Subcutaneous epithelial Ehrlich ascites tumor (EAT) transplants stimulate adja cent mammary duct epithelium in C57BL mice. Present data describe a similar effect for Sarcoma 180, which is of connective tissue origin. Increased mitotic activity, with peak value on the 2d day of tumor growth, occurred in the epithelial cells of mam mary ducts located in a 1-mm. area around the tumor nodule. Inwar...

Mammary tumorigenesis in genetic crosses between the high mammary tumor incidence GR and the low incidence C57BL mouse strains is highly correlated with murine mammary tumor virus expression in milk. Although the F1 and first backcross females had a mammary tumor incidence which was consistent with a single dominant gene segregation, the tumor incidence in the critical second backcross segregan...

We have previously demonstrated that (guanine-2-)-methyltransferase activity in extracts from 9,10-dimethyl-1,2-benzanthracene-induced rat mammary tumors differs from that of nonneoplastic mammary tissue. In this report, we explore further the nature of these differences by purification and characterization of the two major transfer RNA (tRNA) (guanine-2-)-methyltransferases from transplantable...

Lymphocytes from BALB/cCrgl mice react to mouse mammary tumor virus-associated antigen(s) when tested in in vitro blastogenic transformation assays. These mice have a low incidence (less than 1%) of spontaneous mammary tumors and are free from complete mammary tumor virions. We have studied the nature of the lymphoid cells mediating the lymphocyte transformation reaction to purified mammary tum...

Mouse mammary tumors grow preferentially upon transplantation into intact mammary glands compared to cleared mammary fat-pads. Both sites provide stroma of the orthotopic site, but the latter lacks epithelial elements. If epithelium from enzymatically dissociated normal mammary glands is added to the tumor cells prior to injection into cleared fat-pads, tumor growth is comparable to that seen i...

Breast cancer is the most frequent tumor type among women in the United States and in individuals with Li-Fraumeni syndrome. The p53 tumor suppressor gene is altered in a large proportion of both spontaneous breast malignancies and Li-Fraumeni breast cancers. This suggests that loss of p53 can accelerate breast tumorigenesis, yet p53-deficient mice rarely develop mammary tumors. To evaluate the...

Since the development of strains of mice with variations in the incidence of spontaneous mammary tumors, attempts have been made to demonstrate anatomic or physiologic differences between them that might be etiologically related to tumor formation. We have searched for such a variation in the urinary excretion rates of the so-called sex hormones because of the many observations linking these ag...

C3H and C3H backcross mice were given repeated injections of preparations from strain-specific or strain-related mammary tumors of recent spontaneous origin together with Freund's adjuvant. The effect of the course of injections on spontaneous mammary tumor development was studied. Pre t rea tment with mammary tumor tissue did not lead to a significant reduction in spontaneous mammary tumor inc...

A transplanted mammary fibroadenoma was found to grow in 95 per cent of intact adult female rats and the increment of tumor weights was progressive and logarithmic. The growth of the tumor was retarded by ovariectomy and still more when this was combined with adrenalectomy. In ovariectomized rats the growth of the tumor was stimulated by phenolic estrogens, this increase being enhanced when pro...