No effect of RU 486 (mifepristone) on hepatocellular tumorigenesis in orchiectomized male mice induced by 3'-methyl-4-dimethylaminoazobenzene.

Effects of RU 486 (mifepristone) on hepatocellular tumorigenesis in orchiectomized male mice induced by 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) were investigated. Male mice that had been treated with 3'-Me-DAB neonatally were orchiectomized at one month of age, and injected daily with vehicle only or RU 486 at 0.2 or 0.4 mg/day thereafter. In the liver of orchiectomized males injected with vehicle only, adenomatous nodules developed at incidences of 16.2 and 38.5% at 9 and 12 months of age, respectively, but no carcinomas developed at these ages. Injections of RU 486 at 0.2 or 0.4 mg/day neither affect incidences of adenomatous nodules in the liver, their numbers per mouse, and their areas, nor promote the development of carcinomas. The present results suggest that the long term administration of RU 486 has no effects on hepatocellular tumorigenesis.