For invasion assays, transwell filters (Corning Incorporated, Corning, NY, USA) were coated with Matrigel (BD Biosciences) for 24 h, and 2×105 cells were seeded into the upper compartment of the chambers with 100 μl serum-free RPMI-1640 medium. The lower chamber of the transwell was filled with culture media containing 10% FBS as a chemo-attractant. After 48 h incubation, noninvaded cells on the top of the transwell were scraped off with a cotton swab. Cells successfully translocated were fixed with 10% formalin and counted under a light microscope.