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Genome-wide Screen for miRNA Targets Using the MISSION Target ID Library
08:40

Genome-wide Screen for miRNA Targets Using the MISSION Target ID Library

Published on: April 6, 2012

MicroRNA-140 acts as a liver tumor suppressor by controlling NF-κB activity by directly targeting DNA

Akemi Takata1, Motoyuki Otsuka, Takeshi Yoshikawa

  • 1Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Hepatology (Baltimore, Md.)
|August 18, 2012
PubMed
Abstract

Insights

Impaired microRNA-140 function, caused by DDX20 deficiency, promotes liver cancer. This occurs because DDX20 normally suppresses NF-κB activity, and its absence allows increased DNA methyltransferase 1, leading to reduced metallothionein and enhanced NF-κB activity.

Area of Science:

  • Molecular Biology
  • Oncology
  • Gene Regulation

Background:

  • MicroRNAs (miRNAs) are crucial gene regulators, with altered expression linked to various cancers.
  • The role of functional impairment in miRNA machinery components in carcinogenesis, particularly hepatocarcinogenesis, is not well understood.
  • Nuclear factor-κB (NF-κB) activity is implicated in liver cancer development.

Purpose of the Study:

  • To investigate the involvement of miRNA machinery component deregulation and subsequent miRNA functional impairment in hepatocarcinogenesis.
  • To explore the specific role of DDX20 and miRNA-140 in the context of liver cancer.
  • To elucidate the molecular mechanisms linking DDX20 deficiency, miRNA-140 dysfunction, and liver tumor promotion.

Main Methods:

  • Analysis of DDX20 expression in human hepatocellular carcinomas.
  • Investigation of the regulatory relationship between DDX20, NF-κB, and miRNA-140.
  • Identification of direct targets of miRNA-140, such as DNA methyltransferase 1 (Dnmt1).
  • Assessment of the impact of Dnmt1 on metallothionein gene expression and NF-κB activity.
  • Evaluation of hepatocarcinogenesis in miRNA-140-knockout mice.

Main Results:

  • Reduced DDX20 expression was frequently observed in hepatocellular carcinomas.
  • DDX20 deficiency led to impaired miRNA-140 function and increased NF-κB activity.
  • Dnmt1 was identified as a direct target of miRNA-140; its increased expression in DDX20-deficient cells resulted in hypermethylation of metallothionein promoters.
  • Decreased metallothionein expression correlated with enhanced NF-κB activity.
  • MiRNA-140-knockout mice exhibited a propensity for hepatocarcinogenesis, mirroring the phenotype of DDX20 deficiency.

Conclusions:

  • MiRNA-140 functions as a liver tumor suppressor.
  • Impairment of miRNA-140 function, stemming from DDX20 deficiency, is a contributing factor to hepatocarcinogenesis.
  • The DDX20-miRNA-140 axis represents a critical pathway in preventing liver cancer development.

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