Project description:Acute myeloid leukemia (AML) with the t(8;21)(q22;q22) chromosomal translocation is among the most common subtypes of AML and produces the AML1-ETO (AE) oncogenic fusion gene. AML1-ETO expression is critical to for t(8;21) AML leukemogenesis and maintenance. Post-transcriptional regulation of gene expression is often mediated through transcript 3'-untranslated regions (UTR). AML1-ETO uses the 3’UTR of the ETO gene, which is not normally expressed in hematopoietic cells. Therefore, the mechanisms regulating AML1-ETO via the 3’UTR are attractive therapeutic targets. In this study, we examine the regulation of AML1-ETO via the 3’UTR. We demonstrate that AML1-ETO primarily uses a 3.7kb isoform of the ETO 3’UTR in both t(8;21) patients and cell lines. Using a luciferase assay approach, we identify an AML1-ETO 3’UTR fragment between 2.8 and 3.4kb which is negatively regulated, increases expression upon inhibition of microRNA biogenesis, and contains a putative let-7 microRNA target site. We show that let-7b directly represses AML1-ETO through this site. An analysis of The Cancer Genome Atlas AML dataset shows that let-7b and let-7 family miRNA expression is significantly lower in t(8;21) AML than other AMLs. Finally, we demonstrate that let-7b-5p inhibits the proliferation of t(8;21) AML cell lines, rescues expression of AML1-ETO target genes, and promotes differentiation. Our findings establish AML1-ETO as a let-7b target gene and suggest that let-7 based therapeutics may be applied to t(8;21) AML.
Project description:Nearly 10-15% of all acute myeloid leukemia (AML) cases are caused by a recurring chromosomal translocation between 8 and 21, t(8;21). The t(8;21) translocation generates the AML1-ETO leukemia fusion protein. AML1-ETO promotes leukemogenesis by transcriptionally dysregulating important cell-fate genes. Here, to better understand how AML1-ETO deregulates transcription, we performed paired ChIP-Seq analyses of sequence-specific transcription factors, coactivators, corepressors, HDACs, RNA Pol II and acetyl-histone marks in both control and AML1-ETO-depleted Kasumi-1 t(8;21) AML cells.
Project description:Human histone deacetylase 3 (HDAC3) plays an important role in gene transcription in diseased human cells, such as leukemia. The t(8;21) chromosomal translocation is one of the most commonly observed genetic abnormalities associated with acute myeloid leukemia. This translocation generates the AML1-ETO fusion protein between the wild-type RUNX1 transcription factor and wild-type ETO transcriptional corepressor. To better understand the role of HDAC3 in t(8;21) leukemogenesis, the human HDAC3-containing complexes were isolated from stably-transfected HeLa cells by using anti-FLAG immunoprecipitation. The resulting complexes were resolved in SDS-PAGE. The components of the complexes were identified using LC-MS/MS. We report here that the human RUNX1 transcription is a component of the HDAC3 complexes. We demonstrate that HDAC3 and RUNX1 collaboratively repress AML1-ETO-mediated transcription. These results reveal new insight into how AML1-ETO, RUNX1, and HDAC3 crosstalk to deregulate gene transcription in t(8;21) leukemia cells.
Project description:AML1-ETO is regarded as an initial event and plays a pivotal role in t(8;21) acute myeloid leukemia (AML) which is a highly heterogeneous disease. DNA methylation patterns are frequently deregulated in t(8;21) AML, though little is known of the mechanisms through which specific gene sets become aberrantly methylated. Here, We found that the promoter DNA methylation signature of t(8;21) AML blasts differs from those of normal CD34+ bone marrow cells and other AMLs. This signature contains 408 differentially methylated genes, many of which are genes involved in cancer pathway and myeloid leukemia. Database systematic survey and differential methylated regions (DMR) analysis were performed. These study demonstrated that a novel hypermethylated zinc finger containing protein-THAP10 is a target gene and can be epigenetic silenced by AML1-ETO at transcriptional level in t(8;21) AML and silencing of THAP10 by AML1-ETO predicts a poor clinical outcome. Our findings also identified that THAP10 is a bona fide target of miR-383 which can be epigenetic activated by AML1-ETO. In this study, we provided evidence that epigenetic silencing of THAP10 is the mechanistic link between AML1-ETO fusion proteins and tyrosine kinase cascades. In addition, we showed that THAP10 is a nuclear protein which inhibits myeloid proliferation inhibition and promotes differentiation both in vitro and in vivo. Altogether, our results revealed an unexpected and important link between fusion protein AML1-ETO, mir-383, THAP10 and tyrosine cascades in t(8;21) AML.
Project description:The formation of the AML1-ETO fusion protein, resulting from the t(8;21) translocation, is considered to be among the t(8;21) acute myeloid leukemia (AML) initiating events. However, the mechanisms of the oncogenic activity of AML1-ETO remains unclear. In this study, we found that AML1-ETO triggers the heterochromatic silencing of UBXN8 by recognizing the AML1 binding sites and recruiting chromatin remodeling enzymes to the UBXN8 promoter region. Decitabine, a specific inhibitor of DNA methylation, upregulated the expression of UBXN8 in AML1-ETO+ AML cell lines. Overexpression of UBXN8 inhibited the proliferation and colony-forming ability and promoted cell cycle arrest in t(8;21) AML cell lines. Enhancement of UBXN8 level can significantly inhibit the tumor proliferation of AML1-ETO+ cells in vivo. Thus, our results indicated that epigenetic silencing of UBXN8 via its promoter region methylation mediated by the AML1-ETO fusion protein contributes to the leukemogenesis of t(8;21)AML. These results demonstrated the feasibility and effectiveness of the pharmacological disruption of AML1-ETO/HDACs/DNMTs complex and that the UBXN8 targeting maybe an potential therapeutic strategy for t(8;21)AML.
Project description:Cancer cells maintain a sensitive balance between growth-promoting oncogenes and apoptosis inhibitors. We show that WT RUNX1 is required for survival of t(8;21)-Kasumi-1 and inv(16)-ME-1 AML cell lines. The malignant AML phenotype is sustained by a delicate AML1-ETO/RUNX1 balance that involves competition for common DNA binding sites regulating a subset of AML1-ETO/RUNX1 targets. Genome expression was profiled after performing knockdown of RUNX1 and AML1-ETO in Kasumi-1 cells using specific siRNA-oligo nucleotides, and analyzed using Affymetrix Gene 1.0 ST arrays.
Project description:Cancer cells maintain a sensitive balance between growth-promoting oncogenes and apoptosis inhibitors. We show that WT RUNX1 is required for survival of t(8;21)-Kasumi-1 and inv(16)-ME-1 AML cell lines. The malignant AML phenotype is sustained by a delicate AML1-ETO/RUNX1 balance that involves competition for common DNA binding sites regulating a subset of AML1-ETO/RUNX1 targets. Genomewide sequencing data is included herein: Transcription factors RUNX1 c-terminus and n-terminus which is shared with AML1-ETO were profiled independently), AML1-ETO and AP4 were profiled using ChIP-Seq in Kasumi-1 cells, as well as control ChIP-Seq experiments of non immune serum. Two replicates were performed for each transcription factor profiling and control experiment.
Project description:Cancer cells maintain a sensitive balance between growth-promoting oncogenes and apoptosis inhibitors. We show that WT RUNX1 is required for survival of t(8;21)-Kasumi-1 and inv(16)-ME-1 AML cell lines. The malignant AML phenotype is sustained by a delicate AML1-ETO/RUNX1 balance that involves competition for common DNA binding sites regulating a subset of AML1-ETO/RUNX1 targets.
Project description:Cancer cells maintain a sensitive balance between growth-promoting oncogenes and apoptosis inhibitors. We show that WT RUNX1 is required for survival of t(8;21)-Kasumi-1 and inv(16)-ME-1 AML cell lines. The malignant AML phenotype is sustained by a delicate AML1-ETO/RUNX1 balance that involves competition for common DNA binding sites regulating a subset of AML1-ETO/RUNX1 targets.
Project description:Post-transcriptional regulation has emerged as a driver for leukemia development and an avenue for therapeutic targeting. Among post-transcriptional processes, alternative polyadenylation (APA) is globally dysregulated across cancer types. However, limited studies have focused on the prevalence and role of APA in leukemia. Furthermore, it is poorly understood how altered poly(A) site usage of individual genes contributes to malignancy or whether targeting global APA patterns might alter oncogenic potential. By performing 3’RNA sequencing on acute myeloid leukemia (AML) patient samples and healthy hematopoietic stem and progenitor cells (HSPCs), we show that patient cells exhibit global 3’ untranslated region (UTR) shortening and coding sequence (CDS) lengthening due to differences in poly(A) site usage. Among APA regulators, FIP1L1 expression correlated with the degree of APA dysregulation and knockdown of this RNA-binding protein (RBP) reversed the global trends seen in patients. Importantly, FIP1L1 knockdown induced differentiation of t(8;21) cells by promoting 3’UTR lengthening and downregulation of fusion oncoprotein AML1-ETO. In non-t(8;21) cells, knockdown also promoted differentiation by attenuating mTORC1 signaling and reducing MYC protein levels. Our study gives mechanistic insight into the role of APA in AML pathogenesis and provides evidence that targeting global APA patterns can overcome the differentiation block of AML patients.