The Milk Agent in the Origin of Mammary Tumors in Mice

Oral Contraceptives: Relation to Mammary Cancer, Benign Breast Lesions, and Cervical Cancer

“…This and similar studies led to the fe ar that estrogens may cause breast cancer in women. EFFECT OF ESTROGENS Earlier studies on the effect of estrogen on the incidence of mammary carcinoma in male and female mice and the relationship of this response to the strain of mouse and the absence or presence of the mammary tumor virus have been reviewed (6)(7)(8)(9). As shown by Bittner in 1936 (5), nursing mothers with the high spontaneous incidence of breast cancer transmit a milk factor or mammary tumor virus that plays an important role in inducing the high tumor rate in the fe male offspring.…”

The Mammary Tumor Virus in Organs of Mice: Normal Distribution and Postinoculation Localization

“…The presence of the mammary tumor virus (MTV) in normal mammary gland tissue of mice from high mammary cancer strains is well known (1)(2)(3), and the wide distribution of MTV throughout extramammary tissues of such mice has been suggested by several investigators (1,2,4). There is evidence for the presence of the virus in spleen (1,(4)(5)(6)(7)(8), liver ( 5 , 9), placenta (9), testis (lo), Harderian gland ( 1 1 ), seminal vesicle ( 12), contents of the cauda epididymidis (13), male ejaculate (14), and blood (3-5, 10, 15, 16), especially in red blood cells ( 3 ) .…”

“…Since human cytomegalovirus was first isolated by Smith, Rowe, and Weller in 1956, problems have been encountered in maintaining this infectious agent owing to its lability under variety of experimental conditions (1)(2)(3). In the past the strains have either been maintained in serial passage in human embryonic fibroblasts (1,4 ) or frozen (with some stabilizing additive) a t -70" for relatively short periods of time (5,6 ) .…”

The Sarcomatous Transformation of Mammary Carcinoma, of Mice in Isologous Transplantates, in Cell Cultures, and in Reimplantates

“…The tumors of the various strains show structural differences which are due to genetic causes [2,3,10,[16][17][18][49][50][51]. In the older literature the malignancy of these growths had been doubted as their tissue texture was orderly and as they had no métastasés.…”

“…The tumors belong to the carcinomas. They are transplantable, tend to recur, and may be reimplanted from cell cultures.The factor that initiates the development of the tumor is an RNA virus (besides genetic and hormonal influences) [2,3,[11][12][13][16][17][18]. Several investigators have dealt with the morphology and develop ment of those viruses [1, 8, 9, 15-19, 25, 26, 41,42, 51, 52, 57, 58].…”