Induction and Extinction of Mammary Cancer

Abstract

This article describes the induction the induction and suppression of breast cancer in albino rats; the study was conducted to permit the analysis of the mechanisms of the causes and extinction of cancer 2 of the central problems in cancer research. A single feeding of 20 mg of 712 dimethylbenz(a)anthracene (712-DMBA) dissolved in sesame oil developed mammary cancer in all of over 700 healthy female rats of the Sprague-Dawley strain. The mammary cancer evoked by the aromatic hydrocarbons were all rather similar in cytologic appearance and all had the cellular pattern of papillary adenocarcinoma. Experiments also showed that while 712-DMBA and 2-aminophenanthrene were strong carcinogens benz(a)anthracene and phenanthrene did not evoke mammary cancer. It appears that the methyl and amnio groups convert the otherwise inactive parent molecular species to powerful carcinogens. 3 factors seem to determine mammary carcinogenicity in polynuclear aromatic hydrocarbons: 1) the electron transfer 2) the geometric factor and 3) the molecular thickness. Regression of mammary cancer has been induced by 2 types of alteration of the endocrine status the withdrawal of the hormones essential for the life and growth of the cancer usually done through ovariectomy on the administration of appropriate hormones. In an experiment female rats previously induced with mammary cancer through administration of 712-DMBA were given for 30 days 20 mcg of estradiol-17 and 4 mg of progesterone. In a group of 100 rats treated this way 52 were free from cancer at necropsy whereas their control companions succumbed to cancer. This experiment was repeated under more rigorous conditions with rats with large mammary cancers; the results were equally successful.