Abstract B29: Validation of a model of pediatric leukemia based on pluripotent stem cells using mass cytometry
Authors: Domingo-Reines Joan , Kimmey Samuel , Vijayaragavan Kausalia , Bosse Marc , Bendall Sean , Davis Kara , Ramos-Mejía Veronica 
Published: August 2020

Abstract
Pediatric acute myeloid leukemia (AML) is a rare disease characterized by an accumulation of immature white blood cells in the bone marrow and/or peripheral blood. In some cases, it is thought that the predisposition to leukemia begins in utero. Often, leukemogenesis in children is caused by recurrent chromosomal translocations that result in fusion proteins that do not occur in AML in adults. In particular, NUP98-JARID1A is a recurrent fusion that occurs in an aggressive AML characterized by malignant megakaryoblasts. The prognosis for these patients is poor and there are few novel therapies on the horizon. Using human pluripotent stem cells, we can model this disease by recapitulating the events of leukemogenesis with the goal to better understand the pathogenesis of this disease and to identify better treatments for children. To this end, we generated human pluripotent cell lines that express the NUP98-JARID1A (NJ) fusion protein through a lentiviral expression system. These cells have been characterized in the pluripotent state by RNAseq and molecular and cell culture methods. The cell lines can be differentiated to the three germ layers, and we can focus on the myeloid lineage. Here we are using mass cytometry to analyze the differentiation phenotypes of these cells in comparison to both normal bone marrow stem and progenitor populations as well as primary patient samples. Induced pluripotent cells carrying the NJ fusion maintain their pluripotent state by the presence of surface markers and expression of pluripotent genes despite a higher sensitivity to stress and difficulties to culture them. These cells display abnormal mitosis showing multiple poles and bad segregation of chromosomes, which results in aberrant karyotypes. Interestingly, as NJ iPS cells differentiate to the three germ layers, NJ iPS demonstrate a substantial increase in specific mesodermal markers as CD34 and KDR, but without differences in ectoderm or endoderm specific markers. We will discuss comparisons between myeloid developmental populations from NJ iPS cells, wild-type iPS cells differentiated to the myeloid lineage and normal bone marrow. Finally, we compare differentiated NJ iPS leukemic cells to primary patient samples based on their phenotypic and signaling features as determined by CyTOF. In conclusion, we demonstrate an early model of NUP98-JARID1A fusion AML that recapitulates the genomic instability of this leukemia and demonstrates a deregulation of mesodermal development and further myeloid differentiation. NUP98 has been described with 30 other fusion partners, all related to leukemia, and this model may be used as a basis for understanding its role in leukemogenesis.
Citation Format: Joan Domingo-Reines, Samuel Kimmey, Kausalia Vijayaragavan, Marc Bosse, Sean Bendall, Kara Davis, Veronica Ramos-Mejía. Validation of a model of pediatric leukemia based on pluripotent stem cells using mass cytometry [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B29.