We previously demonstrated that epidermal growth factor (EGF) enhances cell migration and invasion of breast cancer cells in a SMAD ubiquitination regulatory factor 1 (SMURF1)-dependent manner and that SMURF1 induces degradation of β-catenin in C2C12 cells. However, the relationship between EGF-induced SMURF1 and β-catenin expression in breast cancer cells remains unclear. So, we investigated if EGF and SMURF1 regulate β-catenin expression in MDAMB231 human breast cancer cells. When MDAMB231 cells were incubated with EGF for 24, 48, and 72 hours, EGF significantly increased expression levels of SMURF1 mRNA and protein while suppressing expression levels of β-catenin mRNA and protein. Overexpression of SMURF1 downregulated β-catenin mRNA and protein, whereas knockdown of SMURF1 increased β-catenin expression and blocked EGF-induced β-catenin downregulation. Knockdown of β-catenin enhanced cell migration and invasion of MDAMB231 cells, while β-catenin overexpression suppressed EGF-induced cell migration and invasion. Furthermore, knockdown of β-catenin enhanced vimentin expression and decreased cytokeratin expression, whereas β -catenin overexpression decreased vimentin expression and increased cytokeratin expression. These results suggest that EGF downregulates β-catenin in a SMURF1-dependent manner and that β-catenin downregulation contributes to EGF-induced cell migration and invasion in MDAMB breast cancer cells.

Introduction
 Materials and Methods
  Cell culture
  Gene knockdown using small interfering RNA
  Western blot analysis
  Reverse transcription-polymerase chain reaction(RT-PCR)
  Migration and invasion assays
  Immunofluorescence staining
  Statistical analysis
 Results
  EGF inversely regulates SMURF1 and β-cateninexpression in MDAMB231 cells
  Smurf1 downregulates β-catenin expression
  Beta-catenin negatively regulates breast cancer cellmigration and invasion
  Beta-catenin inhibits EMT marker expression inMDAMB231 cells
 Discussion
 References

• Arang Kwon(Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University)
• Hyun-Jung Park(Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University)
• Jeong-Hwa Baek(Department of Molecular Genetics, School of Dentistry and Dental Research Institute, Seoul National University) Correspondence to