The saline and dimethylsulfoniopropionate (DMSP) solutions at 5, 10 and 20 m M were preliminarily injected intraperitoneally every other day into two control and three DMSP groups of mice ( n ϭ 8) for 2 wk and thereafter Ehrlich ascites-carcinoma (EAC) cells were peritoneally injected to one control and three DMSP groups of mice, leaving one control group without the EAC injection. Then, the body weight and survival time of all mice were examined over a long rearing time up to 300 d. All

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... ring mice, especially the carcinoma control and 5 m M DMSP-carcinoma group mice, rapidly increased their body weights early and then died by day 50 and day 90, respectively. In contrast, the administration of 10 and 20 m M DMSP solutions prolonged the lives of EAC-bearing mice at the survival rate of 50 and 63% respectively up to 300 d without any side effects. Furthermore, the administration of 10 m M DMSP solution proved to activate the delayed-type hypersensitivity of EAC bearing-mice, and the DMSP solutions over the concentrations of 5 to 30 m M to slightly reduce the dead cells in EAC cells on the synthetic medium. Accordingly, the preliminary supplementation of 10 and 20 m M DMSP solutions to EAC-bearing mice was proven to maintain their lives at high survival rates without direct damage to EAC cells for a long time, probably due to the activation of the immune system without any side effects.