MicroRNA Profiling of EVI1 Deregulated Myeloid Leukemia.

Chromosomal rearrangements involving the EVI1 gene are a recurrent finding in malignant myeloid disorders. These translocations or inversions contribute to ectopic expression of, or to the formation of fusion genes involving the EVI1 gene. EVI1 transcriptional activation has been reported in up to 10% of acute myeloid leukemia (AML) patients, and is a diagnostic marker which predicts a poor outcome. Recently, microRNA deregulation was identified as a major contributor to cancer initiation and progression. Moreover, miRNA genes were shown to be directly regulated by activated proto-oncogenes. In this study, we investigated which miRNA genes are implicated in the transcriptional pathways governed by the EVI1 oncogene. A total of 384 miRNAs were profiled through automated qRT-PCR using high-throughput quantitative stem-loop RT-PCR (Applied Biosystems). In a first step, differential miRNA expression was determined in 5 EVI1 rearranged/EVI1 overexpressing samples, 5 non-rearranged/EVI1 overexpressing samples and 5 non-rearranged/non-EVI1 overexpressing bone marrow samples. Next, up and down regulated miRNAs were analyzed in the leukemic EVI1 overexpressing cell lines Kasumi-3 and UCSD-AML1 following transient EVI1 RNAi knockdown. We will present the detailed results of these profiling studies as well as the results of data mining for identification of putative EVI1 regulated miRNAs. Further functional studies will be performed in order to select validated miRNA target genes and to asses their contribution to the leukemic phenotype. We anticipate that the discovery of such miRNAs may provide new targets for therapeutic intervention.