Acute myeloid leukaemia (AML) is the most common acute leukaemia in adults; however, the genetic aetiology of the disease is not yet fully understood. A quantitative expression profile analysis of 157 mature miRNAs was performed on 100 AML patients representing the spectrum of known karyotypes common in AML. The principle observation reported here is that AMLs bearing a t(15;17) translocation had a distinctive signature throughout the whole set of genes, including the up regulation of a subset of miRNAs located in the human 14q32 imprinted domain. The set included miR-127, miR-154, miR-154*, miR-299, miR-323, miR-368, and miR-370. Furthermore, specific subsets of miRNAs were identified that provided molecular signatures characteristic of the major translocation-mediated gene fusion events in AML. Analysis of variance showed the significant deregulation of 33 miRNAs across the leukaemic set with respect to bone marrow from healthy donors. Fluorescent in situ hybridisation analysis using miRNA-specific locked nucleic acid (LNA) probes on cryopreserved patient cells confirmed the results obtained by real-time PCR. This study, conducted on about a fifth of the miRNAs currently reported in the Sanger database (microrna.sanger.ac.uk), demonstrates the potential for using miRNA expression to sub-classify cancer and suggests a role in the aetiology of leukaemia.

MicroRNAs (miRNAs) are short single-stranded RNAs that have a potentially important role in gene regulation. Using a quantitative real-time polymerase chain reaction assay specific to the mature miRNA, the expression level of a selected group of haematopoietic tissue-specific miRNAs was measured across a set of 30 primary adult acute myeloid leukaemia (AML) with a normal karyotype. The expression levels of each miRNA were correlated with the genome-wide mRNA expression profiles in the same leukaemias. This revealed that miR181a correlated strongly with the AML morphological sub-type and with the expression of genes previously identified through sequence analysis as potential interaction targets. Three other miRNAs, miR-10a, miR-10b and miR-196a-1, showed a clear correlation with HOX gene expression. Leukemia (2007) 21, 912-916.

CEBPA encodes the transcription factor C/EBPalpha and is specifically up-regulated during granulocytic differentiation. The gene is mutated in approximately 20% of patients with acute myeloid leukemia (AML) FAB type M2 and occurs in the absence of the t(8;21). In much the same way as specific translocations are associated with a particular AML FAB type, the identification of non-random associations of gene mutation with karyotype or FAB type may be helpful in elucidating the molecular basis of certain forms of leukemia. To confirm these initial findings, 99 patients with AML FAB type M1 or M2 were screened for CEBPA mutations by use of a PCR-single-strand conformational polymorphism and sequencing approach. Nine CEBPA mutations were identified in eight patients. The mutations were clustered toward the COOH terminal of the protein and occurred exclusively in the intermediate cytogenetic risk group (8/64, 12.5%). Two patients with biallelic mutation, one homozygous for 1137Ins (57 bp) and another with two CEBPA mutations, 1096Ins (27 bp) and 363Ins (GGCC), were observed. There was no evidence for deletion of this region in the other six mutated samples analyzed by fluorescence in situ hybridization with a BAC clone spanning the CEBPA locus. CEBPA mutation status was not demonstrated to be of prognostic importance in this patient group, although this may reflect the selection and size of the AML population studied. In conclusion, mutation of CEBPA is a recurrent finding in AML and appears specific to the intermediate cytogenetic risk group patients.