The role of the RNA binding protein RBM4 on leukemic stem cell activity in acute myeloid leukemia.
Final Report Abstract
The proportion of patients with acute myeloid leukemia (AML) who die from the disease is still around 25%. This is, among other reasons, due to the fact that AML is a stem cell disease, i.e. the fraction of AML cells that initiates the disease and causes relapse has stem cell properties similar to healthy hematopoietic stem cells (HSCs), such as slow progression through the cell cycle and distinct metabolic dependencies and resistance mechanisms to standard chemotherapy drugs, which usually target rapidly dividing progenitor cells. Understanding such stem cell properties in malignant and healthy HSCs is therefore essential to better understand the disease and to develop alternative therapeutic strategies. The fact that not only the classic regulation of gene transcription but also post-transcriptional mechanisms play a role has been increasingly established in recent years. In this project, we functionally investigated the role and mechanism of the RNA binding protein (RBP) RBM4 in AML and in healthy HSCs. We show for the first time that loss of RBM4 via shRNA and CRISPR/Cas9 has a negative effect in particular on the stem cell-enriched CD34+CD45RA- compartment and much less on more mature CD34+CD45RA+ progenitor cells that no longer possess HSC properties. There is also a differentiated effect on the slowly cycling leukemia stem cell (LSC)-enriched CD34+GPR56+ versus the rapidly cycling CD34- GPR56+ compartment in AML. Using RNA-seq after downregulation of RBM4 in primary AML cells, we found that genes significantly upregulated after RBM4 loss are particularly involved in mitosis. Results from cell cycle analyses also suggested that RBM4 may be involved in the G2/M transition. Our results therefore establish the role of an RNA binding protein in cell cycle regulation and indicate a differential vulnerability of healthy and leukemic stem versus progenitor cells with regards to the G2/M checkpoint. Whether and how this can be used therapeutically will be the focus of future projects.
