MicroRNA-494 is a master epigenetic regulator of multiple invasion-suppressor microRNAs by targeting ten eleven translocation 1 in invasive human hepatocellular carcinoma tumors

Hepatology. 2015 Aug;62(2):466-80. doi: 10.1002/hep.27816. Epub 2015 May 6.


Vascular invasion provides a direct route for tumor metastasis. The degree to which microRNA (miRNA) expression plays a role in tumor vascular invasion is unclear. Here, we report that miR-494 is up-regulated in human hepatocellular carcinoma (HCC) tumors with vascular invasion and can promote HCC cell invasiveness by gene inactivation of multiple invasion-suppressor miRNAs. Our results show that ten eleven translocation (TET) methylcytosine dioxygenase, predominantly TET1 in HCC cells, is a direct target of miR-494. The reduced 5'-hydroxymethylcytosine levels observed in the proximal cytosine-phosphate-guanine (CpG) regions of multiple invasion-suppressor miRNA genes are strongly associated with their transcriptional repression upon miR-494 overexpression, whereas enforced DNA demethylation can abolish the repression. Furthermore, TET1 knockdown shows a similar effect as miR-494 overexpression. Conversely, miR-494 inhibition or enforced TET1 expression is able to restore invasion-suppressor miRNAs and inhibit miR-494-mediated HCC cell invasion.

Conclusions: miR-494 can trigger gene silencing of multiple invasion-suppressor miRNAs by inhibiting genomic DNA demethylation by direct targeting of TET1, thereby leading to tumor vascular invasion.

Publication types

  • Comparative Study

MeSH terms

  • Animals
  • Biopsy, Needle
  • Carcinoma, Hepatocellular / genetics*
  • Carcinoma, Hepatocellular / pathology
  • Cell Movement / genetics
  • DNA Methylation
  • DNA-Binding Proteins / genetics*
  • Down-Regulation
  • Female
  • Gene Expression Regulation, Neoplastic
  • Gene Silencing
  • Hep G2 Cells / pathology
  • Heterografts
  • Humans
  • Immunohistochemistry
  • Liver Neoplasms / genetics*
  • Liver Neoplasms / pathology
  • Male
  • Mice
  • Mice, Inbred BALB C
  • MicroRNAs / genetics*
  • Mixed Function Oxygenases
  • Neoplasm Invasiveness / genetics
  • Neoplasm Invasiveness / pathology
  • Proto-Oncogene Proteins / genetics*
  • Real-Time Polymerase Chain Reaction / methods
  • Sampling Studies
  • Translocation, Genetic / genetics*
  • Up-Regulation


  • DNA-Binding Proteins
  • MIRN494 microRNA, human
  • MicroRNAs
  • Proto-Oncogene Proteins
  • Mixed Function Oxygenases
  • TET1 protein, human