The Mll PTD and Flt3 ITD Double Knock-In Mouse Develops Acute Leukemia and Recapitulates Phenotypic, Molecular and Epigenetic Characteristics of the Counterpart Human Acute Myeloid Leukemia

• Published in: Blood 2010-11, Vol.116 (21), p.150-150
• Main Authors: Zorko, Nicholas, Whitman, Susan P., Bernot, Kelsie, Ngangana, Myntee T., Siebenaler, Ronald, Liu, Shujun, Wu, Yue-Zhong, Kalu, Chidimma, Zhang, Xiaoli, Jarjoura, David, Xie, Zhiliang, Chan, Kenneth K., Dorrance, Adrienne M., Lee, Benjamin H., Briesewitz, Roger, Perrotti, Danilo, Marcucci, Guido, Caligiuri, Michael A.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V116.21.150.150

Abstract 150 The Mll PTD and Flt3 ITD are co-present in a subset of adult patients (pts) with cytogenetically normal (CN) acute myeloid leukemia (AML) and poor clinical outcomes. While the single mutant knock-in (KI) mice (Mll PTD or Flt3 ITD) exhibit enhanced myeloid progenitor self-renewal or reduced apoptosis, respectively, neither model develops acute leukemia. We hypothesized that with mutant expression driven via the endogenous promoters, the two mutations may cooperate in vivo to induce an acute leukemia that mimics the human counterpart. Single mutant heterozygous KI mice were crossed to produce the PTD/ITD double KI. PTD/ITD mice were bred with the homozygous Flt3 ITD to generate the PTD/ITD2 genotype. An AML diagnosis was based on blood differentials, immunophenotyping, tissue pathology and transplantability. Real time RT-PCR and 5'-methylcytosine LC/MS assays measured gene expression and global DNA methylation levels, respectively. PTD/ITD and PTD/ITD2 mice developed transplantable, CN-AML/undifferentiated leukemia exhibiting expansion of monocytic/myelomonocytic Gr1±/Mac1+ and/or immature CD3−/CD19−/CD117+/Mac1−/B220lo cell populations, splenomegaly, leukocytosis, anemia and thrombocytopenia. PTD/ITD mice had significantly reduced lifespans compared to mice with single mutant PTD and ITD KIs and wild-type (Wt) controls (medians: 50, 99, 88, 94 weeks, respectively; P2-fold lower in bone marrow (BM) of leukemic PTD/ITD mice compared to age-matched single mutant KIs or Wt controls. HoxA9 and its cofactor Meis1 were upregulated 15- and 5-fold, respectively, in PTD/ITD mice with leukemia versus Wt BM. Yet, compared to Wt BM, single PTD KI exhibited increased HoxA9 (∼6-fold) but not Meis1, implicating an expression threshold for HoxA9 and a crucial role for Meis1 for the development of acute leukemia in the double KI. Consistent with Flt3 being a downstream transcriptional target of Meis1, total Flt3 mRNA (WT and ITD) levels increased 3-fold in the leukemic PTD/ITD mice relative to either single mutant KIs or Wt controls. Furthermore, o