Metastasis and invasion of HCC cells lines in response to LPS. (A) The wound healing assay was employed to determine the migration of HepG2, Huh7, Hep3B and SMMC-7721 cells in response to LPS. Cells were monitored every 24 hours for two days to evaluate the rate of migration into the scratched area. (B) Invasiveness of cells was determined using the Transwell assay. Cells were treated with LPS (10 μg/ml) for 48 hours, and then plated in the upper chamber of the Transwell and allowed to grow for 24 hours in serum-free medium, 5% fetal bovine serum was placed in the lower chamber. The number of cells that invaded through the Matrigel was counted in ten fields under the ×20 objective lens, and is shown as the mean ± standard deviation (*P < 0.05, **P < 0.01). (A) and (B) are representative of at least three independent experiments (× 200). (C) Pictures of metastatic liver nodules in nude mice by splenic-vein injection of HepG2 and SMMC-7721 cells untreated or treated with LPS. H & E staining was performed on serial sections of metastatic tumors and normal liver (× 200). The arrows indicate the metastatic tumor on the surface of the liver. (D) The numbers of nodules were quantified on nude mice livers (n = 10 per group). Values for individual mice are shown above the bars (*P < 0.05). (E) Survival rate of nude mice six weeks after splenic vein injection of HepG2 and SMMC-7721 cells untreated or treated with LPS. HCC, hepatocellular carcinoma; LPS, lipopolysaccharide.