Journal Article

Silencing of miR-370 in Human Cholangiocarcinoma by Allelic Loss and Interleukin-6 Induced Maternal to Paternal Epigenotype Switch

Pawlik, Timothy M., Mezey, Esteban, Allen, Sarah, Gores, Gregory J., Ferguson-Smith, Anne C., Yamanaka, Sumitaka, Mori, Yuriko, Xie, Qing, Ishida, Masaharu, An, Fangmei, Roberts, Lewis R., Selaru, Florin M.

2012

Overview

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.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Alleles / Animals / Biliary tract / Biliary tract cancer / Biology / Blotting, Western / Carcinogenesis / Carcinogens / Cell Line, Tumor / Cholangiocarcinoma / Cholangiocarcinoma - genetics / Cholangiocarcinoma - metabolism / Chromosomes / Colorectal cancer / Demethylation / Deoxyribonucleic acid / Development and progression / DNA / DNA methylation / DNA Methylation - genetics / Dosage and administration / Epigenetics / Epithelium / Gastroenterology / Gene expression / Genetic aspects / Genomes / Genomic imprinting / Growth factors / Hepatology / Hospitals / Humans / Immunoglobulins / Imprinting / In Vitro Techniques / Infectious diseases / Interleukin 6 / Interleukin-6 - pharmacology / Interleukins / Liver / Loss of Heterozygosity - genetics / Loss of Heterozygosity - physiology / Medicine / Methylation / Mice / MicroRNA / MicroRNAs / MicroRNAs - antagonists & inhibitors / MicroRNAs - genetics / miRNA / Neurosciences / Patient outcomes / Physiology / Reverse Transcriptase Polymerase Chain Reaction / Ribonucleic acid / RNA / Rodents / Tissues / Western blotting