Project description:Asxl1 is one of the most commonly mutated genes in malignancies including myelodysplastic syndromes (MDS) and Acute Myeloid Leukemia (AML). We generated a mouse model that harbors the most common mutation on ASXL1 gene detected in MDS patients: c.1934dupG, p.G646WfsX12 at the endogenous murine Asxl1 locus: the G643WfsX12 mutant, from here on referred as Asxl1G643W. Mutations on Asxl1 co-occur with mutations on CEBPA in AML patients, therefore, in order to understand how Asxl1 and Cebpa co-operate, we set up to cross our Cebpa-p30 mutant mouse model with our newly generated Asxl1 G643Wfs12 mutant. In this study we provided mechanistic information about the cooperation between these two factors. Furthermore, our mouse model proved able to recapitulate the chemotherapy response of human patients with Asxl1 mutations, thus representing a potent tool for future preclinical studies focusing on Asxl1 mutant AML.
Project description:The key myeloid transcription factor (TF) CEBPA is frequently mutated in acute myeloid leukemia (AML), but the molecular ramifications of this leukemic driver mutation remain elusive. To investigate CEBPA mutant AML, we compared gene expression changes in human CEBPA mutant AML and in the corresponding CebpaLp30 mouse model, and identified a conserved cross-species transcriptional program. ChIP-seq revealed aberrantly activated enhancers, exclusively occupied by the leukemia-associated CEBPA-p30 isoform. One leukemic-enhancer upstream of Nt5e, encoding CD73, was physically and functionally linked to this conserved AML gene, and could be activated by CEBPA. Targeting of CD73-adenosine signaling increased AML survival in transplanted mice. Our data indicate a first-in-class link between a TF cancer driver mutation and a druggable, direct transcriptional target.
Project description:Acute Myeloid Leukemia (AML) is a heterogeneous disease from the molecular and biological standpoints, and even patients with a specific gene expression profile may present clinical and molecular heterogeneity. We studied the epigenetic profiles of a cohort of patients that shared a common gene expression profile but differed in that only half of them harbored mutations of the CEBPA locus, while the rest presented with silencing of this gene and co-expression of certain T cell markers. DNA methylation studies revealed that these two groups of patients could be readily segregated in an unsupervised fashion based on their DNA methylation profiles alone. Furthermore, CEBPA silencing was associated with the presence of an aberrant DNA hypermethylation signature, which was not present in the CEBPA mutant group. This aberrant hypermethylation occurred more frequently at sites within CpG islands. CEBPA silenced leukemias also displayed marked hypermethylation when compared with normal CD34+ hematopoietic cells, while CEBPA mutant cases showed only mild changes in DNA methylation when compared to these normal progenitors. Biologically, CEBPA silenced leukemias presented with a decreased response to myeloid growth factors in vitro. Keywords: DNA methylation profiling Direct comparison of DNA methylation in leukemic blasts from 8 patients with Acute Myeloid Leukemia (AML) carrying a CEBPA mutation and 8 patients with AML without CEBPA mutation but with silencing of CEBPA expression. Two control groups are included: 8 CD34+ bone marrow samples from healthy donors and 9 samples of T Acute Lymphoblastic Leukemia (T-ALL) patients.
Project description:Acute Myeloid Leukemia (AML) is a heterogeneous disease from the molecular and biological standpoints, and even patients with a specific gene expression profile may present clinical and molecular heterogeneity. We studied the epigenetic profiles of a cohort of patients that shared a common gene expression profile but differed in that only half of them harbored mutations of the CEBPA locus, while the rest presented with silencing of this gene and co-expression of certain T cell markers. DNA methylation studies revealed that these two groups of patients could be readily segregated in an unsupervised fashion based on their DNA methylation profiles alone. Furthermore, CEBPA silencing was associated with the presence of an aberrant DNA hypermethylation signature, which was not present in the CEBPA mutant group. This aberrant hypermethylation occurred more frequently at sites within CpG islands. CEBPA silenced leukemias also displayed marked hypermethylation when compared with normal CD34+ hematopoietic cells, while CEBPA mutant cases showed only mild changes in DNA methylation when compared to these normal progenitors. Biologically, CEBPA silenced leukemias presented with a decreased response to myeloid growth factors in vitro. Experiment Overall Design: Direct comparison of gene expression in leukemic blasts from 8 patients with Acute Myeloid Leukemia (AML) carrying a CEBPA mutation and 8 patients with AML without CEBPA mutation but with silencing of CEBPA expression, and with 9 samples of T Acute Lymphoblastic Leukemia (T-ALL) patients.
Project description:Mutations in CCAAT/enhancer binding protein alpha (CEBPA) are seen in 5-14% of acute myeloid leukemia (AML) and have been associated with a favorable clinical outcome. Most AMLs with CEBPA mutations simultaneously carry two mutations (CEBPAdouble-mut), usually biallelic, while single heterozygous mutations (CEBPAsingle-mut) are less frequently seen. Using denaturing high performance liquid chromatography and nucleotide sequencing we identified among a cohort of 598 newly diagnosed AMLs a subset of 41 CEBPA mutant cases, i.e. 28 CEBPAdouble-mut and 13 CEBPAsingle-mut cases. CEBPAdouble-mut associated with a unique gene expression profile as well as favorable overall and event-free survival, retained in multivariable analysis that included cytogenetic risk, FLT3-ITD and NPM1 mutation, white blood cell count and age. In contrast, CEBPAsingle-mut AMLs did not express a discriminating signature and could not be distinguished from wild type cases as regards clinical outcome. These results demonstrate significant underlying heterogeneity within CEBPA mutation positive AML with prognostic relevance. Experiment Overall Design: Gene expression profiling of 524 cases of de novo AML. Comparisons of cases with double and single CEBPA mutations versus those with wild type CEBPA.
Project description:BACKGROUND: Our previous studies showed that RUNX1 and ASXL1 mutations were frequently co-existed in chronic myelomonocytic leukemia (CMML) and clonal evolution of RUNX1 and/or ASXL1 occurred most frequently in chronic myeloid leukemia (CML) with myeloid blastic crisis. The molecular pathogenesis of cooperation of RUNX1 and ASXL1 mutations has not been reported yet. METHODS: Lentiviral-mediated stable transduction of RUNX1-WT/MT (R135T) in K562 cells which harboring ASXL1-MT (Y591X). RNA was extracted from stable cell line and used for gene-expression microarray analysis. RESULTS: For in vitro study, we overexpressed RUNX1-WT/MT (R135T) in K562 cells which harboring ASXL1-MT (Y591X). We found that RUNX1-MT augmented cell proliferation, colony formation, HOXA gene expression and inhibited megakaryocytic differentiation in ASXL1-MT K562 cells compared to RUNX1-WT or empty vector control. We performed gene expression profile of K562 cells overexpressed with EV, RUNX1-WT and RUNX1-R135T mutation. Gene expression microarray data revealed that 147 genes upregulated more than 2-fold in RUNX1-R135T expressing K562 cells compared to EV control cells. From gene expression data analysis, we found that inhibitor of DNA binding 1 (ID1), a key transcriptional regulator of hematopoietic stem cell (HSC) lineage commitment, is upregulated in RUNX1-R135T-transduced K562 cells compared to EV and RUNX1-WT-expressing cells.
Project description:CEBPA is a key hematopoietic transcription factor (TF), found mutated in 5-14% of all acute myeloid leukemia (AML) cases, but the direct molecular ramifications of this driver mutation remains elusive. To investigate CEBPA-mutant AML, we compared patient aberrant genetic programs with changes in a precise mouse model (Lp30) expressing only the cancer-prevalent truncated CEBPA, p30, and identified a stringent cross-species AML program. Small-scale ChIP-seq methodology revealed aberrantly activated enhancers, exclusively occupied by CEBPA in leukemia. One cancer-enhancer upstream of Nt5e, encoding CD73, was physically and functionally linked to this conserved AML gene, and could be activated by CEBPA. Targeting of CD73-adenosine signaling increased survival in AML transplanted mice. Our data thus indicate a first-in-class link between a TF cancer driver mutation and a druggable, direct transcriptional target.
Project description:We studied gene expression profiles from 65 patients with CN-AML, who all had wild-type NPM1 and no FLT3-ITD. We identified an ASXL1 mutation-associated gene expression signature by comparing 26 ASXL1-mutated and 39 ASXL1-wild type patients. Only NPM1 wild type/FLT3-ITD-negative patients were included in this analysis to avoid potential confounding due to the effects of these two mutations on gene expression.
Project description:A previously predictive CEBPA double mutant (CEBPAdm) signature was hampered by the recently reported CEBPA silenced AML cases that carry a similar gene expression profile (GEP). Two independent AML cohorts were used to train and evaluate the predictive value of the CEBPAdm signature in terms of sensitivity and specificity. A predictive signature was created, containing 25-probe sets by using a logistic regression model with Lasso regularization, which selects discriminative probe sets between the classes, CEBPAdm and all other AML cases, CEBPA wild type (CEBPAwt) and CEBPA single mutant (CEBPAsm). Subsequently, a classifier was trained on the entire HOVON-SAKK cohort based on a two-class approach; CEBPAdm versus all other cases (CEBPAwt and CEBPAsm). This trained classifier subsequently classified 16 candidate CEBPAdm cases in the AMLSG-cohort out of 154 AML cases. This approach showed perfect sensitivity and specificity (both 100%). In addition, we have performed a classification between CEBPAdm ,CEBPAsm, and CEBPAwt to infer if we were able to accurately classify CEBPAsm cases. We observed that all CEBPAsm cases were classified as CEBPAwt, thus CEBPAsm cases do not have a consistent gene expression pattern and are different from the CEBPAdm group. All samples were obtained from untreated patients at the time of diagnosis. Cells used for microarray analysis were collected from the purified fraction of mononuclear cells after Ficoll density centrifugation. Routine diagnostic algorithms, including the characterization of molecular markers are performed.
Project description:Acute Myeloid Leukemia (AML) is a heterogeneous disease from the molecular and biological standpoints, and even patients with a specific gene expression profile may present clinical and molecular heterogeneity. We studied the epigenetic profiles of a cohort of patients that shared a common gene expression profile but differed in that only half of them harbored mutations of the CEBPA locus, while the rest presented with silencing of this gene and co-expression of certain T cell markers. DNA methylation studies revealed that these two groups of patients could be readily segregated in an unsupervised fashion based on their DNA methylation profiles alone. Furthermore, CEBPA silencing was associated with the presence of an aberrant DNA hypermethylation signature, which was not present in the CEBPA mutant group. This aberrant hypermethylation occurred more frequently at sites within CpG islands. CEBPA silenced leukemias also displayed marked hypermethylation when compared with normal CD34+ hematopoietic cells, while CEBPA mutant cases showed only mild changes in DNA methylation when compared to these normal progenitors. Biologically, CEBPA silenced leukemias presented with a decreased response to myeloid growth factors in vitro. Keywords: DNA methylation profiling