Inhibitory effects of synthetic acidic retinoid and polyprenoic acid on the development of hepatoma in rats induced by 3'-methyl-N, N-dimethyl-4-aminoazobenzene.

A study was conducted to investigate the inhibitory effects of acidic retinoid (trimethylmethoxyphenyl analog of retinoic acid ethylester or TMMP) and polyprenoic acid (3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid or E-5166) on the development of hepatoma induced by 3'-methyl-N, N-dimethyl-4-aminoazobenzene (3'-MeDAB) in rats. Morphometric analysis of liver specimens was employed to evaluate the antitumor effects of the compounds in detail, and revealed significant decreases in the number and area of tumors in the TMMP- and E-5166-treated groups. As for adverse effects, retarded growth and marked hypertriglyceridemia were observed only in TMMP-treated rats. During the hepatocarcinogenesis, cellular retinoid-binding protein, F-type or CRBP(F) and cellular retinoic acid-binding protein or CRABP newly appeared in the tumor tissue, particularly in hyperplastic nodules which are the precancerous state of hepatoma. These results suggest that the polyprenoic acid is a good candidate for clinical chemoprevention of hepatoma, targetting its precancerous stage when intracellular receptors for acidic retinoid have emerged.