Inhibition by caffeine of ovarian hormone-induced mammary gland tumorigenesis in female GR mice.

The purpose of this study was to determine whether or not caffeine could influence the development of ovarian hormone dependent mammary tumors in GR mice. Virgin female GR mice were treated daily for 24 weeks with 17 beta-estradiol and progesterone, commencing at 8-10 weeks of age. One week after the onset of hormone treatment, caffeine (500 mg/l drinking water) was administered daily until experiment termination to one-half of the hormone-treated mice. Hormone treatment induced mammary tumors in 95-100% of the mice. Caffeine treatment significantly (P less than 0.05) reduced the mean number of mammary tumors per mouse and significantly (P less than 0.05) increased the mean latency period of mammary tumor appearance.