Combinatorial effects of microRNAs to suppress the Myc oncogenic pathway

Abstract

Many mammalian transcripts contain target sites for multiple miRNAs, although it is not clear to what extent miRNAs may coordinately regulate single genes. We have mapped the interactions between downregulated miRNAs and overexpressed target protein-coding genes in murine and human lymphomas. Myc, one of the hallmark oncogenes in these lymphomas, stands out as the up-regulated gene with the highest number of genetic interactions with downregulated miRNAs in mouse lymphomas. The regulation of Myc by several of these miRNAs is confirmed by cellular and reporter assays. The same approach identifies MYC and multiple Myc targets as a preferential target of down-regulated miRNAs in human Burkitt lymphoma, a pathology characterized by translocated MYC oncogenes. These results indicate that several miRNAs must be coordinately downregulated to enhance critical oncogenes, such as Myc. Some of these Myc-targeting miRNAs are repressed by Myc, suggesting that these tumors are a consequence of the unbalanced activity of Myc versus miRNAs. © 2011 by The American Society of Hematology.