Background: Peroxisome proliferator-activated receptor gamma (PPARgamma) activation has been proposed as a potential therapeutic strategy for various types of human cancer. The aim of this study was to activate PPARgamma and overexpress PGC-1alpha in HepG2 cells in order to analyze their effects on cell motility and E-cadherin expression.
Materials and methods: Adenovirus-mediated gene transfer was performed to overexpress PGC-1alpha in HepG2 human hepatoma cells. Small interference RNA (siRNA) was used to silence the expression of E-cadherin and PPARgamma. Cell motility was assessed by transwell cell migration analysis. Measurements of mRNA and protein expression were done by quantitative RT-PCR and Western blotting.
Results: Treatment with synthetic PPARgamma agonists, thiazolidinediones (rosiglitazone; troglitazone), and adenovirus-delivered overexpression of PPARgamma transcriptional coactivator-1alpha (PGC-1alpha) up-regulated E-cadherin expression and reduced motility of HepG2 cells. Using PPARgamma antagonist GW9662, we demonstrated that both PPARgamma-dependent and -independent pathways were involved in PGC-1alpha-induced up-regulation of E-cadherin. In addition, siRNA-mediated knockdown of E-cadherin expression restored the motility of PGC-1alpha-overexpressing HepG2 cells, indicating that up-regulated E-cadherin is responsible for the lower migratory ability of these cells. Intriguingly, siRNA-mediated silencing of PPARgamma abolished E-cadherin protein expression but also reduced the motility of HepG2 cells.
Conclusion: PPARgamma/PGC-1alpha pathway plays a crucial role in modulating E-cadherin expression and motility of HepG2 cells and may be a potential target for the prevention of HCC metastasis.