Identification of miR-145 targets involved in colon cancer

MicroRNAs (miRNAs) have emerged as important gene regulators and are recognized as key players in tumorigenesis. miR-145 is reported to be down-regulated in several cancers, but knowledge of its targets in colon cancer remains limited. To investigate the role of miR-145 in colon cancer, we have employed a microarray based approach to identify miR-145 targets. Based on seed site enrichment analyses and unbiased word analyses, we found a significant enrichment of miRNA binding sites in the 3’-untranslated regions (UTRs) of transcripts down-regulated upon miRNA overexpression, which represent potential miR-145 targets. Gene Ontology analysis showed an overrepresentation of genes involved in cell death, gene expression, cancer, cell cycle, DNA replication, recombination and repair. A number of the identified miRNA targets have previously been implicated in cancer, including YES, FSCN1, ADAM17, BIRC2, VANGL1 as well as the transcription factor STAT1. Both YES and STAT1 were verified as direct miR-145 targets based on 3’UTR luciferase assays and western blots for endogenous proteins. DLD-1 cells were transfected with 50 nM miR-145 duplex or mock transfected. Total RNA was harvested 24 hours post-transfection and analyzed on Affymetrix HG-U133 Plus 2.0 human arrays.