Analysis of genomic breakpoints in p190 and p210 BCR-ABL indicate distinct mechanisms of formation.

Wessex Regional Genetics Laboratory, Salisbury and Human Genetics Division, University of Southampton School of Medicine, Southampton, UK.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K (Impact Factor: 10.16). 10/2010; 24(10):1742-50. DOI: 10.1038/leu.2010.174
Source: PubMed

ABSTRACT We sought to understand the genesis of the t(9;22) by characterizing genomic breakpoints in chronic myeloid leukemia (CML) and BCR-ABL-positive acute lymphoblastic leukemia (ALL). BCR-ABL breakpoints were identified in p190 ALL (n=25), p210 ALL (n=25) and p210 CML (n=32); reciprocal breakpoints were identified in 54 cases. No evidence for significant clustering and no association with sequence motifs was found except for a breakpoint deficit in repeat regions within BCR for p210 cases. Comparison of reciprocal breakpoints, however, showed differences in the patterns of deletion/insertions between p190 and p210. To explore the possibility that recombinase-activating gene (RAG) activity might be involved in ALL, we performed extra-chromosomal recombination assays for cases with breakpoints close to potential cryptic recombination signal sequence (cRSS) sites. Of 13 ALL cases tested, 1/10 with p190 and 1/3 with p210 precisely recapitulated the forward BCR-ABL breakpoint and 1/10 with p190 precisely recapitulated the reciprocal breakpoint. In contrast, neither of the p210 CMLs tested showed functional cRSSs. Thus, although the t(9;22) does not arise from aberrant variable (V), joining (J) and diversity (D) (V(D)J) recombination, our data suggest that in a subset of ALL cases RAG might create one of the initiating double-strand breaks.

  • Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 04/2013; · 10.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chronic myeloid leukemia (CML) is a rare disease in children and adolescents and various aspects-from molecular genesis to therapy regimen-have been taken over from studies on the more prevalent adult CML. However, differences have been observed between malignancies with identical underlying chromosomal translocations, but occurring at different age groups, suggesting some diversity in the mechanisms of formation and leukemogenesis. A multiplex long-range PCR-based assay was developed to allow fast and reliable amplification of patient-specific BCR-ABL1 fusion sequences from genomic DNA. The localization of breakpoints was analyzed with respect to distribution within the breakpoint cluster regions, sequence features, and association to repetitive elements or motifs associated with DNA recombination. The genomic fusion sites of 59 pediatric CML patients showed a bimodal breakpoint distribution in BCR that was different from the distribution in adult CML cases, but with similarities to BCR-ABL1-positive, acute lymphoblastic leukemia in adults. BCR breakpoints were found more frequently positioned within, or close to, Alu repeats than would be expected based on their overall sequence proportion. Technical aspects of the highly sensitive DNA-based quantification of residual CML cells by specific fusion sequence during tyrosine kinase inhibitor therapy are exemplified in a subcohort of pediatric CML patients. © 2012 Wiley Periodicals, Inc.
    Genes Chromosomes and Cancer 08/2012; 51(11):1045-53. · 3.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Treatment-free remission (TFR) has recently emerged as a goal of treatment in chronic myeloid leukaemia (CML). Molecular remission is sustained in around 30% of imatinib-treated patients who stop treatment after ≥2 years with undetectable minimal residual disease (UMRD) by conventional real-time reverse transcription polymerase chain reaction. An additional 20–30% of patients will lose UMRD, but remain in stable major molecular remission off treatment. Most patients with molecular recurrence have a significant increase in BCR-ABL1 within the first 6 months off treatment, but there are also rare late relapses. As re-treatment with imatinib restores control, a trial of TFR is safe so long as careful molecular monitoring is provided to enable prompt re-treatment. The minimum eligibility criteria for a trial of TFR are not yet defined, but the available data support a MRD level of around a molecular response of 4·5 log for at least 2 years. Factors associated with a higher probability of TFR include low risk Sokal score, prior interferon treatment, longer total duration of imatinib treatment and higher numbers of natural killer cells at the time of imatinib discontinuation. Preliminary data suggest that the rate of TFR in patients treated with more potent tyrosine kinase inhibitors will probably be higher. The biology that underlies TFR is an area of active investigation.
    British Journal of Haematology 04/2014; · 4.94 Impact Factor

Full-text (2 Sources)

Available from
May 23, 2014