Possible Two-Stage Mechanism in Experimental Leukemogenesis

Abstract
The augmenting influence of urethan on leukemogenesis by x-radiation in mice has been found to operate when the urethan treatment follows the radiation, but not when the sequence is reversed. The result is in keeping with the idea that urethan acts as a promoting factor in leukemogenesis, as defined by the twostage mechanism hypothesis of carcinogenesis. It may also have a practical bearing on leukemia development in man.