Transcriptional silencing of Dickkopf gene family by CpG island hypermethylation in human gastrointestinal cancer

World J Gastroenterol. 2008 May 7;14(17):2702-14. doi: 10.3748/wjg.14.2702.


Aim: To clarify alterations of Dickkopfs (Dkks) and Kremen2 (Krm2) in gastrointestinal cancer.

Methods: We investigated the expression profiles and epigenetic alterations of Dkks and Krm2 genes in gastrointestinal cancer using RT-PCR, tissue microarray analysis, and methylation specific PCR (MSP). Cancer cells were treated with the demethylating agent and/or histone deacetylase inhibitor. WST-8 assays and in vitro invasion assays after treatment with specific siRNA for those genes were performed.

Results: Dkks and Krm2 expression levels were reduced in a certain subset of the gastrointestinal cancer cell lines and cancer tissues. This was correlated with promoter hypermethylation. There were significant correlations between Dkks over-expression levels and beta-catenin over-expression in colorectal cancer. In colorectal cancers with beta-catenin over-expression, Dkk-1 expression levels were significantly lower in those with lymph node metastases than in those without. Down-regulation of Dkks expression by siRNA resulted in a significant increase in cancer cell growth and invasiveness in vitro.

Conclusion: Down-regulation of the Dkks associated to promoter hypermethylation appears to be frequently involved in gastrointestinal tumorigenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Cell Line, Tumor
  • Cell Proliferation
  • Chemokines
  • CpG Islands*
  • DNA Methylation*
  • Gastrointestinal Neoplasms / genetics*
  • Gastrointestinal Neoplasms / metabolism
  • Gastrointestinal Neoplasms / pathology
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Immunohistochemistry
  • Intercellular Signaling Peptides and Proteins / genetics*
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Membrane Proteins / genetics
  • Neoplasm Invasiveness
  • Promoter Regions, Genetic
  • RNA Interference*
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / metabolism
  • Receptors, Cell Surface
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / genetics
  • Tissue Array Analysis
  • Transcription, Genetic*
  • Transfection
  • beta Catenin / genetics


  • Adaptor Proteins, Signal Transducing
  • CTNNB1 protein, human
  • Chemokines
  • DKK1 protein, human
  • DKK2 protein, human
  • DKK3 protein, human
  • DKK4 protein, human
  • Intercellular Signaling Peptides and Proteins
  • KREMEN2 protein, human
  • Membrane Proteins
  • RNA, Messenger
  • RNA, Small Interfering
  • Receptors, Cell Surface
  • beta Catenin