The 24-well plate Transwell system with an 8-mm pore size polycarbonate filter membrane (Corning Costar, Corning, NY) was used. The filter membrane was coated with Matrigel (BD Biosciences, San Diego) diluted with serum-free medium and incubated overnight at 37uC. The cell suspensions were seeded to the upper compartment of the Transwell chamber at the cell density of 1610 5 in 100 ml serum free medium. After 24 hours, the medium was removed and the filter membrane was fixed with 4% formalin for 1 hour. The opposite surface of the filter membrane facing the lower chamber was stained with Hoechst 33342 (Sigma-Aldrich) for 3 minutes and the migrated cells were then visualized under an inverted microscope. The protocol of soft agar colony assay is described as follows. Each well (35 mm) of a six-well culture dish was coated with 2 ml bottom agar mixture (DMEM, 10% (v/v) FCS, 0.6% (w/v) agar). After the bottom layer solidified, 2 ml top agarmedium mixture (DMEM, 10% (v/v) FCS, 0.3% (w/v) agar) containing 2610 4 cells was added, and the dishes were incubated at 37uC for 4 weeks. Plates were stained with 0.5 ml of 0.005% crystal violet for 1 hour and then a dissecting microscope was used to count the number of colonies [29] .