Inhibitory effect of PTS2 on hepatoma 22 (H22) tumors. H22 cells (5 × 106 cells/ml) in 0.2 ml of PBS were transplanted subcutaneously into right groins of mice; 24 h after tumor implantation, the mice were injected intraperitoneally with PTS2 (0.25 or 2.5 mg/kg/day; n = 20), DDP (2.5 mg/kg/day; n = 10) or 0.2 ml 0.9% saline (n = 10) for another 10 days. On day 11, all the animals were killed and the tumors dissected out and weighed (A). **P < 0.01 compared with controls. Tumor growth inhibition rate was calculated (B).