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Letters to the Editor
G2DHE super-enhancer structure. However, we could not observe any specific pattern of TF binding sites com- monly relocated to the EVI1 locus in 3q-AML patient and cell line data. Meanwhile, we conclude that breakpoint- RE are not essential for the regulation and maintenance of EVI1 expression in 3q-AML.
In summary, our data show that RE are highly enriched at inv(3)/t(3;3) breakpoint sites in AML and represent a source of genomic vulnerability without providing addi- tional regulatory or activating signal for EVI1 in this leukemia subtype, as evidenced by CRISPR-Cas9 editing experiments in 3q-rearranged cell lines. However, we cannot exclude the involvement of full-length source RE sequences in the formation of 3q rearrangements in ear- lier stages of malignant transformation. Since many retrotransposition-competent RE often become truncated or undergo internal reshuffling upon insertion in a new genomic location,11,12 the presence of resulting chimeric breakpoint-RE sequences would bear no functional con- sequences, which stands in line with the lack of effects observed upon CRISPR-Cas9 editing of breakpoint-RE fusion sequences in our cell line models.
Additionally, the data from the K562 reporter cell line provide an orthogonal confirmation of the minimal G2DHE being sufficient for EVI1 transcriptional activa- tion.1
Jagoda Mika,1 Sophie Ottema,2 Sandra Kiehlmeier,1 Sabrina Kruse,1 Leonie Smeenk,2 Judith Müller,1
Sabrina Schweiggert,1 Carl Herrmann,3 Mathijs Sanders,2 Ruud Delwel2 and Stefan Gröschel1,4,5
1
Molecular Leukemogenesis Group, German Cancer Research
Center, Heidelberg, Germany; 2Department of Hematology, Erasmus University Medical Center, Oncode Institute, Rotterdam, the Netherlands; 3Health Data Science Unit, Medical Faculty Heidelberg and BioQuant, Heidelberg, Germany; 4Internal Medicine V, Heidelberg University Hospital, Heidelberg, Germany
5
and Oncology Center Worms, Worms, Germany
Correspondence:
STEFAN GROESCHEL - stefan.groeschel@dkfz.de doi:10.3324/haematol.2020.277400
Received: December 9, 2020.
Accepted: March 12, 2021.
Pre-published: March 25, 2021.
Disclosures: the authors declare no competing financial interests.
Contributions: JMi, SO, LS, SKi, JMü, SS and SG performed experiments; SO and RD provided RNA-seq data; JMi, SKr, MS and CH analyzed results; JMi made the figures; JMi and SG designed the experiments; JMi and SG wrote the manuscript with input from all authors.
Acknowledgments: the authors would like to thank Claudia Scholl
and Stefan Fröhling (German Cancer Research Center, Heidelberg, Germany and National Center for Tumor Diseases, Heidelberg, Germany). We thank the DKFZ Genomics and Proteomics Core Facility for providing excellent sequencing services and Mathias Utz (German Cancer Research Center, Heidelberg, Germany) for technical assistance.
Funding: this research was supported with a Starting Grant (677209) of the European Research Council (SG), the program “ENHancers And Non-coding Cancer (Epi-)Mutations (ENHANCE)” funded within the DKFZ-NCT3.0 initiative on 'Integrative Projects in Basic Cancer Research‘ (CH, SG), a scholarship of the Helmholtz International Graduate School for Cancer Research (JMi, SKi), a grant of the NCT3.0 basic research (SG), a fellowship from the Daniel den Hoed, Erasmus MC Foundation (LS) and a grant of the Koningin Wilhelmina Fonds from the Dutch Cancer Society (RD, SO).
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