Suppression of rat liver tumorigenesis by 25-hydroxycholesterol and all-trans retinoic acid: differentiation therapy for hepatocellular carcinoma.

To determine whether differentiation therapy is useful in treating patients with hepatoma, we assayed the effects of 25-hydroxycholesterol (25-OH) and/or all-trans retinoic acid (ATRA) on rat AH136B ascites hepatoma cells. Flow cytometric DNA analysis showed that treatment of cells with 25-OH alone induced entry into the sub-G1 phase in a dose-dependent manner. While ATRA alone was ineffective, it enhanced the activity of 25-OH. Condensed and fragmented nuclei occurred mainly in cells treated with 25-OH (4 microg/ml). When cells treated with 25-OH (4 microg/ml), or 25-OH (4 microg/ml) + ATRA (1 microM) were transplanted into Donryu rats, we found that tumor development was completely inhibited; in contrast, rats administered the methanol-treated AH136B cells developed tumors. These findings suggest that AH136B cells in the sub-G1 phase can not recover tumorigenicity, and that the administration of a 3-hydroxy-3-methylglutaryl CoA reductase inhibitor, such as 25-OH, and ATRA may be effective in treating patients with hepatoma.