Genomic characterization implicates iAMP21 as a likely primary genetic event in childhood B-cell precursor acute lymphoblastic leukemia. Blood

Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, UK.
Blood (Impact Factor: 10.45). 06/2011; 117(25):6848-55. DOI: 10.1182/blood-2011-01-329961
Source: PubMed


Intrachromosomal amplification of chromosome 21 (iAMP21) defines a distinct subgroup of childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL) that has a dismal outcome when treated with standard therapy. For improved diagnosis and risk stratification, the initiating genetic events need to be elucidated. To investigate the genetic basis of BCP-ALL, genomes of 94 iAMP21 patients were interrogated by arrays, FISH, and multiplex ligation-dependent probe amplification. Most copy number alterations targeted chromosome 21, reinforcing the complexity of this chromosome. The common region of amplification on chromosome 21 was refined to a 5.1-mb region that included RUNX1, miR-802, and genes mapping to the Down syndrome critical region. Recurrent abnormalities affecting genes in key pathways were identified: IKZF1 (22%), CDKN2A/B (17%), PAX5 (8%), ETV6 (19%), and RB1 (37%). Investigation of clonal architecture provided evidence that these abnormalities, and P2RY8-CRLF2, were secondary to chromosome 21 rearrangements. Patient outcome was uniformly poor with standard therapy irrespective of the presence or absence of these changes. This study has provided evidence that chromosome 21 instability is the only anomaly among those so far investigated that is common to all iAMP21 patients, and therefore the initiating event is likely to be found among the complex structural rearrangements of this abnormal chromosome.

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Available from: Jonathan C Strefford
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    • "Amplified regions on chromosome 21 are found within a 5.1 Mb region containing RUNX1, miR-802, and genes mapping to the Down syndrome critical region. iAMP21 occurs in approximately 2% of older children with B-ALL, and is associated with poorer outcomes when treated with standard therapy, and also increased risk for early and late relapse [56]. The five-year EFS is approximately 29%, with an OS of 71% [57]. "
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    ABSTRACT: In the pediatric population, B-acute lymphoblastic leukemia (B-ALL) is the most prevalent childhood hematological malignancy, as well as the leading cause of childhood cancer-related mortality. Advances in cytogenetics utilizing array-based technologies and next-generation sequencing (NGS) techniques have revealed exciting insights into the genetic basis of this disease, with the hopes of developing individualized treatment plans for affected children. In this comprehensive review, we discuss our current understanding of childhood (pediatric) B-ALL and highlight the most recent genetic advances and their therapeutic implications.
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    • "This abnormal chromosome 21 may vary according to its morphological form. In interphase, the signals are clustered together, except for one signal representing the normal chromosome 21 that is usually located apart from the others(2,7). "
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    • "Routinely, rearrangements in immunoglobulin-chain (Ig) or T-cell receptor genes (TCR) serve as template for the design of tumor cell specific PCRs (Ig/TCR-PCR) [4-7]. Amplification of a part of the long arm of chromosome 21 including the AML1/RUNX1 gene (iAMP21) occurs in 1-2% of ALL [8,9]. "
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