Deficient CEBPA DNA binding function in normal karyotype AML patients is associated with favorable prognosis

CEBPA Mutations in 4708 Patients with Acute Myeloid Leukemia - Differential Impact of bZIP and TAD Mutations on Outcome

Biallelic mutations of the CEBPA gene (CEBPAbi) define a distinct entity associated with favorable prognosis, however the role of monoallelic mutations (CEBPAsm) is poorly understood. We retrospectively analyzed 4708 adult AML patients recruited into Study Alliance Leukemia trials to investigate the prognostic impact of CEBPAsm. CEBPA mutations were identified in 240 patients (5.1%), 131 CEBPAbi and 109 CEBPAsm (60 affecting the amino-terminal transactivation domains (CEBPAsmTAD) and 49 the carboxy-terminal DNA-binding or basic leucine zipper region (CEBPAsmbZIP)). Interestingly, CEBPAbi and CEBPAsmbZIP patients shared several clinical factors, i.e. were significantly younger (median 46 years and 50 years) and had higher WBC counts at diagnosis (median 23.7 and 35.7 109/l) compared to CEBPAsmTAD patients (median age 63 yrs., median WBC 13.1 109/l; p<.001). Co-mutations were also similar in both groups, e.g. GATA2 mutations (35.1% CEBPAbi; 36.7% CEBPAsmbZIP vs. 6.7% CEBPAsmTAD; p<.001) or NPM1 mutations (3.1% CEBPAbi; 8.2% CEBPAsmbZIP vs. 38.3% CEBPAsmTAD; p<.001). CEBPAbi and CEBPAsmbZIP, but not CEBPAsmTAD were associated with significantly improved overall (median OS: 103 and 63 vs. 13 months) and event-free survival (median EFS: 20.7 and 17.1 vs. 5.7 months), in univariate and multivariable analyses. More detailed analysis revealed that the clinical and molecular features as well as the favorable survival were confined to patients showing in-frame mutations in bZIP (CEBPAbZIP-inf). When grouping patients into CEBPAbZIP-inf and CEBPAother (including CEBPAsmTAD and other non-CEBPAbZIP-inf patients), only CEBPAbZIP-inf patients showed superior CR rates and the longest median OS and EFS, arguing for a previously undefined prognostic role of this type of mutations.

Prevalence and Prognostic Impact of CEBPA Gene Mutation (Simplified Assay Technique) in Egyptian Acute Myeloid Leukemia Patients with Normal Cytogenetics

Mutations of the CCAAT/enhancer binding protein alpha (CEBPA) gene have been associated with a favorable outcome in patients with acute myeloid leukemia (AML), especially in those with a normal cytogenetics. However, few studies were done on Egyptian AML patients and none of them look for easier and less expensive method for CEBPA mutation screening. This study is aimed to investigate the prevalence of CEBPA mutations and its clinical and prognostic impact in Egyptian patients with cytogenetically normal AML (CN-AML). This was done using fragment analysis to assess this method as a cheaper and less laborious screening method compared to sequencing. Fluorescent PCR was done to amplify CEBPA gene in DNA extracted from 40 CN-AML patients. This was followed by fragment analysis of post-PCR products using GeneMapper software for detection of CEBPA mutations. CEBPA gene mutations were found in 7/40 CN-AML patients (17.5 %) and it was significantly associated with lower LDH levels (p = 0.039). All patients with CEBPA mutations achieved clinical remission and none of them showed refractoriness, relapsed, or died by the end of the 2 years study period. Furthermore, those patients demonstrate significantly longer overall and disease free survival than those with wild type CEBPA gene (p = 0.001 and 0.004 respectively). CEBPA mutation has a favorable prognostic impact in CN-AML. Fragment analysis is a good, lees laborious and cheaper method that can be used for CEBPA mutation screening in patients with CN-AML.

Whole genome and transcriptome analysis of a novel AML cell line with a normal karyotype

Acute myeloid leukemia (AML) occurs when hematopoietic progenitor cells acquire genetic defects blocking the regulation of normal growth and differentiation. Although recurrent translocations have been identified in AML, almost half of adult AML patients present with a normal karyotype (NK-AML). While cell line models exist to study AML, they frequently have abnormal/unstable karyotypes, while primary cells from NK-AML patients are difficult to maintain in vitro. Here we provide a thorough molecular characterization of a recently established cell line, CG-SH, which has normal cytogenetics, representing a useful new model for NK-AML. Using high-throughput DNA sequencing, we first defined the genetic background of this cell line. In addition to identifying potentially deleterious SNVs in genes relevant to AML, we also found insertions in both GATA2 and EZH2, two genes previously linked to AML. We further characterized the growth of this model system in vitro with a cytokine mix that promotes faster cell growth. We assessed gene expression changes after the addition of cytokines to the culture media and found differential expression in genes implicated in proliferation, apoptosis and differentiation. Our results provide a detailed molecular characterization of genetic defects in this cell line derived from an NK-AML patient.

C/EBPα and MYB regulate FLT3 expression in AML

The interaction between the receptor FLT3 (FMS-like tyrosine kinase-3) and its ligand FL leads to crucial signalling during the early stages of the commitment of haematopoietic stem cells. Mutation or over-expression of the FLT3 gene, leading to constitutive signalling, enhances the survival and expansion of a variety of leukaemias and is associated with an unfavourable clinical outcome for acute myeloid leukaemia (AML) patients. In this study, we used a murine cellular model for AML and primary leukaemic cells from AML patients to investigate the molecular mechanisms underlying the regulation of FLT3 gene expression and identify its key cis- and trans-regulators. By assessing DNA accessibility and epigenetic markings, we defined regulatory domains in the FLT3 promoter and first intron. These elements permit in vivo binding of several AML-related transcription factors, including the proto-oncogene MYB and the CCAAT/enhancer binding protein C/EBPα, which are recruited to the FLT3 promoter and intronic module, respectively. Substantiating their relevance to the human disease, our analysis of gene expression profiling arrays from AML patients uncovered significant correlations between FLT3 expression level and that of MYB and CEBPA. The latter relationship permits discrimination between patients with CEBPA mono- and bi-allelic mutations, and thus connects two major prognostic factors for AML.

Molecular-based classification of acute myeloid leukemia and its role in directing rational therapy: personalized medicine for profoundly promiscuous proliferations

Acute myeloid leukemia (AML) is not a single pathologic entity but represents a heterogeneous group of malignancies. This heterogeneity is exemplified by the variable clinical outcomes that are observed in patients with AML, and it is largely the result of diverse mutations within the leukemic cells. These mutations range from relatively large genetic alterations, such as gains, losses, and translocations of chromosomes, to single nucleotide changes. Detection of many of these mutations is required for accurate diagnosis, prognosis, and treatment of patients with AML. As such, many testing modalities have been developed and are currently employed in clinical laboratories to ascertain mutational status at prognostically and therapeutically critical loci. The assays include those that specifically identify large chromosomal alterations, such as conventional metaphase analysis and fluorescence in situ hybridization, and methods that are geared more toward analysis of small mutations, such as PCR with allele-specific oligonucleotide primers. Furthermore, newer tests, including array analysis and next-generation sequencing, which can simultaneously probe numerous molecular aberrancies within tumor cells, are likely to become commonplace in AML diagnostics. Each testing method clearly has advantages and disadvantages, an understanding of which should influence the choice of test in various clinical circumstances. To aid such understanding, this review discusses both genetic mutations in AML and the clinical tests-including their pros and cons-that may be used to probe these abnormalities. Additionally, we highlight the significance of genetic testing by describing cases in which results of genetic testing significantly influence clinical management of patients with AML.