Carcinogenicity of betel quid. III. Enhancement of 4-nitroquinoline-1-oxide- and N-2-fluorenylacetamide-induced carcinogenesis in rats by subsequent administration of betel nut.

The effect of betel nut on chemical carcinogenesis in the upper digestive tract and liver was examined in two different experimental models with ACI rats. The incidences of neoplasms and preneoplastic lesions of the tongue in animals given 5 ppm 4-nitroquinoline-1-oxide (4-NQO; CAS: 56-57-5) in the drinking water for 16 weeks and followed by 20% betel nut in the diet for 40 weeks were significantly higher than those in animals given 4-NQO alone. No enhancing effect from betel nut on the incidences of neoplastic and preneoplastic lesions in the upper digestive tract was found in animals administered 4-NQO for 12 weeks. The number of altered liver cell foci in rats given 200 ppm N-2-fluorenylacetamide (FAA; CAS: 53-96-3) in the diet for 8 weeks and followed by the betel nut diet for 16 weeks was significantly greater than that in animals fed the FAA diet alone. These results indicate enhancing effects of dietary administration of betel nut on oral carcinogenesis by 4-NQO and hepatocarcinogenesis initiated by FAA.