Effect of Sex Hormones on the Carcinogenic Action of Dimethylbenzanthracene on the Uterus of Intact and Castrated Mice¹

An experimental model of uterine carcinogenesis by implantation of a pearl of pure dimethylbenzanthracene in contact with the cervix or the endometrium of mice was used to test the possible influence of sex hormones on the incidence of malignant lesions. Administered at relatively low, but physiologically active doses, estrogen significantly lowered the incidence of uterine cancer. Ovariectomy also significantly reduced the incidence of malignant uterine lesions. The group of castrated animals receiving estrogen had the lowest incidence of the whole series. These results suggest the possibility that ovariectomy removes the site of synthesis of a promoting agent in this experimental model—conceivably progesterone.