Pituitary role in the estrogen dependency of experimental mammary cancer.

Abstract

These studies were designed to determine whether the growth of experimental hormone-dependent mammary cancer in rats can be exacerbated by estrogen administration after remissions have been induced by different ablative procedures. Subjects were 94 female 50-day-old Sprague-Dawley rats. Mammary tumors were induced by a single feeding of 20 mg of 712-dimethylbenz(a)anthracene. Tumors were 1st detected 8-12 weeks after carcinogen administration. After tumor development 6 animals were left as intact controls. Adrenalectomy plus ovariectomy or hypophysectomy was done 10-20 days after tumors were detected. Tumors regressed in all animals operated on but not in controls. Estrogen administration estradiol benzoate 5 mcg daily for 20-50 days reactivated tumor growth in rats after adrenalectomy plus ovariectomy but not after hypophysectomy. Thyroid L-thyroxine 5 mcg/day and cortisone .5 mg/day for 30 days as replacement therapy for hypophysectomized animals did not alter results. Results indicated that estrogen-stimulated mammary cancer is dependent on the presence of the pituitary gland.