title: Silencing of miR-370 in human cholangiocarcinoma by allelic loss and interleukin-6 induced maternal to paternal epigenotype switch.
abstract: Cholangiocarcinoma (CCA) is a highly lethal malignant tumor arising from the biliary tract epithelium. Interleukin-6 (IL-6) is a major mediator of inflammation and contributor to carcinogenesis within the biliary tree. Previous studies suggested that enforced IL-6 contributes to cholangiocarcinogenesis through hypermethylation of several genes implicated in CCA. However, the precise mechanisms of IL-6 effects in CCA remain unclear. We now demonstrate that microRNA (miR)-370 is underexpressed in a large cohort of human CCA vs. normal liver tissues. In addition, we show that IL-6 induces a time-dependent silencing of miR-370. In addition, demethylation of CCA cells results in upregulation of miR-370. Furthermore, we demonstrate that miR-370 is imprinted, and that the Intergenic Differentially Methylated Region (IG-DMR) responsible for imprinting regulation of this genomic locus is hypermethylated in response to IL-6 treatment. In addition, the IG-DMR is hypermethylated in human CCA specimens compared to normal matched controls, in the same location as the IL-6 induced hypermethylation. Finally, miR-370 was found to regulate WNT10B in luciferase as well as western blotting experiments. Our data indicate that the paternal allele of miR-370 is normally silenced through genomic imprinting and that the overexpression of IL-6 in CCA effectively suppresses the expression of miR-370 from the maternal allele, lending support to the theory that miR-370 silencing in human CCA follows a classic two-hit mechanism.
authors.affiliation: Division of Gastroenterology and Hepatology, Johns Hopkins Hospital, Baltimore, Maryland, United States of America.
authors.forename: Fangmei
authors.initials: F
authors.lastname: An
authors.forename: Sumitaka
authors.initials: S
authors.lastname: Yamanaka
authors.forename: Sarah
authors.initials: S
authors.lastname: Allen
authors.forename: Lewis R
authors.initials: LR
authors.lastname: Roberts
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Pawlik
authors.forename: Qing
authors.initials: Q
authors.lastname: Xie
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishida
authors.forename: Esteban
authors.initials: E
authors.lastname: Mezey
authors.forename: Anne C
authors.initials: AC
authors.lastname: Ferguson-Smith
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Mori
authors.forename: Florin M
authors.initials: FM
authors.lastname: Selaru
mesh_terms: D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D018281:Cholangiocarcinoma / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D015850:Interleukin-6 / Q000494:pharmacology*; D019656:Loss of Heterozygosity / Q000235:genetics / Q000502:physiology*; D051379:Mice; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015850:Interleukin-6; C526503:MIRN370 microRNA, human; D035683:MicroRNAs