Abstract 2643: Thymic precursor cells generate acute myeloid leukemia in NP23-NHD13 double transgenic mice
Authors: Kundu Subhadip , Park Eun Sil , Chung Yang Jo , Barlowe Trevor Stephen , Aplan Peter D. 
Published: July 2017

Oncogenic fusion genes have been identified in a large number of hematologic malignancies. We previously generated mice that expressed either a NUP98-PHF23 (NP23) or NUP98-HOXD13 (NHD13) fusion in the hematopoietic compartment. Both NP23 and NHD13 mice develop a wide variety of leukemias, including myeloid, erythroid, megakaryocytic and lymphoid, at 9-14 months of age. NP23-NHD13 double transgenic mice were generated by interbreeding NP23 and NHD13 mice. Surprisingly, 100% of the NP23-NHD13 double transgenic mice showed rapid onset of acute myeloid leukemia (AML) within 3 months. The leukemias were characterized by extraordinarily high WBC and replacement of the thymus with Mac1+/Gr1+ myeloblasts; the percent of malignant myeloid cells in the thymus was often higher than the bone marrow (BM). It led to the intriguing hypothesis that the AML generated in NP23-NHD13 mice arose in the thymus, as opposed to the BM. We transplanted unfractionated cells from the thymus of a NP23-NHD13 mouse, invaded by Mac1+/Gr1+ AML cells or residual CD4-/CD8- double negative (DN) thymocytes into sub-lethally irradiated recipients. All mice (transplanted with either unfractionated leukemic cells or DN cells from same leukemic mouse) developed Mac1+/Gr1+ AML within 26 days, indicating that the AML was aggressive and transplantable, and could be transmitted by DN thymocytes. The observation that the AML was transmitted by the DN thymocytes or Mac1+/Gr1+ AML suggested that the DN thymocytes may be the cell of origin for this AML. To rule out the possibility that the leukemia in this experiment was transmitted by rare, contaminant Mac1+/Gr1+ cells, we repeated the experiment, twice, using DN thymocytes from 4-5 wk old mice with no signs of leukemia. DN thymocytes again transmitted a Mac1+/Gr1+ AML. We further fractioned DN thymocytes into DN1, DN2, DN3 and DN4 populations; the recipients of DN1 and DN2 populations developed a Mac1+/Gr1+ AML, but DN3 and DN4 recipients were healthy with no signs of engraftment in the peripheral blood. DN thymocytes from non-leukemic NP23-NHD13 mice were cultured on an OP9 stromal layer, which has been shown to support myeloid differentiation in vitro. DN thymocytes from non-leukemic NP23-NHD13 mice cultured on a OP9 stromal layer showed a markedly enhanced ability to differentiate into Mac1+/Gr1+ myeloid lineage cells compared to WT (56% vs 1.4 % at day 10). The NP23-NHD13 cells lost expression of Mac1 and Gr1 after 26 days; with immunophenotype now CD4-, CD8-, CD25-, CD44+, Thy-1.2+ and cKit+, consistent with a self-renewing DN1 thymocyte. These cells were transplanted; all recipients were anemic, and demonstrated engraftment of NP23-NHD13 myeloid cells as well as a less prominent (7.85%-38.5%) population of CD71+/Ter119+ erythroid cells in the BM and spleen. Taken together, these results indicate that NP23-NHD13 thymic progenitors are potently leukemogenic, and retain myeloid and erythroid differentiation potential.

Citation Format: Subhadip Kundu, Eun Sil Park, Yang Jo Chung, Trevor Stephen Barlowe, Peter D. Aplan. Thymic precursor cells generate acute myeloid leukemia in NP23-NHD13 double transgenic mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2643. doi:10.1158/1538-7445.AM2017-2643