Biologic characteristics and chemotherapy of 7,12-dimethylbenz[a]anthracene-induced tumors in rats.

Abstract

Summary The biologic characteristics and susceptibility to steroid therapy were determined for multiple mammary tumors induced in Sprague-Dawley rats by single intragastric doses of DMBA. 3 Tumors were produced in 70–78% of 1016 rats within 120 days of administration of 15, 20, or 30 mg of DMBA. Mortality was 20% in rats given the highest dose. Only 52–63% of the rats had tumors usable for experimental chemotherapy. In 20 representative rats, 86 mammary tumors comprised 97.6% of all masses removed at autopsy, 92% of which were malignant. Growth behavior of tumors was unpredictable, a variable number growing, regressing, or remaining static in the same host. Bilateral ovariectomy on 70 rats produced tumor regression in 57%. These remained tumor free from 11 to less than 35 weeks. Steroids producing complete remission of all tumors in 40% or more of the treated rats were: 5α-androstan-3α, 17β-diol dipropionate; 2α-methyldihydrotestosterone; its propionate, testosterone propionate; 9α-fluoro-11β-hydroxy-17-methyltestosterone; and 6β-methyldihydrotestosterone propionate. 1-Dehydrotestololactone was relatively inactive. Preliminary tests with nonsteroids yielded inconclusive results because of high toxicity.