Project description:Acute myeloid leukemia (AML) progression and relapse is fueled by self-renewing leukemic stem cells (LSCs) whose molecular determinants have been difficult to discern from normal hematopoietic stem cells (HSCs) or to uncover in screening approaches focused on general AML cell properties. We have identified a unique set of RNA binding proteins (RBPs) that are enriched in human AML LSCs but repressed in HSCs. Using an in vivo two step CRISPR-Cas9-mediated screening approach to specifically score for cancer stem cell functionality, we found 32 RBPs essential for LSC propagation and self- renewal in MLL-AF9 translocated AML. Using knockdown or small molecule approaches we show that targeting key hit RBP ELAVL1 impaired LSC-driven in vivo leukemic reconstitution and selectively depleted primitive AML cells vs. normal hematopoietic stem and progenitors. Importantly, knockdown of Elavl1 spared HSCs while significantly reducing LSC numbers across genetically diverse leukemias. Integrative RNA-seq and eCLIP-seq profiling revealed hematopoietic differentiation, RNA splicing and mitochondrial metabolism as key features defining the leukemic ELAVL1-mRNA interactome with the mitochondrial import protein TOMM34 being a direct ELAVL1-stabilized target whose inhibition impairs AML propagation.
Project description:Beta-catenin signaling is required for establishment of leukemic stem cells (LSCs) in acute myeloid leukemia (AML), yet the upstream regulators that can augment this pathway are unknown. Through genome-wide gene expression analysis and functional studies, we identified an important role for GPR84 in MLL AML. Suppression of GPR84 significantly inhibited cell growth in pre-LSCs, reduced LSC frequency and impaired reconstitution of MLL AML. Furthermore, GPR84 conferred a growth advantage to Hoxa9/Meis1a transduced hematopoietic stem cells (HSCs). Our microarray analysis demonstrated that GPR84 overexpression significantly up-regulated a small set of MLL-fusion targets and beta-catenin co-effectors, and down-regulated a hematopoietic cell cycle inhibitor. These data thus reveal a previously unrecognized role of GPR84 in the maintenance of fully developed AML by sustaining aberrant beta-catenin signaling in LSCs. HSC-derived Hoxa9/Meis1a pre-LSCs were transduced with GPR84 cDNA or empty vector, and replated in methylcellulose supplemented with cytokines. Each group contains triplicate samples.
Project description:We performed the first genome-wide expression analysis directly comparing the expression profile of highly enriched normal human hematopoietic stem cells (HSC) and leukemic stem cells (LSC) from patients with acute myeloid leukemia (AML). Comparing the expression signature of normal HSC to that of LSC, we identified 3,005 differentially expressed genes. Using 2 independent analyses, we identified multiple pathways that are aberrantly regulated in leukemic stem cells compared with normal HSC. Several pathways, including Wnt signaling, MAP Kinase signaling, and Adherens Junction, are well known for their role in cancer development and stem cell biology. Other pathways have not been previously implicated in the regulation of cancer stem cell functions, including Ribosome and T Cell Receptor Signaling pathway. This study demonstrates that combining global gene expression analysis with detailed annotated pathway resources applied to highly enriched normal and malignant stem cell populations, can yield an understanding of the critical pathways regulating cancer stem cells. Experiment Overall Design: Total RNAs were isolated from both AML stem cells (9 patients) and normal bone marrow hematopoietic stem cells (HSCs) (4 control subjects).
Project description:Juvenile myelomonocytic leukemia (JMML) is an aggressive hematologic malignancy with myeloproliferative characteristics that affects young children and is associated with significant morbidity and mortality. Leukemia stem cells (LSCs) have been shown to drive relapse and progression in JMML and include Lin-CD34+CD38-/+ hematopoietic stem cells (HSCs)14. We therefore sought to develop cellular immunotherapy against JMML by employing a multi-modal omics strategy, focusing specifically on targeting chemoresistant LSCs
Project description:Despite the advanced understanding of disease mechanisms, the current therapeutic regimens fail to cure most patients with acute myeloid leukemia (AML). In the present study, we address the role of protein synthesis control in AML leukemia stem cell (LSC) function and leukemia propagation. We apply a murine model of mixed-lineage leukemia-rearranged AML to demonstrate that LSCs synthesize more proteins per hour compared with the bulk of leukemia. Using a genetic model that permits inducible and graded regulation of ribosomal subunit joining, we show that defective ribosome assembly leads to a significant survival advantage by selectively eradicating LSCs but not normal hematopoietic stem and progenitor cells. Finally, transcriptomic and proteomic analyses identify a rare subset of LSCs with immature stem cell signature and high ribosome content that underlies the resistance to defective ribosome assembly. Collectively, our study unveils a critical requirement of high protein synthesis rate for LSC function, highlighting ribosome assembly as a therapeutic target in AML.
Project description:Gene expression analysis of AML LSCs vs normal HSCs Total RNA obtained from FACS-sorted AML-LSCs (n=12) and normal HSCs (n=5) were subjected to the microarray analysis
Project description:Leukemia stem cells (LSCs) share several crucial properties with hematopoietic stem cells (HSCs) including self-renewal, cell cycle quiescence, and expression of a CD34+CD38- immunophenotype, which complicates efforts to eradicate AML by therapeutically targeting LSCs without adversely affecting HSCs. Here we report that CD93, a C-type lectin transmembrane receptor, is preferentially expressed on the cell surface of LSCs compared with HSCs in the genetic subtype of AML with genomic rearrangements of the MLL gene. LSCs that selectively express CD93 are actively cycling, and highly enriched for xeno-engraftment potential, yet comprise a minor component of an otherwise quiescent CD34+CD38- compartment of human AML. Notably, CD93 is required for LSC function in MLL leukemogenesis, and is not simply a passive surface marker co-expressed on LSCs. Thus, CD93 selectively marks and essentially maintains LSCs, and identifies them as predominantly cycling, non-quiescent leukemia-initiating cells in MLL-rearranged AML.
Project description:The cyclin-dependent kinases (CDK) CDK6 and CDK4 have redundant functions in regulating cell-cycle progression. We describe a novel role for CDK6 in hematopoietic and leukemic stem cells (HSCs and LSCs) that exceeds its function as cell-cycle regulator. Although hematopoiesis appears regular under steady state conditions Cdk6-/- HSCs do not efficiently repopulate upon competitive transplantation and Cdk6-deficient mice are significantly more susceptible to 5-fluorouracil (5-FU) treatment. We find that activation of HSCs requires CDK6, which interferes with transcription of key regulators including Egr1. The central role of Egr1 is supported by transcriptional profiling of HSCs. The impaired repopulation capacity extends to BCR-ABLp210+ leukemic stem cells. Transplantation with BCR-ABLp210+-infected bone marrow (BM) from Cdk6-/- mice fails to induce disease although recipient mice do harbor LSCs. Egr1 knock-down in cdk6-/- BCR-ABLp210+ LSKs significantly enhances colony formation underlining the importance of the Cdk6-Egr1 axis. Our findings define CDK6 as an important regulator of stem cell activation and as essential component of a transcriptional complex that suppresses Egr1 in HSCs and LSCs. Four-condition experiment, Untreated or polyI:C-treated CDK6-/- cells versus untreated or polyI:C-treated wild-type cells. Biological replicates: 3 untreated replicates, 3 polyI:C-treated replicates.
Project description:RNA binding protein (RBP)-directed post-transcriptional control of stem cell fate represents an underexplored mechanism driving hematopoietic stemness and transformation. We show that a unique set of RBPs are specifically enriched in leukemic stem cells (LSCs) of human primary acute myeloid leukemia (AML) but repressed in normal hematopoietic stem cells. Using an in vivo CRISPR-Cas9-mediated screening approach, we identify 33 key RBPs specifically essential for LSC-mediated MLL-AF9/NrasG12D AML. Knock-down/genetic ablation of the hit RBP Elavl1 in genetically distinct leukemias significantly reduced LSC numbers, and hampered leukemic engraftment. In human AML we show impairment of LSC-driven in vivo leukemic reconstitution and selective depletion of AML progenitors upon ELAVL1 targeting, highlighting the potential clinical importance of our findings. Profiling of the leukemic ELAVL1-mRNA interactome revealed hematopoietic differentiation, RNA splicing and mitochondrial metabolism as major pathways impacted by ELAVL1. Altogether, this work demonstrates that Elavl1 and other RBPs are critical regulators of LSC-survival and self-renewal.
Project description:RNA binding protein (RBP)-directed post-transcriptional control of stem cell fate represents an underexplored mechanism driving hematopoietic stemness and transformation. We show that a unique set of RBPs are specifically enriched in leukemic stem cells (LSCs) of human primary acute myeloid leukemia (AML) but repressed in normal hematopoietic stem cells. Using an in vivo CRISPR-Cas9-mediated screening approach, we identify 33 key RBPs specifically essential for LSC-mediated MLL-AF9/NrasG12D AML. Knock-down/genetic ablation of the hit RBP Elavl1 in genetically distinct leukemias significantly reduced LSC numbers, and hampered leukemic engraftment. In human AML we show impairment of LSC-driven in vivo leukemic reconstitution and selective depletion of AML progenitors upon ELAVL1 targeting, highlighting the potential clinical importance of our findings. Profiling of the leukemic ELAVL1-mRNA interactome revealed hematopoietic differentiation, RNA splicing and mitochondrial metabolism as major pathways impacted by ELAVL1. Altogether, this work demonstrates that Elavl1 and other RBPs are critical regulators of LSC-survival and self-renewal.