The effect of hypophysectomy on 9,10-dimethyl-1,2-benzanthracene-induced carcinogenesis [abstract].

In view of the findings of Moon, Simpson, and Evans (Science, 116:331,1952) that the hypophysectomized rat was refractory to the carcinogenic effect of methyl-cholanthrene, similar experiments have been conducted but using the more powerful carcinogen 9,10-dimethyl-1,2-benzanthracene. The results of 2 separate experiments were as follows: All animals received 5 mg in sesame oil of the carcinogen intramuscularly. In the control animals, 15 showed discrete sarcoma out of 21 animals in 4-5 months. In the hypophysectomized animals only 3 showed comparable sarcoma, but in 7 there was marked abnormal proliferation of fibroblasts suggestive of malignant change. 9 animals were negative, although serial sections were not made. In addition to these findings it was noted that in control animals 6 mammary tumors developed in tissue adjacent to the injection site. 4 of these were of a malignant nature. In the hypophysectomized group no mammary changes were observed. Although these findings are somewhat in accord with the original observations it is believed that the change is quantitative rather than qualitative. Unfortunately, the hypophysectomized animals survived only 3-4 months, and the findings are suggestive that the malignant process occurs but more slowly in the absence of the normal pituitary function. The changes in mammary tissue would seem more clearcut, but are being repeated on a larger series of animals.