IntroductionIn 2008, the World Health Organization classification of Tumors of the Hematopoietic and Lymphoid Tissues included "AML with mutated CEBPA" as a provisional favorable prognostic entity, and a routine CEBPA mutation screening was recommended for all acute myeloid leukemia (AML) patients with no detectable chromosomal abnormalities. 1,2 However, only patients with mutations in both CEBPA alleles (biCEBPA-mutated AML) have a prognostically favorable outcome. [3][4][5][6][7] The biCEBPA patients typically have a combination of an N-terminal frameshift mutation leading to a 30-kDa dominant-negative CEBPA isoform and a C-terminal in-frame mutation in the bZIP region, disrupting dimerization and DNA-binding activities of CEBPA. In murine bone marrow transplantation models, distinct but collaborative roles of both types of CEBPA mutations have been detected. 8 Furthermore, a combination of an N-and C-terminal disruption of the CEBPA gene synergistically resulted in fast and efficient development of leukemia in mice. [8][9][10] These experiments suggest that a biallelic disruption of CEBPA might be responsible for both the differentiation block and the enhanced proliferation of progenitor cells and thus be sufficient for leukemogenesis. Indeed, biCEBPA mutant AML represents as a very homogeneous AML subgroup with a distinct immunophenotype 11 and a characteristic gene expression profile. 3,6,7,12 Furthermore, biCEBPA mutant AML patients rarely have mutations in genes that are frequently mutated in CN-AML, such as the nucleophosmin (NPM1) gene, internal tandem duplications (ITDs) of the FLT3 gene, partial tandem duplications (PTDs) of the MLL gene (MLL-PTD), [3][4][5] or mutations in the TET2, isocitrate dehydrogenase (IDH)-1 and 2 or DNMT3A genes. [13][14][15] To identify potentially cooperating mutations associated with biCEBPAmutated AML, we performed whole exome sequencing. Thereby, we discovered a high frequency of N-terminal zinc finger (ZF1) mutations of GATA2 in patients with biCEBPA-mutated AML. GATA2 is a zinc finger transcription factor important for hematopoietic stem cell proliferation [16][17][18][19] and normal megakaryocytic development. 20 Somatic mutations affecting the C-terminal zinc finger (ZF2) of GATA2 are associated with the progression of chronic myeloid leukemia (CML), 21 Submitted January 12, 2012; accepted The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ''advertisement'' in accordance with 18 USC section 1734. For personal use only. on May 12, 2018. by guest www.bloodjournal.org From whereas hereditary GATA2 ZF2 mutations predispose to AML and myelodysplastic syndrome. 22 Mutations targeting either of the 2 ZFs were described as a rare event in the M5 subtype of AML. 23 Here, we report a unique association of GATA2 ZF1 mutations and biCEBPA mutations in AML. Methods PatientsIn this analysis, we included diagnostic bone marrow or peripheral blood samples from 160 adult AML p...

A challenge for the development of therapies selectively targeting leukemic stem cells in acute myeloid leukemia (AML) is their similarity to normal hematopoietic stem cells (HSCs). Here we demonstrate that the leukemia-propagating cell in murine CALM/AF10-positive AML differs from normal HSCs by B220 surface expression and immunoglobulin heavy chain rearrangement. Furthermore, depletion of B220+ cells in leukemic transplants impaired development of leukemia in recipients. As in the murine model, human CALM/AF10-positive AML was characterized by CD45RA (B220)-positive, IG DH-JH rearranged leukemic cells. These data demonstrate in a murine leukemia model that AML can be propagated by a transformed progenitor with lymphoid characteristics, which can be targeted by antibodies that do not crossreact with normal HSCs.

As a result of a whole-exome sequencing study, we report three mutant alleles in SEC24D, a gene encoding a component of the COPII complex involved in protein export from the ER: the truncating mutation c.613C>T (p.Gln205(∗)) and the missense mutations c.3044C>T (p.Ser1015Phe, located in a cargo-binding pocket) and c.2933A>C (p.Gln978Pro, located in the gelsolin-like domain). Three individuals from two families affected by a similar skeletal phenotype were each compound heterozygous for two of these mutant alleles, with c.3044C>T being embedded in a 14 Mb founder haplotype shared by all three. The affected individuals were a 7-year-old boy with a phenotype most closely resembling Cole-Carpenter syndrome and two fetuses initially suspected to have a severe type of osteogenesis imperfecta. All three displayed a severely disturbed ossification of the skull and multiple fractures with prenatal onset. The 7-year-old boy had short stature and craniofacial malformations including macrocephaly, midface hypoplasia, micrognathia, frontal bossing, and down-slanting palpebral fissures. Electron and immunofluorescence microscopy of skin fibroblasts of this individual revealed that ER export of procollagen was inefficient and that ER tubules were dilated, faithfully reproducing the cellular phenotype of individuals with cranio-lentico-sutural dysplasia (CLSD). CLSD is caused by SEC23A mutations and displays a largely overlapping craniofacial phenotype, but it is not characterized by generalized bone fragility and presented with cataracts in the original family described. The cellular and morphological phenotypes we report are in concordance with the phenotypes described for the Sec24d-deficient fish mutants vbi (medaka) and bulldog (zebrafish).

Key Points• AML patients with isolated trisomy 13 have a very poor clinical outcome • Isolated trisomy 13 in AML is associated with a high frequency of mutations in SRSF2 (81%) and RUNX1 (75%)In acute myeloid leukemia (AML), isolated trisomy 13 (AML113) is a rare chromosomal abnormality whose prognostic relevance is poorly characterized. We analyzed the clinical course of 34 AML113 patients enrolled in the German AMLCG-1999 and SAL trials and performed exome sequencing, targeted candidate gene sequencing and gene expression profiling. Relapse-free (RFS) and overall survival (OS) of AML113 patients were inferior compared to other ELN Intermediate-II patients (n5855) (median RFS, 7.8 vs 14.1 months, P 5 .006; median OS 9.3 vs. 14.8 months, P 5 .004). Besides the known high frequency of RUNX1 mutations (75%), we identified mutations in spliceosome components in 88%, including SRSF2 codon 95 mutations in 81%. Recurring mutations were detected in ASXL1 (44%) and BCOR (25%). Two patients carried mutations in CEBPZ, suggesting that CEBPZ is a novel recurrently mutated gene in AML. Gene expression analysis revealed a homogeneous expression profile including upregulation of FOXO1 and FLT3 and downregulation of SPRY2. This is the most comprehensive clinical and biological characterization of AML113 to date, and reveals a striking clustering of lesions in a few genes, defining AML113 as a genetically homogeneous subgroup with alterations in a few critical cellular pathways. Clinicaltrials.gov identifiers:

The online version of this article has a Supplementary Appendix. BackgroundThe RUNX1 (AML1) gene is a frequent mutational target in myelodysplastic syndromes and acute myeloid leukemia. Previous studies suggested that RUNX1 mutations may have pathological and prognostic implications. Design and MethodsWe screened 93 patients with cytogenetically normal acute myeloid leukemia for RUNX1 mutations by capillary sequencing of genomic DNA. Mutation status was then correlated with clinical data and gene expression profiles. ResultsWe found that 15 out of 93 (16.1%) patients with cytogenetically normal acute myeloid leukemia had RUNX1 mutations. Seventy-three patients were enrolled in the AMLCG-99 trial and carried ten RUNX1 mutations (13.7%). Among these 73 patients RUNX1 mutations were significantly associated with older age, male sex, absence of NPM1 mutations and presence of MLL-partial tandem duplications. Moreover, RUNX1-mutated patients had a lower complete remission rate (30% versus 73% P=0.01), lower relapse-free survival rate (3-year relapse-free survival 0% versus 30.4%; P=0.002) and lower overall survival rate (3-year overall survival 0% versus 34.4%; P<0.001) than patients with wild-type RUNX1. RUNX1 mutations remained associated with shorter overall survival in a multivariate model including age and the European LeukemiaNet acute myeloid leukemia genetic classification as covariates. Patients with RUNX1 mutations showed a unique gene expression pattern with differential expression of 85 genes. The most prominently up-regulated genes in patients with RUNX1-mutated cytogenetically normal acute myeloid leukemia include lymphoid regulators such as HOP homeobox (HOPX), deoxynucleotidyltransferase (DNTT, terminal) and B-cell linker (BLNK), indicating lineage infidelity. ConclusionsOur findings firmly establish that RUNX1 mutations are a marker of poor prognosis and provide insights into the pathogenesis of RUNX1 mutation-positive acute myeloid leukemia. (ClinicalTrials.gov identifier NCT00266136)Key words: RUNX1, mutations, prognosis, acute myeloid leukemia. Haematologica 2012;97(12):1909-1915. doi:10.3324/haematol.2012 This is an open-access paper. CitationRUNX1 mutations in cytogenetically normal acute myeloid leukemia are associated with a poor prognosis and up-regulation of lymphoid genes ABSTRACT© F e r r a t a S t o r t i F o u n d a t i o n

Chromosomal translocations generating fusion proteins are frequently found in human leukemias. The fusion proteins play an important role in leukemogenesis by subverting the function of one or both partner proteins. The leukemogenic CALM-AF10 fusion protein is capable of interacting with the histone H3 lysine 79 (H3K79)-specific methyltransferase hDOT1L through the fused AF10 moiety. This interaction leads to local H3K79 hypermethylation on Hoxa5 loci, which up-regulates the expression of Hoxa5 and contributes to leukemogenesis. However, the long latency of leukemogenesis of CALM-AF10 transgenic mice suggests that the direct effects of fusion oncogene are not sufficient for the induction of leukemia. In this study, we show that the CALM-AF10 fusion protein can also greatly reduce global H3K79 methylation in both human and murine leukemic cells by disrupting the AF10-mediated association of hDOT1L with chromatin. Cells with reduced H3K79 methylation are more sensitive to gamma-irradiation and display increased chromosomal instability. Consistently, leukemia patients harboring CALM-AF10 fusion have more secondary chromosomal aberrations. These findings suggest that chromosomal instability associated with global epigenetic alteration contributes to malignant transformation in certain leukemias, and that leukemias with this type of epigenetic alteration might benefit from treatment regimens containing DNA-damaging agents. This study is registered with www.clinicaltrials.gov as NCT00266136.

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Purpose Cytogenetically normal (CN) acute myeloid leukemia (AML) is the largest and most heterogeneous cytogenetic AML subgroup. For the practicing clinician, it is difficult to summarize the prognostic information of the growing number of clinical and molecular markers. Our purpose was to develop a widely applicable prognostic model by combining well-established pretreatment patient and disease characteristics. Patients and Methods Two prognostic indices for CN-AML (PINA), one regarding overall survival (OS; PINAOS) and the other regarding relapse-free survival (RFS; PINARFS), were derived from data of 572 patients with CN-AML treated within the AML Cooperative Group 99 study ( www.aml-score.org ). Results On the basis of age (median, 60 years; range, 17 to 85 years), performance status, WBC count, and mutation status of NPM1, CEBPA, and FLT3-internal tandem duplication, patients were classified into the following three risk groups according to PINAOS and PINARFS: 29% of all patients and 32% of 381 responding patients had low-risk disease (5-year OS, 74%; 5-year RFS, 55%); 56% of all patients and 39% of responding patients had intermediate-risk disease (5-year OS, 28%; 5-year RFS, 27%), and 15% of all patients and 29% of responding patients had high-risk disease (5-year OS, 3%; 5-year RFS, 5%), respectively. PINAOS and PINARFS stratified outcome within European LeukemiaNet genetic groups. Both indices were confirmed on independent data from Cancer and Leukemia Group B/Alliance trials. Conclusion We have developed and validated, to our knowledge, the first prognostic indices specifically designed for adult patients of all ages with CN-AML that combine well-established molecular and clinical variables and that are easily applicable in routine clinical care. The integration of both clinical and molecular markers could provide a basis for individualized patient care through risk-adapted therapy of CN-AML.