Effect of red ginseng on natural killer cell activity in mice with lung adenoma induced by urethan and benzo(a)pyrene.

It was previously reported that red ginseng extract inhibited carcinogenesis by urethan, DMBA, and aflatoxin B1 [Yun et al: Cancer Detect Prevent 1983; 6:515-25]. In an attempt to investigate the mechanism of the anticarcinogenic effect of ginseng, the natural killer (NK) activity and the incidence of lung adenoma were followed over a period of 48 weeks postinjection with urethan or benzo(a)pyrene. The NK activity was markedly depressed from 4 weeks to 24 weeks after injection of carcinogens. This decreased NK activity was returned to the level of controls by administration of ginseng. At the same time, a lower incidence of lung adenoma was noted following administration of ginseng to urethan-injected mice. However, the lung adenoma induced by benzo(a)pyrene began to occur at 48 weeks in which NK activity had naturally declined to a level too low to be affected by ginseng, and administration of ginseng did not decrease the incidence. In conclusion, these results suggest that the anticarcinogenic effect of ginseng may be related to the augmentation of NK activity.