The effects of ellagic acid and 13-cis-retinoic acid on N-nitrosobenzylmethylamine-induced esophageal tumorigenesis in rats.

Ellagic acid (EA) and 13-cis-retinoic acid (CRA), both alone and in combination, were tested for their ability to inhibit N-nitrosobenzylmethylamine-induced tumors in the rat esophagus. Groups of male rats were fed AIN-76A diet containing EA (4 g/kg), CRA (240 mg/kg), or a combination of EA and CRA (4 g/kg and 240 mg/kg), respectively, for 25 weeks. Two weeks after initiation of the diets, NBMA (0.5 mg/kg per injection) was administered s.c. once weekly for 15 weeks. After 25 weeks on the diets, the animals were necropsied. The incidence of esophageal tumors was 97-100% in all NBMA-treated groups. The multiplicity of tumors in NBMA-treated groups was reduced significantly by EA (60%), but not by CRA, or by EA + CRA. These results demonstrate that EA and CRA do not act synergistically to inhibit NBMA-induced esophageal tumorigenesis.