Lack of Growth of a Pregnancy-Dependent Mouse Mammary Tumor (TPDMT-4) in the Absence of Pituitary Hormones2

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Abstract
Mammary tumors of line TPDMT-4, established in DDD mice, were characterized by growth during pregnancy and regression after parturition; this resulted in higher growth peaks in subsequent pregnancies in breeders and no growth in virgins. The effect of hypophysectomy on tumor growth in mice given 17/β-estradiol (E) and progesterone (P) or deoxycorticosterone acetate (DCA) was investigated. Growth of cancers occurred in E+Pand E+DCA-treated virgins, but not in cholesterol-treated virgins. Tumors did not grow to palpable sizes in cholesterol-, E+P−, and E+DCA-treated hypophysectomized virgins; this indicated that pituitary hormones were essential for tumor growth. Impalpable but microscopic tumors were obtained at necropsy in 1 of 5 cholesterol-treated, 5 of 10 E+P-treated, and 3 of 6 E+DCA-treated hypophysectomized animals. The neoplasms showed ductal and tubular structures that were lined by a single layer of well-differentiated cuboidal epithelium, which suggested that the tumor line might be derived from ductal cells.

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