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DSB leads to MLL translocation
Key Event Relationship Overview
AOPs Referencing Relationship
|AOP Name||Adjacency||Weight of Evidence||Quantitative Understanding||Point of Contact||Author Status||OECD Status|
|Inhibitor binding to topoisomerase II leading to infant leukaemia||adjacent||High||Not Specified||Agnes Aggy (send email)||Open for comment. Do not cite||EAGMST Under Review|
Life Stage Applicability
Key Event Relationship Description
There is evidence that the inappropriate joining of ‘hanging ends’ following DSB happens in the same transcriptional factory (hub), and the result is a fusion gene and ultimately protein product (Cowell & Austin 2012; Pendleton et al 2014; Sanjuan-Pla et al 2015). The first part of this description has not been shown in the putative target cell, which is still not unequivocally identified, but for the second part there is ample evidence of formation of MLL-AF4 fusion product that has been a result of a very early chromosomal translocation and rejoining. It is of interest that the simultaneously induced specific DSBs in the MLL gene and two different translocation partners (AF4 and AF9) by engineered nucleases in human HSPCs resulted in specific ‘patient-like’ chromosomal translocations (Breese et al 2016).
Evidence Supporting this KER
The KER as such is biologically plausible and strong. DNA strand breaks, if not resulting in cell death, may lead to chromosomal translocation in the surviving cell population (McClendon et al. 2007). DNA breaks and MLL rearrangements by etoposide and bioflavonoids have been demonstrated in human fetal liver haematopoietic stem cells, in human embryonic stem cells and in human prehaematopoietic mesenchymal stem cells as well as in cord blood mononuclear cells (Ishii et al 2002; Blanco et al 2004; Moneypenny et al 2006; Bueno et al 2009; Menendez et al 2009), which shows that DSB (in this specific case due to TopoII poisoning) -associated MLL rearrangements are produced in appropriate human cells in utero.
Uncertainties and Inconsistencies
A target cell, i.e. leukaemia-initiating cell, has not been identified with sufficient confidence and consequently there is no target cell model to recapitulate the linkage between TopoII inhibition (‘poisoning’) and the production of DSB in an appropriate target. Recently, by the expression of engineered nucleases (TALENs) to induce simultaneous patient specific double strand breaks in the MLL gene and two different known translocation partners (AF4 and AF9), Breese et al (2015) were able to produce specific chromosomal translocations in K562 cells and in primary HSPCs.
Known modulating factors
Known Feedforward/Feedback loops influencing this KER
Domain of Applicability
Seminal studies demonstrated an in utero, pre-natal origin of these MLLr in monozygotic twins with concordant B-ALL, in retrospective analysis in Guthrie cards and cord bloods (Ford et al., 1993; Gale et al., 1997). A single-pulse of etoposide induces DSBs measured by g-H2AX staining in all primary cell types tested (hESC, fetal-, neonatal- and adult-derived CD34+ HSPCs)(Rodriguez et al. 2020).
Blanco JG, Edick MJ, Relling MV. Etoposide induces chimeric Mll gene fusions. FEDERATION OF AMERICAN SOCIETIES FOR EXPERIMENTAL BIOLOGY (FASEB) 2004; 18(1):173–5. doi: 10.1096/fj.03-0638fje
Breese EH, Buechele C, Dawson C, Cleary ML, Porteus MH. Use of Genome Engineering to Create Patient Specific MLL Translocations in Primary Human Hematopoietic Stem and Progenitor Cells. Public Library of Science (PLoS ONE) 2015 Sep 9;10(9):e0136644. doi: 10.1371/journal.pone.0136644.
Buechele C, Breese EH, Schneidawind D, Lin CH, Jeong J, Duque-Afonso J, Wong SH, Smith KS, Negrin RS, Porteus M, Cleary ML. MLL leukemia induction by genome editing of human CD34+ hematopoietic cells. Blood 2015 Oct 1;126(14):1683-1694. doi: 10.1182/blood-2015-05-646398.
Chen W, Li Q, Hudson WA, Kumar A, Kirchhof N, Kersey JH. A murine Mll-AF4 knock-in model results in lymphoid and myeloid deregulation and hematologic malignancy. Blood Journal 2006; 108(2):669–77. doi: 10.1182/blood-2005-08-3498
Cowell IG and AustinInt CA. Mechanism of Generation of Therapy Related Leukemia in Response to Anti-Topoisomerase II Agents. J. Environ. Res. Public Health 2012, 9(6), 2075-2091; https://doi.org/10.3390/ijerph9062075
Ford, A. M., Ridge, S. A., Cabrera, M. E., Mahmoud, H., Steel, C. M., Chan, L. C., & Greaves, M. (1993). In utero rearrangements in the trithorax-related oncogene in infant leukaemias. Nature, 363(6427), 358–60. https://doi.org/10.1038/363358a0
Gale, K. B., Ford, A. M., Repp, R., Borkhardt, A., Keller, C., Eden, O. B., & Greaves, M. F. (1997). Backtracking leukemia to birth: identification of clonotypic gene fusion sequences in neonatal blood spots. Proceedings of the National Academy of Sciences of the United States of America, 94(25), 13950–4. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/9391133
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Ishii E, Eguchi M, Eguchi-Ishimae M, Yoshida N, Oda M, Zaitsu M, et al. In vitro cleavage of the MLL gene by topoisomerase II inhibitor (etoposide) in normal cord and peripheral blood mononuclear cells. International journal of hematology. 2002; 76(1):74–9.
Li Z, Sun B, Clewell RA, Adeleye Y, Andersen ME, Zhang Q. Dose-response modeling of etoposide-induced DNA damage response. Toxicological Sciences 2014 Feb;137(2):371-84. doi: 10.1093/toxsci/kft259.
Libura J, Slater DJ, Felix CA, Richardson C. Therapy-related acute myeloid leukemia-like MLL rearrangements are induced by etoposide in primary human CD34+ cells and remain stable after clonal expansion. Blood Journal 2005; 105(5):2124–31. doi: 10.1182/blood-2004-07-2683
Libura J, Ward M, Solecka J, Richardson C. Etoposide-initiated MLL rearrangements detected at high frequency in human primitive hematopoietic stem cells with in vitro and in vivo long-term repopulating potential. European Journal of Haematology 2008; 81(3):185–95. doi: 10.1111/j.1600-0609.2008.01103.x
McClendon AK, Osheroff N. DNA Topoisomerase II, Genotoxicity and Cancer. Mutation Research 2007; 623 (1-2): 83-97.
Moneypenny CG, Shao J, Song Y, Gallagher EP. MLL rearrangements are induced by low doses of etoposide in human fetal hematopoietic stem cells. Carcinogenesis. 2006; 27(4):874–81. Epub 2005/12/27. doi: 10.1093/carcin/bgi322
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Nanya M, Sato M, Tanimoto K, Tozuka M, Mizutani S, Takagi M. Dysregulation of the DNA Damage Response and KMT2A Rearrangement in Fetal Liver Hematopoietic Cells. Public Library of Science (PLoS ONE). 2015 Dec 11;10(12):e0144540. doi: 10.1371/journal.pone.0144540.
Pendleton M1, Lindsey RH Jr, Felix CA, Grimwade D, Osheroff N. Topoisomerase II and leukemia. Ann N Y Acad Sci. 2014 Mar;1310:98-110. doi: 10.1111/nyas.12358. Epub 2014 Feb 3.
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Rodríguez‐Cortez, V C, Menéndez, P, 2020. Genotoxicity of permethrin and clorpyriphos on human stem and progenitor cells at different ontogeny stages: implications in leukaemia development. EFSA supporting publication 2020: 17( 5): EN‐1866. 35 pp. doi: 10.2903/sp.efsa.2020.EN‐1866
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