Abstract
The t(8;21)(q22;q22) translocation is one of the most common genetic abnormalities in acute myeloid leukemia (AML), identified in 15% of all cases of AML, including 40–50% of FAB M2 subtype and rare cases of M0, M1 and M4 subtypes1,2,3,4. The most commonly known AML1-ETO fusion protein (full-length AML1-ETO) from this translocation has 752 amino acids and contains the N-terminal portion of RUNX1 (also known as AML1, CBFα2 or PEBP2αB), including its DNA binding domain, and almost the entire RUNX1T1 (also known as MTG8 or ETO) protein5. Although alterations of gene expression and hematopoietic cell proliferation have been reported in the presence of AML1-ETO, its expression does not lead to the development of leukemia6,7,8,9. Here, we report the identification of a previously unknown alternatively spliced isoform of the AML1-ETO transcript, AML1-ETO9a, that includes an extra exon, exon 9a, of the ETO gene. AML1-ETO9a encodes a C-terminally truncated AML1-ETO protein of 575 amino acids. Expression of AML1-ETO9a leads to rapid development of leukemia in a mouse retroviral transduction–transplantation model. More importantly, coexpression of AML1-ETO and AML1-ETO9a results in the substantially earlier onset of AML and blocks myeloid cell differentiation at a more immature stage. These results indicate that fusion proteins from alternatively spliced isoforms of a chromosomal translocation may work together to induce cancer development.
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Acknowledgements
We wish to thank J. Biggs for critical editing of this manuscript, P. Burgoyne for MF-1 mice, P. Erickson for ETO antibodies, K. Kopecky for providing information on individuals with AML in accordance with HIPAA regulation, M. Shen for maintaining mouse colonies, M. Carroll and members of the Zhang lab for discussions. This work was supported by US National Institutes of Health grants CA104509 and CA096735 to D.-E.Z. A.B. was supported by US National Research Service Award fellowship F32HL079900. The Stein Endowment Fund has partially supported the departmental molecular biology service laboratory for DNA sequencing and oligonucleotide synthesis. This is manuscript 17819-MEM from The Scripps Research Institute.
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M.Y., E.K., L.F.P., A.B., Y.M., Y.W. participated in experiments. I.-M.C., Z.C., J.D.R. and C.L.W. provided leukemia patient samples. D.-E.Z. supervised the project and wrote the manuscript.
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Supplementary information
Supplementary Fig. 1
Standard curves representing the log of starting amount (pg) of DNA versus the PCR threshold cycle number (CT) (PDF 70 kb)
Supplementary Fig. 2
Detection of AE and AE9a protein expression in leukemic mice (PDF 145 kb)
Supplementary Fig. 3
Analysis of lineage marker expression in peripheral blood cells of leukemic mice by flow cytometry (PDF 95 kb)
Supplementary Table 1
Differential counts of peripheral blood cells and parameters related to leukemogenesis (PDF 99 kb)
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Yan, M., Kanbe, E., Peterson, L. et al. A previously unidentified alternatively spliced isoform of t(8;21) transcript promotes leukemogenesis. Nat Med 12, 945–949 (2006). https://doi.org/10.1038/nm1443
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DOI: https://doi.org/10.1038/nm1443
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