Bacillus Calmette-Guérin vaccination and skin tumor promotion with croton oil in mice.

Abstract

Summary Charles River mice were painted once with dimethylbenz(a)anthracene (tumor initiation), followed by repeated applications of croton oil (tumor promotion). The i.v. injection of Bacillus Calmette-Guerin (BCG) 3 weeks prior to the initiation of croton oil treatment reduced the incidence and rate of appearance of both benign and malignant skin tumors. After 50 applications of croton oil, (2/week for 25 weeks), it was possible to demonstrate that the BCG-treated mice without tumors had a smaller spleen index and showed a greater cell-mediated immunological responsiveness to purified protein derivative than did the BCG-treated mice with the greatest number of tumors in the same group. Tubercle organisms were isolated from spleen cultures of the BCG-treated mice, regardless of their capacity to respond to in vivo and in vitro tests with purified protein derivative as antigen.