title: Epigenetic silencing of miR-708 enhances NF-κB signaling in chronic lymphocytic leukemia.
abstract: MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression and their deregulation is involved in tumor development. Epigenetic gene silencing in cancer by DNA methylation contributes to the silencing of tumor-suppressor genes, including miRNAs. We have recently shown that the promoter of miR-708 is aberrantly methylated in chronic lymphocytic leukemia (CLL). To characterize the molecular signaling networks that are influenced by miR-708, we performed a luciferase-based screen evaluating the effects of ectopic miR-708 expression on leukemia-relevant signaling pathways. We found that miR-708 strongly repressed NF-κB signaling, a pathway known to be deregulated in CLL. Among the predicted miR-708 targets was IKKβ (inhibitor of kappa light polypeptide gene enhancer in B cells, kinase-β/IKBKB), a key kinase facilitating NF-κB signaling. We validated the interaction of miR-708 with the 3'-untranslated region of IKKβ and found that miR-708 overexpression represses endogenous IKKβ. Phosphorylation of the IKKβ target IκBα and expression of known NF-κB target genes were impaired by miR-708. Furthermore, we identified an enhancer region downstream of the miR-708 promoter that displays a distinct DNA methylation status in CLL. High enhancer methylation is significantly correlated with lower miR-708 expression and is predominantly found in patients with poor prognosis and shorter time to treatment. These results demonstrate that miR-708 regulates the NF-κB pathway by targeting IKKβ, and that methylation of a key enhancer region contributes to its suppression in CLL.
authors.affiliation: Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Constance
authors.initials: C
authors.lastname: Baer
authors.affiliation: Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Oakes
authors.affiliation: Division of Hematology, Department of Internal Medicine, the Ohio State University, Columbus, OH.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Ruppert
authors.affiliation: Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ), Heidelberg, Germany.|Department of Hematology, Oncology and Stem Cell Transplantation, University of Freiburg Medical Center, Freiburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Claus
authors.affiliation: Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Soo-Zin
authors.initials: SZ
authors.lastname: Kim-Wanner
authors.affiliation: Cooperation Unit Mechanisms of Leukemogenesis, German Cancer Research Center (DKFZ), Heidelberg, Germany.|Department of Internal Medicine III, University of Ulm, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Mertens
authors.affiliation: Department of Translational Oncology, National Center for Tumor Diseases (NCT), German Cancer Research Center (DKFZ), Heidelberg, Germany.|Department of Medicine V, University of Heidelberg, Heidelberg, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Zenz
authors.affiliation: Department of Internal Medicine III, University of Ulm, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Stilgenbauer
authors.affiliation: Division of Hematology, Department of Internal Medicine, the Ohio State University, Columbus, OH.
authors.forename: John C
authors.initials: JC
authors.lastname: Byrd
authors.affiliation: Division of Epigenomics and Cancer Risk Factors, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Plass
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D002460:Cell Line; D019175:DNA Methylation / Q000235:genetics; D044127:Epigenesis, Genetic / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D020868:Gene Silencing / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics*; D035683:MicroRNAs / Q000235:genetics*; D016328:NF-kappa B / Q000235:genetics*; D010766:Phosphorylation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*
chemical_list: D020413:3' Untranslated Regions; C568528:MIRN708 microRNA, human; D035683:MicroRNAs; D016328:NF-kappa B; D051550:I-kappa B Kinase
keywords: DNA methylation; IKKβ; NF-κB; epigenetics; miR-708; microRNA