Cell invasion assayTranswell invasion assay was performed to assess cell invasion. The upper surface of the filter (pore size, 8.0 μm;Biosciences, Heidelberg, Germany) was coated with basement membrane Matrigel (BD Bioscience) at a concentrationof 2 mg/ml and incubated at 4◦C for 3 h. Cells (2 × 104) were seeded into the upper chamber with 200 μl serum-freemedium. The lower chamber was supplemented with 750 μl medium containing 10% FBS. Following incubation for24 h at 37◦C, cells were fixed with 4% polyoxymethylene and stained with 0.5% crystal violet (Sigma–Aldrich). Then,stained cells were counted under a microscope. Five visual fields were selected and the average number was calculated.