SEARCH

SEARCH BY CITATION

Keywords:

  • Down syndrome;
  • acute myeloid leukaemia;
  • transient myeloproliferative disorder;
  • GATA1;
  • trisomy 21

Summary

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

Children with Down syndrome (DS) have a marked increase in susceptibility to Acute Megakaryoblastic Leukaemia (DS-AMKL) and the closely linked neonatal preleukaemic syndrome, Transient Myeloproliferative Disorder (DS-TMD). The distinct stages of DS-TMD and DS-AMKL provide an excellent tractable model to study leukaemogenesis. This review focuses on recent studies describing clinical, haematological and biological features of DS-AMKL and DS-TMD. The findings from these studies suggest that mutations in the key haemopoietic regulator GATA1 (GATA binding protein 1) in DS-AMKL and DS-TMD may be useful in diagnosis and assessing minimal residual disease. These findings raise the possibility of population-based screening strategies for DS-TMD and the development of treatment to eliminate the preleukaemic TMD clone to prevent DS-AMKL. Advances in our understanding of perturbed haemopoiesis in DS, the role of GATA1 and of cooperating mutations are also discussed. These findings have implications for leukaemia biology more broadly given the frequency of acquired trisomy in other human leukaemias.

Children with Down syndrome (DS) have a markedly increased risk of developing acute leukaemia compared to individuals without DS even though their risk of developing solid tumours is much lower than the general population (Hasle et al, 2000; Patja et al, 2006). In the last 6 years there has been particular interest in acute leukaemias in DS following a number of key papers which provided important insight into the molecular basis of both DS-associated Acute Myeloid Leukaemia (AML) [reviewed in (Vyas & Crispino, 2007)] and Acute Lymphoblastic Leukaemia (ALL) (Bercovich et al, 2008; Kearney et al, 2009). AML in DS has a number of distinct features, which make it, and the closely linked neonatal syndrome, Transient Myeloproliferative Disorder (TMD), an excellent in vivo multi-step model of myeloid leukaemogenesis. This review outlines the clinical and haematological features of DS AML and TMD and discusses recent advances in our understanding of the molecular pathogenesis of these conditions.

Brief overview of DS

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

DS due to Trisomy 21 (T21) is the commonest chromosomal abnormality in humans. The most recent data for DS in the UK comes from the National Down Syndrome Cytogenetic Register (NDSCR), which reported a total of 1877 diagnoses of DS in the UK in 2006 (http://www.wolfson.qmul.ac.uk/ndscr/reports/NDCSRreport0708.pdf). In 1132 cases (60%) the diagnosis was made antenatally; >90% of these resulted in terminations; and there was a total of 767 live births with DS, giving a prevalence of 1·2 children with DS per 1000 live births. First described by Down in 1866, this multi-system disorder was only recognised in 1959 as resulting from the presence of three copies (trisomy) of all (or part) of chromosome 21, usually in all cells (Lejeune et al, 1959). A review of DS is out of the scope of this article and can be found elsewhere (Roizen & Patterson, 2003; Hoyme, 2004). Importantly, haematological abnormalities are common (Webb et al, 2007).

Haematological abnormalities in DS

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

The spectrum of haematological abnormalities in newborns and children with DS includes a variety of benign and malignant abnormalities of the blood count and blood film (Starc, 1992; David et al, 1996; Kivivuori et al, 1996; Watts et al, 1999; de Hingh et al, 2005; Henry et al, 2007; Webb et al, 2007) which are summarised in Table I.

Table I.   Haematological abnormalities in Down syndrome.
Neonates
 Transient myeloproliferative disorder (TMD); also known as Transient Abnormal Myelopoiesis (TAM)
 Non-specific changes: neutropenia, thrombocytopenia, increased peripheral blood nucleated red cells and polycythaemia
 Abnormal myeloid cell granulation, giant platelets
Infants and children
 Acute myeloid (megakaryoblastic) leukaemia (AMKL)
 Myelodysplasia
 Acute lymphoblastic leukaemia

In addition, population-based (Hasle et al, 2000) and cancer-based registries (Zipursky et al, 1992; Hasle et al, 2000; Zipursky, 2000) and clinical trials [reviewed in (Lange, 2000)] indicate that there is between a 10- to 27-fold increased risk of ALL in patients with DS and a 46- to 83-fold increased risk of AML with a particular susceptibility to acute megakaryoblastic disease (DS-AMKL). The overall incidence of leukaemia in DS is estimated to be in the order of 10- to 36-fold excess risk. There is also a virtually unique predisposition to TMD, a clonal disorder characterised by circulating peripheral blast cells and dysplastic features, most marked in the red cell and megakaryocyte lineages.

Clinical and haematological features of AMKL in DS

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

One of the most characteristic features of DS-associated AML is that the vast majority of cases of AML in DS (c. 70%) are megakaryoblastic (Gamis et al, 2003; Zeller et al, 2005). AMKL in DS has a number of distinct features and it is now considered a specific sub-type of AML in DS in the World Health Organization (WHO) classification (Hasle et al, 2003) called Myeloid Leukaemia of Down Syndrome (ML-DS). As well as the characteristic megakaryoblastic morphology and immunophenotype, virtually all cases of DS-AMKL occur within the first 5 years of life (Hasle et al, 2008), have a distinct molecular signature (discussed below) (Bourquin et al, 2006) and have the characteristic antecedent preleukaemic TMD in 20–30% of cases. By contrast, cases of AML occurring in older DS patients are rarely megakaryoblastic and are much less common (Hasle et al, 2008).

Overt leukaemia in DS children is preceded in about 70% of cases by an indolent pre-phase, characterised by thrombocytopenia and dysplastic changes in the bone marrow, often with accompanying marrow fibrosis, which may last several months or even years before it progresses to overt AMKL and may or may not be preceded by a clinical diagnosis of TMD (Lange et al, 1998; Creutzig et al, 2005). The median age at presentation of AMKL is 1·8 years (Creutzig et al, 2005). Other presenting characteristics of AMKL are also distinct from those with sporadic AML: most patients have a low presenting white blood cell (WBC) count and do not show meningeal involvement; the blood typically shows reduced numbers of normal cells, with dysplastic changes in all myeloid lineages, and circulating blasts (Fig 1); the bone marrow aspirate and trephine show dysplasia, increased blasts, abnormal megakaryocytes and variable myelofibrosis (Gamis et al, 2003; Creutzig et al, 2005; Ross et al, 2005; Zeller et al, 2005; Rao et al, 2006; Webb et al, 2007). Immunophenotypically AMKL blasts typically co-express stem/progenitor cell markers (CD34, CD33, CD117) myeloid (CD33), megakaryocytic (CD42b and CD41) and erythroid markers (CD36 and Glycophorin A) as well as the T cell marker, CD7 (Yumura-Yagi et al, 1992; Karandikar et al, 2001; Langebrake et al, 2005).

image

Figure 1.  Blast cells and giant platelets in peripheral blood from a child with DS-AMKL.

Download figure to PowerPoint

Although the morphological, immunophenotypic and cytochemical profile of the blasts is similar to that of blasts seen in TMD (see later) (Creutzig et al, 1996; Lange et al, 1998; Langebrake et al, 2005; Massey et al, 2006), the cytogenetic profile in DS-AMKL is distinct from TMD in which cytogenetic abnormalities, apart from T21, are uncommon (Forestier et al, 2008). Neither the non-random favourable cytogenetic changes that characterise sporadic AML, such as t(8;21), t(15;17), t(9;11) and inv(16), nor the AMKL-associated translocations, t(1;22) and t(1;3), occur in DS-associated AMKL [reviewed in (Lange, 2000; Malinge et al, 2009)]. Unlike sporadic AML, the cytogenetic abnormalities do not provide clear insight into the molecular pathogenesis of DS-AMKL. The most frequently occurring cytogenetic abnormalities are additional copies of chromosome 8 and/or 21 (in addition to the +21c), which each occur in c. 10–15% of cases (Creutzig et al, 1996; Lange et al, 1998; Forestier et al, 2008). Monosomy 7 and –5/5q- can also be observed (together in c. 10–20% of cases). Unlike non-DS AML, where loss of all or part of chromosomes 5 and/or 7 confers an adverse prognosis, the prognostic impact in DS-AMKL is unclear (Gamis et al, 2003; Gamis, 2005).

Children with DS-AMKL have a superior outcome when compared with children with sporadic AML (Gamis et al, 2003; Creutzig et al, 2005; Zeller et al, 2005; Rao et al, 2006). Recent results show long-term survival for the majority of DS children: the probability of overall survival (pOS) ranges from 74–91% (Nordic group 10-year pOS 74%, = 61; the Children’s Cancer Group (CCG), the CCG 2891 trial, 5-year pOS 79%, = 161; AML- BFM SG (Berlin-Frankfürt-Münster Study Group), 3-year pOS 91%, = 67 and the Medical Research Council (MRC) 5-year pOS, 75%, = 36). Given that most treatment failure in DS children is due to chemotherapy-related toxicity and as a numbers of studies have reported hypersensitivity of DS-AMKL blast cells to chemotherapy compared with AML cells from non-DS individuals (Taub et al, 1997; Frost et al, 2000; Yamada et al, 2001; Zwaan et al, 2002; Ravindranath, 2003), the current European treatment protocol is investigating the efficacy of reduced-intensity chemotherapy (Creutzig et al, 2005). Some investigators have linked blast cell sensitivity in DS-AMKL to a gene-dosage effect of chromosome 21 localized genes, such as cystathionine-beta-synthase, the increased levels of expression of which may contribute to cytarabine sensitivity in DS (Taub et al, 1996, 1999, 2000; Taub & Ge, 2005). Interestingly, DS ALL cells do not differ in drug sensitivity when compared with non-DS ALL cells, which suggests that sensitivity is cell-lineage specific rather than simply associated with a gene-dosage effect of chromosome 21 localized genes (Frost et al, 2000; Zwaan et al, 2002).

Clinical and haematological features of TMD

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

TMD has a very variable presentation in the fetus and the newborn. Data from three recent prospective series involving more than 200 neonates found a median age at diagnosis of TMD of 3–7 d and almost all cases presented within 2 months of birth (Massey et al, 2006; Klusmann et al, 2008; Muramatsu et al, 2008). A small proportion of newborns (c. 10%) are asymptomatic and only present with circulating blast cells, with or without leucocytosis. Other clinical features include hepatomegaly, splenomegaly, serous effusions and, in up to 10% of patients, liver fibrosis due to blast cell infiltration that can rarely cause fulminant liver failure (Zipursky, 2003; Massey et al, 2006; Klusmann et al, 2008). Leucocytosis and thrombocytopenia are common. Thrombocytosis is more rarely seen. About a quarter of patients have abnormal liver transaminases and abnormal laboratory coagulation parameters (Table II). The blast cells in TMD usually have the ‘blebby’ appearance characteristic of megakaryoblasts and typically express CD33, CD38, CD117, CD34, CD7, CD56, CD36, CD71, CD42b, thrombopoietin receptor, erythropoietin receptor and interleukin 3 receptor-α (Yumura-Yagi et al, 1992; Girodon et al, 2000; Karandikar et al, 2001; Langebrake et al, 2005). TMD may also present during fetal life, usually with hydrops fetalis. Hydrops in a fetus with T21 may be an indication of TMD (Robertson et al, 2003; Heald et al, 2007; Klusmann et al, 2008), as 27% of these fetuses were found to have myeloproliferative disorder by Smrcek et al (2001).

Table II.   Summary of clinical and haematological features of TMD.
Cardiopulmonary
 Pericardial effusion
 Pulmonary oedema
Liver
 Hepatosplenomegaly
 Hepatic fibrosis
 Obstructive jaundice
 Liver failure
 Ascites
Haematological
 Leucocytosis (or white cell count may be normal)
 Abnormal platelet count: reduced or raised (may be normal) Haemoglobin: may be reduced, raised or normal
 Increased peripheral blood blast cells
Other
 Skin rash

Though the frequency of TMD is estimated to be around 10%, the true incidence of TMD is unknown as it can occur in asymptomatic neonates, and blood counts and blood films are not routinely performed on newborns with DS. Moreover, even when circulating blasts are detected the diagnosis can be difficult. Circulating immature blasts may be present in the peripheral blood of unwell babies without TMD. Diagnostic difficulty is also common in infants with phenotypically normal mosaic DS in which the only clue to the diagnosis is a blood film picture typical of TMD. We suggest that all newborns with DS should have a full blood count and blood film within the first week of life; if there are any haematological or clinical findings suggestive of TMD, analysis of peripheral blood cells for GATA1 mutation is strongly recommended as GATA1 mutations are a hallmark of TMD. Babies that have a GATA1 mutation should then be followed up 3 monthly to monitor development of AMKL (see below). A bone marrow aspirate is not necessary as findings in the marrow mirror those in blood (and often are less impressive), and add little where the diagnosis is indicated by clinical findings and examination of the blood (Massey et al, 2006; Webb et al, 2007).

Most neonates with TMD do not need chemotherapy as the clinical and laboratory abnormalities spontaneously resolve within 3–6 months after birth. However, symptomatic babies with TMD, especially those with high blast counts or liver dysfunction, may benefit from low-dose cytosine arabinoside. Chemotherapy is usually given at the treating physician’s discretion and various groups have reported similar dosage schedules and response. In the Pediatric Oncology Group (POG) study 9481, 10 mg/m2 per dose or 1·2–1·5 mg/kg per dose was given subcutaneously or intravenously by slow injection twice a day for 7 d (Massey et al, 2006). In the AML-BFM study, 0·5–1·5 mg/kg was administered for 3–12 d (Klusmann et al, 2008). As TMD blasts are highly sensitive to cytarabine, there is generally a rapid response, characterised by the disappearance of peripheral blasts by day 7 of treatment. However, this is not always the case, especially in babies with severe liver disease associated with fibrosis. Here the response to chemotherapy is poor and overall there is a poor prognosis. Overall, TMD has been reported to have a mortality of c. 20%. (Zipursky, 2003; Massey et al, 2006; Klusmann et al, 2008; Muramatsu et al, 2008).

Although TMD resolves in the majority of DS infants, c. 20–30% subsequently go on to develop full-blown AMKL, usually within in the first 4 years of life (Zipursky, 2003; Massey et al, 2006; Klusmann et al, 2008; Muramatsu et al, 2008). AMKL develops either by overt progression or after an apparent remission of TMD with AMKL arising many months later, presumably from a subclone of persisting TMD cells that acquire a selective advantage. This hypothesis can be tested by monitoring the size of the mutant TMD clone, either by immunophenotype or quantitative GATA1 polymerase chain reaction, ideally in peripheral blood. If the hypothesis is shown to be correct by this means, the practical significance would be that one could follow babies who have had TMD that has resolved and predict which babies may later develop AMKL. The implications of this are discussed in Future Directions.

TMD and AMKL as a model of myeloid leukaemogenesis

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

A number of lines of evidence point to TMD and DS-associated AMKL being linked clonal conditions with a distinct pathogenetic basis tightly linked to T21. First, haemopoietic cells in both conditions are uniquely marked by the presence of acquired, N-terminal truncating mutations in the key megakaryocyte-erythroid transcription factor, GATA1 (Wechsler et al, 2002; Groet et al, 2003; Hitzler et al, 2003; Rainis et al, 2003; Xu et al, 2003; Ahmed et al, 2004). GATA1 mutations occur at high frequency in T21 patients (c. 4%) of all DS neonates from a recent study of 526 neonatal blood spots (Pine et al, 2007) and 25% of patients with DS-AMKL have multiple, independent GATA1 mutations (Ahmed et al, 2004). GATA1 mutations are not detected in other DS and non-DS leukaemias. Importantly, similar N-terminal GATA1 mutations, in the absence of T21, cause quite a different phenotype with anaemia and neutropenia but are not leukaemogenic (Hollanda et al, 2006).

The importance of T21 is underscored by the observation of rare TMD/AMKL cases in non-DS neonates who have T21 only in their haemopoietic cells (Rainis et al, 2003; Carpenter et al, 2005; Cushing et al, 2006). Further, GATA1 mutations are not detectable in remission samples after treatment of DS-AMKL establishing that they do contribute to the pathogenesis of the leukaemia [reviewed in (Vyas & Crispino, 2007)]. In addition, in cases of TMD progressing to AMKL, the same GATA1 mutations have been found in both TMD and AMKL cells, confirming the clonal relationship between the two disorders (Ahmed et al, 2004). (Fig 2A). TMD and AMKL blasts also have an identical, or very similar, and distinct immunophenotype, as described above (Langebrake et al, 2005).

image

Figure 2.  TMD, AMKL and GATA1 mutations. (A) Our model for the relationship between acquisition of GATA1 mutations, clone size and phenotype of TMD and AMKL. (B) Location and consequence of acquired mutations in GATA1. Genomic DNA encoding GATA1 is shown. The exons are depicted as boxes and numbered. The open parts of the exons are 5′ and 3′ non-coding regions. The shaded areas are coding regions. Positions of the two translational start sites (ATG) are marked by arrowheads. Locations of acquired GATA1 mutations in TMD and AMKL are shown as grey rounded pins. The effect of the mutations is the production of GATA1s protein.

Download figure to PowerPoint

Thus, there are three known distinct sets of genetic events in the pathogenesis of DS TMD/AMKL. First, a fetal haemopoietic cell needs to be trisomic for chromosome 21. Second, acquired fetal GATA1 mutations are required. Given the high frequency of GATA1 mutations in T21 neonatal blood cells and that children with DS are not cancer prone in general, this suggests that the T21/GATA1 interaction imparts a selective advantage rather than the T21 being a mutator phenotype. Finally, as not all TMD cases progress to AMKL, additional, as yet unidentified, genetic or epigenetic events are required for progression to AMKL.

The role of T21 in DS-AMKL and TMD

Several lines of evidence indicate the leukaemia-initiating population in DS-AMKL is in the fetal liver. First, the natural history of TMD provides strong indirect evidence of involvement of fetal liver haemopoietic stem cells (HSC)/progenitor cells: the disease develops in utero and spontaneously resolves within months of birth as haemopoiesis in fetal liver ceases and fully switches to bone marrow (BM) (Zipursky, 2003; Massey et al, 2006; Klusmann et al, 2008; Muramatsu et al, 2008). Second, severe TMD cases have progressive blast cell liver infiltration with relative sparing of BM (Zipursky, 2003). Third, data from transgenic mice expressing N-terminal truncated GATA1 show an altered megakaryocyte lineage proliferation/differentiation phenotype only in fetal liver progenitors and not post-natal cells (Li et al, 2005). Finally, our laboratory recently found, for the first time, that perturbation of the fetal liver haemopoietic compartment in human DS precedes acquisition of GATA1 mutations, with an expansion of megakaryocyte-erythroid progenitors (MEP) and increased clonogenicity (Tunstall-Pedoe et al, 2008). This was confirmed by others, who also showed T21 fetal liver CD34+ cells had enhanced erythroid and megakaryocytic engraftment in a murine xenograft transplantation assay (Chou et al, 2008). The combination of these studies suggests that critical aspects of myeloid progenitor cell self-renewal and lineage selection are altered in human fetal DS.

The molecular basis of this perturbation in haemopoiesis is unclear. T21 may impact on biology in multiple complex ways (Roper & Reeves, 2006). Many T21 genes may affect fetal haemopoiesis, either primarily or via other cell types, and the effects may be exerted indirectly via disomic genes. However, despite the potential complexity of downstream consequences, the primary genetic lesion is altered DNA dosage of all or part of chromosome 21. Genotype-phenotype studies in DS children with partial T21 have led to the identification and progressive refinement of the ‘Down syndrome Critical Region’ (DSCR), which is now estimated to cover a 4·3–5·4 Mb region of chromosome 21 on q22. (Delabar et al, 1993; Ronan et al, 2007) This potentially reduces the number of candidate genes involved in DS leukaemogenesis although the functional correlation between DSCR genes and clinical phenotype is still controversial (Lyle et al, 2008).

Plausible candidate genes with roles in megakaryocyte/erythroid differentiation or leukaemogenesis and which have been investigated in DS-AMKL and TMD include RUNX1, BACH1 and ETS2 and ERG (Rainis et al, 2003; Bourquin et al, 2006; Stankiewicz & Crispino, 2009). However, none of these genes has been shown to definitively play a role in DS-AMKL and/or TMD. Two microarray studies comparing DS-AMKL with AMKL in non-DS patients have been reported, which have in common discriminating patterns of gene expression for 76 genes, including genes relevant to erythropoiesis, such as Glycophorin A (GYPA) and CD36 and megakaryopoiesis, including BACH1, a suppressor of megakaryocyte differentiation (Bourquin et al, 2006; Ge et al, 2006). However, these studies do not shed insight into the key chromosome 21 genes that drive the perturbation of haemopoiesis. There are also five different microRNAs encoded on chromosome 21, four of which are known to be expressed in human megakaryocyte lineage cells: MIR125B1 has been reported to be over expressed in TMD and AMKL samples in comparison with normal megakaryocytes (Klusmann et al, 2007); MIR99A expression increases during normal megakaryocyte differentiation while MIR155 and MIRLET7C are expressed early in differentiation and decrease with megakaryocyte maturation (Garzon et al, 2006).

Another approach to investigating the role of T21 in DS-associated leukaemogenesis is to use mouse models of DS, such as the Ts65Dn mouse, which is trisomic for segments of mouse chromosome 16 including orthologues of many of the genes on Hsa21 (Kirsammer et al, 2008), or Tc-1 mice, which contain an almost complete copy of Hsa21 (O’Doherty et al, 2005). Although megakaryopoiesis is abnormal in these Ts65Dn mice, they do not develop leukaemia or a TMD-like picture (Kirsammer et al, 2008). Similarly, Tc-1 mice do not develop leukaemia and appear to have no significant haematological abnormalities although other aspects of human DS are recapitulated in these mice (O’Doherty et al, 2005; Galante et al, 2009). These data, as well as the data from mice engineered to express GATA1s in place of full length GATA1 (see below) (Li et al, 2005), mean that human studies will be essential in identifying the key molecular events resulting from T21 in DS haemopoietic cells.

The role of GATA1 in DS-AMKL and TMD

Although the DNA mutations of GATA1 are varied, and may consist of large or small deletions and insertions in Exon 2 or at the beginning of Exon 3, the functional consequences are predicted to always result in exclusive production of a shorter GATA1 protein (GATA1s) with an N-terminal 84-amino-acid truncation (Fig 2B). The mechanism(s) by which the N-terminus truncated mutations of GATA1 transform haemopoietic cells have been investigated in murine models (Kuhl et al, 2005; Li et al, 2005; Muntean & Crispino, 2005). Retrovirus-mediated expression of GATA1s in murine fetal GATA1-deficient megakaryocyte progenitors showed that GATA1s had impaired ability to regulate their excessive proliferation compared to full length GATA1 (Kuhl et al, 2005; Muntean & Crispino, 2005). Similarly, generation of mice with ‘knock in’ mutations, which generate exclusively GATA1s, exhibit abnormal proliferation and differentiation of megakaryocyte progenitors; these effects were noted only in fetal, and not post-natal, progenitors (Li et al, 2005). Gene expression profiles of murine megakaryocytes expressing GATA1s versus full length GATA1 suggest that changes in GATA1-mediated regulation of a number of other transcription factors, including GATA2, IKZF1, MYB and MYC, are likely to be responsible for at least some of the functional effects of GATA1s expression in fetal megakaryocytes (Li et al, 2005). It is also possible that there are significant effects not only directly attributable to GATA1s but due to the loss of expression of full length GATA1, as suggested by the data from Stachura et al (2006) who showed that loss of full length GATA1 expression impaired growth and differentiation of murine fetal/embryonic haemopoietic progenitors.

Gene expression profiling of primary haemopoietic cells from DS-AMKL and TMD patients has also been used to investigate the role of GATA1s in human DS (Lightfoot et al, 2004; McElwaine et al, 2004; Bourquin et al, 2006; Ge et al, 2006). These have identified distinct expression ‘signatures’, which distinguish DS-AMKL from non-DS AMKL and identify some of the genes that may be involved, including GATA1 itself, BACH1, SON and, supporting the murine data, GATA2 and MYC (Bourquin et al, 2006).

One area of continuing uncertainty and great interest is the extent to which differential interaction of GATA1s and full length GATA1 with RUNX1 might be involved in DS-AMKL [reviewed in (Vyas & Crispino, 2007)]. RUNX1 is an attractive candidate becuase it is found on the DSCR, mutations in the DNA-binding domain of RUNX1 are found in AML with acquired T21 (Preudhomme et al, 2000) and there is some evidence that RUNX1 interacts with GATA1 during megakaryocyte differentiation (Elagib et al, 2003). However, RUNX1 trisomy is not required for abnormal megakaryopoiesis in the Ts65Dn mouse model (Kirsammer et al, 2008) and preliminary gene expression studies do not show significantly increased RUNX1 expression either in T21 fetal liver (Chou et al, 2008; Tunstall-Pedoe et al, 2008) or in DS-AMKL compared to non-DS AMKL (Bourquin et al, 2006). In addition, recent data suggest that the N-terminal sequences of GATA1 may not be required for RUNX1 binding (Xu et al, 2006).

Interaction between T21 and GATA1s.  A key question is the nature of the biological and molecular interaction between T21 and acquisition of an N-terminal GATA1 mutation that results in the characteristic phenotype of TMD and AMKL. Biological synergy is also seen in other leukaemias, for example KIT mutation in Core Binding Factor (CBF) leukaemia. These cases of synergy probably arise where biological pathways affected by the leukaemogenic changes intersect and cooperate to provide synergistic growth advantage. Thus, as T21 by itself profoundly increases the frequency of MEP, we have speculated that this expanded cell compartment may provide an expanded pool of cells in which N-terminal GATA1 mutations are further selected as they have an additional selective growth advantage. The molecular mechanisms that underpin this suggested synergy will be important to elucidate and are likely to provide general principles that will be of wider interest in the leukaemia field.

Molecular pathogenesis of progression of TMD to AMKL

The data reviewed above strongly suggest that T21 and GATA1 mutations together are insufficient to cause AMKL in DS. The additional mutations needed to transform TMD blast cells are not known although mutations in several candidate genes have been identified recently, including JAK3, JAK2, TP53 and FLT3 (Malkin et al, 2000; Hirose et al, 2003; De Vita et al, 2007; Kiyoi et al, 2007; Klusmann et al, 2007; Norton et al, 2007; Malinge et al, 2008; Sato et al, 2008) (Walters et al, 2006). The role of these mutations is not yet clear. JAK2 and FLT3 mutations appear to occur in a small proportion of cases (2/32 and 2/35 cases tested, respectively) whereas JAK3 mutations have been reported in seven patients (out of 53 tested) and TP53 in six patients (out of 28 tested) [reviewed in (Malinge et al, 2009)]. In contrast to the JAK2 mutations found in myeloproliferative disorders and in DS-ALL, the JAK3 mutations in DS-AMKL are heterogeneous both in their distribution within the gene and their functional effects (Walters et al, 2006; De Vita et al, 2007; Malinge et al, 2008; Sato et al, 2008).

Future directions

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

DS-AMKL and TMD have provided fascinating insights into the steps by which normal HSC/progenitors are transformed into leukaemic cells and the role of T21 in this process. These findings have implications for leukaemogenesis in general, particularly given the frequency of acquired T21 in other human leukaemias. The identification of GATA1 mutations in virtually all cases of TMD and AMKL offers the potential to accelerate and refine the diagnosis of TMD, hitherto a descriptive diagnosis, and to accurately measure the kinetics of the mutant GATA1 clone as a tool for minimal residual disease measurement. The next few years are likely to yield significant new insights into TMD and AMKL. Ongoing prospective population-based studies in the UK from our group and those in Europe are likely to define normal haematological parameters for newborns with DS and, more specifically, the incidence of TMD and the haematology of TMD. Ongoing studies will also address the role of monitoring GATA1 mutant clone in TMD as a means to identify infants at higher risk of developing AMKL. Groups are also addressing the question of whether pre-emptive chemotherapy treatment of babies with TMD could prevent DS-AMKL. This is an important question but it will be critical to consider who merits treatment (as only 20–30% of babies with TMD will develop AMKL) and what the optimal treatment schedule is required. Ideally, one would want to identify the group at high risk (or certain risk) of developing DS-AMKL to enrol in a clinical trial. It is likely that components of the molecular mechanism of how T21 and GATA1s perturb haemopoieisis (target genes and pathways), and how these two genetic changes synergise to promote transformation will be unravelled. Additional genetic and epigenetic changes may also come to light. Ultimately, these principles may well transfer across not only to DS-ALL but other leukaemias more generally.

Acknowledgements

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References

AR and AN are Leukaemia Research Fund Clinical Research Fellows. Research in Down syndrome leukaemias in IR and PV’s laboratories is funded by a Programme Grant from the Leukaemia Research Fund. IR is funded in part by the Imperial College London Comprehensive Biomedical Research Centre and PV in part by the Oxford Partnership Comprehensive Biomedical Research Centre, both of which received funding from the Department of Health’s NIHR Biomedical Research Centres funding scheme.

References

  1. Top of page
  2. Summary
  3. Brief overview of DS
  4. Haematological abnormalities in DS
  5. Clinical and haematological features of AMKL in DS
  6. Clinical and haematological features of TMD
  7. TMD and AMKL as a model of myeloid leukaemogenesis
  8. Future directions
  9. Acknowledgements
  10. References
  • Ahmed, M., Sternberg, A., Hall, G., Thomas, A., Smith, O., O’Marcaigh, A., Wynn, R., Stevens, R., Addison, M., King, D., Stewart, B., Gibson, B., Roberts, I. & Vyas, P. (2004) Natural history of GATA1 mutations in Down syndrome. Blood, 103, 24802489.
  • Bercovich, D., Ganmore, I., Scott, L.M., Wainreb, G., Birger, Y., Elimelech, A., Shochat, C., Cazzaniga, G., Biondi, A., Basso, G., Cario, G., Schrappe, M., Stanulla, M., Strehl, S., Haas, O.A., Mann, G., Binder, V., Borkhardt, A., Kempski, H., Trka, J., Bielorei, B., Avigad, S., Stark, B., Smith, O., Dastugue, N., Bourquin, J.P., Tal, N.B., Green, A.R. & Izraeli, S. (2008) Mutations of JAK2 in acute lymphoblastic leukaemias associated with Down’s syndrome. Lancet, 372, 14841492.
  • Bourquin, J.P., Subramanian, A., Langebrake, C., Reinhardt, D., Bernard, O., Ballerini, P., Baruchel, A., Cave, H., Dastugue, N., Hasle, H., Kaspers, G.L., Lessard, M., Michaux, L., Vyas, P., Van Wering, E., Zwaan, C.M., Golub, T.R. & Orkin, S.H. (2006) Identification of distinct molecular phenotypes in acute megakaryoblastic leukemia by gene expression profiling. Proceedings of the National Academy of Sciences of the United States of America, 103, 33393344.
  • Carpenter, E., Valverde-Garduno, V., Sternberg, A., Mitchell, C., Roberts, I., Vyas, P. & Vora, A. (2005) GATA1 mutation and trisomy 21 are required only in haematopoietic cells for development of transient myeloproliferative disorder. British Journal of Haematology, 128, 548551.
  • Chou, S.T., Opalinska, J.B., Yao, Y., Fernandes, M.A., Kalota, A., Brooks, J.S., Choi, J.K., Gewirtz, A.M., Danet-Desnoyers, G.A., Nemiroff, R.L. & Weiss, M.J. (2008) Trisomy 21 enhances human fetal erythro-megakaryocytic development. Blood, 112, 45034506.
  • Creutzig, U., Ritter, J., Vormoor, J., Ludwig, W.D., Niemeyer, C., Reinisch, I., Stollmann-Gibbels, B., Zimmermann, M. & Harbott, J. (1996) Myelodysplasia and acute myelogenous leukemia in Down’s syndrome. A report of 40 children of the AML-BFM Study Group. Leukemia, 10, 16771686.
  • Creutzig, U., Reinhardt, D., Diekamp, S., Dworzak, M., Stary, J. & Zimmermann, M. (2005) AML patients with Down syndrome have a high cure rate with AML-BFM therapy with reduced dose intensity. Leukemia, 19, 13551360.
  • Cushing, T., Clericuzio, C.L., Wilson, C.S., Taub, J.W., Ge, Y., Reichard, K.K. & Winter, S.S. (2006) Risk for leukemia in infants without Down syndrome who have transient myeloproliferative disorder. Journal of Pediatrics, 148, 687689.
  • David, O., Fiorucci, G.C., Tosi, M.T., Altare, F., Valori, A., Saracco, P., Asinardi, P., Ramenghi, U. & Gabutti, V. (1996) Hematological studies in children with Down syndrome. Pediatric Hematology and Oncology, 13, 271275.
  • De Vita, S., Mulligan, C., McElwaine, S., Dagna-Bricarelli, F., Spinelli, M., Basso, G., Nizetic, D. & Groet, J. (2007) Loss-of-function JAK3 mutations in TMD and AMKL of Down syndrome. British Journal of Haematology, 137, 337341.
  • Delabar, J.M., Theophile, D., Rahmani, Z., Chettouh, Z., Blouin, J.L., Prieur, M., Noel, B. & Sinet, P.M. (1993) Molecular mapping of twenty-four features of Down syndrome on chromosome 21. European Journal of Human Genetics, 1, 114124.
  • Elagib, K.E., Racke, F.K., Mogass, M., Khetawat, R., Delehanty, L.L. & Goldfarb, A.N. (2003) RUNX1 and GATA-1 coexpression and cooperation in megakaryocytic differentiation. Blood, 101, 43334341.
  • Forestier, E., Izraeli, S., Beverloo, B., Haas, O., Pession, A., Michalova, K., Stark, B., Harrison, C.J., Teigler-Schlegel, A. & Johansson, B. (2008) Cytogenetic features of acute lymphoblastic and myeloid leukemias in pediatric patients with Down syndrome: an iBFM-SG study. Blood, 111, 15751583.
  • Frost, B.M., Gustafsson, G., Larsson, R., Nygren, P. & Lonnerholm, G. (2000) Cellular cytotoxic drug sensitivity in children with acute leukemia and Down’s syndrome: an explanation to differences in clinical outcome? Leukemia, 14, 943944.
  • Galante, M., Jani, H., Vanes, L., Daniel, H., Fisher, E.M., Tybulewicz, V.L., Bliss, T.V. & Morice, E. (2009) Impairments in motor coordination without major changes in cerebellar plasticity in the Tc1 mouse model of Down syndrome. Human Molecular Genetics, 18, 14491463.
  • Gamis, A.S. (2005) Acute myeloid leukemia and Down syndrome evolution of modern therapy – state of the art review. Pediatric Blood & Cancer, 44, 1320.
  • Gamis, A.S., Woods, W.G., Alonzo, T.A., Buxton, A., Lange, B., Barnard, D.R., Gold, S. & Smith, F.O. (2003) 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. Journal of Clinical Oncology, 21, 34153422.
  • Garzon, R., Pichiorri, F., Palumbo, T., Iuliano, R., Cimmino, A., Aqeilan, R., Volinia, S., Bhatt, D., Alder, H., Marcucci, G., Calin, G.A., Liu, C.G., Bloomfield, C.D., Andreeff, M. & Croce, C.M. (2006) MicroRNA fingerprints during human megakaryocytopoiesis. Proceedings of the National Academy of Sciences of the United States of America, 103, 50785083.
  • Ge, Y., Dombkowski, A.A., LaFiura, K.M., Tatman, D., Yedidi, R.S., Stout, M.L., Buck, S.A., Massey, G., Becton, D.L., Weinstein, H.J., Ravindranath, Y., Matherly, L.H. & Taub, J.W. (2006) Differential gene expression, GATA1 target genes, and the chemotherapy sensitivity of Down syndrome megakaryocytic leukemia. Blood, 107, 15701581.
  • Girodon, F., Favre, B., Couillaud, G., Carli, P.M., Parmeland, C. & Maynadie, M. (2000) Immunophenotype of a transient myeloproliferative disorder in a newborn with trisomy 21. Cytometry, 42, 118122.
  • Groet, J., McElwaine, S., Spinelli, M., Rinaldi, A., Burtscher, I., Mulligan, C., Mensah, A., Cavani, S., Dagna-Bricarelli, F., Basso, G., Cotter, F.E. & Nizetic, D. (2003) Acquired mutations in GATA1 in neonates with Down’s syndrome with transient myeloid disorder. Lancet, 361, 16171620.
  • Hasle, H., Clemmensen, I.H. & Mikkelsen, M. (2000) Risks of leukaemia and solid tumours in individuals with Down’s syndrome. Lancet, 355, 165169.
  • Hasle, H., Niemeyer, C.M., Chessells, J.M., Baumann, I., Bennett, J.M., Kerndrup, G. & Head, D.R. (2003) A pediatric approach to the WHO classification of myelodysplastic and myeloproliferative diseases. Leukemia, 17, 277282.
  • Hasle, H., Abrahamsson, J., Arola, M., Karow, A., O’Marcaigh, A., Reinhardt, D., Webb, D.K., Van Wering, E., Zeller, B., Zwaan, C.M. & Vyas, P. (2008) Myeloid leukemia in children 4 years or older with Down syndrome often lacks GATA1 mutation and cytogenetics and risk of relapse are more akin to sporadic AML. Leukemia, 22, 14281430.
  • Heald, B., Hilden, J.M., Zbuk, K., Norton, A., Vyas, P., Theil, K.S. & Eng, C. (2007) Severe TMD/AMKL with GATA1 mutation in a stillborn fetus with Down syndrome. Nature Clinical Practice. Oncology, 4, 433438.
  • Henry, E., Walker, D., Wiedmeier, S.E. & Christensen, R.D. (2007) Hematological abnormalities during the first week of life among neonates with Down syndrome: data from a multihospital healthcare system. American Journal of Medical Genetics. Part A, 143, 4250.
  • De Hingh, Y.C., Van Der Vossen, P.W., Gemen, E.F., Mulder, A.B., Hop, W.C., Brus, F. & De Vries, E. (2005) Intrinsic abnormalities of lymphocyte counts in children with down syndrome. Journal of Pediatrics, 147, 744747.
  • Hirose, Y., Kudo, K., Kiyoi, H., Hayashi, Y., Naoe, T. & Kojima, S. (2003) Comprehensive analysis of gene alterations in acute megakaryoblastic leukemia of Down’s syndrome. Leukemia, 17, 22502252.
  • Hitzler, J.K., Cheung, J., Li, Y., Scherer, S.W. & Zipursky, A. (2003) GATA1 mutations in transient leukemia and acute megakaryoblastic leukemia of Down syndrome. Blood, 101, 43014304.
  • Hollanda, L.M., Lima, C.S., Cunha, A.F., Albuquerque, D.M., Vassallo, J., Ozelo, M.C., Joazeiro, P.P., Saad, S.T. & Costa, F.F. (2006) An inherited mutation leading to production of only the short isoform of GATA-1 is associated with impaired erythropoiesis. Nature Genetics, 38, 807812.
  • Hoyme, F. (2004) Chromosomal clinical abnormalities. In: Nelson’s Textbook of Paediatrics, pp. 384. WB Saunders, Philadelphia.
  • Karandikar, N.J., Aquino, D.B., McKenna, R.W. & Kroft, S.H. (2001) Transient myeloproliferative disorder and acute myeloid leukemia in Down syndrome. An immunophenotypic analysis. American Journal of Clinical Pathology, 116, 204210.
  • Kearney, L., Gonzalez De Castro, D., Yeung, J., Procter, J., Horsley, S.W., Eguchi-Ishimae, M., Bateman, C.M., Anderson, K., Chaplin, T., Young, B.D., Harrison, C.J., Kempski, H., Wai, E.S.C., Ford, A.M. & Greaves, M. (2009) Specific JAK2 mutation (JAK2R683) and multiple gene deletions in Down syndrome acute lymphoblastic leukemia. Blood, 113, 646648.
  • Kirsammer, G., Jilani, S., Liu, H., Davis, E., Gurbuxani, S., Le Beau, M.M. & Crispino, J.D. (2008) Highly penetrant myeloproliferative disease in the Ts65Dn mouse model of Down syndrome. Blood, 111, 767775.
  • Kivivuori, S.M., Rajantie, J. & Siimes, M.A. (1996) Peripheral blood cell counts in infants with Down’s syndrome. Clinical Genetics, 49, 1519.
  • Kiyoi, H., Yamaji, S., Kojima, S. & Naoe, T. (2007) JAK3 mutations occur in acute megakaryoblastic leukemia both in Down syndrome children and non-Down syndrome adults. Leukemia, 21, 574576.
  • Klusmann, J.H., Reinhardt, D., Hasle, H., Kaspers, G.J., Creutzig, U., Hahlen, K., Van Den Heuvel-Eibrink, M.M. & Zwaan, C.M. (2007) Janus kinase mutations in the development of acute megakaryoblastic leukemia in children with and without Down’s syndrome. Leukemia, 21, 15841587.
  • Klusmann, J.H., Creutzig, U., Zimmermann, M., Dworzak, M., Jorch, N., Langebrake, C., Pekrun, A., Macakova-Reinhardt, K. & Reinhardt, D. (2008) Treatment and prognostic impact of transient leukemia in neonates with Down syndrome. Blood, 111, 29912998.
  • Kuhl, C., Atzberger, A., Iborra, F., Nieswandt, B., Porcher, C. & Vyas, P. (2005) GATA1-mediated megakaryocyte differentiation and growth control can be uncoupled and mapped to different domains in GATA1. Molecular and Cellular Biology, 25, 85928606.
  • Lange, B. (2000) The management of neoplastic disorders of haematopoiesis in children with Down’s syndrome. British Journal of Haematology, 110, 512524.
  • Lange, B.J., Kobrinsky, N., Barnard, D.R., Arthur, D.C., Buckley, J.D., Howells, W.B., Gold, S., Sanders, J., Neudorf, S., Smith, F.O. & Woods, W.G. (1998) Distinctive demography, biology, and outcome of acute myeloid leukemia and myelodysplastic syndrome in children with Down syndrome: Children’s Cancer Group Studies 2861 and 2891. Blood, 91, 608615.
  • Langebrake, C., Creutzig, U. & Reinhardt, D. (2005) Immunophenotype of Down syndrome acute myeloid leukemia and transient myeloproliferative disease differs significantly from other diseases with morphologically identical or similar blasts. Klinische Padiatrie, 217, 126134.
  • Lejeune, J., Gautier, M. & Turpin, R. (1959) [Study of somatic chromosomes from 9 mongoloid children.]. Comptes rendus hebdomadaires des séances de l’Académie des sciences, 248, 17211722.
  • Li, Z., Godinho, F.J., Klusmann, J.H., Garriga-Canut, M., Yu, C. & Orkin, S.H. (2005) Developmental stage-selective effect of somatically mutated leukemogenic transcription factor GATA1. Nature Genetics, 37, 613619.
  • Lightfoot, J., Hitzler, J.K., Zipursky, A., Albert, M. & Macgregor, P.F. (2004) Distinct gene signatures of transient and acute megakaryoblastic leukemia in Down syndrome. Leukemia, 18, 16171623.
  • Lyle, R., Bena, F., Gagos, S., Gehrig, C., Lopez, G., Schinzel, A., Lespinasse, J., Bottani, A., Dahoun, S., Taine, L., Doco-Fenzy, M., Cornillet-Lefebvre, P., Pelet, A., Lyonnet, S., Toutain, A., Colleaux, L., Horst, J., Kennerknecht, I., Wakamatsu, N., Descartes, M., Franklin, J.C., Florentin-Arar, L., Kitsiou, S., Ait Yahya-Graison, E., Costantine, M., Sinet, P.M., Delabar, J.M. & Antonarakis, S.E. (2008) Genotype-phenotype correlations in Down syndrome identified by array CGH in 30 cases of partial trisomy and partial monosomy chromosome 21. European Journal of Human Genetics, 17, 454466.
  • Malinge, S., Ragu, C., Della-Valle, V., Pisani, D., Constantinescu, S.N., Perez, C., Villeval, J.L., Reinhardt, D., Landman-Parker, J., Michaux, L., Dastugue, N., Baruchel, A., Vainchenker, W., Bourquin, J.P., Penard-Lacronique, V. & Bernard, O.A. (2008) Activating mutations in human acute megakaryoblastic leukemia. Blood, 112, 42204226.
  • Malinge, S., Izraeli, S. & Crispino, J.D. (2009) Insights into the manifestations, outcomes, and mechanisms of leukemogenesis in Down syndrome. Blood, 113, 26192628.
  • Malkin, D., Brown, E.J. & Zipursky, A. (2000) The role of p53 in megakaryocyte differentiation and the megakaryocytic leukemias of Down syndrome. Cancer Genetics and Cytogenetics, 116, 15.
  • Massey, G.V., Zipursky, A., Chang, M.N., Doyle, J.J., Nasim, S., Taub, J.W., Ravindranath, Y., Dahl, G. & Weinstein, H.J. (2006) 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. Blood, 107, 46064613.
  • McElwaine, S., Mulligan, C., Groet, J., Spinelli, M., Rinaldi, A., Denyer, G., Mensah, A., Cavani, S., Baldo, C., Dagna-Bricarelli, F., Hann, I., Basso, G., Cotter, F.E. & Nizetic, D. (2004) 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. British Journal of Haematology, 125, 729742.
  • Muntean, A.G. & Crispino, J.D. (2005) Differential requirements for the activation domain and FOG-interaction surface of GATA-1 in megakaryocyte gene expression and development. Blood, 106, 12231231.
  • Muramatsu, H., Kato, K., Watanabe, N., Matsumoto, K., Nakamura, T., Horikoshi, Y., Mimaya, J., Suzuki, C., Hayakawa, M. & Kojima, S. (2008) Risk factors for early death in neonates with Down syndrome and transient leukaemia. British Journal of Haematology, 142, 610615.
  • Norton, A., Fisher, C., Liu, H., Wen, Q., Mundschau, G., Fuster, J.L., Hasle, H., Zeller, B., Webb, D.K., O’Marcaigh, A., Sorrell, A., Hilden, J., Gamis, A., Crispino, J.D. & Vyas, P. (2007) Analysis of JAK3, JAK2, and C-MPL mutations in transient myeloproliferative disorder and myeloid leukemia of Down syndrome blasts in children with Down syndrome. Blood, 110, 10771079.
  • O’Doherty, A., Ruf, S., Mulligan, C., Hildreth, V., Errington, M.L., Cooke, S., Sesay, A., Modino, S., Vanes, L., Hernandez, D., Linehan, J.M., Sharpe, P.T., Brandner, S., Bliss, T.V., Henderson, D.J., Nizetic, D., Tybulewicz, V.L. & Fisher, E.M. (2005) An aneuploid mouse strain carrying human chromosome 21 with Down syndrome phenotypes. Science, 309, 20332037.
  • Patja, K., Pukkala, E., Sund, R., Iivanainen, M. & Kaski, M. (2006) Cancer incidence of persons with Down syndrome in Finland: a population-based study. International Journal of Cancer, 118, 17691772.
  • Pine, S.R., Guo, Q., Yin, C., Jayabose, S., Druschel, C.M. & Sandoval, C. (2007) Incidence and clinical implications of GATA1 mutations in newborns with Down syndrome. Blood, 110, 21282131.
  • Preudhomme, C., Warot-Loze, D., Roumier, C., Grardel-Duflos, N., Garand, R., Lai, J.L., Dastugue, N., Macintyre, E., Denis, C., Bauters, F., Kerckaert, J.P., Cosson, A. & Fenaux, P. (2000) High incidence of biallelic point mutations in the Runt domain of the AML1/PEBP2 alpha B gene in Mo acute myeloid leukemia and in myeloid malignancies with acquired trisomy 21. Blood, 96, 28622869.
  • Rainis, L., Bercovich, D., Strehl, S., Teigler-Schlegel, A., Stark, B., Trka, J., Amariglio, N., Biondi, A., Muler, I., Rechavi, G., Kempski, H., Haas, O.A. & Izraeli, S. (2003) Mutations in exon 2 of GATA1 are early events in megakaryocytic malignancies associated with trisomy 21. Blood, 102, 981986.
  • Rao, A., Hills, R.K., Stiller, C., Gibson, B.E., De Graaf, S.S., Hann, I.M., O’Marcaigh, A., Wheatley, K. & Webb, D.K. (2006) 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. British Journal of Haematology, 132, 576583.
  • Ravindranath, Y. (2003) Down syndrome and acute myeloid leukemia: the paradox of increased risk for leukemia and heightened sensitivity to chemotherapy. Journal of Clinical Oncology, 21, 33853387.
  • Robertson, M., De Jong, G. & Mansvelt, E. (2003) Prenatal diagnosis of congenital leukemia in a fetus at 25 weeks’ gestation with Down syndrome: case report and review of the literature. Ultrasound in Obstetrics and Gynecology, 21, 486489.
  • Roizen, N.J. & Patterson, D. (2003) Down’s syndrome. Lancet, 361, 12811289.
  • Ronan, A., Fagan, K., Christie, L., Conroy, J., Nowak, N.J. & Turner, G. (2007) Familial 4.3 Mb duplication of 21q22 sheds new light on the Down syndrome critical region. Journal of Medical Genetics, 44, 448451.
  • Roper, R.J. & Reeves, R.H. (2006) Understanding the basis for Down syndrome phenotypes. PLoS Genetics, 2, e50.
  • Ross, J.A., Spector, L.G., Robison, L.L. & Olshan, A.F. (2005) Epidemiology of leukemia in children with Down syndrome. Pediatric Blood & Cancer, 44, 812.
  • Sato, T., Toki, T., Kanezaki, R., Xu, G., Terui, K., Kanegane, H., Miura, M., Adachi, S., Migita, M., Morinaga, S., Nakano, T., Endo, M., Kojima, S., Kiyoi, H., Mano, H. & Ito, E. (2008) Functional analysis of JAK3 mutations in transient myeloproliferative disorder and acute megakaryoblastic leukaemia accompanying Down syndrome. British Journal of Haematology, 141, 681688.
  • Smrcek, J.M., Baschat, A.A., Germer, U., Gloeckner-Hofmann, K. & Gembruch, U. (2001) Fetal hydrops and hepatosplenomegaly in the second half of pregnancy: a sign of myeloproliferative disorder in fetuses with trisomy 21. Ultrasound in Obstetrics and Gynecology, 17, 403409.
  • Stachura, D.L., Chou, S.T. & Weiss, M.J. (2006) Early block to erythromegakaryocytic development conferred by loss of transcription factor GATA-1. Blood, 107, 8797.
  • Stankiewicz, M.J. & Crispino, J.D. (2009) ETS2 and ERG promote megakaryopoiesis and synergize with alterations in GATA-1 to immortalize hematopoietic progenitor cells. Blood, 113, 33373347.
  • Starc, T.J. (1992) Erythrocyte macrocytosis in infants and children with Down syndrome. Journal of Pediatrics, 121, 578581.
  • Taub, J.W. & Ge, Y. (2005) Down syndrome, drug metabolism and chromosome 21. Pediatric Blood & Cancer, 44, 3339.
  • Taub, J.W., Matherly, L.H., Stout, M.L., Buck, S.A., Gurney, J.G. & Ravindranath, Y. (1996) Enhanced metabolism of 1-beta-D-arabinofuranosylcytosine in Down syndrome cells: a contributing factor to the superior event free survival of Down syndrome children with acute myeloid leukemia. Blood, 87, 33953403.
  • Taub, J.W., Stout, M.L., Buck, S.A., Huang, X., Vega, R.A., Becton, D.L. & Ravindranath, Y. (1997) Myeloblasts from Down syndrome children with acute myeloid leukemia have increased in vitro sensitivity to cytosine arabinoside and daunorubicin. Leukemia, 11, 15941595.
  • Taub, J.W., Huang, X., Matherly, L.H., Stout, M.L., Buck, S.A., Massey, G.V., Becton, D.L., Chang, M.N., Weinstein, H.J. & Ravindranath, Y. (1999) Expression of chromosome 21-localized genes in acute myeloid leukemia: differences between Down syndrome and non-Down syndrome blast cells and relationship to in vitro sensitivity to cytosine arabinoside and daunorubicin. Blood, 94, 13931400.
  • Taub, J.W., Huang, X., Ge, Y., Dutcher, J.A., Stout, M.L., Mohammad, R.M., Ravindranath, Y. & Matherly, L.H. (2000) Cystathionine-beta-synthase cDNA transfection alters the sensitivity and metabolism of 1-beta-D-arabinofuranosylcytosine in CCRF-CEM leukemia cells in vitro and in vivo: a model of leukemia in Down syndrome. Cancer Research, 60, 64216426.
  • Tunstall-Pedoe, O., Roy, A., Karadimitris, A., De La Fuente, J., Fisk, N.M., Bennett, P., Norton, A., Vyas, P. & Roberts, I. (2008) Abnormalities in the myeloid progenitor compartment in Down syndrome fetal liver precede acquisition of GATA1 mutations. Blood, 112, 45074511.
  • Vyas, P. & Crispino, J.D. (2007) Molecular insights into Down syndrome-associated leukemia. Current Opinion in Pediatrics, 19, 914.
  • Walters, D.K., Mercher, T., Gu, T.L., O’Hare, T., Tyner, J.W., Loriaux, M., Goss, V.L., Lee, K.A., Eide, C.A., Wong, M.J., Stoffregen, E.P., McGreevey, L., Nardone, J., Moore, S.A., Crispino, J., Boggon, T.J., Heinrich, M.C., Deininger, M.W., Polakiewicz, R.D., Gilliland, D.G. & Druker, B.J. (2006) Activating alleles of JAK3 in acute megakaryoblastic leukemia. Cancer Cell, 10, 6575.
  • Watts, T.L., Murray, N.A. & Roberts, I.A. (1999) Thrombopoietin has a primary role in the regulation of platelet production in preterm babies. Pediatric Research, 46, 2832.
  • Webb, D., Roberts, I. & Vyas, P. (2007) Haematology of Down syndrome. Archives of Disease in Childhood. Fetal and Neonatal Edition, 92, F503F507.
  • Wechsler, J., Greene, M., McDevitt, M.A., Anastasi, J., Karp, J.E., Le Beau, M.M. & Crispino, J.D. (2002) Acquired mutations in GATA1 in the megakaryoblastic leukemia of Down syndrome. Nature Genetics, 32, 148152.
  • Xu, G., Nagano, M., Kanezaki, R., Toki, T., Hayashi, Y., Taketani, T., Taki, T., Mitui, T., Koike, K., Kato, K., Imaizumi, M., Sekine, I., Ikeda, Y., Hanada, R., Sako, M., Kudo, K., Kojima, S., Ohneda, O., Yamamoto, M. & Ito, E. (2003) Frequent mutations in the GATA-1 gene in the transient myeloproliferative disorder of Down syndrome. Blood, 102, 29602968.
  • Xu, G., Kanezaki, R., Toki, T., Watanabe, S., Takahashi, Y., Terui, K., Kitabayashi, I. & Ito, E. (2006) Physical association of the patient-specific GATA1 mutants with RUNX1 in acute megakaryoblastic leukemia accompanying Down syndrome. Leukemia, 20, 10021008.
  • Yamada, S., Hongo, T., Okada, S., Watanabe, C., Fujii, Y., Hori, H., Yazaki, M., Hanada, R. & Horikoshi, Y. (2001) Distinctive multidrug sensitivity and outcome of acute erythroblastic and megakaryoblastic leukemia in children with Down syndrome. International Journal of Hematology, 74, 428436.
  • Yumura-Yagi, K., Hara, J., Kurahashi, H., Nishiura, T., Kaneyama, Y., Osugi, Y., Sakata, N., Inoue, M., Tawa, A., Okada, S. & Kawa-Ha, K. (1992) Mixed phenotype of blasts in acute megakaryocytic leukaemia and transient abnormal myelopoiesis in Down’s syndrome. British Journal of Haematology, 81, 520525.
  • Zeller, B., Gustafsson, G., Forestier, E., Abrahamsson, J., Clausen, N., Heldrup, J., Hovi, L., Jonmundsson, G., Lie, S.O., Glomstein, A. & Hasle, H. (2005) Acute leukaemia in children with Down syndrome: a population-based Nordic study. British Journal of Haematology, 128, 797804.
  • Zipursky, A. (2000) Susceptibility to leukemia and resistance to solid tumors in Down syndrome. Pediatric Research, 47, 704.
  • Zipursky, A. (2003) Transient leukaemia – a benign form of leukaemia in newborn infants with trisomy 21. British Journal of Haematology, 120, 930938.
  • Zipursky, A., Poon, A. & Doyle, J. (1992) Leukemia in Down syndrome: a review. Pediatric Hematology and Oncology, 9, 139149.
  • Zwaan, C.M., Kaspers, G.J., Pieters, R., Hahlen, K., Huismans, D.R., Zimmermann, M., Harbott, J., Slater, R.M., Creutzig, U. & Veerman, A.J. (2002) Cellular drug resistance in childhood acute myeloid leukemia is related to chromosomal abnormalities. Blood, 100, 33523360.