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Monitoring of childhood ALL using BCR-ABL1 genomic breakpoints identifies a subgroup with CML-like biology

Lenka Hovorkova, Marketa Zaliova, Nicola C. Venn, Kirsten Bleckmann, Marie Trkova, Eliska Potuckova, Martina Vaskova, Jana Linhartova, Katerina Machova Polakova, Eva Fronkova, Walter Muskovic, Jodie E. Giles, Peter J. Shaw, Gunnar Cario, Rosemary Sutton, Jan Stary, Jan Trka and Jan Zuna

Key Points

  • Combination of Ig/TCR and BCR-ABL1 genomic approach for MRD monitoring in childhood ALL reveals patients with CML-like disease.

  • Monitoring ALL using BCR-ABL1 genomic breakpoint is feasible and enables the most specific and sensitive MRD quantification.

Publisher's Note: There is an Inside Blood Commentary on this article in this issue.

Abstract

We used the genomic breakpoint between BCR and ABL1 genes for the DNA-based monitoring of minimal residual disease (MRD) in 48 patients with childhood acute lymphoblastic leukemia (ALL). Comparing the results with standard MRD monitoring based on immunoglobulin/T-cell receptor (Ig/TCR) gene rearrangements and with quantification of IKZF1 deletion, we observed very good correlation for the methods in a majority of patients; however, >20% of children (25% [8/32] with minor and 12.5% [1/8] with major-BCR-ABL1 variants in the consecutive cohorts) had significantly (>1 log) higher levels of BCR-ABL1 fusion than Ig/TCR rearrangements and/or IKZF1 deletion. We performed cell sorting of the diagnostic material and assessed the frequency of BCR-ABL1-positive cells in various hematopoietic subpopulations; 12% to 83% of non–ALL B lymphocytes, T cells, and/or myeloid cells harbored the BCR-ABL1 fusion in patients with discrepant MRD results. The multilineage involvement of the BCR-ABL1-positive clone demonstrates that in some patients diagnosed with BCR-ABL1-positive ALL, a multipotent hematopoietic progenitor is affected by the BCR-ABL1 fusion. These patients have BCR-ABL1-positive clonal hematopoiesis resembling a chronic myeloid leukemia (CML)–like disease manifesting in “lymphoid blast crisis.” The biological heterogeneity of BCR-ABL1-positive ALL may impact the patient outcomes and optimal treatment (early stem cell transplantation vs long-term administration of tyrosine-kinase inhibitors) as well as on MRD testing. Therefore, we recommend further investigations on CML-like BCR-ABL1-positive ALL.

  • Submitted November 7, 2016.
  • Accepted March 17, 2017.
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