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: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.
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:SPO11-promoted DNA double-strand breaks (DSBs) formation is a crucial step for meiotic recombination, and it is indispensable to detect the broken DNA ends accurately for dissecting the molecular mechanisms behind. Here, we report a novel technique, named DEtail-seq (DNA End tailing followed by sequencing), that can directly and quantitatively capture the meiotic DSB 3’ overhang hotspots at single-nucleotide resolution.
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: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. Keywords: Gene expression profiling by arrays
Project description:By WHO 2008, CEBPA-mutated AML became a provisional subentity, but it remains to be clarified how CEBPAmut AML with multilineage dysplasia (MLD; ?50% dysplastic cells in 2-3 lineages) but no other MDS-related feature should be classified. We investigated 108 CEBPAmut AML (15.7-87.6 years) for the impact of MLD and genetic features. MLD-positive patients differed from MLD-negative only by lower mean WBC counts (p=0.004), but not by other blood values, biologic characteristics, cytogenetic risk profiles, or additional molecular markers (NPM1mut, FLT3-ITD/TKD, RUNX1, MLL-PTD, IDH1/2). Biallelic CEBPAmut differed from wild-type-cases by differential expression of 213 genes, but did not differ significantly between MLD-positive/-negative patients. Survival outcomes were improved for females and those <60 years, intermediate versus adverse karyotypes (p=0.021), and for biallelic versus monoallelic/homozygous CEBPAmut (p=0.060) in case of FLT3-ITD-negativity. In contrast, 2-year OS (MLD+: 56.5%; MLD-: 65.5%) and 2-year EFS (MLD+: 13.8 months; MLD-: 16.3 months) did not differ significantly between MLD-positive/-negative patients. By univariable Cox regression analysis, gender, age, WBC count and MRC-cytogenetic risk category only were prognostically relevant for OS, while MLD was irrelevant. Therefore, CEBPAmut AML patients should be characterized only according to mut-status, cytogenetic risk groups, or additional mutations, whereas dysplasia is not relevant for this subtype. The sample preparation assay for gene expression profiling using Affymetrix HG-U133 Plus 2.0 microarrays and subsequent data analysis were previously described. Only cases with biallelic CEBPA mutations were investigated by gene expression profiling due to previous reports that only double mutated cases conferred a specific gene expression signature, while monoallelic cases could not be discriminated from CEBPA wild-type cases. We performed comparison of gene expression profiles of 20 cases with biallelic CEBPA mutations and of 10 cases without CEBPA mutations.