Invasion and migration assays were performed using a 24 well transwell insert (8 µm pore filters, BD Bioscience, Bedford, MA) with and without matrigel-coated membrane, respectively. Briefly, for migration assays, after filling the lower part of the transwell with RPMI plus 10% FBS, A549 cells (5×103) suspended in serum-free RPMI were added to the upper part of the transwell, and incubated for 6 hr at 37 °C. The cells were allowed to migrate to the bottom of the membrane. After incubation, the cells migrated to the lower surface of the transwell were fixed with methanol for 5 min and stained with 0.1% crystal violet. For invasion assays, the transwell was coated with 100 µl (1 mg/ml) matrigel (BD Bioscience, Bedford, MA). A549 cells (5×103) were plated onto the upper part of the matrigel-coated transwell chamber and incubated for 24 hr. The invaded cells were then fixed with methanol, stained and counted. The number of invading or migrating cells was determined by counting five high-power fields (400) on each membrane and was calculated as the mean number of cells per field (21 (link)).