In brief, cancer cells were serum-starved
overnight and then pre-treated with GA for 24h. Then cells
were suspended and added to the upper chamber of the
Transwell chambers that were coated with Matrigel (BD
Biosciences, USA) before experiment. The non-invasive
cells were slightly removed from the upper surface by a
cotton-tipped swab after 24h incubation. Invading cells on
the bottom surface of the filter were fixed and then stained
with 0.1% crystal violet. The invading cell numbers were
quantified by counting the stained cells under microscope
(Nikon Instruments Inc.) at a magnification of 200×.