Methylation profiles reveal distinct subgroup of hepatocellular carcinoma patients with poor prognosis

PLoS One. 2014 Aug 5;9(8):e104158. doi: 10.1371/journal.pone.0104158. eCollection 2014.

Abstract

Hepatocellular Carcinoma (HCC) is one of the leading causes of cancer-associated mortality worldwide. However, the role of epigenetic changes such as aberrant DNA methylation in hepatocarcinogenesis remains largely unclear. In this study, we examined the methylation profiles of 59 HCC patients. Using consensus hierarchical clustering with feature selection, we identified three tumor subgroups based on their methylation profiles and correlated these subgroups with clinicopathological parameters. Interestingly, one tumor subgroup is different from the other 2 subgroups and the methylation profile of this subgroup is the most distinctly different from the non-tumorous liver tissues. Significantly, this subgroup of patients was found to be associated with poor overall as well as disease-free survival. To further understand the pathways modulated by the deregulation of methylation in HCC patients, we integrated data from both the methylation as well as the gene expression profiles of these 59 HCC patients. In these patients, while 4416 CpG sites were differentially methylated between the tumors compared to the adjacent non-tumorous tissues, only 536 of these CpG sites were associated with differences in the expression of their associated genes. Pathway analysis revealed that forty-four percent of the most significant upstream regulators of these 536 genes were involved in inflammation-related NFκB pathway. These data suggest that inflammation via the NFκB pathway play an important role in modulating gene expression of HCC patients through methylation. Overall, our analysis provides an understanding on aberrant methylation profile in HCC patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Carcinoma, Hepatocellular / classification*
  • Carcinoma, Hepatocellular / genetics*
  • Cluster Analysis
  • CpG Islands / genetics
  • DNA Methylation / genetics*
  • Disease-Free Survival
  • Female
  • Gene Expression Regulation, Neoplastic
  • Genetic Loci
  • Humans
  • Liver Neoplasms / classification*
  • Liver Neoplasms / genetics*
  • Male
  • Middle Aged
  • NF-kappa B / metabolism
  • Reproducibility of Results
  • Sequence Analysis, DNA
  • Signal Transduction / genetics

Substances

  • NF-kappa B

Associated data

  • GEO/GSE57956
  • GEO/GSE57957

Grants and funding

This work is supported by grants from the National Medical Research Council (NMRC) (NMRC/1131/2007 and NMRC/1238/2009), the BioMedical Research Council (BMRC) (BMRC06/1/21/19/449) of Singapore and the Singapore Millennium Foundation (SMF), as well as block funding from the National Cancer Centre, SINGAPORE and the DUKE-NUS Graduate Medical School to A/Prof Caroline Lee. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.