Haematologica (Jan 2023)

TAL1 activation in T-cell acute lymphoblastic leukemia: a novel oncogenic 3’ neo-enhancer

  • Charlotte Smith,
  • Ashish Goyal,
  • Dieter Weichenhan,
  • Eric Allemand,
  • Anand Mayakonda,
  • Umut Toprak,
  • Anna Riedel,
  • Estelle Balducci,
  • Manisha Manojkumar,
  • Anastasija Pejkovska,
  • Oliver Mücke,
  • Etienne Sollier,
  • Ali Bakr,
  • Kersten Breuer,
  • Pavlo Lutsik,
  • Olivier Hermine,
  • Salvatore Spicuglia,
  • Vahid Asnafi,
  • Christoph Plass,
  • Aurore Touzart

DOI
https://doi.org/10.3324/haematol.2022.281583
Journal volume & issue
Vol. 108, no. 5

Abstract

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T-cell acute lymphocytic leukemia protein 1 (TAL1) is one of the most frequently deregulated oncogenes in T-cell acute lymphoblastic leukemia (T-ALL). Its deregulation can occur through diverse cis-alterations, including SIL-TAL1 microdeletions, translocations with T-cell Receptor loci, and more recently described upstream intergenic non-coding mutations. These mutations consist of recurrent focal microinsertions that create an oncogenic neo-enhancer accompanied by activating epigenetic marks. This observation laid the groundwork for an innovative paradigm concerning the activation of proto-oncogenes via genomic alterations of non-coding intergenic regions. However, for the majority of T-ALL expressing TAL1 (TAL1+), the deregulation mechanism remains 'unresolved'. We took advantage of H3K27ac and H3K4me3 chromatin immunoprecipitation sequencing data of eight cases of T-ALL, including five TAL1+ cases. We identified a putative novel oncogenic neo-enhancer downstream of TAL1 in an unresolved monoallelic TAL1+ case. A rare but recurrent somatic heterozygous microinsertion within this region creates a de novo binding site for MYB transcription factor. Here we demonstrate that this mutation leads to increased enhancer activity, gain of active epigenetic marks, and TAL1 activation via recruitment of MYB. These results highlight the diversity of non-coding mutations that can drive oncogene activation.