CD97 is a Critical Regulator of Acute Myeloid Leukemia Stem Cell Function
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ABSTRACT: Despite significant efforts to improve therapies for acute myeloid leukemia (AML), clinical outcomes remain poor. Understanding the mechanisms that regulate the development and maintenance of leukemic stem cells (LSC) is important to reveal new therapeutic opportunities. We have identified CD97, a member of the adhesion class of G-protein coupled receptors (GPCRs), as a frequently upregulated antigen of AML blasts that is a critical regulator of blast function. High levels of CD97 correlate with poor prognosis, and silencing of CD97 reduces disease aggressiveness in vivo. In order to analyze the functional pathways associated with CD97 expression, we generated RNA-sequence data from scrambled shRNA transfected (s-shRNA) and CD97 KD human AML cell line HL60, as well as from MLL-AF9 (MA9) transduced GMPs isolated from CD97-/- and WT mice. These phenotypes are due to CD97’s function to promote proliferation, survival, and the maintenance of the undifferentiated state in leukemic blasts. Collectively, our data credential CD97 as a promising therapeutic target on LSCs in AML.
Project description:High HOXA expression correlates with poor clinical outcome in AML, particularly those harboring MLL rearrangements (MLLr). The necessity of the HOXA cluster for the maintenance of MLLr-leukemia has not been elucidated. Primary leukemias were generated by transduction of MLL-AF9 (MA9) into hematopoietic stem and progenitor cells from compound Cre responsive transgenic mice for conditional deletion of the Hoxa locus. Hoxa deletion resulted in reduced proliferation, colony formation and repopulating ability in transplanted mice in which surviving leukemic cells retained at least one copy of the Hoxa cluster (Hoxa-del). Comparative RNA-seq analysis of leukemic MA9-Hoxa-wild type (WT) and MA9-Hoxa-del cells identified a unique gene signature.
Project description:Glioblastoma (GBM) stem cells (GSCs) are largely associated with a poor prognosis of GBM. Although the importance of identifying and validating molecular markers in GBM has been emphasized, single markers covering all GSCs are lacking. Through in vitro antibody screening, in this study, we demonstrated that CD97 identifies GSCs as a novel surface marker. Compared to conventional well-known GSC markers, such as CD133, CD44 and CD15, only CD97 was notably detected in all tested patient-derived GSCs. GBM patients expressing high levels of CD97 experienced worse clinical outcomes, and were predictive of poor overall survival in the public database. CD97 is required for GSC proliferation and self-renewal and was shown to reduce mouse survival with aggressive tumor progression in an orthotopic xenograft model. A comparative transcriptomic analysis revealed that CD97 triggers mTORC2 signaling through Akt (S473) phosphorylation, enhancing the expression of downstream genes, including ARHGAP1, BZW1, and BZW2. Moreover, inhibition of mTORC2 signaling with the pharmacological inhibitor JR-AP2-011 suppressed GSC proliferation, self-renewal, and downstream gene expression. Furthermore, sorting of CD97-enriched cells from patient-derived GSCs revealed that CD97 promotes GSC self-renewal and tumorigenicity via mTORC2/AKT signaling. Thus, our findings suggest that CD97 may be a general GSC enrichment marker in GBM and that the CD97-related pathway might serve as a therapeutic target for GBM.
Project description:Acute myeloid leukemia (AML) is a clonal hematopoietic malignancy, characterized by expansion of immature leukemic blasts in the bone marrow. In AML, specific tyrosine kinases have been implicated in leukemogenesis, and are associated with poor treatment outcome. However, targeted therapy using kinase inhibitors (KIs) has had limited success, and may be improved by proper patient selection. We performed phosphotyrosine (pY) based, label-free phosphoproteomics to identify hyperphosphorylated, active kinases in two FLT3+ AML Pt samples.
Project description:We analyzed the transcriptome differences of wild-type, CD97- and Gα13-deficient (Adgre5-/- and CD11c-cre x Gna13fl/fl) type-2 conventional dendritic cells (cDC2s) in spleen. Three technical repeats of ~10^5 cells per sample from each of one mouse were included. Compared to wild-type cDC2s, CD97- and Gα13-deficient cDC2s differentially expressed many genes, but CD97- and Gα13-deficient cDC2s were almost the same. GSEA showed that Mrtf-a dependent genes were upregulated in CD97- and Gα13-deficient cDC2s, which code for cytoskeleton proteins. These data support that CD97-Gα13 signaling regulates splenic cDC2 motility by the actin cytoskeleton.
Project description:Acute myeloid leukemia (AML) is a clonal hematopoietic malignancy, characterized by expansion of immature leukemic blasts in the bone marrow. In AML, specific tyrosine kinases have been implicated in leukemogenesis, and are associated with poor treatment outcome. However, targeted therapy using kinase inhibitors (KIs) has had limited success, and may be improved by proper patient selection. We performed phosphotyrosine (pY) based, label-free phosphoproteomics to identify hyperphosphorylated, active kinases in two FLT3+ AML Pt samples and this data is deposited in PXD015639 . Here are the corresponding lysate samples
Project description:Leukemic blasts are immune cells gone awry. We hypothesized that dysregulation of inflammatory pathways contributes to the maintenance of their leukemic state and can be exploited as a cell-intrinsic, self-directed immunotherapy. To this end, we applied genome-wide screens to discover genetic vulnerabilities in acute myeloid leukemia (AML) cells that are also implicated in inflammatory pathways. We identified the immune modulator interferon regulatory factor 2 binding protein 2 (IRF2BP2) as a selective dependency in AML. We validated AML cell dependency on IRF2BP2 with genetic and protein degradation approaches in vitro and genetically in vivo. Chromatin and global gene expression studies demonstrated that IRF2BP2 represses IL1B/TNFA signaling via NF-KB, and IRF2BP2 perturbation results in an acute inflammatory state leading to AML cell death. These findings elucidate a hitherto unexplored AML dependency, reveal cell-intrinsic inflammatory signaling as a mechanism priming leukemic blasts for regulated cell death, and establish IRF2BP2-mediated transcriptional repression as a mechanism for blast survival.
Project description:Leukemic blasts are immune cells gone awry. We hypothesized that dysregulation of inflammatory pathways contributes to the maintenance of their leukemic state and can be exploited as a cell-intrinsic, self-directed immunotherapy. To this end, we applied genome-wide screens to discover genetic vulnerabilities in acute myeloid leukemia (AML) cells that are also implicated in inflammatory pathways. We identified the immune modulator interferon regulatory factor 2 binding protein 2 (IRF2BP2) as a selective dependency in AML. We validated AML cell dependency on IRF2BP2 with genetic and protein degradation approaches in vitro and genetically in vivo. Chromatin and global gene expression studies demonstrated that IRF2BP2 represses IL1B/TNFA signaling via NF-KB, and IRF2BP2 perturbation results in an acute inflammatory state leading to AML cell death. These findings elucidate a hitherto unexplored AML dependency, reveal cell-intrinsic inflammatory signaling as a mechanism priming leukemic blasts for regulated cell death, and establish IRF2BP2-mediated transcriptional repression as a mechanism for blast survival.
Project description:The overall outcome of patients with acute myeloid leukemia (AML) remains poor and more effective strategies are urgently needed. Adefovir dipivoxil (ADV) is an oral prodrug of the nucleotide analogue adefovir that inhibits viral DNA polymerase and is a Food and Drug Administration (FDA)-approved drug for the treatment of hepatitis B virus. Preliminary evidence of the anti-leukemic activity of ADV was recently reported in a patient with acute promyelocytic leukemia. Herein we report on the anti-leukemic activity of ADV, alone and in combination with venetoclax (VEN), an oral FDA-approved BCL-2 inhibitor, for the treatment of AML. We observed a significant increase in apoptosis and reduction of cell growth both in AML cell lines and CD34+ blasts, but not in healthy donor CD34+ cells, after exposure to ADV. The combination of ADV and VEN had synergistic anti-leukemic activity and significantly reduced leukemia stem cell (LSC) burden and prolonged survival of AML murine (i.e., MllPTD/WT/Flt3ITD/ITD) and patient derived xenograft (PDX) models, likely by interfering with the bioenergetic metabolism of leukemic blasts and decreasing their apoptotic threshold. Our results provide a rationale for translating this “all oral” regimen to the clinic for treatment of AML patients, especially those requiring low intensity therapy.
Project description:Beta-catenin has a central role for self-renewal of leukemic stem cells in Mixed Lineage Leukemia (MLL)-arranged acute myeloid leukemia (AML), however its upstream modulators that can enhance this pathway remain largely unexplored. Through genome-wide gene expression analysis, we identified a previously unknown role for the G protein Gaq in MLL-arranged AML. Inhibition of Gaq reduces the level of active beta-catenin expression and impairs the maintenance of MLL-rearranged AML. Our microarray analysis uncovers a novel functional role for Gaq in leukemia maintenance. GFP-positive leukemic cells flow-sorted by BD Influx⢠cell sorter from bone marrow of the primary AML mice induced by MLL-AF9 oncogene were lentivirally transduced with Gaq shRNA (TRCN0000295412, Sigma) or Scrambled control (SHC016, Sigma), and replated in methylcellulose supplemented with IL3. Each group contains triplicate samples.