Effects of SIRT1 activity on migration and invasion of hepatocellular carcinoma (HCC) cell lines. (A) SIRT1 protein levels were higher in all HCC cell lines. (B) Invasiveness of cells was determined using the Transwell assay. SMMC-7721 and HepG2 cells were treated with nicotinamide (10 mM) or resveratrol (50 μmol/L) for 48 or 72 h. Cells were then plated in the upper chamber of the Transwell and allowed to grow for 48 h in serum-free medium, while 10% fetal bovine serum was placed in the lower chamber. The number of cells that invaded through the Matrigel was counted in 10 fields under a × 20 objective lens and is shown as the mean ± standard deviation (*P < 0.05). (C) A wound healing assay was employed to determine migration of HepG2 and SMMC-7721 cells in response to an SIRT1 inhibitor or activator. Cells were monitored every 24 h for 2 days to evaluate the rate of migration into the scratched area. (B) and (C) are representative of at least three independent experiments (×200).