A conserved microRNA signature related to cellular transformation by the RAS oncogene (miRNA)

The differential expression of microRNAs in Ras transformed epithelial cells of human and rat origin was investigated. Here we describe the group of miRNAs differentially expressed in two Ras transformed cell lines and defined it as a miRNA Ras signatures. We show that expression of these miRNAs are also affected in different primary tumors with high frequency of Ras mutation. We demonstate that introduction of different miRNAs lost during Ras transformation have big influence on cellular phenotype and mRNA expression. Importance of Ras pathway dependent transcription factors for miRNA regulation was shown as well. The complexity of miRNA – signal transduction pathways interactions and importance of miRNA regulation in Ras dependent malignant tumor formation is discussed. MiRNA microarrays were constructed using the NCODETM multi-species microarray probe set V1 (Invitrogen, CA, USA). Oligos were spotted at a concentration of 30µM on epoxy treated slides (Corning®, NY, USA) using the MicroGrid compact microarrayer (Genomic Solutions, Ann Arbor, USA) equipped with a MicroSpot 2500 quill pins. 100 ng of small RNA fraction were labelled using the NCODETM miRNA labeling system (Invitrogen, CA, USA) according to the manufacturer’s instructions.