Oncogenic activation of glypican-3 by c-Myc in human hepatocellular carcinoma

Hepatology. 2012 Oct;56(4):1380-90. doi: 10.1002/hep.25891.


Glypican-3 (GPC3) is a heparan sulfate proteoglycan that has an important role in cell growth and differentiation, and its function in tumorigenesis is tissue-dependent. In hepatocellular carcinoma (HCC), the overexpression of GPC3 has been demonstrated to be a reliable diagnostic indicator. However, the mechanisms that regulate the expression and function of GPC3 remain unclear. The oncoprotein c-Myc is a transcription factor that plays a significant role in more than 50% of human tumors. We report here that GPC3 is a transcriptional target of c-Myc and that the expression of c-Myc is also regulated by GPC3, thus forming a positive feedback signaling loop. We found that the overexpression of c-Myc could induce GPC3 promoter-dependent luciferase activity in luciferase reporter experiments. Furthermore, mutational analysis identified c-Myc-binding sites within the GPC3 promoter. The exogenous overexpression of c-Myc increased the endogenous messenger RNA (mRNA) and protein levels of GPC3. Chromatin immunoprecipitation experiments revealed the binding of c-Myc to the endogenous GPC3 promoter, indicating that c-Myc can directly transcriptionally activate GPC3. Interestingly, GPC3 can also elevate c-Myc expression. Overexpression of GPC3 increased c-Myc protein levels, whereas the knockdown of GPC3 reduced c-Myc expression levels. Lastly, the elevated levels of c-Myc correlate with the overexpression of GPC3 in human HCC samples.

Conclusion: These data provide new mechanistic insight into the roles of GPC3 and of c-Myc in the development of HCC.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Analysis of Variance
  • Biopsy, Needle
  • Carcinoma, Hepatocellular / genetics*
  • Carcinoma, Hepatocellular / pathology
  • Cell Cycle / genetics
  • Cell Cycle / physiology
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Glypicans / genetics
  • Glypicans / metabolism*
  • Hepatocytes / cytology
  • Hepatocytes / metabolism
  • Humans
  • Immunohistochemistry
  • Liver Neoplasms / genetics*
  • Liver Neoplasms / pathology
  • Male
  • Middle Aged
  • Promoter Regions, Genetic / genetics
  • Promoter Regions, Genetic / physiology
  • Proto-Oncogene Proteins c-myc / genetics*
  • Proto-Oncogene Proteins c-myc / metabolism
  • RNA, Messenger / genetics
  • Sampling Studies
  • Sensitivity and Specificity
  • Tissue Culture Techniques
  • Transcriptional Activation
  • Tumor Cells, Cultured
  • Up-Regulation


  • GPC3 protein, human
  • Glypicans
  • Proto-Oncogene Proteins c-myc
  • RNA, Messenger