Antitumor effect of geranylamine derivatives on human hepatoma

In this study, we examined the antitumor activities of isoprenoid derivatives conjugated with substrates of energy metabolism in human hepatoma-bearing athymic mice. Among these compounds, N-geranylpyruvic amide, N-geranyl-p-pyruvaminobenzoic amide, N,N'-digeranylmalic diamide and N,N'-digeranyl-O-acetylmalic diamide had strong antitumor effects. These geranylamine derivatives also inhibited in vitro cell growth. Sugar conjugates of geranylamine, geranic acid and mevalonic acid did not show any antitumor effect in vivo or in vitro. Although the geranylamine derivatives had no impact on the cell cycle distribution at 24 h, a sub-G1 (apoptotic) peak of varying magnitude was seen in DNA histograms of cells treated with the derivatives for 48 h. However, the geranylamine derivatives did not inhibit protein isoprenylation, which has been reported in cancer cells treated with several natural isoprenoids. These results suggest that the geranylamine derivatives conjugated with malic acid and pyruvic acid have a different mechanism of antitumor activity from that of natural isoprenoids.