The inhibition of croton oil-promoted mouse skin tumorigenesis by steroid hormones.

Tumors in female Swiss Millerton mouse skin were initiated with 25 pg 7,12-dimethylbenz(a)anthracene and, 2 weeks later, were promoted 3 times/week with 0.2 ml of 0.5% croton oil. Four steroid hormones in 0.2 ml of acetone were applied percutaneously at 6 and 30 jug 5 times/week. A fifth steroid was applied at the 30-^g dose. Tumor inhibition by the hormones was dose dependent in the order dexamethasone > Schering No. 11572 > prednisolone > hydrocortisone > cortisone. There was a general correlation between the antiinflammatory and antitumor activities of the steroids.