Anti-tumor effects of 25-hydroxycholesterol and low-dose recombinant tumornecrosis factor-alpha on rat liver tumorigenesis: Modulated differentiation therapy for hepatocellular carcinoma

Previously, we have demonstrated that treatment of rat AH136B ascites hepat oma cells with 25-hydroxycholesterol (25-OH) induces apoptosis. In this stu dy, to elucidate whether modulated differentiation therapy may be useful in treating patients with hepatoma, we assayed the effects of 25-OH and/or tu mor necrosis factor-alpha (TNF) on rat AH136B ascites hepatoma cells in viv o. Here we show that a high concentration of TNF (250 U/ml) mediated a stro nger cytocidal effect than a low concentration of TNF (25 U/ml) in vitro. F low cytometric DNA analysis also showed that treatment of cells with the hi gh concentration of TNF (250 U/ml) increased the percentage of AH136B cells in the Go/G1 phase, while 25 U/ml of TNF did not cause any marked change i n cell kinetics. In in vivo experiments, 25-OH (80 mu g/rat) and TNF (500 U /rat) were administered after transplanting AH136B cells into Donryu rats i ntraperitoneally. We found that tumor development was completely inhibited by this treatment in 3 of 9 rats, and their 40-day survival rate was 44%; i n contrast, rats administered 25-OH (80 mu g/rat) alone or TNF (500 U/ml) a lone developed peritonitis carcinomatosa, and died within 13 days of inocul ation. These findings suggest that local combined treatment with 25-hydroxy cholesterol and low-dose TNF can induce synergistic antitumor effects.