The modifying effects of administrating yeast, Zinc (Zn) and enriched Zn yeast (Zn-Yeast) during the initiation phase or the post initiation phase on 4-nitroquinoline 1-oxide (4-NQO)-induced tongue tumorigenesis were investigated in male F344 rats. Rats aged 6 weeks were given 4-NQO at 20 ppm for 8 weeks to induce tongue neoplasms. Both of yeast and Zn-yeast were produced and provided by Oriental Yeast Co. Ltd., Japan. Starting 1 week before 4-NQO administration, animals were fed the experimental diets containing 5% Yeast, 1% Yeast, 5% Zn-Yeast, 1% Zn-Yeast, 2500 ppm Zn(CH3COO)2, 500 ppm Zn(CH3COO)2 for 10 weeks, and then maintained on a basal diet for 32 weeks. Starting 1 week after the cessation of 4-NQO exposure, the experimental groups given 4-NQO and a basal diet were fed the experimental diets for 32 weeks. At the termination, feeding of 1% Yeast, 1% Zn-Yeast containing diets during the initiation phase, and all of administration of experimental diets during post-initiation phase significantly inhibited the incidence of tongue carcinoma, when compared with 4-NQO alone group. Dietary Yeast, Zn and Zn-Yeast decreased the cell proliferating activity of tongue carcinoma. These findings might indicate possible chemopreventive effects of yeast, Zn enriched yeast and Zn on tongue tumorigenesis.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]