Inhibition of mammary tumorigenesis in nulliparous C3H mice by chronic feeding of the synthetic retinoid, N-(4-hydroxyphenyl)-retinamide.

Feeding of N-(hydroxyphenyl)retinamide (4-HPR) (1.0 mM/kg diet) for 39 weeks to 2 month old nulliparous C3H/Crgl mice significantly (p less than 0.01) reduced the incidence of mammary tumors; 98 control mice developed a total of 235 mammary tumors, 100 4-HPR treated mice developed 171 mammary tumors. Feeding the same dietary level of 4-HPR to 4-6 month old multiparous C3H mice for 14 weeks did not significantly influence the development of mammary tumors; 78 control mice developed a total of 115 mammary tumors; 78 4-HPR treated mice developed 130 mammary tumors. Body weight gains were comparable among 4-HPR treated mice and control mice. Significant suppression of mouse mammary gland tumorigenesis in vivo by dietary retinoids (nulliparous C3H mice) has heretofore not been reported.