Acute myeloid leukemia (AML) is an aggressive cancer with a poor prognosis, for which mainstream treatments have not changed for decades. To identify additional therapeutic targets in AML, we ...optimize a genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) screening platform and use it to identify genetic vulnerabilities in AML cells. We identify 492 AML-specific cell-essential genes, including several established therapeutic targets such as DOT1L, BCL2, and MEN1, and many other genes including clinically actionable candidates. We validate selected genes using genetic and pharmacological inhibition, and chose KAT2A as a candidate for downstream study. KAT2A inhibition demonstrated anti-AML activity by inducing myeloid differentiation and apoptosis, and suppressed the growth of primary human AMLs of diverse genotypes while sparing normal hemopoietic stem-progenitor cells. Our results propose that KAT2A inhibition should be investigated as a therapeutic strategy in AML and provide a large number of genetic vulnerabilities of this leukemia that can be pursued in downstream studies.
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•Optimized CRISPR platform for identification of genome-wide genetic vulnerabilities•Catalog of genetic vulnerabilities in acute myeloid leukemia cell lines•KAT2A inhibition induces myeloid differentiation and apoptosis•KAT2A inhibition arrests the growth of primary AML cells, but not of normal progenitors
Tzelepis et al. optimize a CRISPR-Cas9-based platform for the performance of genome-wide recessive screens and apply it to identify genetic vulnerabilities of human AML cells. They identify several known therapeutic targets including BRD4, DOT1L, and MEN1, and numerous additional candidates. They provide data proposing KAT2A as a potential therapeutic target.
Epigenetic regulators, such as EZH2, are frequently mutated in cancer, and loss-of-function
mutations are common in myeloid malignancies. We have examined the importance of cellular context for Ezh2 ...loss during the evolution of acute myeloid leukemia (AML), where we observed stage-specific and diametrically opposite functions for Ezh2 at the early and late stages of disease. During disease maintenance, WT Ezh2 exerts an oncogenic function that may be therapeutically targeted. In contrast, Ezh2 acts as a tumor suppressor during AML induction. Transcriptional analysis explains this apparent paradox, demonstrating that loss of
derepresses different expression programs during disease induction and maintenance. During disease induction,
loss derepresses a subset of bivalent promoters that resolve toward gene activation, inducing a feto-oncogenic program that includes genes such as
, whose overexpression phenocopies
loss to accelerate AML induction in mouse models. Our data highlight the importance of cellular context and disease phase for the function of Ezh2 and its potential therapeutic implications.
A safe and efficient therapy for patients with the bone marrow failure syndrome Diamond-Blackfan Anemia (DBA) is urgently needed. To identify novel drug candidates for DBA, a small molecule screen ...was performed using c-Kit positive E14.5 fetal liver cells from a DBA mouse model in which the DBA phenotype is induced upon doxycycline (DOX)-inducible silencing of Rps19, the most frequently mutated gene in DBA (Jaako et al. PMID: 21989989). Test compounds were added 24 hours after cell seeding and DOX addition. After four days the number of live metabolically active cells in each well was estimated based on quantitation of intracellular ATP. Fifteen commercial annotated small-molecule libraries (3 800 molecules) and 10 500 selected compounds from a diverse compound library were screened. Between the screens we identified 20 molecules that reproducibly increased proliferation of rps19-deficient erythroid progenitors 4-8 fold in a concentration-dependent manner. Hits from annotated libraries included inhibitors of TGFb receptor, DYRK and Casein kinases. The most potent hits however were compounds in a series of thienopyridines, with an unknown target profile, but with a core structure suggesting kinase inhibition activity. Database searches revealed that the structure-activity relationships (SAR) of 12 active and 10 inactive analogues were similar to that of a series of thienopyridines previously reported as bone anabolic agents by unknown mechanism (Saito et al. PMID: 23453217). The most potent analogues described by Saito et al. as bone anabolic agents were synthesized, and the compounds rescue also RPS19-deficient erythroid cell proliferation in a potent manner (EC50= 20-50 nM). In an attempt to identify the molecular target of these compounds, six actives including thienopyridines 15k and 15w were subjected to kinase profiling against 468 kinases (DiscoverX). Three of the compounds targeted cyclin- dependent kinases CDK8 and its paralog CDK19, and in particular the most potent molecule (15w) is a highly selective CDK8 inhibitor. To confirm whether CDK8 inhibition underlies the rescue of the DBA phenotype, structurally unrelated and potent CDK8 inhibitors including CCT-251545, Senexin A, Senexin B, and Sel120-34A were also evaluated. All tested CDK8-inhibitors rescue proliferation and erythroid maturation of c-kit+ cells from the DBA mouse in a concentration-dependent manner. To further investigate the potential of CDK8 as a therapeutic target in DBA several CDK8 inhibitors were evaluated in erythroid cultures of primary DBA patient cells. CDK8 inhibitors 15w, Senexin B and Sel120-34A increase erythroid progenitor proliferation 5-10 fold of CD34+ peripheral blood cells from three DBA patients (RPS19, RPS26, RPL35a mutations), and increase the fraction of transferrin receptor (CD71) and glycophorin A positive cells in culture. Healthy CD34+ peripheral blood treated with CDK8 inhibitors show no increase in proliferation. Finally, we show that bone marrow failure and anemia in the DBA mouse model is partially rescued (RBC and Hemoglobin levels, p<0.001) after 8 daily oral doses (30mg/kg) of CDK8 inhibitor Sel120-34A. Since CDK8 is the regulatory subunit of the Mediator complex, acting as a regulator of RNA pol II transcription the therapeutic effect of CDK8 inhibitors likely involves direct changes in gene expression. RNA-Seq and gene set enrichment analysis on DBA mouse model cells treated with CDK8 inhibitor Sel120-34A shows p53 target genes are induced in RPS19-deficient cells and that CDK8 inhibitor treatment reverses this change, agreeing with previous reports that CDK8 can regulate transcription of p53 target genes. We confirm CDK8-inhibitor treatment reverses nuclear localization of p21 in RPS19-deficient cell lines. The most significant effect in gene set analysis however is the rescue of MYC-target gene expression, including increased expression of several ribosomal protein genes. In summary, selective and potent CDK8 inhibitors dramatically improve proliferation and maturation of erythroid progenitors in an animal model for DBA and in primary DBA patient cells. The therapeutic effect involves reduced expression of p53-target genes and increased expression of MYC-target genes. Given lack of adverse effects at effective doses in vivo, further development of SEL120-34A as a treatment for DBA patients is warranted.
Rzymski:Selvita S.A.: Employment, Equity Ownership. Johansson:LU Holding: Patents & Royalties. Lundbäck:LU Holding: Patents & Royalties. Mazan:Selvita S.A.: Employment. Majewska:Selvita S.A.: Employment. Brzózka:Selvita S.A.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Flygare:LU Holding: Patents & Royalties: Patent.
Heme oxygenase-1 (HO-1) is a cytoprotective, proangiogenic and anti-inflammatory enzyme that is often upregulated in tumors. Overexpression of HO-1 in melanoma cells leads to enhanced tumor growth, ...augmented angiogenesis and resistance to anticancer treatment. The effect of HO-1 in host cells on tumor development is, however, hardly known.
To clarify the effect of HO-1 expression in host cells on melanoma progression, C57BL/6xFvB mice of different HO-1 genotypes, HO-1
, HO-1
, and HO-1
, were injected with the syngeneic wild-type murine melanoma B16(F10) cell line. Lack of HO-1 in host cells did not significantly influence the host survival. Nevertheless, in comparison to the wild-type counterparts, the HO-1
and HO-1
males formed bigger tumors, and more numerous lung nodules; in addition, more of them had liver and spleen micrometastases. Females of all genotypes developed at least 10 times smaller tumors than males. Of importance, the growth of primary and secondary tumors was completely blocked in HO-1
females. This was related to the increased infiltration of leukocytes (mainly lymphocytes T) in primary tumors.
Although HO-1 overexpression in melanoma cells can enhance tumor progression in mice, its presence in host cells, including immune cells, can reduce growth and metastasis of melanoma.
In vertebrates, the first haematopoietic stem cells (HSCs) with multi-lineage and long-term repopulating potential arise in the AGM (aorta-gonad-mesonephros) region. These HSCs are generated from a ...rare and transient subset of endothelial cells, called haemogenic endothelium (HE), through an endothelial-to-haematopoietic transition (EHT). Here, we establish the absolute requirement of the transcriptional repressors GFI1 and GFI1B (growth factor independence 1 and 1B) in this unique trans-differentiation process. We first demonstrate that Gfi1 expression specifically defines the rare population of HE that generates emerging HSCs. We further establish that in the absence of GFI1 proteins, HSCs and haematopoietic progenitor cells are not produced in the AGM, revealing the critical requirement for GFI1 proteins in intra-embryonic EHT. Finally, we demonstrate that GFI1 proteins recruit the chromatin-modifying protein LSD1, a member of the CoREST repressive complex, to epigenetically silence the endothelial program in HE and allow the emergence of blood cells.
The histone H3 Lys27-specific demethylase UTX (or KDM6A) is targeted by loss-of-function mutations in multiple cancers. Here, we demonstrate that UTX suppresses myeloid leukemogenesis through ...noncatalytic functions, a property shared with its catalytically inactive Y-chromosome paralog, UTY (or KDM6C). In keeping with this, we demonstrate concomitant loss/mutation of KDM6A (UTX) and UTY in multiple human cancers. Mechanistically, global genomic profiling showed only minor changes in H3K27me3 but significant and bidirectional alterations in H3K27ac and chromatin accessibility; a predominant loss of H3K4me1 modifications; alterations in ETS and GATA-factor binding; and altered gene expression after Utx loss. By integrating proteomic and genomic analyses, we link these changes to UTX regulation of ATP-dependent chromatin remodeling, coordination of the COMPASS complex and enhanced pioneering activity of ETS factors during evolution to AML. Collectively, our findings identify a dual role for UTX in suppressing acute myeloid leukemia via repression of oncogenic ETS and upregulation of tumor-suppressive GATA programs.
Recent studies have established that during embryonic development, hematopoietic progenitors and stem cells are generated from hemogenic endothelium precursors through a process termed endothelial to ...hematopoietic transition (EHT). The transcription factor RUNX1 is essential for this process, but its main downstream effectors remain largely unknown. Here, we report the identification of Gfi1 and Gfi1b as direct targets of RUNX1 and critical regulators of EHT. GFI1 and GFI1B are able to trigger, in the absence of RUNX1, the down-regulation of endothelial markers and the formation of round cells, a morphologic change characteristic of EHT. Conversely, blood progenitors in Gfi1- and Gfi1b-deficient embryos maintain the expression of endothelial genes. Moreover, those cells are not released from the yolk sac and disseminated into embryonic tissues. Taken together, our findings demonstrate a critical and specific role of the GFI1 transcription factors in the first steps of the process leading to the generation of hematopoietic progenitors from hemogenic endothelium.
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