Pediatric Acute Megakaryoblastic Leukemia not associated to Down Syndrome (non-DS AMKL) is a rare disease with a dismal prognosis. Around 15% of patients carry the chromosomal translocation t(1;22) that originates the fusion oncogene RBM15-MKL1, which is linked to an earlier disease onset (median of 6months of age) and arises in utero. Here we report the generation of two hPSC cell lines constitutively expressing the oncogene RBM15-MKL1, resulting in an increased expression of known RBM15-MKL1 gene targets. These cell lines represent new disease models of pediatric AMKL to study the impact of the RBM15-MKL1 oncogene on human embryonic hematopoietic development.
HoxA9 is an evolutionarily conserved homeobox gene implicated in embryo development. To study the roles of Hoxa9 during human development we generated a transgenic H9 (hESC) line that overexpresses HoxA9 and the Enhanced Green Fluorescent Protein (EGFP), and a control H9 with a stable expression of the EGFP. The resulting H9-HoxA9-EGFP and H9-EGFP cell lines allow an efficient visualization of hESCs by fluorescent microscopy, quantification by flow cytometry and cell differentiation tracking. Both transgenic cell lines maintained the pluripotent phenotype, the ability to differentiate into all three germ layers and a normal karyotype.
Pediatric acute myeloid leukemia (AML) is a rare and heterogeneous disease that remains the major cause of mortality in children with leukemia. To improve the outcome of pediatric AML we need to gain knowledge on the biological bases of this disease. NUP98-KDM5A (NK5A) fusion protein is present in a particular subgroup of young pediatric patients with poor outcome. We report the generation and characterization of human Embryonic Stem Cell (hESC) clonal lines with inducible expression of NK5A. Temporal control of NK5A expression during hematopoietic differentiation from hESC will be critical for elucidating its participation during the leukemogenic process.
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.
The Notch ligand DLL4 has key roles during embryonic development of different tissues, but most of the data comes from animal models. Here we describe the generation and characterization of 2 human Pluripotent Stem Cell (hPSC) lines that overexpress DLL4, as well as the two corresponding control hPSC lines. DLL4 expression can be detected at the mRNA and protein level, and does not affect the pluripotency of the cells. These hPSC lines can be used to study the role of DLL4 during human embryonic development.
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