MicroRNAs Distinguish Cytogenetic Subgroups in Pediatric AML and Contribute to Complex Regulatory Networks in AML-Relevant Pathways

Abstract

BackgroundThe role of microRNAs (miRNAs), important post-transcriptional regulators, in the pathogenesis of acute myeloid leukemia (AML) is just emerging and has been mainly studied in adults. First studies in children investigate single selected miRNAs, however, a comprehensive overview of miRNA expression and function in children and young adults is missing so far.Methodology/Principal FindingsWe here globally identified differentially expressed miRNAs between AML subtypes in a survey of 102 children and adolescent. Pediatric samples with core-binding factor AML and promyelocytic leukemia could be distinguished from each other and from MLL-rearranged AML subtypes by differentially expressed miRNAs including miR-126, -146a, -181a/b, -100, and miR-125b. Subsequently, we established a newly devised immunoprecipitation assay followed by rapid microarray detection for the isolation of Argonaute proteins, the hallmark of miRNA targeting complexes, from cell line models resembling core-binding factor and promyelocytic leukemia. Applying this method, we were able to identify Ago-associated miRNAs and their targeted mRNAs.Conclusions/SignificancemiRNAs as well as their mRNA-targets showed binding preferences for the different Argonaute proteins in a cell context-dependent manner. Bioinformatically-derived pathway analysis suggested a concerted action of all four Argonaute complexes in the regulation of AML-relevant pathways. For the first time, to our knowledge, a complete AML data set resulting from carefully devised biochemical isolation experiments and analysis of Ago-associated miRNAs and their target-mRNAs is now available.

miRNA biogenesis: Biological impact in the development of cancer

“…One strand (the miRNA-guide strand) is loaded onto the RNA-induced silencing complex (RISC), formed by the association of Dicer, TRBP, PACT, most commonly the Argonaute 2 protein (Ago2) 22,26 and GW182, which promotes Argonaute stability. 27 The resultant complex between mature miRNA and RISC is denominated miRSC. In mammals, selection of the guide strand is dictated by thermodynamic stability, the less stable strand at the 5é nd has more probability of being incorporated into the RISC; the remaining strand (miRNA*-passenger strand) is excluded and generally degraded.…”

“…During this process, Ago2, a protein with RNA cleavage activity, together with GW182, which interacts with the cytoplasmic poly(A)-binding protein (PABP) and the PAN2-PAN3 and CCR4-NOT deadenylase 27 plays a central role in miRNA-mediated mRNA silencing. 32 There are at least 3 possible mechanisms by which miRNA mediate repression of gene expression: (1) mRNA target hybridization and degradation, (2) translation inhibition during the initiation or elongation phases and (3) mRNA decay by its recruitment to P bodies 33,34 (Fig.…”

“…Genomic approaches have shown that some miRNA subpopulations preferentially bind to a certain argonaute protein (Ago1, Ago3, Ago4 -which might be redundant-and Ago2) in a context dependent manner with different implications in carcinogenesis. 134,27 Conversely, miRNA incorporation to the RISC complex might be regulated and influenced by different factors; one of them is incorporation of ago 3, which enhances the incorporation of the passenger strand of the tumor suppressor let-7a (let7-a*) to the RISC complex, and by consequence, promotes its biological activity in cancer cells. It seems that Ago3 modulates the ratio between microRNA guide and passenger strands.…”

OKT3 prevents xenogeneic GVHD and allows reliable xenograft initiation from unfractionated human hematopoietic tissues

“…The utility of working with primary human samples is obvious, and the recent deluge of information obtained from proteomic and nucleic acid analyses of these samples is significant. [28][29][30][31][32][33] The advances made in our understanding of the molecular mechanisms driving human disease cannot be overstated. However, the ability to use primary patient samples in functional and translational studies is frequently limited by the inability to propagate these samples in vitro and in vivo.…”

Systematic literature review on Parkinson's disease and Childhood Leukaemia and mode of actions for pesticides

“…The translocation t(8;21)(q22;q22), leading to the gene fusion of AML1 and ETO (also known as MTG8), is one of the most frequently detected chromosomal translocations in AML, accounting for ~15% of all AML cases (Cheng et al, 2011;Daschkey et al, 2013;Zhang et al, 2002). A correlation between genomic breakpoints in AML1 and ETO and topoisomerase II DNA cleavage sites has been implicated, suggesting a potential role of topoisomerase II in the fusion of these genes (Zhang et al, 2002).…”