Niemeyer, C.M.

Applicability of a reproducible flow cytometry scoring system in the diagnosis of refractory cytopenia of childhood (Article)

2013-03-15T00:00:00Z

Aberrant DNA methylation characterizes juvenile myelomonocytic leukemia with poor outcome (Article)

2011-05-05T00:00:00Z

Aberrant DNA methylation contributes to the malignant phenotype in virtually all types of cancer, including myeloid leukemia. We hypothesized that CpG island hypermethylation also occurs in juvenile myelomonocytic leukemia (JMML) and investigated whether it is associated with clinical, hematologic, or prognostic features. Based on quantitative measurements of DNA methylation in 127 JMML cases using mass spectrometry (MassARRAY), we identified 4 gene CpG islands with frequent hypermethylation: BMP4 (36% of patients), CALCA (54%), CDKN2B (22%), and RARB (13%). Hypermethylation was significantly associated with poor prognosis: when the methylation data were transformed into prognostic scores using a LASSO Cox regression model, the 5-year overall survival was 0.41 for patients in the top tertile of scores versus 0.72 in the lowest score tertile (P = .002). Among patients given allogeneic hematopoietic stem cell transplantation, the 5-year cumulative incidence of relapse was 0.52 in the highest versus 0.10 in the lowest score tertile (P = .007). In multivariate models, DNA methylation retained prognostic value independently of other clinical risk factors. Longitudinal analyses indicated that some cases acquired a more extensively methylated phenotype at relapse. In conclusion, our data suggest that a high-methylation phenotype characterizes an aggressive biologic variant of JMML and is an important molecular predictor of outcome.

Complex karyotype newly defined: The strongest prognostic factor in advanced childhood myelodysplastic syndrome (Article)

2010-11-11T00:00:00Z

To identify cytogenetic risk factors predicting outcome in children with advanced myelodysplastic syndrome, overall survival of 192 children prospectively enrolled in European Working Group of Myelodysplastic Syndrome in Childhood studies was evaluated with regard to karyotypic complexity. Structurally complex constitutes a new definition of complex karyotype characterized by more than or equal to 3 chromosomal aberrations, including at least one structural aberration. Five-year overall survival in patients with more than or equal to 3 clonal aberrations, which were not structurally complex, did not differ from that observed in patients with normal karyotype. Cox regression analysis revealed the presence of a monosomal and structurally complex karyotype to be strongly associated with poor prognosis (hazard ratio = 4.6, P < .01). Notably, a structurally complex karyotype without a monosomy was associated with a very short 2-year overall survival probability of only 14% (hazard ratio = 14.5; P < .01). The presence of a structurally complex karyotype was the strongest independent prognostic marker predicting poor outcome in children with advanced myelodysplastic syndrome.

Germline CBL mutations cause developmental abnormalities and predispose to juvenile myelomonocytic leukemia (Article)

2010-08-08T00:00:00Z

CBL encodes a member of the Cbl family of proteins, which functions as an E3 ubiquitin ligase. We describe a dominant developmental disorder resulting from germline missense CBL mutations, which is characterized by impaired growth, developmental delay, cryptorchidism and a predisposition to juvenile myelomonocytic leukemia (JMML). Some individuals experienced spontaneous regression of their JMML but developed vasculitis later in life. Importantly, JMML specimens from affected children show loss of the normal CBL allele through acquired isodisomy. Consistent with these genetic data, the common p.371Y>H altered Cbl protein induces cytokine-independent growth and constitutive phosphorylation of ERK, AKT and S6 only in hematopoietic cells in which normal Cbl expression is reduced by RNA interference. We conclude that germline CBL mutations have developmental, tumorigenic and functional consequences that resemble disorders that are caused by hyperactive Ras/Raf/MEK/ERK signaling and include neurofibromatosis type 1, Noonan syndrome, Costello syndrome, cardiofaciocutaneous syndrome and Legius syndrome.

Mutational analysis of SHOC2, a novel gene for Noonan-like syndrome, in JMML (Article)

2010-01-28T00:00:00Z

Mutations in CBL occur frequently in juvenile myelomonocytic leukemia (Article)

2009-11-20T00:00:00Z

Juvenile myelomonocytic leukemia is an aggressive myeloproliferative disorder characterized by malignant transformation in the hematopoietic stem cell compartment with proliferation of differentiated progeny. Seventy-five percent of patients harbor mutations in the NF1, NRAS, KRAS, or PTPN11 genes, which encode components of Ras signaling networks. Using single nucleotide polymorphism arrays, we identified a region of 11q isodisomy that contains the CBL gene in several JMML samples, and subsequently identified CBL mutations in 27 of 159 JMML samples. Thirteen of these mutations alter codon Y371. In this report, we also demonstrate that CBL and RAS/PTPN11 mutations were mutually exclusive in these patients. Moreover, the exclusivity of CBL mutations with respect to other Ras pathway-associated mutations indicates that CBL may have a role in deregulating this key pathway in JMML.

HLA-identical umbilical cord blood transplantation from a sibling donor in juvenile myelomonocytic leukemia (Article)

2009-02-01T00:00:00Z

T-cell receptor Vβ CDR3 oligoclonality frequently occurs in childhood refractory cytopenia (MDS-RC) and severe aplastic anemia (Article)

2008-06-01T00:00:00Z

(Very) severe acquired aplastic anemia ((v)SAA) and myelodysplastic syndrome (MDS) are rare diseases in childhood. (V)SAA is a bone marrow (BM) failure syndrome characterized by immune-mediated destruction of hematopoietic progenitors. MDS is a malignant clonal stem cell disorder, of which the hypoplastic variant is, in case of absence of a cytogenetic clone, difficult to separate from (v)SAA. Recently, studies provided a molecular signature of autoimmunity in adult (v)SAA, by showing oligoclonality based on the length of the TCR Vβ CDR3 region. We investigated retrospectively the frequency and the discriminative value of TCR Vβ CDR3 oligoclonality in pediatric (v)SAA and MDS patients. Peripheral blood (PB) and/or BM mononuclear cell samples of pediatric patients with (v)SAA (n=38), refractory cytopenia (MDS-RC) (n=28) and 18 controls were analysed via TCR Vβ heteroduplex PCR analysis of extracted RNA. A skewed TCR Vβ CDR3 repertoire was found in 21/38 (v)SAA and in 17/28 RC patients in contrast to 2/18 in the control group. These data suggest an overlapping group of RC and SAA patients that may share a common immune-mediated pathogenesis. Prospective studies are required to establish the clinical value of TCR Vβ CDR3 repertoire analysis to predict the clinical response in these patients.

Concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia in a 2-year-old child (Article)

2008-01-01T00:00:00Z

We present a case of a 2-year-old girl, who developed concomitant EBV-related B-cell proliferation and juvenile myelomonocytic leukemia (JMML). JMML was initially not recognized because of predominant B-cell proliferation. The activating N-RAS mutation was retrospectively already detectable at this early stage. Our findings support the hypothesis that EBV may contribute to JMML pathogenesis by stimulating pre-existing malignant clones. However, such stimulation of leukemic clone does not require the direct incorporation of the virus into myeloid progenitors. Most probably a cytokine burst resulting from EBV infection allows expansion of pre-existing malignant myeloid progenitors. Further studies are required to delineate exact mechanisms of EBV-related promotion of the JMML clone.

Role of mutation independent constitutive activation of FLT3 in juvenile myelomonocytic leukemia (Article)

2007-11-01T00:00:00Z

FLT3 gene mutations have been identified as prognostic factors in myeloid malignancies. Furthermore, FLT3 can be activated by wild type overexpression or ligand-dependent in leukemic cells co-expressing FLT3 ligand (FLT3L). So far no data are available on FLT3/FLT3L expression and activation in JMML. In 51 clinical JMML samples, activating mutations were screened, FLT3 and FLT3L mRNA levels were assessed and the sensitivity of JMML cells to the FLT3 inhibitor PKC412 was tested by MTT assays. No evidence for constitutively activation of FLT3/FLT3L was found in JMML, indicating that FLT3 inhibitors are unlikely to be effective in JMML.

Mutation analysis of the BRAF oncogene in juvenile myelomonocytic leukemia (Article)

2007-11-01T00:00:00Z

Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative/ myelodysplastic disorder associated with mutations in the Ras-Raf-MEK-ERK- signaling pathway. B-Raf plays a central role in this pathway. In 65 screened JMML patients we identified no BRAF mutations and we conclude that this gene is unlikely to play a role in the pathogenesis of JMML.

Monosomy 7 and deletion 7q in children and adolescents with acute myeloid leukemia: An international retrospective study (Article)

2007-06-01T00:00:00Z

Monosomy 7 (-7) and deletion 7q [del(7q)] are rare in childhood acute myeloid leukemia (AML). We retrospectively collected data on 258 children with AML or refractory anemia with excess blasts in transformation (RAEB-T) and -7 or del(7q) with or without other cytogenetic aberrations [± other]. Karyotypes included -7 (n = 90), -7 other (n = 82), del(7q) (n = 21), and del(7q) other (n = 65). Complete remission (CR) was achieved in fewer patients with -7 ± other compared with del(7q) ± other (61% versus 89%, P < .001). Overall, the 5-year survival rate was 39% (SE, 3%). Survival was superior in del(7q) ± other compared with -7 ± other (51% versus 30%, P < .01). Cytogenetic aberrations considered favorable in AML [t(8;21)(q22;q22), inv(16)(p13q22), t(15;17)(q22;q21), t(9;11)(p22;q23)] (n = 24) were strongly associated with del(7q) and a higher 5-year survival rate compared with del(7q) without favorable cytogenetics (75% versus 46%, P = .03). Patients with -7 and inv(3),-5/del(5q), or +21 had a 5-year survival rate of 5%. Stem cell transplantation analyzed as a time-dependent variable had no impact on overall survival. However, patients not achieving CR had a 31% survival rate after stem cell transplantation. Childhood AML with chromosome 7 aberrations represents a heterogeneous group of disorders with additional cytogenetic aberrations having a major prognostic impact which should be reflected in future riskgroup stratification.

Mutation analysis of Son of Sevenless in juvenile myelomonocytic leukemia [8] (Article)

2007-05-01T00:00:00Z

Immunosuppressive therapy with anti-thymocyte globulin and cyclosporine A in selected children with hypoplastic refractory cytopenia (Article)

2007-03-01T00:00:00Z

It is currently unknown whether immunosuppressive therapy or hematopoietic stem cell transplantation is the most appropriate treatment strategy for children with refractory cytopenia and normal karyotype or trisomy 8. We report on 31 children with hypoplastic refractory cytopenia treated with immunosuppressive therapy consisting of antithymocyte globulin and cyclosporine. At 6 months, 22 of 29 evaluable patients had a complete or partial response; a total of ten patients achieved a complete response at varying time points. Six patients subsequently received a transplant because of non-response, progression to advanced myelodysplastic syndrome or evolution of monosomy 7. Overall and failure-free survival rates at 3 years were 88% and 57%, respectively.

Second allogeneic hematopoietic stem cell transplantation (HSCT) results in outcome similar to that of first HSCT for patients with juvenile myelomonocytic leukemia [4] (Article)

2007-03-01T00:00:00Z

JAK2 V617F mutation is a rare event in juvenile myelomonocytic leukemia [9] (Article)

2007-02-01T00:00:00Z