Geranylgeranoic acid (GGA) has been developed as a preventive agent against second primary hepatoma. Recently, GGA was reported to induce cell death in human hepatoma cells via TLR4-mediated pyroptosis. We have reported that GGA is enzymatically biosynthesized from mevalonic acid in human hepatoma-derived cells and that endogenous GGA is found in most organs of rats. In addition, we found that upregulation of endogenous GGA levels by zaragozic acid A (ZAA) induced cell death in human hepatoma-derived cells. Therefore, we investigated the age-related changes in hepatic GGA and the possibility of suppressing hepatocarcinogenesis by GGA supplementation using male C3H/HeN mice that spontaneously develop hepatoma. We measured endogenous GGA and mRNA of monoamine oxidase (BMAOB), a key enzyme of GGA biosynthesis, in the liver of male C3H/HeN mice aged 6–93 weeks. We also tried suppressing spontaneous hepatocarcinogenesis by a single administration of GGA to C3H/HeN mice. Hepatic GGA content and Maob mRNA expression level age-dependently decreased in male C3H/HeN mice; some of which produced spontaneous hepatoma in 2 years. A single oral administration of GGA at 11 months of age significantly prevented hepatoma in terms of the number and weight of tumors per mouse at 24 months. Oral supplementation with GGA or geranylgeraniol significantly increased endogenous hepatic GGA contents dose-dependently; and ZAA dramatically upregulated hepatic GGA. In this study; we found an age-dependent decrease in hepatic endogenous GGA in male C3H/HeN mice and efficient prevention of spontaneous hepatoma by a single administration of GGA at 11 months of age.

Inhibitory effects of 4,5-didehydrogeranylgeranoic acid (dGGA) on the development of tumors were investigated in spontaneous hepatoma mice, C3H/HeNCrj. Experiment 1: Male mice at 8 weeks of age were raised on a basal diet, and then provided with a diet containing 0.02% dGGA from 32 to 91 weeks of age. Experiment 2: dGGA was administered to the animals only once at different time points, from 2 months to 17 months after birth, respectively. Experiment 3: dGGA was administered twice to the mice at different time points: at 5 months and 11 months, and at 8 months and 11 months, respectively. When the inhibitory effects on tumor development were evaluated with the incidences of tumors, average numbers, and weight of tumors per mouse, there was a marked relationship between the time of single or dual dosing and the inhibitory effects of dGGA. The greatest inhibitory effects were observed in Experiment 3 in the group of animals given dGGA at the ages of 8 and 11 months, which were far superior to the results with a large dose of the compounds for a long time. These results might indicate that dGGA administered at the right time in the right amount effectively prevents the development of cancer.