Acute Megakaryoblastic Leukemia (AMKL) is a subtype of acute myeloid leukemia (AML) in which cells morphologically resemble abnormal megakaryoblasts. While rare in adults, AMKL accounts for 4–15% of newly diagnosed childhood AML1–3. AMKL in patients without Down syndrome (non-DS-AMKL) is frequently associated with poor outcomes. Previous efforts have identified chimeric oncogenes in a significant number of cases, including RBM15-MKL1, CBFA2T3-GLIS2, KMT2A gene rearrangements and NUP98-KDM5A4–6. The etiology of 30–40% of cases, however, remains unknown. To better understand the genomic landscape of non-DS-AMKL, we performed RNA and exome sequencing on specimens from 99 patients (75 pediatric and 24 adult). We demonstrate that pediatric non-DS-AMKL is a heterogeneous malignancy that can be divided into seven subgroups with varying outcomes. These subgroups are characterized by chimeric oncogenes with cooperating mutations in epigenetic and kinase signaling genes. Overall, these data shed light on the etiology of AMKL and provide useful information for treatment tailoring.

Posttranscriptional control of gene expression is important for defining both normal and pathological cellular phenotypes. In vitro, RNA-binding proteins (RBPs) have recently been shown to play important roles in posttranscriptional regulation; however, the contribution of RBPs to cell specification is not well understood. Here, we determined that the RBP insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) is specifically overexpressed in mixed lineage leukemia-rearranged (MLLrearranged) B-acute lymphoblastic leukemia (B-ALL), which constitutes a subtype of this malignancy associated with poor prognosis and high risk of relapse. IGF2BP3 was required for the survival of B-ALL cell lines, as knockdown led to decreased proliferation and increased apoptosis. Enforced expression of IGF2BP3 provided murine BM cells with a strong survival advantage, led to proliferation of hematopoietic stem and progenitor cells, and skewed hematopoietic development to the B cell/myeloid lineage. Cross-link immunoprecipitation and high throughput sequencing uncovered the IGF2BP3-regulated transcriptome, which includes oncogenes MYC and CDK6 as direct targets. IGF2BP3 regulated transcripts via targeting elements within 3' untranslated regions (3'UTR), and enforced IGF2BP3 expression in mice resulted in enhanced expression of Myc and Cdk6 in BM. Together, our data suggest that IGF2BP3-mediated targeting of oncogenic transcripts may represent a critical pathogenetic mechanism in MLL-rearranged B-ALL and support IGF2BP3 and its cognate RNA-binding partners as potential therapeutic targets in this diseas

Key Points• Risk-adapted therapy and broad use of HSCT resulted in a significant improvement in outcome.• AUTO-or ALLO-HSCT in high-risk patients resulted in a cumulative incidence of leukemia relapse superimposable to that of SR.We evaluated the outcome of 482 children with acute myeloid leukemia (AML) enrolled in the Associazione Italiana di Ematologia e Oncologia Pediatrica AML 2002/01 trial. Treatment was stratified according to risk group; hematopoietic stem cell transplantation (HSCT) was used in high-risk (HR) children. Patients with core binding factor leukemia achieving complete remission (CR) after the first induction course were considered standard risk (SR; 99 patients), whereas the others (n 5 383) were assigned to the HR group. Allogeneic (ALLO) or autologous (AUTO) HSCT was employed, respectively, in 141 and 102 HR patients after consolidation therapy. CR, early death, and induction failure rates were 87%, 3%, and 10%, respectively. Relapse occurred in 24% of patients achieving CR. The 8-year overall survival (OS), event-free survival (EFS), and disease-free survival (DFS) were 68%, 55%, and 63%, respectively. OS, EFS, and DFS for SR and HR patients were 83%, 63%, and 66% and 64%, 53%, and 62%. DFS was 63% and 73% for HR patients given AUTO-HSCT and ALLO-HSCT, respectively. In multivariate analysis, risk group, white blood cell >100 3 10 9 /L at diagnosis, and monosomal karyotype predicted poorer EFS. Risk-oriented treatment and broad use of HSCT result in a long-term EFS comparing favorably with previously published studies on childhood AML. (Blood. 2013; 122(2):170-178)

Key Points• NUP98/KDM5A, CBFA2T3/ GLIS2, KMT2A-rearrangements, and monosomy 7 are associated with poor outcome; RBM15/ MKL1 and others fare better.• Screening for NUP98/ KDM5A, RBM15/MKL1, CBFA2T3/GLIS2, and KMT2A rearrangements combined with conventional karyotyping is advisable.Genetic abnormalities and early treatment response are the main prognostic factors in acute myeloid leukemia (AML). Acute megakaryoblastic leukemia (AMKL) is a rare subtype of AML. Deep sequencing has identified CBFA2T3/GLIS2 and NUP98/KDM5A as recurrent aberrations, occurring in similar frequencies as RBM15/MKL1 and KMT2A-rearrangements. We studied whether these cytogenetic aberrations can be used for risk group stratification. To assess frequencies and outcome parameters of recurrent cytogenetic aberrations in AMKL, samples and clinical data of patients treated by the Associazione Italiana Ematologia Oncologia Pediatrica, Berlin-Frankfurt-Munster Study Group, Children's Oncology Group, Dutch Childhood Oncology Group, and the Saint Louis Hôpital were collected, enabling us to screen 153 newly diagnosed pediatric AMKL cases for the aforementioned aberrations and to study their clinical characteristics and outcome. CBFA2T3/GLIS2 was identified in 16% of the cases; RBM15/MKL1, in 12%; NUP98/KDM5A and KMT2A rearrangements, in 9% each; and monosomy 7, in 6%. These aberrations were mutually exclusive. RBM15/MKL1-rearranged patients were significantly younger. No significant differences in sex and white blood cell count were found. NUP98/KDM5A, CBFA2T3/GLIS2, KMT2A-rearranged lesions and monosomy 7 (NCK-7) independently predicted a poor outcome, compared with RBM15/MKL1-rearranged patients and those with AMKL not carrying these molecular lesions. NCK-7-patients (n 5 61) showed a 4-year probability of overall survival of 35 6 6% vs 70 6 5% in the RBM15/MKL1-other groups (n 5 92, P < .0001) and 4-year probability of event-free survival of 33 6 6% vs 62 6 5% (P 5 .0013), the 4-year cumulative incidence of relapse being 42 6 7% and 19 6 4% (P 5 .003), respectively. We conclude that these genetic aberrations may be used for risk group stratification of pediatric AMKL and for treatment tailoring. (Blood. 2016;127(26):3424-3430)

SummaryMitochondria are key players in the regulation of T cell biology by dynamically responding to cell needs, but how these dynamics integrate in T cells is still poorly understood. We show here that the mitochondrial pro-fission protein Drp1 fosters migration and expansion of developing thymocytes both in vitro and in vivo. In addition, we find that Drp1 sustains in vitro clonal expansion and cMyc-dependent metabolic reprogramming upon activation, also regulating effector T cell numbers in vivo. Migration and extravasation defects are also exhibited in Drp1-deficient mature T cells, unveiling its crucial role in controlling both T cell recirculation in secondary lymphoid organs and accumulation at tumor sites. Moreover, the observed Drp1-dependent imbalance toward a memory-like phenotype favors T cell exhaustion in the tumor microenvironment. All of these findings support a crucial role for Drp1 in several processes during T cell development and in anti-tumor immune-surveillance.