and 13 had acute non-lymphoblastic leukaemia (ANLL). The median age of the subjects at diagnosis was 3.8 years (range = 0-15.9 years). Patients with ANLL were significantly younger (P = 0.001) and all patients under 2 years of age had ANLL. Out of the 28 patients with ALL, 23 (82%) entered primary remission, and of these 23 individuals, 10 remained alive and in continuous remission (CR) after a median of 11.6 years (range = 8.9-20.0 years). Out of the 13 patients with ANLL, five (38%) entered remission and four remained in CR after a median of 16.0 years (range = 9.1-19.2 years). Treatment -related toxicities were common: eight patients with ALL and two with ANLL died of septicaemia. Actuarial, event-free survival rates at 5 years were 53% and 43% for adequately treated subjects with ALL and ANLL, respectively.

CONCLUSIONS

Standard leukaemia chemotherapy is effective in patients with DS. However, because toxicities are unacceptably frequent, specific anti-leukaemia regimens are needed for subjects with DS design.

Recent insights into the mechanisms of myeloid leukemogenesis in Down syndrome

GATA-1 is the founding member of a transcription factor family that regulates growth and maturation of a diverse set of tissues. GATA-1 is expressed primarily in hematopoietic cells and is essential for proper development of erythroid cells, megakaryocytes, eosinophils, and mast cells. Although loss of GATA-1 leads to differentiation arrest and apoptosis of erythroid progenitors, absence of GATA-1 promotes accumulation of immature megakaryocytes. Recently, we and others have reported that mutagenesis of GATA1 is an early event in Down syndrome (DS) leukemogenesis. Acquired mutations in GATA1 were detected in the vast majority of patients with acute megakaryoblastic leukemia (DS-AMKL) and in nearly every patient with transient myeloproliferative disorder (TMD), a "preleukemia" that may be present in as many as 10% of infants with DS. Although the precise pathway by which mutagenesis of GATA1 contributes to leukemia is unknown, these findings confirm that GATA1 plays an important role in both normal and malignant hematopoiesis. Future studies to define the mechanism that results in the high frequency of GATA1 mutations in DS and the role of altered GATA1 in TMD and DS-AMKL will shed light on the multistep pathway in human leukemia and may lead to an increased understanding of why children with DS are markedly predisposed to leukemia.

Increased age at diagnosis has a significantly negative effect on outcome in children with Down syndrome and acute myeloid leukemia: a report from the Children's Cancer Group Study 2891

PURPOSE

To determine the outcome of children with Down syndrome (DS) and acute myeloid leukemia (AML) receiving standard timing chemotherapy without bone marrow transplantation (BMT), with determination of prognostic factors.

PATIENTS AND METHODS

Children with DS and newly diagnosed AML or myelodysplasia were prospectively enrolled on Children's Cancer Group study 2891 (N = 161) and treated uniformly with four standard timing induction courses of dexamethasone, cytarabine arabinoside, 6-thioguanine, etoposide, daunorubicin (DCTER) followed by intensively timed high-dose cytarabine.

RESULTS

Children with DS were significantly younger at diagnosis than those without (median age, 1.8 v 7.5 years, respectively; P <.001), with more megakaryocytic leukemia (70% v 6%; P <.001). Higher complete remission rates (91%) were achieved in children with DS than among those without DS (75%; P <.001). Equivalent grade 3 to 4 toxicity (29% v 30%; P =.84) was seen, though children with DS had greater pulmonary toxicity (P <.01) during induction and mucositis during intensification (P =.12). Children with DS had significantly better 8-year event-free survival (EFS; 77% v 21% standard and 40% intensive induction; P <.0001). Multivariate analysis in children with DS revealed that only age at diagnosis of 2 years or older was a risk factor for greater relapse risk (odds ratio, 4.9; P =.006) and worse survival. Children between ages 0 to 2 years (n = 94) had a 6-year EFS of 86%; those from 2 to 4 years (n = 58), 70%; and those older than 4 years (n = 9), 28%. Remission failures were the primary reason for worse 6-year EFSs (1% in those 0 to 2 years v 14% if >2 years; P =.002).

CONCLUSION

Outcome for children with DS and AML is excellent with standard induction therapy, but declines with increasing age.

Lack of circulating megakaryoblasts in newborn peripheral blood: development and validation of a sensitive flow cytometric detection method

It is currently thought that approximately 1% of children with Down syndrome will develop a "premalignant" syndrome known as transient myeloproliferative disorder (TMD). Prospective, population-based studies of the incidence of TMD in Down syndrome infants is lacking. Although most cases of TMD resolve by 1 year of age, data suggest that 10% to 20% of Down syndrome patients with TMD develop AML-M7 (megakaryoblastic leukemia). To identify the true incidence of TMD in the Down syndrome population, a sensitive, rapid, and cost-effective method of quantifying circulating megakaryoblasts in large numbers of patients was needed. In this pilot study, the authors tested the hypothesis that there are fewer than 1% megakaryoblasts of nucleated cells circulating in the blood of normosomic infants. Four-antigen flow cytometry was used to establish the percentage of megakaryoblasts present in each of 100 cord blood samples collected blindly from "normosomic" live births. There was a mean percentage of 0.017% megakaryoblasts in 100 cord blood samples from normosomic infants. Flow cytometry proved to be a sensitive, rapid, and reproducible method for the quantification of megakaryoblasts. Less than 1% of circulating nucleated cells in the blood of newborn infants are megakaryoblasts, providing a comparison population for the authors' larger proposed incidence study.

GATA1 mutations in transient leukemia and acute megakaryoblastic leukemia of Down syndrome

Children with constitutional trisomy 21 (Down syndrome) have an approximately 500-fold increased risk of developing acute megakaryoblastic leukemia (AMKL), a form of acute myeloid leukemia. Unique to newborn infants with Down syndrome is a transient leukemia (TL), also referred to as transient myeloproliferative syndrome, that undergoes spontaneous remission in the majority of cases but in approximately 20% is followed by AMKL later in life. Recently mutations of the gene encoding the hematopoietic transcription factor GATA1 were shown to be specific for AMKL of Down syndrome. Here, we demonstrate that GATA1 mutations are present in blasts of TL and show the identical GATA1 mutation in sequential samples collected from a patient during TL and subsequent AMKL. These findings suggest a model of malignant transformation in Down syndrome AMKL in which GATA1 mutations are an early event and AMKL arises from latent TL clones following initial apparent remission.

The childhood leukemias

Advances in treatment and prognosis of childhood leukemia are considered a remarkable success of modern medicine. Childhood leukemia, once considered a universally fatal disease, now boasts overall cure rates ranging from 75% to 85% for acute lymphocytic leukemia (ALL) and cure rates approaching 40% to 50% for acute myelogenous leukemia (AML). Inherent to this success is the expertise nurses provide when caring for children with leukemia. Understanding the classifications of leukemia and the specific therapies help direct the specialized care children with leukemia need. This article provides an overview of childhood leukemias, diagnostic and classification methods used to differentiate and evaluate childhood leukemias, and treatment strategies applied toward various forms of childhood leukemias.