Identification and interrogation of the gene regulatory network of CEBPA-double mutant acute myeloid leukemia

Flow cytometry in acute myeloid leukemia and detection of minimal residual disease

Acute myeloid leukemia (AML) is a common type of acute leukemia (AL), belonging to malignant tumors of the hematopoietic system with the characteristics of rapid disease development, control with extreme difficulties, easy recurrence, poor prognosis, and incidence rate increasing with age. The traditionally diagnostic standard of French American British (FAB), being based on the morphological examination with high human subjectivity, can no longer meet the demand of clinical diagnosis and treatment of AML. Requirements of objective accuracy and low-dose sample, have become the indispensable method for AML diagnosis and monitoring prognosis. Flow cytometry is a modern technology that can quickly and accurately detect the series, antigen distribution, differentiation stage of AML cells, minimal residual lesions after AML therapy, so as to provide the great significance in guiding clinical diagnosis, hierarchical treatment, and prognosis judgement. This article will systematically elaborate on the application of flow cytometry in the diagnosis and classification of AML, and the detection of minimal residual lesions, thereby providing reference significance for dynamic monitoring and prognostic observation of AML with different immune subtypes of FAB.

Impact of different CEBPA mutations on therapeutic outcome in acute myeloid leukemia

Biallelic mutations of the CEBPA gene (CEBPAbi) are generally associated with favorable prognosis in patients with acute myeloid leukemia (AML). Monoallelic mutations of the CEBPA gene in carboxy-terminal DNA-binding region (CEBPAsmbZIP) and amino-terminal transactivation domains (CEBPAsmTAD) indicate distinct clinical characteristics and therapeutic outcomes. However, further investigation is required to fully understand these differences. In this retrospective study, we enrolled 77 AML patients with CEBPA mutations, including 53 with CEBPAbi, 12 with CEBPAsmbZIP and 12 with CEBPAsmTAD. The clinical characteristics of the three CEBPAmut groups presented significant differences in age, FAB classification, hemoglobin level and platelet count at diagnosis. The CEBPAsmTAD group exhibited shorter 2-year overall survival (OS) and relapse-free survival (RFS) compared to the CEBPAbi group and CEBPAsmbZIP group in AML patients. The most common co-mutations observed in CEBPAmut AML patients were TET2 and GATA2, which had no effect on prognosis. 2-year RFS of 27 CEBPAmut AML patients who underwent allo-HSCT was better than those who did not. MRD3 positive was identified as an influencing factor for 2-year OS and RFS. Allo-HSCT was found to improve the prognosis of CEPBAmut AML patients with positive MRD3 and adverse co-mutations.

CEBPA mutations in acute myeloid leukemia: implications in risk stratification and treatment

Mutations in CCAAT enhancer binding protein α (CEBPA) occur in approximately 10% of patients with de novo acute myeloid leukemia (AML). Emerging evidence supports that in-frame mutations in the basic leucine zipper domain of CEBPA (CEBPAbZIP-inf) confer a survival benefit, and CEBPAbZIP-inf replaced CEBPA double mutations (CEBPAdm) as a unique entity in the 2022 World Health Organization (WHO-2022) classification and International Consensus Classification (ICC). However, challenges remain in daily clinical practice since more than 30% patients with CEBPAbZIP-inf die of AML despite intensive treatment. This review aims to provide a comprehensive summary of the heterogeneities observed in AML with CEBPAdm and CEBPAbZIP-inf, and will discuss the prognostic implications of concurrent mutations and novel mechanistic targets that may inform future drug development. The ultimate goal is to optimize clinical management and to provide precision medicine for this category of patients.

Leukemic stem cells activate lineage inappropriate signalling pathways to promote their growth

Acute Myeloid Leukemia (AML) is caused by multiple mutations which dysregulate growth and differentiation of myeloid cells. Cells adopt different gene regulatory networks specific to individual mutations, maintaining a rapidly proliferating blast cell population with fatal consequences for the patient if not treated. The most common treatment option is still chemotherapy which targets such cells. However, patients harbour a population of quiescent leukemic stem cells (LSCs) which can emerge from quiescence to trigger relapse after therapy. The processes that allow such cells to re-grow remain unknown. Here, we examine the well characterised t(8;21) AML sub-type as a model to address this question. Using four primary AML samples and a novel t(8;21) patient-derived xenograft model, we show that t(8;21) LSCs aberrantly activate the VEGF and IL-5 signalling pathways. Both pathways operate within a regulatory circuit consisting of the driver oncoprotein RUNX1::ETO and an AP-1/GATA2 axis allowing LSCs to re-enter the cell cycle while preserving self-renewal capacity.

A C/ebpα isoform specific differentiation program in immortalized myelocytes

The transcription factor CCAAT-enhancer binding factor alpha (C/ebpα) is a master controller of myeloid differentiation that is expressed as long (p42) and short (p30) isoform. Mutations within the CEBPA gene selectively deleting p42 are frequent in human acute myeloid leukemia. Here we investigated the individual genomics and transcriptomics of p42 and p30. Both proteins bound to identical sites across the genome. For most targets, they induced a highly similar transcriptional response with the exception of a few isoform specific genes. Amongst those we identified early growth response 1 (Egr1) and tribbles1 (Trib1) as key targets selectively induced by p42 that are also underrepresented in CEBPA-mutated AML. Egr1 executed a program of myeloid differentiation and growth arrest. Oppositely, Trib1 established a negative feedback loop through activation of Erk1/2 kinase thus placing differentiation under control of signaling. Unexpectedly, differentiation elicited either by removal of an oncogenic input or by G-CSF did not peruse C/ebpα as mediator but rather directly affected the cell cycle core by upregulation of p21/p27 inhibitors. This points to functions downstream of C/ebpα as intersection point where transforming and differentiation stimuli converge and this finding offers a new perspective for therapeutic intervention.