Publications (4)87.39 Total impact
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Article: The significance of PTEN and AKT aberrations in pediatric T-cell acute lymphoblastic leukemia.
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ABSTRACT: Background PI3K/AKT pathway mutations are found in T-cell acute lymphoblastic leukemia, but their overall impact and associations with other genetic aberrations is unknown. PTEN mutations have been proposed as secondary mutations that follow NOTCH1-activating mutations and cause cellular resistance to γ-secretase inhibitors. DESIGN AND METHODS: The impact of PTEN, PI3K and AKT aberrations was studied in a genetically well-characterized pediatric T-cell leukemia patient cohort (n=146) treated on DCOG or COALL protocols. RESULTS: PTEN and AKT E17K aberrations were detected in 13% and 2% of patients, respectively. Defective PTEN-splicing was identified in incidental cases. Patients without PTEN protein but lacking exon-, splice-, promoter mutations or promoter hypermethylation were present. PTEN/AKT mutations were especially abundant in TAL- or LMO-rearranged leukemia but nearly absent in TLX3-rearranged patients (P=0.03), the opposite to that observed for NOTCH1-activating mutations. Most PTEN/AKT mutant patients either lacked NOTCH1-activating mutations (P=0.006) or had weak NOTCH1-activating mutations (P=0.011), and consequently expressed low intracellular NOTCH1, cMYC and MUSASHI levels. T-cell leukemia patients without PTEN/AKT and NOTCH1-activating mutations fared well, with a cumulative incidence of relapse of only 8% versus 35% for PTEN/AKT and/or NOTCH1-activated patients (P=0.005). Conclusions PI3K/AKT pathway aberrations are present in 18% of pediatric T-cell acute lymphoblastic leukemia patients. Absence of strong NOTCH1-activating mutations in these cases may explain cellular insensitivity to γ-secretase inhibitors.Haematologica 04/2012; 97(9):1405-13. · 6.42 Impact Factor -
Article: Oncogenic IL7R gain-of-function mutations in childhood T-cell acute lymphoblastic leukemia.
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ABSTRACT: Interleukin 7 (IL-7) and its receptor, formed by IL-7Rα (encoded by IL7R) and γc, are essential for normal T-cell development and homeostasis. Here we show that IL7R is an oncogene mutated in T-cell acute lymphoblastic leukemia (T-ALL). We find that 9% of individuals with T-ALL have somatic gain-of-function IL7R exon 6 mutations. In most cases, these IL7R mutations introduce an unpaired cysteine in the extracellular juxtamembrane-transmembrane region and promote de novo formation of intermolecular disulfide bonds between mutant IL-7Rα subunits, thereby driving constitutive signaling via JAK1 and independently of IL-7, γc or JAK3. IL7R mutations induce a gene expression profile partially resembling that provoked by IL-7 and are enriched in the T-ALL subgroup comprising TLX3 rearranged and HOXA deregulated cases. Notably, IL7R mutations promote cell transformation and tumor formation. Overall, our findings indicate that IL7R mutational activation is involved in human T-cell leukemogenesis, paving the way for therapeutic targeting of IL-7R-mediated signaling in T-ALL.Nature Genetics 09/2011; 43(10):932-9. · 35.53 Impact Factor -
Article: PHF6 mutations in T-cell acute lymphoblastic leukemia.
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ABSTRACT: Tumor suppressor genes on the X chromosome may skew the gender distribution of specific types of cancer. T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy with an increased incidence in males. In this study, we report the identification of inactivating mutations and deletions in the X-linked plant homeodomain finger 6 (PHF6) gene in 16% of pediatric and 38% of adult primary T-ALL samples. Notably, PHF6 mutations are almost exclusively found in T-ALL samples from male subjects. Mutational loss of PHF6 is importantly associated with leukemias driven by aberrant expression of the homeobox transcription factor oncogenes TLX1 and TLX3. Overall, these results identify PHF6 as a new X-linked tumor suppressor in T-ALL and point to a strong genetic interaction between PHF6 loss and aberrant expression of TLX transcription factors in the pathogenesis of this disease.Nature Genetics 03/2010; 42(4):338-42. · 35.53 Impact Factor -
Article: NOTCH1 extracellular juxtamembrane expansion mutations in T-ALL.
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ABSTRACT: Heterodimerization domain (HD) mutations in NOTCH1 induce ligand-independent activation of the receptor and contribute to the pathogenesis of one-third of human T-cell lymphoblastic leukemias (T-ALLs). Here we report a novel class of activating mutations in NOTCH1 leading to aberrant activation of NOTCH1 signaling in T-cell lymphoblasts. These so-called juxtamembrane expansion (JME) alleles consist of internal duplication insertions in the vicinity of exon 28 of the NOTCH1 gene encoding the extracellular juxtamembrane region of the receptor. Notably, structure-function analysis of leukemia-derived and synthetic JME mutants demonstrated that the aberrant activation of NOTCH1 signaling is dependent on the number of residues introduced in the extracellular juxtamembrane region of the receptor and not on the specific amino acid sequence of these insertions. JME NOTCH1 mutants are effectively blocked by gamma-secretase inhibitors and require an intact metalloprotease cleavage site for activation. Overall, these results show a novel mechanism of NOTCH1 activation in T-ALL and provide further insight on the mechanisms that control the activation of NOTCH1 signaling.Blood 05/2008; 112(3):733-40. · 9.90 Impact Factor
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Institutions
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2012
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Erasmus MC
Rotterdam, South Holland, Netherlands
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