It is reasonable to assume that in experimentally induced cancer the carcinogen localizes in the target tissue where the tumor eventually appears. Dao, Bock, and Crouch2 fed single doses of 3-methylcholanthrene to female rats according to the method of Huggins3 and assayed the amount of carcinogen present in the various tissues. The only tissues which retained significant amounts of the carcinogen were breast and fat. It is a well-known fact that mammary cancer may readily be induced in the female rat by oral feeding of 3-methylcholanthrene. It is, then, an established fact that carcinoma may be produced at a distant site in the body of an experimental animal by systemic administration of any one of several carcinogens.1,3-5
The target tissue may be altered by changing certain factors or conditions of the experimental animal. Factors which can be varied under controlled conditions are age, nutrition, and hormonal status
RYAN JF, MOCK LF, BOLASNY B, VAN PROHASKA J. Inhibition of Mammary Cancer Induction in Rats with Corticosteroids. Arch Surg. 1962;85(1):70–73. doi:10.1001/archsurg.1962.01310010074010
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