Hormonal Requirements for the Growth of Mammary Adenocarcinoma (MTW9) in Rats1

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Abstract
The hormonal requirements for the growth of a hormone-dependent mammary adenocarcinoma (MTW9) have been studied. Rapid growth of mammary tumor implants in intact female rats was confirmed following coimplantation of pituitary tumor MtTW5. Mammary tumor growth was prevented by oophorectomy prior to, or shortly after, tumor implantation. If oophorectomy was delayed beyond 14 days, suppression of mammary tumor growth was less effective. Growth of MtTW5 was not affected by oophorectomy. Mammary tumor growth did not occur in oophorectomized rats with pituitary tumor; however, if these rats were injected with a combination of estradiol-17β and progesterone, mammary tumor growth was similar to that in intact animals. If estradiol-17β or progesterone was injected singularly, mammary tumor growth occurred but was retarded as compared with intact animals. Transplanted mammary tumor did not grow in intact or castrated male rats unless ovarian hormones were injected. Isografts of whole pituitary glands implanted into the kidney capsule in animals without pituitary tumor stimulated the growth of mammary tumor implants in intact and hypophysectomized female rats. Oophorectomy of animals bearing pituitary isografts inhibited mammary tumor growth. Administration of ovarian hormones to these animals promoted mammary tumor growth. Administration of a combination of prolactin, growth hormone, estradiol and progesterone to intact animals inoculated with mammary tumor alone stimulated the growth of mammary tumor. (Endocrinology75: 249, 1964)