Deregulated Survival Pathways Confer Erythropoietin-Independent Survival and Proliferation in Erythroleukemia Progenitor Cells
Master of Science (MS)
Biological and Environmental Sciences
Date of Award
Abnormal erythropoietin (Epo) signaling in erythroid precursor cells is a characteristic of Acute Erythroid Leukemia (AEL). AEL is defined by the uncontrolled proliferation of maturation-arrested erythroid precursor cells. Since Epo signaling controls normal erythropoiesis, we hypothesize that dysregulated survival pathways confer Epo-independent survival and proliferation in erythroleukemia progenitor cells. To test this hypothesis, we developed two Epo-independent cell lines, UT-7/CI1 and UT-7/CI2 from the Epo-dependent erythroid progenitor cell line UT-7/Epo. Unlike parental UT-7/Epo cells, UT-7/CI1 and UT-7/CI2 cells survived in the absence and presence of Epo. In colony forming cell assay, UT-7/CI1 and UT-7/CI2 cells formed colonies resembling Colony Forming Unit-Erythroid (CFU-E), which are immature erythroid colonies normally dependent of Epo for survival. Furthermore, heme content was similar among UT-7/Epo, UT-7/CI1, and UT-7/CI2 cells. Epo was not detected in the culture media of UT-7/CI1 and UT-7/CI2 cells at 24, 48, and 72 hours, indicating they do not produce Epo as a means of autocrine signaling. Since UT-7/CI1 and UT-7/CI2 cells do not depend on Epo for survival, the signaling pathways of the signal transducer and activator of transcription (STAT) and mitogen-activated protein kinase (MEK) family, which are typically involved in Epo signaling, were investigated. Western blotting demonstrated an increase in STAT3 phosphorylation in UT-7/CI2 cells as well as an increase in p44/42 and p38 phosphorylation in UT-7/CI1 cells. The Janus Kinase (JAK) inhibitor Ruxolitinib induced apoptosis and Caspase3 cleavage in UT-7/Epo and UT-7/CI2 cells, but not UT-7/CI1 cells. However, The MEK1/2 inhibitor U0126 induced apoptosis and Caspase3 cleavage in UT-7/CI1 cells. Overall, the results from this study indicate that UT-7/CI1 cells are dependent on abnormal MEK1/2 signaling for Epo-independent survival whereas UT-7/CI2 cells are dependent on abnormal JAK signaling.
Cell and Developmental Biology | Life Sciences
Morris, Madeleine, "Deregulated Survival Pathways Confer Erythropoietin-Independent Survival and Proliferation in Erythroleukemia Progenitor Cells" (2020). Electronic Theses & Dissertations. 355.