Acute megakaryoblastic leukaemia (AMKL) and transient myeloproliferative disorder (TMD) in Down syndrome: a multi-step model of myeloid leukaemogenesis

Concise review: preleukemic stem cells: molecular biology and clinical implications of the precursors to leukemia stem cells

Recent experimental evidence has shown that acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) arise from transformed immature hematopoietic cells following the accumulation of multiple stepwise genetic and epigenetic changes in hematopoietic stem cells and committed progenitors. The series of transforming events initially gives rise to preleukemic stem cells (pre-LSC), preceding the formation of fully transformed leukemia stem cells (LSC). Despite the established use of poly-chemotherapy, relapse continues to be the most common cause of death in AML and MDS. The therapeutic elimination of all LSC, as well as pre-LSC, which provide a silent reservoir for the re-formation of LSC, will be essential for achieving lasting cures. Conventional sequencing and next-generation genome sequencing have allowed us to describe many of the recurrent mutations in the bulk cell populations in AML and MDS, and recent work has also focused on identifying the initial molecular changes contributing to leukemogenesis. Here we review recent and ongoing advances in understanding the roles of pre-LSC, and the aberrations that lead to pre-LSC formation and subsequent LSC transformation.

Transient myeloproliferative disease: keeping a high index of suspicion

Transient myeloproliferative disorder (TMD) can be found in well or ill newborns with Down syndrome. Although it is a relatively harmless process for most, in some children, TMD can present as a life-threatening state requiring critical care. As the disease is seemingly uncommon, some providers may lack a sense of urgency in the dissemination of TMD awareness; however, one can never know on whose door this patient may knock tomorrow. Advanced practice professionals should be prepared for the TMD patient that may present without warning. The goals of this article are to discuss common presentations, diagnosis, and management; and to bring attention to this often de-emphasized disease.

Transient Myeloproliferative Disorder and Down Syndrome: Is there a link?

An extremely premature male neonate presented with an unusual multisystem dysfunction within the first 24 to 48 hours of life. The unfolding of clinical events and investigations revealed a transient myeloproliferative disorder (TMD). TMD was the main indication for karyotyping of this premature infant without clinical symptoms of Down syndrome. The awareness of TMD in a newborn warrants karyotype analysis to look for trisomy 21 and a close surveillance because of its potential progression to true leukaemia.

Inherited platelet disorders including Glanzmann thrombasthenia and Bernard-Soulier syndrome

Inherited platelet disorders (IPDs) are a heterogeneous group of diseases affecting platelet production, morphology, and function. The degree of thrombocytopenia and functional abnormality of platelets determines the clinical manifestations. Although severe deficiencies may cause excessive bleeding beginning in early childhood, most of IPDs have mild bleeding tendencies and therefore are not always easy to distinguish from acquired platelet disorders. The diagnosis of IPD may require extensive laboratory investigation, because current routine laboratory tests are not satisfactory for differential diagnosis in some cases, and most of the specific tests are not readily available in many countries. This review summarizes the classification and clinical and molecular characteristics of known IPDs, including Bernard-Soulier syndrome and Glanzmann thrombasthenia, with a focus on current challenges in the laboratory diagnosis and management of bleeding in these patients.

Prominent megakaryocytic dysplasia after regression of transient abnormal myelopoiesis associated with GATA-1 mutation

About a quarter of children with Down syndrome and transient abnormal myelopoiesis (TAM) progress to acute megakaryoblastic leukemia (AMKL). We describe isolated dysmegakaryopoiesis despite complete resolution of TAM in an 18-month-old girl, who developed AMKL 6 months later.

Neonatal vesiculopustular eruption associated with transient myeloproliferative disorder: report of four cases

BACKGROUND

Transient myeloproliferative disorder (TMD) affects up to 10% of patients with Down syndrome (DS). A small proportion of newborns are asymptomatic and only manifest circulating blast cells, with or without leukocytosis, while others present with hepatomegaly, splenomegaly, serous effusions, and liver fibrosis. Few cases in the literature also have skin manifestations, described as crusted, erythematous, vesiculopustular eruptions occurring mainly on the face, with spreading to the trunk and extremities.

MATERIALS AND METHODS

Four patients with DS and TMD were studied due to the presence of cutaneous eruptions. Systemic involvement, work-up, and follow-up were documented for each patient. Our results were compared with the previously reported cases.

RESULTS

All patients were males, with ages ranging from 1 to 20 days at the time of diagnosis. In three patients, the eruption was papulopustular, and two of them also had vesicles. In one patient, lesions resembled bullous impetigo. In all, the lesions involved the face, followed by the extremities in three and the trunk in two patients. Pathergy phenomena was present in one patient. Hepatomegaly and a leukemoid reaction were present in all patients. Bone marrow showed an M7 immunophenotype in three patients and normal cellularity in one. Follow-up ranged from 2 to 11 months, during which the patients were healthy.

CONCLUSIONS

Recognition of the cutaneous eruptions associated with TMD in neonate patients with DS may lead to early diagnosis and avoidance of unnecessary chemotherapy. However, because leukemia may develop later, careful follow-up is mandatory in all cases.

Altered hematopoiesis in trisomy 21 as revealed through in vitro differentiation of isogenic human pluripotent cells

Trisomy 21 is associated with hematopoietic abnormalities in the fetal liver, a preleukemic condition termed transient myeloproliferative disorder, and increased incidence of acute megakaryoblastic leukemia. Human trisomy 21 pluripotent cells of various origins, human embryonic stem (hES), and induced pluripotent stem (iPS) cells, were differentiated in vitro as a model to recapitulate the effects of trisomy on hematopoiesis. To mitigate clonal variation, we isolated disomic and trisomic subclones from the same parental iPS line, thereby generating subclones isogenic except for chromosome 21. Under differentiation conditions favoring development of fetal liver-like, γ-globin expressing, definitive hematopoiesis, we found that trisomic cells of hES, iPS, or isogenic origins exhibited a two- to fivefold increase in a population of CD43(+)(Leukosialin)/CD235(+)(Glycophorin A) hematopoietic cells, accompanied by increased multilineage colony-forming potential in colony-forming assays. These findings establish an intrinsic disturbance of multilineage myeloid hematopoiesis in trisomy 21 at the fetal liver stage.

Characterization of novel genomic alterations and therapeutic approaches using acute megakaryoblastic leukemia xenograft models

Acute megakaryoblastic leukemia (AMKL) is a heterogeneous disease generally associated with poor prognosis. Gene expression profiles indicate the existence of distinct molecular subgroups, and several genetic alterations have been characterized in the past years, including the t(1;22)(p13;q13) and the trisomy 21 associated with GATA1 mutations. However, the majority of patients do not present with known mutations, and the limited access to primary patient leukemic cells impedes the efficient development of novel therapeutic strategies. In this study, using a xenotransplantation approach, we have modeled human pediatric AMKL in immunodeficient mice. Analysis of high-throughput RNA sequencing identified recurrent fusion genes defining new molecular subgroups. One subgroup of patients presented with MLL or NUP98 fusion genes leading to up-regulation of the HOX A cluster genes. A novel CBFA2T3-GLIS2 fusion gene resulting from a cryptic inversion of chromosome 16 was identified in another subgroup of 31% of non-Down syndrome AMKL and strongly associated with a gene expression signature of Hedgehog pathway activation. These molecular data provide useful markers for the diagnosis and follow up of patients. Finally, we show that AMKL xenograft models constitute a relevant in vivo preclinical screening platform to validate the efficacy of novel therapies such as Aurora A kinase inhibitors.

Trisomy 21-associated defects in human primitive hematopoiesis revealed through induced pluripotent stem cells

Patients with Down syndrome (trisomy 21, T21) have hematologic abnormalities throughout life. Newborns frequently exhibit abnormal blood counts and a clonal preleukemia. Human T21 fetal livers contain expanded erythro-megakaryocytic precursors with enhanced proliferative capacity. The impact of T21 on the earliest stages of embryonic hematopoiesis is unknown and nearly impossible to examine in human subjects. We modeled T21 yolk sac hematopoiesis using human induced pluripotent stem cells (iPSCs). Blood progenitor populations generated from T21 iPSCs were present at normal frequency and proliferated normally. However, their developmental potential was altered with enhanced erythropoiesis and reduced myelopoiesis, but normal megakaryocyte production. These abnormalities overlap with those of T21 fetal livers, but also reflect important differences. Our studies show that T21 confers distinct developmental stage- and species-specific hematopoietic defects. More generally, we illustrate how iPSCs can provide insight into early stages of normal and pathological human development.

Hematopoietic overexpression of the transcription factor Erg induces lymphoid and erythro-megakaryocytic leukemia

The transcription factor encoded by the E-twenty-six (ETS)-related gene, ERG, is an essential regulator of hematopoietic stem cell function and a potent human oncoprotein. Enforced expression of ERG in murine hematopoietic cells leads to the development of a well-characterized lymphoid leukemia and a less well-defined non lymphoid disease. To clarify the latter, we generated murine bone marrow chimeras with enforced Erg expression in engrafted hematopoietic progenitor cells. As expected, these mice developed lymphoid leukemia. However, the previously reported non lymphoid disease that developed was shown to be a uniform, transplantable leukemia with both erythroid and megakaryocytic characteristics. In vivo, this disease had the overall appearance of an erythroleukemia, with an accumulation of immature erythroblasts that infiltrated the bone marrow, spleen, liver, and lung. However, when stimulated in vitro, leukemic cell clones exhibited both erythroid and megakaryocytic differentiation, suggesting that transformation occurred in a bipotential progenitor. Thus, in mice, Erg overexpression induces the development of not only lymphoid leukemia but also erythro-megakaryocytic leukemia.

Low bone turnover and low BMD in Down syndrome: effect of intermittent PTH treatment

Trisomy 21 affects virtually every organ system and results in the complex clinical presentation of Down syndrome (DS). Patterns of differences are now being recognized as patients' age and these patterns bring about new opportunities for disease prevention and treatment. Low bone mineral density (BMD) has been reported in many studies of males and females with DS yet the specific effects of trisomy 21 on the skeleton remain poorly defined. Therefore we determined the bone phenotype and measured bone turnover markers in the murine DS model Ts65Dn. Male Ts65Dn DS mice are infertile and display a profound low bone mass phenotype that deteriorates with age. The low bone mass was correlated with significantly decreased osteoblast and osteoclast development, decreased bone biochemical markers, a diminished bone formation rate and reduced mechanical strength. The low bone mass observed in 3 month old Ts65Dn mice was significantly increased after 4 weeks of intermittent PTH treatment. These studies provide novel insight into the cause of the profound bone fragility in DS and identify PTH as a potential anabolic agent in the adult low bone mass DS population.

Biology and management of transient abnormal myelopoiesis (TAM) in children with Down syndrome

Children with Down syndrome (DS) have an increased risk of Acute Myeloid Leukaemia (ML-DS), particularly megakaryoblastic leukaemia, which is clonally -related to the neonatal myeloproliferative syndrome, Transient Abnormal Myelopoiesis (TAM) unique to infants with DS. Molecular, biological, and clinical data indicate that TAM is initiated before birth when fetal liver haematopoietic cells trisomic for chromosome 21 acquire mutations in GATA1. TAM usually resolves spontaneously by 6 months; however 20-30% subsequently develop ML-DS harbouring the same GATA1 mutation(s). This review focuses on recent studies describing haematological, clinical and biological features of TAM and discusses approaches to diagnose, treat and monitor minimal residual disease in TAM. An important unanswered question is whether ML-DS is always preceded by TAM as it may be clinically and possibly haematologically 'silent'. We have briefly discussed the role of population-based screening for TAM and development of treatment strategies to eliminate the preleukaemic TAM clone, thereby preventing ML-DS.

N- and C-terminal transactivation domains of GATA1 protein coordinate hematopoietic program

Transcription factor GATA1 regulates the expression of a cluster of genes important for hematopoietic cell differentiation toward erythroid and megakaryocytic lineages. Three functional domains have been identified in GATA1, a transactivation domain located in the N terminus (N-TAD) and two zinc finger domains located in the middle of the molecule. Although N-TAD is known as a solitary transactivation domain for GATA1, clinical observations in Down syndrome leukemia suggest that there may be additional transactivation domains. In this study, we found in reporter co-transfection assays that transactivation activity of GATA1 was markedly reduced by deletion of the C-terminal 95 amino acids without significant attenuation of the DNA binding activity or self-association potential. We therefore generated transgenic mouse lines that expressed GATA1 lacking the C-terminal region (GATA1-ΔCT). When we crossed these transgenic mouse lines to the Gata1-deficient mouse, we found that the GATA1-ΔCT transgene rescued Gata1-deficient mice from embryonic lethality. The embryos rescued with an almost similar level of GATA1-ΔCT to endogenous GATA1 developed beyond embryonic 13.5 days, showing severe anemia with accumulation of immature erythroid cells, as was the case for the embryos rescued by endogenous levels of GATA1 lacking N-TAD (GATA1-ΔNT). Distinct sets of target genes were affected in the embryos rescued by GATA1-ΔCT and GATA1-ΔNT. We also found attenuated GATA1 function in cell cycle control of immature megakaryocytes in both lines of rescued embryos. These results thus demonstrate that GATA1 has two independent transactivation domains, N-TAD and C-TAD. Both N-TAD and C-TAD retain redundant as well as specific activities for proper hematopoiesis in vivo.

Increased dosage of the chromosome 21 ortholog Dyrk1a promotes megakaryoblastic leukemia in a murine model of Down syndrome

Individuals with Down syndrome (DS; also known as trisomy 21) have a markedly increased risk of leukemia in childhood but a decreased risk of solid tumors in adulthood. Acquired mutations in the transcription factor-encoding GATA1 gene are observed in nearly all individuals with DS who are born with transient myeloproliferative disorder (TMD), a clonal preleukemia, and/or who develop acute megakaryoblastic leukemia (AMKL). Individuals who do not have DS but bear germline GATA1 mutations analogous to those detected in individuals with TMD and DS-AMKL are not predisposed to leukemia. To better understand the functional contribution of trisomy 21 to leukemogenesis, we used mouse and human cell models of DS to reproduce the multistep pathogenesis of DS-AMKL and to identify chromosome 21 genes that promote megakaryoblastic leukemia in children with DS. Our results revealed that trisomy for only 33 orthologs of human chromosome 21 (Hsa21) genes was sufficient to cooperate with GATA1 mutations to initiate megakaryoblastic leukemia in vivo. Furthermore, through a functional screening of the trisomic genes, we demonstrated that DYRK1A, which encodes dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A, was a potent megakaryoblastic tumor-promoting gene that contributed to leukemogenesis through dysregulation of nuclear factor of activated T cells (NFAT) activation. Given that calcineurin/NFAT pathway inhibition has been implicated in the decreased tumor incidence in adults with DS, our results show that the same pathway can be both proleukemic in children and antitumorigenic in adults.

Oxidative Stress and Down Syndrome: A Route toward Alzheimer-Like Dementia

Down syndrome (DS) is one of the most frequent genetic abnormalities characterized by multiple pathological phenotypes. Indeed, currently life expectancy and quality of life for DS patients have improved, although with increasing age pathological dysfunctions are exacerbated and intellectual disability may lead to the development of Alzheimer's type dementia (AD). The neuropathology of DS is complex and includes the development of AD by middle age, altered free radical metabolism, and impaired mitochondrial function, both of which contribute to neuronal degeneration. Understanding the molecular basis that drives the development of AD is an intense field of research. Our laboratories are interested in understanding the role of oxidative stress as link between DS and AD. This review examines the current literature that showed oxidative damage in DS by identifying putative molecular pathways that play a central role in the neurodegenerative processes. In addition, considering the role of mitochondrial dysfunction in neurodegenerative phenomena, results demonstrating the involvement of impaired mitochondria in DS pathology could contribute a direct link between normal aging and development of AD-like dementia in DS patients.

GATA Transcription Factors and Cancer

It has been almost a quarter century since it was first appreciated that a class of oncogenes contained in rapidly transforming avian retroviruses encoded DNA-binding transcription factors. As with other oncogenes, genetic recombination with the viral genome led to their overexpression or functional alteration. In the years that followed, alterations of numerous transcription factors were shown to be causatively involved in various cancers in human patients and model organisms. Depending on their normal cellular functions, these factors were subsequently categorized as proto-oncogenes or tumor suppressor genes. This review focuses on the role of GATA transcription factors in carcinogenesis. GATA factors are zinc finger DNA binding proteins that control the development of diverse tissues by activating or repressing transcription. GATA factors thus coordinate cellular maturation with proliferation arrest and cell survival. Therefore, a role of this family of genes in human cancers is not surprising. Prominent examples include structural mutations in GATA1 that are found in almost all megakaryoblastic leukemias in patients with Down syndrome; loss of GATA3 expression in aggressive, dedifferentiated breast cancers; and silencing of GATA4 and GATA5 expression in colorectal and lung cancers. Here, we discuss possible mechanisms of carcinogenesis vis-à-vis the normal functions of GATA factors as they pertain to human patients and mouse models of cancer.

Transient myeloproliferative disorder in a newborn with down syndrome treated with rasburicase for the risk of development of tumor lysis syndrome: A case report

INTRODUCTION

Transient myeloproliferative disorder is a hematologic abnormality characterized by an uncontrolled proliferation of myeloblasts in peripheral blood and bone marrow that primarily affects newborns and babies with Down syndrome. Tumor lysis syndrome is rarely associated with transient myeloproliferative disorder.

CASE PRESENTATION

Transient myeloproliferative disorder was diagnosed in a seven-day-old baby girl with Down syndrome, who was referred to our department due to hyperleukocytosis. Our patient developed tumor lysis syndrome, successfully treated with rasburicase, as a complication of transient myeloproliferative disorder resulting from rapid degradation of myeloid blasts after initiation of effective chemotherapy.

CONCLUSIONS

Tumor lysis syndrome is rarely reported as a complication of transient myeloproliferative disorder. To the best of our knowledge, this is the first case of a newborn with Down syndrome and transient myeloproliferative disorder treated with rasburicase for developing tumor lysis syndrome.

Sonographic markers of aneuploidies at 6-10 weeks of gestation

OBJECTIVES

To determine if sonographic features of live embryos at 6-10 weeks' gestation are altered in aneuploidies.

METHODS

Embryonic crown rump length (CRL), embryonic heart rate, gestational sac diameter (GSD) and yolk sac diameter (YSD) were measured by transvaginal sonography in 5603 live embryos from singleton pregnancies at 6-10 weeks' gestation. The measurements were expressed as differences from the expected normal mean for CRL (delta values) and median delta values in the aneuploid cases were compared to the euploid group.

RESULTS

5393 pregnancies resulted in the live birth of phenotypically normal neonates and these cases constituted the euploid group. In 55 cases there was subsequent prenatal diagnosis of aneuploidies (trisomy 21, n=28; trisomy 18, n=10; trisomy 13, n=10; triploidy, n=4; Turner syndrome, n=3). The median and interquartile range (IQR) of delta embryonic heart rate in trisomy 18 was -19.44 (-23.77 to -7.20)bpm and in trisomy 13 it was 11.12 (7.25 to 20.39)bpm, which were significantly lower and higher, respectively, than in euploid embryos (median -0.05, IQR -6.18 to 6.21bpm). The median delta YSD in trisomy 21 was higher than in euploid fetuses (median 0.56, IQR 0.23 to 0.79 and median -0.17, IQR -3.11 to 2.82 mm). There were no other significant differences in measurements between the groups.

CONCLUSION

At 6-10 weeks' gestation there are sonographically detectable differences between euploid and trisomic embryos.

Congenital acute leukemia with initial indolent presentation--a case report

BACKGROUND

Congenital acute leukemia is a rare event, presenting usually as an aggressive disease with a poor prognosis. A differential diagnosis is the transient myeloproliferative disorder observed in Down syndrome. We describe the case of an apparently healthy newborn male child presenting with normal peripheral blood (PB) counts but with a blast population on differentials. The child's condition and the blast population remained unchanged during the first year of life.

METHODS

Bone marrow and PB were morphologically analyzed. Multiparametric flow cytometry was performed at the time of diagnosis and repeated at 1 year. These studies were completed by cytogenetic and molecular analyses.

RESULTS

Bone marrow contained 40% of undifferentiated blasts. Multiparametric flow cytometry showed low expression of CD38, HLA-DR, and CD33 markers. All other markers were negative. Constitutional and blast cell karyotypes were normal. Fluorescence in situ hybridization analysis showed no rearrangement. Molecular studies were negative. The blast percentage remained stable during several months. After 1 year, the PB counts showed thrombocytopenia, with an increase of blast cells exhibiting the same phenotype. Clinically, an enlarged spleen was found. The child did not respond to chemotherapy and only partially to gemtuzumab ozogamicin. A cord blood cell transplantation was finally performed. With a follow-up of 12 months, the child is doing well.

CONCLUSIONS

To our knowledge, this is the first case of congenital acute leukemia with initially indolent course in a newborn without Down syndrome. This observation emphasizes the importance of a careful follow-up.

[GATA1 analysis in myeloproliferative disorders associated to trisomy 21]

INTRODUCTION

Neonatal transient myeloproliferative disorder and acute megakaryoblastic leukaemia of Down syndrome are considered different manifestations of the same disease. In most cases, transient myeloproliferative disorders require no treatment, while acute megakaryoblastic leukaemia of Down's syndrome is characterised by an increased sensitivity to chemotherapy and its treatment should be adapted with a reduction in dose intensity. Both entities share specific mutations at exón 2 of the transcription factor GATA1.

PATIENTS AND METHODS

We analysed biological features and GATA1 mutations in 4 patients with transient abnormal myelopoiesis (2) and acute megakaryoblastic leukaemia (2) including one phenotypically normal trisomy 21 mosaicism. We found abnormal GATA1 mutated clones in each case, and a specific point mutation at exón 2 was detected in three cases. Given the heterogeneous phenotype of megakaryoblastic blasts and the low percentage of blasts at presentation, the recognition of GATA1 mutations was helpful for diagnosis. In addition, molecular remission was established in 2 patients after subsequent normal mutational GATA1 analysis.

CONCLUSIONS

We conclude that GATA1 mutational study is a useful tool for the diagnosis and management of trisomy 21 associated myeloproliferative disorders.