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Biochemistry - Hematology - Molecular Biology - Oncology


IKAROS Deletions Dictate a Unique Gene Expression Signature in Patients with Adult B-Cell Acute Lymphoblastic Leukemia
Published: Wednesday, July 25, 2012
Author: Ilaria Iacobucci et al.

by Ilaria Iacobucci, Nunzio Iraci, Monica Messina, Annalisa Lonetti, Sabina Chiaretti, Emanuele Valli, Anna Ferrari, Cristina Papayannidis, Francesca Paoloni, Antonella Vitale, Clelia Tiziana Storlazzi, Emanuela Ottaviani, Viviana Guadagnuolo, Sandra Durante, Marco Vignetti, Simona Soverini, Fabrizio Pane, Robin Foà, Michele Baccarani, Markus Müschen, Giovanni Perini, Giovanni Martinelli

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.

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