Kentaro Oki

Aberrant activation of ALK kinase by a novel truncated form ALK protein in neuroblastoma

Anaplastic lymphoma kinase (ALK) was originally identified from a rare subtype of non-Hodgkins lymphomas carrying t(2;5)(p23;q35) translocation, where ALK was constitutively activated as a result of a fusion with nucleophosmin (NPM). Aberrant ALK fusion proteins were also generated in inflammatory fibrosarcoma and a subset of non-small-cell lung cancers, and these proteins are implicated in their pathogenesis. Recently, ALK has been demonstrated to be constitutively activated by gene mutations and/or amplifications in sporadic as well as familial cases of neuroblastoma. Here we describe another mechanism of aberrant ALK activation observed in a neuroblastoma-derived cell line (NB-1), in which a short-form ALK protein (ALKdel2-3) having a truncated extracellular domain is overexpressed because of amplification of an abnormal ALK gene that lacks exons 2 and 3. ALKdel2-3 was autophosphorylated in NB-1 cells as well as in ALKdel2-3-transduced cells and exhibited enhanced in vitro kinase activity compared with the wild-type kinase. ALKdel2-3-transduced NIH3T3 cells exhibited increased colony-forming capacity in soft agar and tumorigenicity in nude mice. RNAi-mediated ALK knockdown resulted in the growth suppression of ALKdel2-3-expressing cells, arguing for the oncogenic role of this mutant. Our findings provide a novel insight into the mechanism of deregulation of the ALK kinase and its roles in neuroblastoma pathogenesis.

IDH1 and IDH2 mutations are rare in pediatric myeloid malignancies

Deficiency of the GPI anchor caused by a somatic mutation of the PIG-A gene in paroxysmal nocturnal hemoglobinuria. Cell 1993; 73: 703–711. 4 Maciejewski JP, Mufti GJ. Whole genome scanning as a cytogenetic tool in hematologic malignancies. Blood 2008; 112: 965–974. 5 Gondek LP, Tiu R, Haddad AS, O’Keefe CL, Sekeres MA, Theil KS et al. Single nucleotide polymorphism arrays complement metaphase cytogenetics in detection of new chromosomal lesions in MDS. Leukemia 2007; 21: 2058–2061. 6 Bessler M, Mason P, Hillmen P, Luzzatto L. Somatic mutations and cellular selection in paroxysmal nocturnal haemoglobinuria. Lancet 1994; 343: 951–953. 7 Endo M, Ware RE, Vreeke TM, Singh SP, Howard TA, Tomita A et al. Molecular basis of the heterogeneity of expression of glycosyl phosphatidylinositol anchored proteins in paroxysmal nocturnal hemoglobinuria. Blood 1996; 87: 2546–2557. 8 Young NS, Maciejewski JP. Genetic and environmental effects in paroxysmal nocturnal hemoglobinuria: this little PIG-A goes ‘Why? Why? Why?’. J Clin Invest 2000; 106: 637–641.

B-lymphoblastic lymphoma with the TCF3-PBX1 fusion gene

Lymphoblastic lymphoma (LBL) is a rare subtype of non-Hodgkin lymphoma (NHL) seen primarily in children or young adults. The frequency of T-cell lymphoblastic lymphomas (T-LBL) are predominant and frequency of B-cell LBL (B-LBL) are only 10~20% of LBL. Therefore, B-LBL account for 1 ~11% of NHL.[1][

Abstract 71: Mutational analysis for IDH1 and IDH2 in pediatric leukemia

Recently, mutational and epigenetic profiling of a large acute myeloid leukemia (AML) patient cohort revealed that NADP+dependent isocitrate dehydrogenase (IDH)1/2-mutated AMLs display global DNA hypermethylation and a specific hypermethylation signature, suggesting a shared proleukemogenic effect. To explore the involvements of IDH1/2 in the pathogenesis in pediatric hematological malignancies. We analyzed mutations that involve the activation sites of IDH1/2 using polymerase chain reaction amplification/sequencing in a total of 244 samples of pediatric myeloid malignancies as well as infantile leukemia including 17 AML-derived cell lines, 115 primary cases of AML, 28 primary cases of MDS, 15 primary cases of juvenile myelomonocytic leukaemia (JMML), 6 chronic myeloid leukemia (CML)-derived cell line, 18 primary cases of CML and 45 infantile leukemia(6 AML and 39 acute lymphoblastic leukemia (ALL) patients). Moreover, to assess whetherIDH1/2 mutations overlap with known gene abnormalities, such as FLT3, c-KIT, and NPM1 mutations, mutational analyses of FLT3, c-KIT, and NPM1 were also performed. The common IDH2 R140Q mutation was detected in a single AML case, whereas no IDH1 mutation was detected in samples of myeloid malignancies. Although no IDH2 mutation was detected in infantile leukemias, novel P127S, H133I and I130V of IDH1 mutations were detected in 4 of 45 (8.9%) infantile ALL cases. No IDH1 and IDH2 mutations were detected in the JMML, MDS, or CML samples examined. Six AML samples including one cell line had c-KIT mutations (D816V, N822K, or D419fs), 12 AML cases had FLT3-ITD and 10 infantile leukemia cases had FLT3 mutations (D835E or I836). The NPM1 mutation was detected in 2 of 132 AML samples. The AML case harboring the IDH2 mutation, Case 39 was a 12-year-old boy diagnosed as AML-M2 according to the French-American-British cooperative group classification system having t(8;21)(q22;q22), showed no abnormalities of NPM1, c-KIT, and FLT3. Remarkably, among 4 infantile ALL cases with IDH1 mutations, 3 cases showed mixed lineage leukemia(MLL) rearrangements with t(4;11). The FLT3-D835 mutation was found in 1 of 4 patients with IDH1 mutations. These results suggest that although the involvements of IDH1/2 mutations in the pathogenesis of pediatric myeloid malignancies are extremely rare, closely positioned to near activation site, R132 IDH1, these IDH1 mutations are the candidate second genetic events in a subset of MLL-leukemia. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 71. doi:1538-7445.AM2012-71