The transwell invasion assay was performed using the transwell chamber with a Matrigel-coated filter. A total of 5 × 104 cells to be tested were starved in serum and growth factor-free medium overnight and then plated on the top chamber with or without agents as indicated for 18 h, followed by removal of cells inside the upper chamber with cotton swabs, and the invasive cells on the lower side were fixed, stained with 0.1% crystal violet solution and counted using light microscope. The experiment was repeated three times.