Carcinogenic Effect of Estradiol and of Theelin in Marsh-Buffalo Mice
Authors: Fritz Bischoff, M. Louisa Long, J. Jerome Rupp, Georgena J. Clarke
Journal: Cancer Research (1942)

(From the Chemical Laboratory, Santa Barbara Cottage Hospital Research Institute, Santa Barbara, Calif.) (Received for publication September I5, I94 I) The present report is concerned with a comparison in Marsh-Buffalo mice of the action of estradiol with that of theelin when injected over a long period and in massive doses. Studies performed in this laboratory indicate that the Marsh-Buffalo strain is highly suscep- tible to mammary cancer and markedly resistant to the carcinogenic effect of exogenous theelin. Since the relation between estradiol and theelin in catabolism is not known, it appeared desirable to ascertain whether estradiol would be more effective, and whether the intact ovary inhibited the influence or acted synergisti- cally to exogenous estradiol. Suntzeff et al. (5) state,  strain New Buffalo nonbreeding ,nice injected with estrin the percentage of tumors developing was relatively low, although it was somewhat higher than in nonbreeding control mice. There is thus some indication that the mammary gland of New Buffalo mice is relatively resistant to the stimulating action of  Since these workers used only 2 to 7 mice per experiment, this work must be regarded as pre- liminary in nature. We were, therefore, prompted to repeat these experiments on a larger scale, since resistance to carcinogenesis caused by theelin in a high cancer strain would be a phenomenon which could not readily be ignored. The results of our experi- ment published to date (I), in which crystalline theclin was used, confirmed the original suggestion of Suntzeff et al. that the mammary gland of the Marsh-Buffalo mouse is relatively resistant to the stimulating action of estrin. The incidence of mammary cancer in our control Marsh-Buffalo mice parallels the data originally published by Marsh (3) and confirmed by Murray and Hoffman (4)- It should be noted that the data of Suntzcff et al. indicate a considerably lower cancer incidence, and in this respect only is there a divergence in results. Since the studies reported in this paper were completed, Suntzeff et al. (6) have published additional data on the Marsh-Buffalo strain, and conclude that the estrogen dosage raised the incidence of tumors in nonbreeding mice to approximately that of the breeders. This deduction is obviously unwarranted as the standard deviation of the mean for the number of animals used equals the difference. In our opinion, the data again demonstrate that mice of the Marsh-Buffalo strain are highly resistant to estrogen carcinogenesis, and justify the characterization of this strain as having a relatively low incidence of cancer in Dr. Loeb's laboratory. EXPERI~ENTAL At 22 days of age, litter-mate females were divided into 3 groups of 4 ~ mice per group. One group served This investigation was aided by a grant from The Inter- national Cancer Research Foundation. as a control and received injections of sesame oil. An- other group received injections of estradiol. 1 The third group was ovariectomized at weaning, and received estradiol in the same amount as did the group os intact mice. The amount of estradiol administered in these experiments corresponds to the larger amounts os theelin administered in our previous experiments with theelin (I). The estradiol was dissolved in sesame oil (2 mgm. per cc.) and was administered intramuscu- larly or subcutaneously in doses of o.o 4 cc. twice weekly for a period of 6 months. Each surviving mouse re- ceived a total dose of 3.3 to 4.2 mgm. estradiol. The controls received o.o 4 cc. sesame oil twice weekly over a 6-nlonth period. The first injections were given at the age of r to 2 months. Since the purpose of these experiments was to com- pare the action of estradiol with that of theelin, the data of experiments with mice receiving theelin, which have been published (i), are retabulated and compared with experiments in which estradiol was used. Forty mice received theelin in each experimental group. In Tables I and II are tabulated the cumulated percentage incidences of adenocarcinoma of the breast, lympho- sarcoma, spontaneous death, and combined influences removing animals from the experiment. Spontaneous death is used as a measure of toxicity. At autopsy, some of these animals were found to have lympho- sarcoma. With the development of a palpable tumor, the animal was removed from the experimental group and sacrificed after the tumor had developed in di- ameter to 1.5 cm. RESULTS Toxicity.--In the controls of both the theelin and estradiol series, the 13 and i2 per cent incidence (cumulative) of death before the 7th month is higher than is usually encountered for control mice. In a series of I2o virgin female mice housed and fed under strictly analogous conditions, but not given sesame oil, only I mouse died in a similar period. A slightly toxic effect of the sesame oil is indicated. In same 7- month period, 35 per cent of the theelin-dosed mice, x The authors are indebted to the Schering Corporation for the supply of alpha estradiol. 52