Effects of lycopene and Sho-saiko-to on hepatocarcinogenesis in a rat model of spontaneous liver cancer.

The Long-Evans Cinnamon (LEC) rat is a well-characterized model of spontaneous hepatocarcinogenesis. It has been shown that dietary administration of lycopene or the herbal medicine Sho-saiko-to (TJ-9) has anticarcinogenic activity, although the mechanism by which these products protect against carcinogenesis is not well known. We investigated the outcome of administration of lycopene and TJ-9 on the occurrence of hepatic neoplasia in LEC rats. A diet containing 0.005% lycopene (originally the product of tomato oleoresin containing 13% lycopene) and 1% TJ-9 (crude extracts of 7 herbs: bupleurum root, pinellia tuber, scutellaria root, jujube fruit, ginseng root, glycyrrhiza root, and ginger rhizome) was administered from 6 weeks of age until the rats were sacrificed at 76 weeks of age, at which time most of the nontreated animals were known to have hepatocellular carcinoma (HCC). Development of HCC in treated groups was analyzed histologically by comparison with untreated controls. Glutathione S-transferase placental form (GST-P) was analyzed by an immunohistochemical method. Concentration of copper, iron, and zinc, which appear to play a role in hepatocarcinogenesis in LEC rats, was analyzed. The percent areas of HCC in the liver specimens of control, lycopene, and TJ-9 groups were 17.9 +/- 17.1%, 27.2 +/- 20.8%, and 27.6 +/- 18.4%, respectively. These intergroup differences were not significant. The percent area, number of areas, and mean size of area staining positively for GST-P revealed no significant differences between the groups. The number of GST-P-positive areas within the HCC lesions was greater in the TJ-9 group than in the control or lycopene group (p = 0.024 and p = 0.012, respectively). The study also demonstrated a lower concentration of iron in livers of the lycopene group than the control group (p = 0.019). There were no differences in serum alpha-fetoprotein levels or the cumulative survival rates between the groups. In conclusion, long-term administration of lycopene or TJ-9 did not reduce the risk of hepatocarcinogenesis in LEC rats.