title: EZH2 mutations and promoter hypermethylation in childhood acute lymphoblastic leukemia.
abstract: OBJECTIVE
  Acute lymphoblastic leukemia (ALL) is the most common malignancy in children and young adults. The polycomb repressive complex 2 (PRC2) has been identified as one of the most frequently mutated epigenetic protein complexes in hematologic cancers. PRC2 acts as an epigenetic repressor through histone H3 lysine 27 trimethylation (H3K27me3), catalyzed by the histone methyltransferase enhancer of zeste homolog 2 protein (EZH2).
  
  
  METHODS
  To study the prevalence and clinical impact of PRC2 aberrations in an unselected childhood ALL cohort (n = 152), we performed PRC2 mutational screenings by Sanger sequencing and promoter methylation analyses by quantitative pyrosequencing for the three PRC2 core component genes EZH2, suppressor of zeste 12 (SUZ12), and embryonic ectoderm development (EED). Targeted deep next-generation sequencing of 30 frequently mutated genes in leukemia was performed to search for cooperating mutations in patients harboring PRC2 aberrations. Finally, the functional consequence of EZH2 promoter hypermethylation on H3K27me3 was studied by Western blot analyses of primary cells.
  
  
  RESULTS
  Loss-of-function EZH2 mutations were detected in 2/152 (1.3 %) patients with common-ALL and early T-cell precursor (ETP)-ALL, respectively. In one patient, targeted deep sequencing identified cooperating mutations in ASXL1 and TET2. EZH2 promoter hypermethylation was found in one patient with ETP-ALL which led to reduced H3K27me3. In comparison with healthy children, the EZH2 promoter was significantly higher methylated in T-ALL patients. No mutations or promoter methylation changes were identified for SUZ12 or EED genes, respectively.
  
  
  CONCLUSIONS
  Although PRC2 aberrations seem to be rare in childhood ALL, our findings indicate that EZH2 aberrations might contribute to the disease in specific cases. Hereby, EZH2 promoter hypermethylation might have functionally similar consequences as loss-of-function mutations.
authors.affiliation: Abteilung Hämatologie und Internistische Onkologie, Klinik für Innere Medizin II, Universitätsklinikum Jena, Erlanger Allee 101, 07740, Jena, Germany.
authors.forename: Vivien
authors.initials: V
authors.lastname: Schäfer
authors.affiliation: Sektion für Hämatologie, Onkologie und Stammzelltransplantation, Klinik für Kinder- und Jugendmedizin, Universitätsklinikum Jena, Kochstrasse 2, 07745 Jena, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Ernst
authors.affiliation: Abteilung Hämatologie und Internistische Onkologie, Klinik für Innere Medizin II, Universitätsklinikum Jena, Erlanger Allee 101, 07740, Jena, Germany.
authors.forename: Jenny
authors.initials: J
authors.lastname: Rinke
authors.affiliation: Abteilung Hämatologie und Internistische Onkologie, Klinik für Innere Medizin II, Universitätsklinikum Jena, Erlanger Allee 101, 07740, Jena, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Winkelmann
authors.affiliation: Sektion für Hämatologie, Onkologie und Stammzelltransplantation, Klinik für Kinder- und Jugendmedizin, Universitätsklinikum Jena, Kochstrasse 2, 07745 Jena, Germany.
authors.forename: James F
authors.initials: JF
authors.lastname: Beck
authors.affiliation: Abteilung Hämatologie und Internistische Onkologie, Klinik für Innere Medizin II, Universitätsklinikum Jena, Erlanger Allee 101, 07740, Jena, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hochhaus
authors.affiliation: Sektion für Hämatologie, Onkologie und Stammzelltransplantation, Klinik für Kinder- und Jugendmedizin, Universitätsklinikum Jena, Kochstrasse 2, 07745 Jena, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Gruhn
authors.affiliation: Abteilung Hämatologie und Internistische Onkologie, Klinik für Innere Medizin II, Universitätsklinikum Jena, Erlanger Allee 101, 07740, Jena, Germany. thomas.ernst@med.uni-jena.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ernst
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D019175:DNA Methylation; D000071221:Enhancer of Zeste Homolog 2 Protein / Q000235:genetics*; D044127:Epigenesis, Genetic; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics*; D011401:Promoter Regions, Genetic
chemical_list: C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein
keywords: Acute lymphoblastic leukemia; Childhood; EED; EZH2; Pediatric; SUZ12