title: MicroRNA-21 (miR-21) post-transcriptionally downregulates tumor suppressor Pdcd4 and stimulates invasion, intravasation and metastasis in colorectal cancer.
abstract: Tumor-suppressor Pdcd4 inhibits transformation and invasion and is downregulated in cancers. So far, it has not been studied as to whether miRNAs, suppressing target expression by binding to the 3'-UTR, regulate Pdcd4 or invasion. The present study was conducted to investigate the regulation of Pdcd4, and invasion/intra-vasation, by miRNAs. A bioinformatics search revealed a conserved target-site for miR-21 within the Pdcd4-3'-UTR at 228-249 nt. In 10 colorectal cell lines, an inverse correlation of miR-21 and Pdcd4-protein was observed. Transfection of Colo206f-cells with miR-21 significantly suppressed a luciferase-reporter containing the Pdcd4-3'-UTR, whereas transfection of RKO with anti-miR-21 increased activity of this construct. This was abolished when a construct mutated at the miR-21/nt228-249 target site was used instead. Anti-miR-21-transfected RKO cells showed an increase of Pdcd4-protein and reduced invasion. Moreover, these cells showed reduced intra-vasation and lung metastasis in a chicken-embryo-metastasis assay. In contrast, overexpression of miR-21 in Colo206f significantly reduced Pdcd4-protein amounts and increased invasion, while Pdcd4-mRNA was unaltered. Resected normal/tumor tissues of 22 colorectal cancer patients demonstrated an inverse correlation between miR-21 and Pdcd4-protein. This is the first study to show that Pdcd4 is negatively regulated by miR-21. Furthermore, it is the first report to demonstrate that miR-21 induces invasion/intravasation/metastasis.
authors.affiliation: Department of Experimental Surgery and Molecular Oncology of Solid Tumors, Medical Faculty Mannheim, University of Heidelberg, Germany.
authors.forename: I A
authors.initials: IA
authors.lastname: Asangani
authors.forename: S A K
authors.initials: SA
authors.lastname: Rasheed
authors.forename: D A
authors.initials: DA
authors.lastname: Nikolova
authors.forename: J H
authors.initials: JH
authors.lastname: Leupold
authors.forename: N H
authors.initials: NH
authors.lastname: Colburn
authors.forename: S
authors.initials: S
authors.lastname: Post
authors.forename: H
authors.initials: H
authors.lastname: Allgayer
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology*; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics*; D001483:Base Sequence; D018938:Caco-2 Cells; D002642:Chick Embryo; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D035683:MicroRNAs / Q000502:physiology*; D008969:Molecular Sequence Data; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D034622:RNA Interference; D016601:RNA-Binding Proteins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014407:Tumor Cells, Cultured
chemical_list: D051017:Apoptosis Regulatory Proteins; C524940:MIRN21 microRNA, human; D035683:MicroRNAs; C114487:PDCD4 protein, human; D016601:RNA-Binding Proteins