Hormone-Dependent Mammary Tumors in Strain GR/A Mice. III. Effectiveness of Supplementary Hormone Treatments in Inducing Tumorous Phase Growth2

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Abstract
AHempts were made to initiate hormone-dependent tumor (HDT) transformation in ductal phase mammary outgrowths. These outgrowths, when carried in virgin GR/A mice, were not tumorous and usually resembled the host's mammary glands. After 2–3 months' initial growth, the following hormone treatments were initiated: 1) An isologous pituitary was implanted into each fat pad having previously received an HOT transplant. Some neoplastic transformation of the pregnancy-dependent tumor outgrowth occurred after 1–2 months; all 10 mammary glands were well stimulated and had many hyperplastic alveolar nodules. 2) In experiments involving exogenous hormone administration, estrogen or progesterone administered alone caused no neoplastic changes in the 2- to 3-month-old ductal phase outgrowths. However, 1 mg progesterone plus 1 µg estrogen daily given sc for 3 weeks to both ovariectomized and intact mice with HDT transplants caused neoplastic changes in the outgrowths and induced small ductal hyperplasias in the host glands. Termination of hormone treatment resuHed in a return to the normal ductal structure. The addition of 100 µg prolactin and 100 µg growth hormone to the progesterone and estrogen mixture did not further alter transplants but increased stimulation to the host glands.