Abstract
Concentration and term of chemical carcinogens must be the most important variants for their effectiveness. A two-phase carcinogenesis experiment induced by a chemical carcinogen (DMBA) was conducted. The purpose of this experiment was set on the verification of the most suitable concentration and term for the two-phase carcinogenesis that is induced by identical on hamster's buccal pouches.
A 10-week application of 0.1% DMBA acted as an initiator and a 6-week application of 0.5% DMBA did as a promoter. The reverse order of those two did not induce tumors.A 6-week interval (intermission) between those two was the most suitable for this carcinogenesis model. Those results were unexpectedly similar to Odukoya and Shklar's work (1982).
Only a 10-week application of 0.1% DMBA or a 6-week application of 0.5% DMBA caused no tumors at all. The effect of the 10-week application of 0.1% DMBA for an initiator was not reversible for at least 8 weeks.
Although the method of this experiment is not along with that of Berenblum's two-phase carcinogenesis, this experiment shows clearly that there are two or more phases in the process of the DMBA induced carcinogenesis.
