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Iacobucci I.,University of Bologna | Lonetti A.,University of Bologna | Messa F.,University of Turin | Ferrari A.,University of Bologna | And 19 more authors.
Leukemia | Year: 2010

The main reason for the unfavorable clinical outcome of BCR-ABL1-positive acute lymphoblastic leukemia (ALL) is genetic instability. However, how normal B-cell precursors acquire the genetic changes that lead to transformation has not yet been completely defined. We investigated the expression of the activation-induced cytidine deaminase (AID) and its role in clinical outcome in 61 adult BCR-ABL1-positive ALL patients. AID expression was detected in 36 patients (59%); it correlated with the BCR-ABL1 transcript levels and disappeared after treatment with tyrosine kinase inhibitors. Different AID splice variants were identified: full-length isoform; AIDΔE4a, with a 30-bp deletion of exon 4; AIDΔE4, with the exon 4 deletion; AIDins3, with the retention of intron 3; AIDΔE3-E4 isoform without deaminase activity. AID-FL predominantly showed cytoplasmic localization, as did the AID-ΔE4a and AID-ΔE3E4 variants, whereas the C-terminal-truncated AID-ΔE4 showed a slightly increased nuclear localization pattern. AID expression correlated with a higher number of copy number alterations identified in genome-wide analysis using a single-nucleotide polymorphism array. However, the expression of AID at diagnosis was not associated with a worse prognosis. In conclusion, BCR-ABL1-positive ALL cells aberrantly express different isoforms of AID that may act as mutators outside the immunoglobulin (Ig) gene loci in promoting genetic instability. © 2010 Macmillan Publishers Limited All rights reserved.

Iacobucci I.,University of Bologna | Iraci N.,University of Bologna | Iraci N.,University of Cambridge | Messina M.,University of Rome La Sapienza | And 19 more authors.
PLoS ONE | Year: 2012

Background: Deletions of IKAROS (IKZF1) frequently occur in B-cell precursor acute lymphoblastic leukemia (B-ALL) but the mechanisms by which they influence pathogenesis are unclear. To address this issue, a cohort of 144 adult B-ALL patients (106 BCR-ABL1-positive and 38 B-ALL negative for known molecular rearrangements) was screened for IKZF1 deletions by single nucleotide polymorphism (SNP) arrays; a sub-cohort of these patients (44%) was then analyzed for gene expression profiling. Principal Findings: Total or partial deletions of IKZF1 were more frequent in BCR-ABL1-positive than in BCR-ABL1-negative B-ALL cases (75% vs 58%, respectively, p = 0.04). Comparison of the gene expression signatures of patients carrying IKZF1 deletion vs those without showed a unique signature featured by down-regulation of B-cell lineage and DNA repair genes and up-regulation of genes involved in cell cycle, JAK-STAT signalling and stem cell self-renewal. Through chromatin immunoprecipitation and luciferase reporter assays we corroborated these findings both in vivo and in vitro, showing that Ikaros deleted isoforms lacked the ability to directly regulate a large group of the genes in the signature, such as IGLL1, BLK, EBF1, MSH2, BUB3, ETV6, YES1, CDKN1A (p21), CDKN2C (p18) and MCL1. Conclusions: Here we identified and validated for the first time molecular pathways specifically controlled by IKZF1, shedding light into IKZF1 role in B-ALL pathogenesis. © 2012 Iacobucci et al.

Falini B.,University of Perugia | Macijewski K.,Munich Leukemia Laboratory GmbH | Weiss T.,Munich Leukemia Laboratory GmbH | Bacher U.,University of Hamburg | And 15 more authors.
Blood | Year: 2010

NPM1-mutated acute myeloid leukemia (AML) is a provisional entity in the 2008 World Health Organization (WHO) classification of myeloid neoplasms. The significance of multilineage dysplasia (MLD) in NPM1-mutated AML is unclear. Thus, in the 2008 WHO classification, NPM1-mutated AML with MLD is classified as AML with myelodysplasia (MD)-related changes (MRCs). We evaluated morphologically 318 NPM1-mutated AML patients and found MLD in 23.3%. Except for a male predominance and a lower fms-related tyrosine kinase 3-internal tandem duplication (FLT3-ITD) incidence in the MLD+ group, no differences were observed in age, sex, cytogenetics, and FLT3 - tyrosine kinase domain between NPM1-mutated AML with and without MLD. NPM1-mutated AML with and without MLD showed overlapping immunophenotype (CD34 negativity) and gene expression profile (CD34 down-regulation, HOX genes up-regulation). Moreover, overall and event-free survival did not differ among NPM1-mutated AML patients independently of whether they were MLD+ or MLD-, the NPM1-mutated/FLT3-ITD negative genotype showing the better prognosis. Lack of MLD impact on survival was confirmed by multivariate analysis that highlighted FLT3-ITD as the only significant prognostic parameter in NPM1-mutated AML. Our findings indicate that NPM1 mutations rather than MLD dictate the distinctive features of NPM1-mutated AML. Thus, irrespective of MLD, NPM1-mutated AML represents one disease entity clearly distinct from AML with MRCs. © 2010 by The American Society of Hematology.

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